All Torqued Up


Let’s talk about torque, not the kind you generate when you pedal your bike, but the kind you use to hold your bike together. In Zen and the Art of Motorcycle Maintenance there is a scene involving a young “mechanic” stripping bolts on the protagonist’s motorcycle because he lacks “mechanic’s feel”. OK, I can relate to that, and mechanic’s feel is great. I like to think I have it. And I use it for lots of bolts and nuts on a bicycle.

But for some connectors, notably those clamping on carbon fiber, I’ll whip out a torque wrench.

I am not going to write a why and how manual on torque; that wouldn’t be esoteric, would it? Instead I’ll poke around the “nuts and bolts” of bicycle assembly.

Why do certain connectors require certain torques? One answer is so they won’t come unscrewed during use. But the more general answer is to generate tension in the connector, thereby applying a compressive load between items to be joined. If there were a convenient way to measure connector tension directly, that’s what we’d all do. But there isn’t, so we use torque as a proxy.

Actually that’s not entirely accurate. In industrial applications it’s being done by several manufacturers, with Direct Tension Indicating Bolts.

The problem with torque as a proxy for tension is that the condition of the threads affects the relationship between torque and tension. Clean vs dirty, lubricated vs dry, old vs new. Generally, torque values assume clean threads in good condition with some level of lubrication, but that still leaves a wide margin of error. That bolts aren’t snapping off or coming loose every day speaks I think to the large window of allowable torque on these things.

By the way, I generally lubricate threads before makeup… generally. I consider the use of grease or anti-seize compound as much a corrosion inhibition measure as a lubrication measure.

Component manufacturers usually include torque recommendations in their assembly instructions. Shimano especially does a great job with their online TechDocs Library.

Now, in esoteric fashion, let’s talk about torque.

I always use a torque wrench for:

  1. Shimano’s 5mm crankarm pinchbolts. This is a heavily loaded interface, and the consequence of insufficient torque is severe. 12-14 NM.
  2. Stem/handlebar and stem/steerer bolts, those 4mm bolts that must be tightened to 5 NM. Interestingly the stem/handlebar interface must be tight enough to never slip, while the stem/steerer interface is better off slipping in a crash. I use a preset “torque key”. Mine is made by Ritchey. There are several brands. Park Tools makes one. You do know not to put carbon assembly paste on your steerer tube to stem interface, right?
  3. Seatpost clamp bolt on a carbon fiber seatpost. 5 NM. Over-tighten this one and you can deform/damage/break your seatpost. Not tight enough and your seat will slide down while you ride. This is what carbon assembly paste is for.
  4. Sometimes I use a torque wrench for threaded bottom brackets and crank bolts of the 8mm and 10mm variety. I have found that “good and tight” with a full-size socket wrench or a long-handled Park shop hex key is about right for the 25 NM crank threads. I use a 15” breaker bar for 30-40 NM bottom bracket threads.

Things that irk me:

  1. I hate aluminum chainring bolts. They break. The female half is very thin-walled and loaded in tension (hoop-stress). Check with a magnet to see if yours are steel. I’ve quieted more than a few noisy bikes by replacing a broken chainring bolt.
  2. 2mm hex bolts like on Zipp wheels and most brake pad holders. OK, the bolts themselves don’t bother me, it’s the people who overtighten and round them out, or force me to round them out trying to remove them. The loads on these interfaces are very small. Be gentle. Do not overtighten. Use your fingertips, not your hands. Shop tip – jam an appropriately sized Torx head into a rounded out 2mm hex to get the bolt out, then get a new bolt.

Zipp 2mmAbove: Itsy bitsy 2mm bolt on the bearing adjustment collar of a Zipp hub.

  1. Ball-end (Bondhus) hex wrenches. I once had the task of extracting a seatpost bolt containing a broken 4mm ball-end from a Bondhus wrench. Shimano used to warn not to use a ball-end wrench to install their dear derailleurs, but I can’t seem to find the reference now. (See Bad Torque Recommendations below.)


 Things I’d like to see:

More Torx bolts. I would love it if Shimano would spec Torx bolts for their Crankarm pinchbolts. Kudos to Campy who have used Torx bolts in lots of places for many years.

A good idea:

If you are riding a thru-axle bike, tighten the thru-axle bolt with the wrench you plan to carry on the road or trail. Some of the torque specs are like 10 NM and higher. You may not be able to loosen a fully torqued thru-axle with that cute little multi-tool. You can apply this same idea to the lug nuts on your car. When you get home from the tire shop, check to see if you can budge each lug nut (one at a time, please) with the lug wrench in your trunk. Better to learn this at home than out on the road.

 Bad torque recommendation IMO:

Shimano calls for 8-10 NM on their rear derailleur mounting bolt. That’s just way more than necessary. There’s just not that much load on this interface. I use about 5 NM. I once had the pleasure of working on a damaged Dura-Ace titanium derailleur mounting bolt. It was expanded in six places, corresponding to the six contact points of the hex wrench. The bolt was literally jammed inside the housing and would not pivot. I didn’t see it being assembled, so I don’t know all the details, but the deformation clearly occurred during installation. Maybe the builder used a Bondhus wrench. Like any good garage mechanic I honed down the high spots a few thousandths of an inch until the OD was in tolerance and re-assembled the derailleur.

Damaged Derailleur BoltAbove: Dura-Ace titanium rear derailleur post deformed by hex wrench during installation.

 Torque wrench calibration:

If you have at least two torque wrenches, use them against each other to calibrate them. Of course they might both be wrong, but at least they’ll be consistent. If I have a torsion bar torque wrench and a “click” type, I’ll trust the torsion bar wrench.

Calibrating Torque WrenchAbove: Testing two torque wrenches against each other.

Or you could perform a dead-weight test.

DeadWtCalTwoAbove: 20 lb load at 6” = 120 inch lbs or about 14 NM (I clamped a 10mm hex wrench in my vise and installed a 10mm socket on my torque wrench.)


Pedal threads are self-tightening due to something called precession. I grease pedal threads for corrosion prevention and I torque them pretty lightly (10-15 NM?). I think what’s important is removing and re-greasing the threads every so often, at least once a year. I have gotten pedals out of cranks for people when no one else could, (remember the mnenomic “Back Off”) but I have also thrown away cranks because I could not get the pedals out.

Brake and derailleur cable pinch bolts:

These are scary. I always feel like I’m gonna twist off the actuation arm or something. What is really important is to route the wire under the pinchbolt properly. There is always a groove. And the cable is meant to lay in that groove, so it is not simply gripped between two flat plates. Take off the bolt and inspect the mounting surface to see where the groove is and route the cable accordingly. Shimano calls for 6-8 NM and that feels really high! I don’t use a torque wrench. I screw ‘em down pretty tight and give the cable a good hard tug.

Cassette lock-ring:

This is a toughie. To tighten cassette lock-rings I put my cassette tool face up in a vise and rotate the wheel by hand. The freehub body is very thin in the area of the threads, and like a chain-ring bolt, it’s under hoop stress, so I’m very gentle. I have seen a steel freehub split from hoop stress. Many freehubs are aluminum, dimensionally identical to their steel counterparts, so not nearly as strong.

Hand-tightening CassetteAbove: Tightening a cassette lock-ring by feel.

Shimano’s recommended torque is 30-50 NM! I had never measured the torque I apply, so I took a break from writing and went to the garage for a while. I tightened a lock-ring by hand with the tool in the vise as shown above, then I put the torque wrench to it. It took about 25 ftlbs (34 NM) to tighten it further, so I’m in range.

Torquing CassetteAbove: Applying 25 ftlbs torque to a cassette lockring

Now that I’ve got you worried about all the nuts and bolts on your bike I’ll just sign off without further comment.






OCD Handlebar and Saddle Alignment

Reader Samuel D asked if I could write something about getting handlebars and saddles straight.

Challenge Taken!

I’ll go one further and show you how I get brake levers at the same height and equally toed in.

The analog nature of saddle and handlebar alignment has always bothered me. There is no indexing as to the correct position. It comes down to eyeballing it and getting close enough.

Brief diversion for a story: Years ago I crashed and separated my right shoulder. For a few months after that attack by a ferocious bunny rabbit, I rode with my bars intentionally canted slightly to the right, until I recovered my range of motion in my shoulder.

Back to work: My methods still all come down to eyeball. I just use techniques and tools to augment my eyeballing ability.

This isn’t about fit. Maybe you want your bar-drops pointing down a bit; maybe you like them horizontal. Maybe you prefer your saddle pointing slightly one way or another for some reason. Maybe you like your brake levers high or low. Fine, Go for it.

This is about getting:

1.      Your brake levers at the same height on the bars

2.      And parallel (or equally toed in, the way I like mine)

3.      Your handlebars perpendicular to your front wheel

4.      Your saddle parallel to your frame.

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Brake Lever Height – Many handlebars come with index markings to assist you getting both levers at the same height. In my opinion this is just a good starting point.



My technique for getting levers at the same height is low tech but very effective. After snugging down the levers at what looks like a good position, place a straight edge on the front of the levers. In the picture I am using a dowel. The key is locating the dowel in a notch, crook, or other identifiable feature on the front of each lever. Then sight past the straight edge to the top of the bars. Move your line of sight up and down until the top of the bars is hidden by the dowel. The bar top should all disappear at the same time. Adjust one lever or the other until it does.

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Brake Lever Toe-in – I like my brake levers toed in. I actually like them toed in a lot. I find this gives me a more natural wrist and shoulder position. People have seen my levers and asked if they got that way in a crash. No, that’s how I like ‘em. Getting equal toe-in is difficult. There are no good hard straight lines on brake levers. They’re kind of rounded all over, for obvious ergonomic reasons. I just stand over the bike, sight down on them, and try to get them even.

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Just for fun today I laid a goniometer next to the outsides of my levers and determined that my levers are toed in 12 degrees relative to my drops, give or take a degree.



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Handlebar Perpendicularity (that’s a fun word) Before beginning this post my method was focused on getting the stem parallel to the front wheel. Taking that idea to the next level, I have a laser level device from Home Depot that throws a line of red light. It’s meant to be used for hanging pictures, but with a little ingenuity, I got it to throw a line on the stem and the front wheel. It’s better than plain eyeball, but the stem is too short for a really accurate comparison. And a slightly crooked stem is really annoying in the middle of a long ride.

A professional mechanic once showed me his method. With the stem binder bolts loose, stand the bike on the fork and the brake levers. In this position, tighten the binder bolts. The bars will be parallel to the fork dropouts, in theory. But there are a few assumptions in the technique. Your floor must be flat, your brake levers must be at the correct height (or not mounted yet), and on some thru-axle bikes the fork dropouts are not symmetrical.

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Anyway that demonstration did give me the idea to focus on making the bars parallel to the front axle instead of making the stem parallel to the wheel.

With the front wheel off, stab the fork over a dowel laying on the ground. For a thru-axle fork, run the dowel thru the dropouts. Then sight down from the front edge of the bars. Move your line of sight forward and backward until the dowel is just hidden, and as for lever positioning, adjust until the dowel disappears all at once.

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A funner but I think no more accurate twist on this method is to shine a light down from above and adjust until the shadow of the front edge of the bars just eclipses the dowel.

Saddle Parallelity (parallelness?) What’s the noun for a state of existence in which two lines are parallel? I asked a mathematician friend. She said it was probably parallelism, which also happens to be a literary term… OK.

I usually sight along the top of the saddle to the stem cap nut. The stem cap nut is always on the center line of the bike, no matter where the bars are, so it’s a good reference point.

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I dunno, maybe it’s a little to the left. What do you think?

An improvement is to lay a straightedge atop the saddle and let it extend forward. It should point to the stem cap nut. The hard part is determining the centerline of the saddle.

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Or if you’re feeling high tech, whip out your laser lever again.

Or you could go buy a bike with an aero seatpost and hope it’s manufactured straight.

Tailwinds and Sunshine





Esoteric Observations on an Extra Large Time Trial Bike with an Internally Routed Rear Hydraulic Rim Brake Below the Bottom Bracket

If you are ever offered the opportunity to work on an extra large time trial bike with an internally routed rear hydraulic rim brake below the bottom bracket, turn around slowly and run like hell!

I’m joking; it was a great experience but it was challenging, and by the time I finished I knew I’d write a post about it.

My friend (Let’s call him Flywheel), brought me his bike for some service.

This bike is a slippery speed machine. Everything is internal or shrouded. It’s quite aerodynamic. But this design is less than ideal when it comes to service and repair.

Among a few other relatively easy tweaks, the bike had a frozen rear brake. As the brake caliper was located below the bottom bracket I can’t say I was surprised. If you’ve been reading my blog you know how I feel about brakes under the bottom bracket. And Flywheel is a big guy, over six feet tall and solid, so good brakes are important for him. At least here in the Houston area we don’t have any serious downhills.

I think I’ll organize this conversation in reverse order – “A below the bottom bracket hydraulic rim brake that is internally routed on a time trial bike, size extra large”.

1.      Brake mounted below the bottom bracket:

Here’s a picture taken after reconstruction, nice and clean!

This is just a bad idea! Hey, let’s put a piece of safety critical equipment under the bottom bracket – the dirtiest place on the bike.

At least on this bike there was a shroud covering the brake, though this was for aerodynamic effect and was obviously ineffective at protecting the brake from water and debris ingress.

I think this is an interface problem. The brake manufacturer makes some assumptions about the location and orientation of the caliper on the bike. For instance, on another bike I serviced, the caliper return spring is located in a pocket that effectively forms an upward-facing cup when mounted below the bottom bracket. Put that brake on the seatstays or fork and the pocket easily sheds debris and water. Below the bottom bracket it collects them! I think that if they were designing a brake for mounting below the bottom bracket, they would build it differently.

On Flywheel’s bike, there are no upward facing cups, but there are unsealed thrust bearings on the pivot studs each containing ten 1/16” balls. Upon disassembly I found forty rusty little lumps of steel.

I replaced the bearings and restored the mechanical function of the brake. What does it mean: “Do not disassemble; no user-serviceable parts inside”?

And here’s a picture of a fully functional thrust bearing of the same design from a ten year old Campy Record fork-mounted front brake. These bearings can last in the right environment.

Now you’re wondering how I came to be disassembling a Campy Record fork-mounted front brake. Well, the return spring broke, but that’s a subject for another post.

After restoring mechanical function, it was time to bleed the brakes. The hydraulic access port on the caliper faces down, of course. So flip the bike upside down to attach the syringe to the caliper, flip it back to attach the bleed syringe to the lever, bleed but watch for air bubbles which are trying to rise into the caliper because the caliper port is facing down now, flip the bike back upside down to detach the syringe at the caliper and cap the caliper port. Flip the bike upside right, detach the lever syringe and cap the lever port. This all would not be so difficult if there was any way to clamp the bike in a pivoting workstand, but there isn’t. (Is there?)

Anyway, I got the brake bled and restored hydraulic function, but that proved to be short-lived for reasons as yet unknown. I hope Flywheel lets me work on it some more.

2.      Hydraulic Rim Brakes

OK, on hydraulic rim brakes the pads are farther away from the hydraulics and therefore less likely to get fluid-contaminated. That’s about the only benefit I can name for hydraulic rim brakes.

Hydraulic disc brakes eliminate the (flexible) lever arms and cable friction. The hydraulic rim brakes on this bike do eliminate the cable friction, but they leave a rather Rube Goldberg mechanical system in place. Watch this one minute video of the brake in action.

SRAM hydraulic rim brakes at least employ a simpler, probably stiffer, mechanical system.

SRAM Red HRR brake caliper – note the adjuster barrel and release tab. It looks very much like a mechanical rim brake. You can even see the end of the return spring sticking out from behind the left arm.

Hydraulic disc brakes self-adjust for pad wear. Hydraulic rim brakes don’t.

Also, hydraulic disc brakes eliminate the need for return springs. The minute amount of piston retraction in a disc brake is courtesy of piston seal elasticity. Hydraulic rim brakes require a much larger range of motion, the same as mechanical rim brakes, so return springs are still required.

I just don’t see a compelling need for the addition of hydraulics to a rim brake system. I think fitting rim brakes with hydraulics was a step in the long range conspiracy …I mean plan… to introduce disc brakes to road cycling.

To reference an imperfect analogy, we have moved past hydraulic rim brakes the way we moved past CFL lighting. Man, wouldn’t you hate to have been the owner of a CFL factory when LED lights came out.

Anybody remember HID bicycle headlights?

3.      Internal Routing

As a mechanic, internal routing just makes everything harder, with hydraulic systems doubly so. Aside from the normal difficulties of tracing and fishing cables through a frame, doing so usually requires cutting off the “olive” terminations and fitting new ones, a much more tedious and error-prone operation than routing standard brake cables.

At least this bike, being ETAP-equipped, did not have shifter cabling all over. (There was a bit of wiring in the cockpit; blips on the bar-ends wired to a shifter unit on the stem, all internally wired of course.)

It’s a shame that all the cockpit wiring is so neatly tucked away except the last bit to the button box.

4.      Time Trial Bike

I really have nothing much against time trial bikes. I don’t own one and I don’t want one, but that’s just me. My only complaint as it relates to this post is those cute little aero brake levers with their limited travel. They never work very well, and I think there a few flaws in the design of these specific levers, but that’s beyond today’s scope. And that’s all I have to say about that.

5.      Extra Large Bike

I eventually got everything sorted, put on the wheels, and realized I couldn’t even straddle the top tube, or reach the pedals from the saddle, even with the saddle all the way down. I had to test-ride the bike standing in front of the saddle! That’s a picture I’m glad I don’t have. Hey mechanics, how do you road test a bike that is too big to ride?



PS: Sorry if I sound annoyed. I’m not. Really. I enjoy this stuff. I promise not to rant so much in my next post.

How do You Even Bend the Stem On a Presta Valve?


If you ride a bike, you know what a Presta valve is. If you don’t know what a Presta is, then this article may not be very interesting to you. If you do know, you still might not care. That’s why my blog is called Esoteric Observations on Bicycles and Cycling.

For a long time I have been wondering how people manage to bend or break the little stem on the end of a Presta valve. Yes, I know, it happens attaching a pump or removing it. But really, is it that delicate? Let’s find out.

I attached a string to the nut of a presta valve on an old tube and exerted a lateral force (measuring the force with my Park Tools DS-1 digital scale of course).

At about 15 lbs the stem broke off, right where you’d expect it to, at the point of highest stress, where it enters the neck of the valve body. I was surprised that it broke rather than bent, based on the number of bent stems I’ve seen over the years. It must have been harder and more brittle than average.

I’m not sure what my advice should be based on this little experiment with a sample size of one. Be more careful attaching and removing the chuck from the valve? Spend more for a premium quality chuck than you did for your pump? That’s about all I have to say about breaking off the stem, but let’s keep talking about Presta valves.

Did you ever notice how you have to get above the pressure in the tire to start air flowing? Two things are at work here, both related to the little cone-shaped rubber seal inside the valve.

First, the rubber sticks to the metal, and you have to generate enough force to push it free. Some valves are worse than others. I’ve had valves that required 140-150 psi to unseat a valve with 90 psi behind it. The solution to this is to depress the stem by hand momentarily to unstick the rubber. This does let some air out of the tire, so don’t hold the stem down long. I like to bump the stem with my chuck. I get a satisfying “pffft”, letting me know I have unstuck the rubber without letting out significant air. And no, I have never bent a stem by doing this.

Second, because of the conical shape of the seal, the diameter at the inside of the seal is larger than the diameter at the outside. The pressure in the tire is acting on a (slightly) larger area than the pressure from your pump. So it takes a higher pressure from the pump than what is in the tire to initiate flow. After the valve is unseated and air is flowing, the differential area issue goes away.

There is no spring in a presta valve. (That’s why you want to screw the nut down after inflating your tire.) Gravity, pressure differential, and air flow determine the position of the stem within the valve body. I wonder if there is a preferred valve orientation for inflation. If the stem is pointing down (stem at the top of the wheel) gravity will reseat it after each pump stroke. If the stem is pointing up (stem at the bottom of the wheel) it will fall away from the seat, and remain there until backflow pushes it into place. I wonder if this matters at all.

If your tube has a broken stem, you can still inflate the tire and go for a ride, maybe. Just be sure you place the stem at the top of the tire (pointing down) so it will fall back into place after each pump stroke, instead of falling into the tube. The other day my friend Eric (aka Bobke) described getting this wrong once. Oops.

Also, a story is told of how in 1985 during a bicycle speed record attempt John Howard’s rear tire went flat at almost 150 miles an hour. Quoting from a 1990 LA Times article:

“Three-time U.S. Olympian John Howard was mounted on the prototype bicycle that featured a double-reduction gear setup and was nearing 150 m.p.h. when the rear tire went flat … The flat tire could have killed him … There were 1,600 Gs (the measure of gravity against an accelerating object) on the valve spring of the tire.”

I was wondering if the given reasoning is a valid explanation of the world’s fastest bicycle flat tire, so I did some calculations. Feel free to check my work.

I assume this was a Schrader valve like the ones on your car tires and not a Presta, because of the mention of a spring. Stirring in some realistic numbers like 30”(?) wheel diameter and a one gram valve stem weight (I measured it), I get about 1200 Gs and a centrifugal force of about 2.5 pounds trying to offseat the stem. Fighting that force are the air pressure in the tire and the spring in the valve itself. The valve seat seal surface is about 2.8mm diameter (I measured it), so 100 psi would exert a force of about a pound, and the valve spring exerts about a ¾ lb closing force (I measured it).

One and three quarters is less than two and a half, so, yes, the valve stem could really have been forced offseat causing this flat. There may also be some things going on with the distribution of air pressure within the spinning tire. I can imagine that the pressure is higher near the outside than at the rim, but, never mind.

Two final thoughts on Presta valves:

One – in this age of wonder materials, why are inner tube valves still made of brass?

Two – the cap, use it or throw it away? I don’t use the cap, do you?

How Many Standards Do We Need for Bicycle Rear Axle Size?


From as far back as I can remember until the mid-1980’s, road bicycles – commonly called “ten-speeds” – were built to a de facto standard. They all looked pretty much alike. Granted there were cheap department store versions and expensive hand-built models with Italian names like Colnago and Bottecchia. But critical interface dimensions were common among bikes back then, with the exception of a few French and Italian thread selections.

Since the mid-80s cycling has existed in a state of continual innovation. In fact I’ll send half a dozen Killa’s Garage stickers to the first reader to email me the name of the bicycle manufacturer that uses the phrase “Innovate or Die” as their corporate mantra. Granted, innovation can be a really good thing. It’s the business equivalent of evolution through natural selection. But natural selection is painful. Things go extinct. I have a garage full of bicycle fossils to prove it.

I could rant about the rise of multiple bottom bracket and headset sizes in the past ten (twenty?) years, but let’s stay focused on a more recent phenomenon, the explosion of rear wheel axle options.

For eons the distance between rear dropouts (where the rear wheel fits) was 120mm. Freewheels had five cogs. Then one day somebody decided that we needed six cogs on our freewheels. Six cogs wouldn’t fit where five did. So a new standard distance between rear dropouts was introduced – 126mm.

Just like that, your 120mm bike frame and rear hub became extinct.

Somebody decided to cram seven cogs in the same 126mm space and it worked, but when they tried to fit eight, they said, we need a new wider standard – and 130mm dropout spacing was born.

Boom, your 126mm frame and rear hub went the way of the dodo!

Oh, and about that same time they switched from freewheels to cassettes/freehubs. A cassette/freehub combination does the same thing as a freewheel. It’s just a different design, and it’s not interchangeable with a freewheel.

Nine, ten and eleven cog cassettes followed, and thankfully they all fit in the same 130mm spacing, even on the same freehub (sometimes). Twelve cog cassettes are coming, and apparently they fit in the same 130mm spacing. Phwew, evolutionary convergence!

On a separate but related evolutionary path, mountain bike builders set their own standard of 135mm. The extra width was said to allow wider spoke flange spacing for greater lateral stiffness. Or maybe it was just to ensure that you couldn’t use your road hub on a mountain bike. Whatever.

So far this was evolution plodding along at a reasonable pace, 3 to 4 standards over something like 30 years. The Cambrian Explosion of rear axle evolution began about five years ago with the introduction of thru-bolt axles and the evolution shows no sign of abating.

Manufacturers began marketing disc brakes for first mountain bikes, then road bicycles, which led to the use of thru-bolt axles for reasons beyond the scope of this discussion, making obsolete the quick-release system we have used since its invention in 1930 by Tullio Campagnolo, god rest his soul.

A thru-bolt axle requires a thru-bolt compatible frame, so your bicycle frame just went extinct again. Daaah!

Thru-bolt axles were a primordial soup, so manufacturers rushed to evolve their preferred design standard. As a result, at least three different “standard” thru-bolt dropout spacings and three axle diameter choices were developed in a period of less than five years.

Rear Dropout Spacings (mm):

Quick release – 120, 126, 130, 135 (MTB), and 140 thru 160 (Tandem), all being driven to extinction by thru-bolt axle development.

 Thru-Bolt – 142, 142+*, and 148 aka Boost

Thru-Bolt Axle Diameters (mm): 12, 15, and 20

*The difference between 142 and 142+ seems to be a 2mm lateral shift in position of the right spoke flange and the cassette.

And that’s just the rear axle. One bicycle manufacturer recently decided that the front dropout spacing of 100mm that we’ve used just about forever needs to be increased to 110mm. Daaaaah!

Look out, here comes an asteroid!!!!

For a more serious discussion of bicycle rear hubs, complete with pictures that have arrows pointing to cool things, visit In fact, if it has anything to do with a bike, BikeGremlin has probably written about it.

Bicycles and Aluminum Corrosion Again

SpaceShuttleYes, this relates to today’s Esoteric Observation on Bicycles and Cycling – Image from

I never meant for this to become Killa’s Esoteric Observations on Aluminum Corrosion blog, but here we are. In a recent post I wrote about a corroded stem face plate on a friend’s bike. Another episode of aluminum corrosion was brought to my attention recently in a pretty spectacular manner.

The rider in front of me (Let’s call him RocketMan) suddenly lost control and fell on straight level ground. He might have hit a bump or something, or not. Read on. I and another rider swerved around him but the third rider back (We’ll call him Mario) T-boned RocketMan, broke a few of RocketMan’s ribs, destroyed his (Mario’s) classic steel Masi frame, launched over the bars, and fractured a vertebra upon touchdown (but that’s another story.)

Pardon a brief diversion to the topic of bicycle wheel engineering. Mario reported to me that despite absorbing enough force to buckle his frame tubes, his front wheel remains absolutely true!


Back to aluminum corrosion. This is not an article about the crash, but rather about the cause. The primary cause of this crash was, in my opinion, a corroded handlebar.

The bicycle of RocketMan ended up in my garage because, well, I’m the guy’s mechanic. Both drops (Drops are the lower curved ends of road bicycle handlebars) of his aluminum handlebars were broken. The right drop was completely broken off, the left was still attached by about a quarter of the circumference of the aluminum tube.

Aluminum bars usually bend. They don’t usually break. And RocketMan fell on his left side, so how did he break the right drop? I only had to un-wrap his handlebar tape to see that corrosion had eaten through most of the metal just above the brake levers – exactly where sweat drips off your hands and collects under the tape.

What I think happened to cause this crash is that RocketMan hit a small bump while riding on the drops, or corrosion simply reached a critical level. I think his right drop broke off first, causing him to lose control and fall. The left drop, I think, broke on impact with the ground.

The evidence suggests crevice corrosion just like the stem face plate I wrote about previously. Here the interface between tape and handlebar creates the crevice, and sweat is the electrolyte. That white stuff is not salt, It’s aluminum hydroxide. And there was a lot of it under the tape!

I’ve seen plenty of corroded handlebars over the years. I’ve seen scary-corroded bars that I thought would crumple like paper that I couldn’t bend or break. These were the worst I’ve ever seen. A metallurgical analysis of the remaining metal would be very interesting, for a certain definition of interesting.

Some riders will go without changing tape for five years. (Oh, you’re supposed to change it?) RocketMan’s bars had been taped up and ridden for about 15 months, not unusually long, but most of it in very sweat-inducing Texas heat and humidity. How much do you sweat? How often do you look under the tape on your bars?

Let’s take a few lessons from this failure:

  • Inspection, inspection, inspection. Look under your tape every six months or so, especially if you ride in hot humid climates. It’s relatively easy to un-tape back to the levers and re-wrap.
  • Or just go ahead and change tape more frequently. It’s pretty cheap, and everyone knows that new tape makes you faster. This is a result of the well-known “New Stuff Principle”.
  • Change your handlebars if they’re corroded.
  • I’ve never been a fan of carbon fiber handlebars (because they tend to break on impact rather than bend) but at least they don’t suffer from this insidious failure mode. It’s something to consider if aluminum bars don’t last for you.

By the way, RocketMan is a retired space shuttle astronaut. In one of those cosmic coincidences of life the aluminum oxidation process that caused his crash is the same chemical reaction that powered his Space Shuttle solid rocket boosters.

You look Great in Fluorescent Yellow!


Scan the picture at the top of this article quickly. What jersey would you rather be wearing on roads full of distracted drivers?

Riding in Daylight

About ten years ago a good friend of mine confessed that he always wears a fluorescent yellow jersey when he rides his bike. At the time my collection of jerseys included – like many of you, I’m sure – an assortment of team colors and charity ride commemorative tops. I felt that, well, hi-viz yellow is kinda’ dorky. I didn’t tell my friend that, of course. But I remember the conversation like it was yesterday, and it started me thinking.

Then about five years ago another friend described his observations concerning jersey color during a cross-country ride from Seattle to Miami. He noticed that in a group of riders a mile or so up the road, the only rider he could always spot was the one in hi-viz yellow. The rest, in various team kit colors, might as well have been wearing camouflage. Road-camo he called it. That conversation convinced me.

I’ve been buying nothing but hi-viz yellow jerseys ever since. I still have some road-camo jerseys, and I still wear them when my hi-viz yellows are dirty, but I wear the yellow whenever I can, and I’m tossing the older jerseys as they age.

I also found a deal on a six-pack of bright yellow socks (six pairs, twelve socks, Pearl Izumi if you must know). I wear these socks exclusively when I ride. I think that my yellow-clad ankles bobbing up and down provide a strong association with the concept of cyclist in the minds of drivers. I also like to think that this association will cause a driver to avoid me rather than run me down. What do you wear when you ride?

Riding in the Dark

Fluorescent yellow is great in daylight, but at night it just looks sort of gray. You need lights and reflective surfaces when it’s dark.

Retroreflective material is that silver-looking stuff sewn into the seams or in patches on some clothing. It’s amazing stuff. Try taking a flash picture at night of someone wearing a patch of retroreflective material. You can’t. The stuff throws so much light back at you that it ruins your exposure, leaving everything else in darkness.

Reflectivity is great, if the car/bike/runner/hog/deer hurtling toward you has lights. If not, there’ll be no light to reflect. You need active lighting. Red in back and white in front seem appropriate. I’ve no data to back this up but I believe this color choice helps orient you in others’ minds as approaching or receding. I don’t know what the hogs and deer think.

You also need a headlight to be able to see where you are going. Hogs and deer don’t wear reflectors. There are lots of affordable rechargeable lights available that will throw enough light to see and be seen. I like at least 400 lumens in front and 100-200 lumens in back. Once you’ve made the investment in rechargeable lights, why not run them in daylight too? Most of these lights will run for many hours in flash mode, and they’re bright enough to garner attention even in sunlight. Did you notice the headlight in the picture?

Taillights, in my experience, are highly directional. Be sure yours is aimed towards the rear, maybe slightly left (slightly right in England?) and level. If you clip your tail light to your seat bag or clamp it to a seat-stay, there’s a good chance it is pointing to the ground or up into the eyes of the rider behind you, and not back down the road. Do this: Lean your bike against a post or something, turn on your taillight, and walk back about 100 feet. What do you see? Move left, right, up, down. Adjust your light so the brightest action is where a driver would be sitting as he approaches you.

Are you safe because you look like a construction worker in hi-viz yellow and you’re all lit up. No, you could still get hurt in a number of ways. But at least you’ve greatly reduced the chance of someone looking down at you on the ground and saying “Sorry, I didn’t see you”.





What Keeps Me Up at Night

My personal insecurity comes out after an evening of wrenching in Killa’s Garage.  I wake up at three AM unsure of whether I have properly tightened all the critical bolts on a friend’s bike. I can’t go back to sleep until I have sent my friend a note to check that whatever I worked on is tight.

Most concerning for me are the cable fixing bolts on the derailleurs and brake calipers, especially on the brake calipers.

I worry about this because as I am stringing up a component, I make a preliminary guess on cable tension then snug down the cable clamp bolt just enough to operate the component and check my guess. Then I loosen the bolt a bit, make any adjustment, and do the final tightening. This way I don’t mash the cable in more than one place. It is essential that I remember to perform the final tightening step on each clamp bolt.

In case you were wondering, Shimano’s recommended torque for derailleur and brake fixing bolts is 6-7nm.

So I walk around the bike with 4mm and 5 mm wrenches and talk to each bolt (all of them, not just the cable clamping bolts) one final time before taking the bike down off the rack. “Hello, front derailleur mounting bolt, did I loosen you today? Did I retighten you…?” I don’t think this means I’m crazy, as long as they don’t start talking back.

Pro Tip for Cable installation: Don’t cut any cables until you have everything strung up and working. It is relatively easy to pull and re-thread an uncut cable. A cut cable will likely fray and become a throw-away.

Pro Tip for Front Brake Re-Cabling: If you use a fork mount work stand as I do, you can’t make front brake adjustments with the bike on the work stand because, well, the front wheel is not there. Keep a block of wood (or something else) handy that is a little wider than an average rim. Use this block to make a preliminary adjustment of cable tension with the pinch bolt.


Writing this post has given me two continuous improvement ideas: 1. Attach a small T-bar across the top of my wood block so it will stay in position without brake pad pressure. 2. Attach the block to my workstand with a piece of string so it is always handy.

With a little practice you can get close enough on the first try so that you can make your final adjustment with the adjuster barrel alone. You still will need to center the brake with the wheel in place. But that’s easy if you follow my tutorial on Centering Dual-Pivot Brake Calipers the Right Way.

No Cyclists Were Harmed in the Corrosion Failure of This Stem

Philip (not Eric’s real name) was starting his morning ride. As he hit the little bump at the end of his driveway, his handlebars rotated loosely downward. I wasn’t there, but I imagine that as he thought he was about to do an up-close inspection of the ground around his front tire he said “Oh, shoot” or something like that.

The faceplate on his handlebar stem had failed.


Note: This is not carbon fiber. It is a faux carbon paint effect on an aluminum faceplate. Separation of the paint from the aluminum under it may have contributed to the corrosion. Read on.

Fortunately the faceplate structure and the remaining two bolts, while insufficient to prevent rotation, did prevent total and immediate separation of his bars from his stem, allowing him to maintain control.

This might be a good time to go look at the bottom of your stem and see if there is a mass of white crumbly powder around the bolts. I’ll wait…

Yes? Interestingly that’s not salt, though its presence is due to the presence of the chloride in your sweat. It is aluminum hydroxide, produced by crevice corrosion, as described in this article on Corrosion of Aluminum and Its Alloys: Forms of Corrosion and a slew of other scholarly articles on the topic.

The aluminum in the aluminum hydroxide came from your stem, and it is a sign of deterioration in a critical high-stress area.

Sweat drips off your chin onto the stem (especially if you ride hunched over areobars or on a stationary trainer), gets in the crevices around the bolts, and creates a reaction cell, which strips aluminum from your stem faceplate to generate the aluminum hydroxide.

A couple of other nasty places for crevice corrosion are under your handlebar tape and at the rear brake cable stop on your top tube.

I don’t know why, but some people really do seem to have more corrosive sweat. Maybe it’s got to do with pH, or salinity, or some organic components. Don’t send me samples of your sweat. I’m really not that interested.

Sometimes I apply a thick anti-oxidant paste made for use on aluminum house wiring to prevent this form of corrosion.

And Now a Totally Tangential Esoteric Observation: Aluminum loves to oxidize!

Aluminum is generally corrosion-resistant. This is because aluminum oxide forms a hard smooth protective film on the surface of otherwise unprotected aluminum. Aluminum oxide is so passive because it exists in a low energy state. It’s in this low energy state because aluminum gives up lots of energy when combined with oxygen. Aluminum is in fact a common ingredient in solid rocket propellant.

Thermite is another widely used fun and practical application of aluminum oxidation. Powdered aluminum and powdered iron oxide (plain old rust) are mixed together. Something pretty hot, like a fireworks sparkler, is applied to get the reaction kicked off, and all the oxygen moves from the iron to the aluminum. It doesn’t explode. It just burns vigorously. The reaction is so exothermic that the mixture becomes molten! The heavier iron sinks to the bottom, while the lighter aluminum oxide floats to the top. The process is handy for esoteric jobs like welding railroad rails together and rendering cannons unusable before capture by an enemy. Oh, and The Mythbusters do a really good episode where they use thermite in an attempt to cut a car in half.

With Great Power Comes Great Complexity


I recently posted about my experience with SRAM’s ETAP system. It doesn’t have much by way of optionality. You click, it shifts. It will display current gear selection on an ANT+ device, and that’s about it. There is apparently a wireless communication protocol for firmware updates via a USB dongle, but SRAM has yet to issue any updates, so I’m just assuming that functionality really exists.

Anyway my friend Dan, AKA 6-0, just got a Canyon with the newest Ultegra Di2 groupset. Talk about feature-packed. It can be set up for manual, semi-synchro, or full-synchro modes. It will transmit to your display unit (Garmin et al) current gear selection, battery condition, and even a signal when it is about to change chainrings, because, yes, in Synchro mode it will change chainrings if required to get to the “next gear”.

(But as far as I know there is still no way to turn off the lockout of the last two cogs while on the small chainring, except to lie about your chainring sizes.)

With so much optionality, it behooved (behove?) Shimano to design a connection to smartphones to make configuration changes, and sure enough they did. There is even a plug-in device to upgrade older Di2 to the new capability. But setup of all the wires and signals is apparently not exactly intuitive.

Dan, being the thoughtful guy he is, wrote out some tips and hints on the setup process, including some really useful links to YouTube videos, etc. So without further ado, here are Dan’s Esoteric Observations On:



28 JUNE 2018

By Dan Denham

This guide is intended to assist persons who have Shimano Di2 shift systems that are capable of communicating with bike computers via ANT+ and Bluetooth to smart devices.  This requires the system to have Shimano [smart] batteries such as those found in the new Ultegra 8000 Di2 group set and the Dura-Ace 9100 group set.  These may be internal or external to the bike frame.  For Bluetooth communication, older Di2 systems must have their batteries upgraded to Shimano smart batteries, and install a small “D-Fly” ANT+/BT LE wireless unit in order to communicate with handheld smart devices (see Final Note at the bottom).  Communicating with bike computers enables the rider to view various data fields related to the status of gearing, shift mode, and battery condition.  The Di2 system can also be periodically and temporarily connected via Bluetooth LE (herein also referred to as Bluetooth, BT LE, or BT) to easily update firmware or make programming changes to shifting methods and to button functions.

This guide is not intended to explain the numerous ways that Di2 wiring configurations and connections may be made.  For that, the reader should consult the User Manual or Dealer’s Manual for Di2 shift system which is readily available online at Shimano’s website (see reference below).

From reading user reviews (and by personal experience), connecting a smart device to Di2 for the initial connection has a high probability of failing during the initial firmware update.  At this point, the Di2 system is likely to be unresponsive (“bricked”) and can only be restored by connecting with a PC and running the E-TUBE program.


  • Shimano Di2 Groupset – any generation
  • Shimano Smart Battery BT-DN110 (internal) or BM-DN100 (external)
  • Wireless Unit – recommend “D-Fly” Bluetooth LE / ANT+ capable unit EW-WU111 (connection ports on opposite ends) or EW-WU101 (connection ports on same end).
  • You will need an extra connection wire to insert the wireless unit into the system. Use the length appropriate to where the unit is installed.  150mm is the shortest available.
  • Cheap ($4-$7) Shimano TL-EW02 tool recommended to avoid damaging connectors.
  • Shimano USB unit and cable (Di2 battery charger SM-BCR2 or SM-PCE1 PC interface device) to connect the Di2 group set to PC computer. These connect to the Junction A box charging port and are only required to set up the system the very first time.  They are not needed again if you plan on connecting via a Bluetooth smart device thereafter.
  • E-TUBE Project program for PC. For smart phones and tablets, download and install respective E-TUBE apps (see References below).


  • Install Di2 System Required items listed above, as needed. There are various ways to install them.  Refer to appropriate manuals, diagrams, or YouTube videos for installing them.
  • Ensure that the Di2 battery has sufficient charge prior to initial connection, especially new bikes and batteries.
  • Ensure that the PC desktop will not accidentally lose power or shut down during initial connection. A PC laptop with a fully charged battery is better.
  • Download and install the E-TUBE program to the PC.
  • Ensure that the initial connection to Di2 is performed where the PC has a strong wireless signal and it is connected to the web. It will check online to find the latest firmware versions of all Di2 components and download newer versions if available.


  1. Install D-Fly wireless unit (and smart battery if necessary) in/on bicycle.
  2. Connect bike computer to the Di2 system via ANT+ to add Di2 communication between the two.
  3. Connect PC to the Di2 system via the E-TUBE Project program and run the program to view and make desired changes to Di2 gearing, shift speed, BT passkey, etc.
  4. Disconnect E-TUBE Project program via the program menu choice to turn off the Di2 system BT signal.
  5. Connect smart device wirelessly to the Di2 system via the E-TUBE app for it to view and make changes.
  6. Disconnect the smart device through the app settings as in Step 4 above. The shifters will not respond if the app and BT are still connected.  Leaving BT on in the Di2 system rapidly drains the Di2 battery.


When installing the wireless unit, do not complete the tie-down or closing up the access point until you have successfully communicated with your bike computer.  You will have to disconnect the unit and reconnect it to complete the process (according to the User’s Manual for the EW-WU111 unit).

  1. After installing the wireless D-Fly unit to the Di2 system, put your bike computer into connection mode in the same way you did to recognize other ANT+ components such as speed and cadence sensors. Let your computer search for the Di2 device and then add it to your bike computer’s list of connected ANT+ components.  You may wish to check data fields on your bike computer at this point if you have any set up.
  2. You may need to disconnect and reconnect the battery to complete the setup if you do not see any data. If you have an external battery, remove it and reinstall it.  If you have an internal battery, disconnect the wireless unit from the system (at both of its ends to ensure that it is not still connected to the battery).  Wait a few moments and reconnect it.  Wait about 30 seconds for the wireless unit to begin transmitting again.  Note:  It may also take this long for you to see Di2 data fields populate when you start a new ride.
  3. You may finish physical tie-down or mounting at this point since you should not have to make further disconnections to the wireless unit. Or you may wish to finish this after making BT LE connections to smart devices.


It is highly recommended that you make your very first connection using a PC and the PC E-TUBE program before connecting with BT using a smart phone or tablet.  If you make the initial connection with a BT-connected smart device, it often fails while updating the firmware of the individual Di2 components.  Since the PC is hard-wired to your Di2 system and there is no passkey, PIN, or code required to make the connection, there is little likelihood of failure during the initial connection setup process.  The PC program also allows you to set the BT passkey that you can use later with smart devices.  If you make the initial connection with a smart device, you will enter the default 000000 BT passkey, change it to a new one, update or attempt to update firmware, forget the BT device, connect and enter the new passkey, while risking failure and “bricking” the Di2 system.

  1. Connect your PC to the bicycle’s Di2 system with either an SM-BCR2 or SM-PCE1 to an SM-JC40/JC41 Junction A box through its charging port and a USB port on the PC, or an unused port on one of your Di2 system components.  If you have an Ultegra 8000 Di2 system with a Junction A, connect your battery charger (SM-BCR2) cable in the charging port of the Junction A (SM-JC41) and the other end into a USB port on the PC.  Other setups may require you to find an unused port on one of your Di2 components to connect an SM-PCE1 to.
  2. Run the E-TUBE Project program to update firmware and change other settings such as BT passkey code to a personal one. Note:  Each Di2 component has its own firmware version.  It may take a few minutes to check and update all components.  This allows the user to employ various vintage Di2 components (“Frankenstein” setup) and still work.  However, note the battery and wireless component requirements above for ANT+ and BT connectivity.  Shimano says that all Di2 components should work except the earliest generation.  Shimano has a compatibility chart on its E-TUBE Project website (see References below).
  3. Disconnect the program using the appropriate menu item. You should now be able to connect via smart device BT connection.  See Step 4 for this.
  4. To make a BT connection with a smart device (phone or tablet), ensure that its BT mode is turned on, start the E-TUBE app, and press the button on the Junction A box for about 1 second or until you see alternating red and green LEDs flash. The app will search until it finds the bike’s Di2 BT wireless signal and asks for the passkey.  Enter the passkey you set up in Step 2 above.  If you failed to set up a new passkey while running the program from a PC, the passkey will still be the default 000000.  Enter that number.  The app should ask you to set a new passkey.  After setting the new passkey, disconnecting BT and closing the app, go to your smart device’s settings and forget the E-TUBE Project Di2 device since that is the only way to get rid of the default passkey on your smart device.  Start the app again, press the Junction A button until its red and green LED lights alternate flashing, let the app find the E-TUBE Di2 system, and enter the new passkey.  BE SURE TO DISCONNECT THE SMART DEVICE FROM THE Di2 SYSTEM THROUGH THE APP AND CLOSE THE APP.  THE DI2 SHIFTERS WILL NOT WORK WHILE CONNECTED AND BATTERY DRAINAGE WILL BE ACCELERATED.


It is advisable to read all component manuals, user reviews, and watch videos on YouTube to educate yourself on installation, troubleshooting, and programming of Di2 wireless components and bike computers.  The wireless unit will work with Garmin, Wahoo, and perhaps other BT-capable bike computers.  Please confirm that your bike computer will work with ANT+ Di2 before purchasing a wireless unit.

  • Installing EW-WU111 to Canyon Aeroad 2018 This YouTube video shows how to install the transmitter inside the bottom bracket area of the bike on a Canyon Aeroad (Canyon Ultimate and Endurace Di2 bikes are wired the same).  Please read the comments to the video since complications can arise fishing out the junction box as well as how to upgrade the firmware and reset the Di2 system after installing the transmitter.  You will need snap ring pliers ($5 at Harbor Freight) to remove the plastic cover and a hook or needle nose pliers to fish out the Junction B box from the down tube.  You should also use the small plastic TL-EW02 Shimano tool to break and make electrical connections.
  • E-TUBE Project main page for PCs and Smart Devices on the web. You can also download the PC program here:
  • Best price on EW-WU111 and extension wire is at The length of extension wire depends on where you place or mount the wireless unit and where the battery is located if you place it inside your frame.  The cheap TL-EW02 tool from Amazon for 2-day delivery (as Prime member).
  • Excellent webpage with instructions and links to other sites with documentation:
  • Shimano’s website for technical manuals:
  • Shimano Dealer’s manual for the Ultegra R8050 series:
  • Most detailed article on Di2 setup, by Lennard Zinn:
  • Read reviews on the EW-WU111 on for discussion regarding installation and troubleshooting.
  • Watch other videos on YouTube to see how to program for full synchronous shifting (using rear shifter), continuous shifting, programing shifters and hidden buttons, and connecting to bike computers.


FINAL NOTE:  I find the term “D-Fly” is confusing to me.  I ask the question, is D-Fly the wireless unit, a bike computer that can communicate wirelessly with Di2, or is it simply the capability to communicate wirelessly between Di2 and a bicycle computer.  It seems to depend on who is writing the article or manual.  I find it best just to refer to the specific components being used, i.e., the wireless unit, the bike computer, ANT+/BT capable, etc.