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Tech & Wearables

Technical FAQ: Indoor training sweat corrosion, stem raiser safety, lower gears with Campagnolo CT 11-speed

Keeping your bike on the trainer all the time doesn't make it maintenance free.

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Have a question for Lennard? Please email us veloqna@comcast.net to be included in Technical FAQ.

Dear Lennard,

Been riding a steel frame on my trainer, had a stuck cable, and took a look underneath to find the bottom bracket shell totally corroded from sweat. Bummer. Perhaps my duh can lead you to suggest some kind of regular cleaning for folks like me with a spare permanently on the trainer.

Real pity, a beautiful handbuilt Mondonico on its last legs. Alas.

– Jeff

Dear Jeff,

This is a good warning that indoor riders should heed, even if the bike they use on the trainer is not made of steel. Aluminum can corrode, too, and I’m not just talking about the frame when I mention it. I have seen many bikes where the stem and aluminum headset spacers were absolutely cemented to each other and to a carbon fork steering tube from sweat corrosion. I have also seen aluminum cable-splitters on travel bikes fail after corroding through from sweat dripping onto them. And frozen-in aluminum seatposts, bottom brackets, and headsets can happen on frames made of any material.

When riding a trainer, I highly recommend protecting the bike from sweat; draping a thick towel over the stem and top tube is probably sufficient. And periodically pulling the bike off of the trainer and cleaning it as you suggest, especially in areas where sweat can collect, is well worth the time it takes to do it.

― Lennard

Dear Lennard,

Following back surgery, I find a need to elevate my handlebar beyond what I can accomplish with riser bars and angled stems. I have been reading conflicting opinions regarding the use of a short stem raiser on a road bike with a carbon steerer tube. What is your opinion?

– Howard

Dear Howard,

I don’t think there is a one-size-fits-all answer to this question. It depends on your weight, your riding style, the terrain and road surfaces you ride on, the length of the stem and of the stem raiser, the steering tube in question, and, most critically, proper installation.

For those unfamiliar, this is a stem raiser. In principle, if it is installed properly so that (1) the steering tube is fully inserted into it (the top of the steering tube is inserted beyond the top bolt of the stem raiser) and (2) the clamp bolts are tightened to proper torque, it provides a similar level of security to simply clamping a stem onto a steering tube.

The difference is that weight on the handlebar is magnified due to more leverage on the steering tube when the stem is clamped onto a stem raiser than when the same stem is clamped directly to the steering tube. That said, the increased leverage is offset somewhat by the more upright riding position resulting in less weight on the hands. And, in many cases, the rider has taken the additional step of using a stem with a steep up-angle (like 35 degrees); this further reduces the weight on the handlebar due to the higher position, and it reduces the leverage on the steering tube due to the reduced horizontal projection of the stem caused by the steep upward angle. Also, provided there is sufficient length of the steering tube above the headset to still ensure its full insertion into the stem raiser, the stress riser created on the steering tube at the top of the headset can be reduced somewhat by having a spacer (or spacers) between the headset and the stem raiser. (At least one spacer below the stem is a good idea even without a stem raiser.)

I think if your fork’s steering tube is in good condition and you are not a heavy rider and don’t ride at high speed on bumpy descents, there is little reason to worry about using a stem raiser. I recommend periodically removing the stem raiser and the top headset cup and inspecting the steering tube for damage from its top down to where it protrudes from the headset.

― Lennard

Dear Lennard,

I ride and love Campagnolo Record/Chorus 11-speed components on both of my road bikes and use compact cranks (34-50). I have gradually gone to cassettes with larger sprockets and have now settled on using a 29T for the largest rear cog. As you know, that is the largest Campagnolo makes in 11-speed.

Even with the 34-29, I could still use an even lower gear at times. I’d prefer not to have to buy a whole new 12-speed groupset just to get a little bit lower gear. I hate to admit it, but I’m thinking one-to-one gearing would now be ideal for the really steep stuff.

Does anyone make a 30- or 32-tooth small chainring that will fit my 11-speed cranks? Ideally, in stainless steel? The cranks I use are the older, five-arm style, and the bolt circle diameter is 110 mm, I believe.

– Jon

Dear Jon,

First off, Campagnolo Compact chainrings use a proprietary BCD (bolt circle diameter) and are not interchangeable with other 110mm BCD chainrings. That’s because only four of the holes are on the 110mm bolt circle; the fifth hole, which sits behind the crankarm, is at a different radius from the center. You can forget about finding a 30 or 32 tooth small chainring that will fit your 11-speed Campy CT crank, much less one in stainless steel. Here’s why:

The first hurdle to finding your dream chainring is that aftermarket chainring makers have little motivation to make chainrings using the Campagnolo CT specifications. That’s because, relative to standard 110mm BCD chainrings, there are few cranks out there that they fit on.

Your second hurdle (an insurmountable one) is that it is impossible to make a usable 30-tooth 110mm BCD chainring and probably a 32-tooth as well. That’s because the bolts would be right where the chain needs to go. Look at this 33-tooth 110mm BCD chainring. You can see that those bolt holes are almost out to the base of the tooth valleys. The bottom edge of the chain probably hits the bolts on this 33-tooth ring, so doing a 110BCD chainring with any fewer teeth would not work.

If you want a lower gear and want to stay with your drivetrain, I recommend using a larger cog than a 29T, which means getting a non-Campagnolo freehub body and cassette. As I demonstrated in this article, the spacing between cogs on all 11-speed cassettes is essentially the same. So, you can replace your freehub body with a Shimano/SRAM 11-speed-compatible freehub body (or replace your rear wheel) and put on an 11-32 or 11-34 11-speed cassette; the latter achieves your one-to-one gearing objective with your existing chainrings.

You will probably need a longer chain, and almost any 11-speed chain will do. If the b-screw adjustment alone will not prevent pinching the chain between the upper jockey wheel and the large cog, you can use a RoadLink derailleur-hanger extension.

― Lennard


Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder and purveyor of non-custom huge bikes , a former U.S. national team rider, co-author of “The Haywire Heart,” and author of many bicycle books including “Zinn and the Art of Road Bike Maintenance,” “DVD, as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”
He holds a bachelor’s in physics from Colorado College.

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