Technical FAQ: Sealant stains, Shimano wheels, and more

Lennard Zinn has some tips for helping readers clean sealant off their bikes, mixing Shimano cassettes, and more.

Removing a Caffélatex sealant stain

Dear Lennard,
I had a can of Caffélatex blow up in my car on a hot day. I wondered where it all went and a few weeks later I found out. It had oxidized to a red rust color on my bike and car. Do you have any clue how to remove this? I have tried simple green and soap with no luck. I hate to admit I as a chemist am asking a physicist about chemistry.
— Dean

Dear Dean,
Thanks for asking anyway! You can easily wash Caffélatex off before it dries, and you can easily peel if off for a couple of days after it becomes solid. After that, especially on hard surfaces, it gradually turns into a paint-like stain that’s very difficult to remove.

To get those stains off, Effetto Mariposa sells something called Caffélatex Remover. It is among a new class of chemicals for the dry-cleaning industry believed to be less toxic; these came to dry cleaning after most of the previously-used chemicals were abandoned under suspicions of being carcinogenic. I have not tried it, but Effetto Mariposa claims that, “Caffélatex Remover is incredibly effective and not fast evaporating nor toxic (simply an “eye irritant” if it gets in the eyes). Applying one drop on the stain and allowing some seconds to work, it will remove Caffélatex stains. It’s also a charm to free sealant-stuck valves (especially useful for tubulars with non-removable valve cores) and delete permanent ink/water based stickers from components.”
― Lennard

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Dura-Ace freehub compatibility

Dear Lennard,
I have an older, but still perfectly good, Shimano Dura-Ace 7850-C24 wheelset that has been in use with an Ultegra 10-speed drivetrain. I was upgrading the bike to an 11-speed Ultegra setup and discovered that the 11-speed cassette will not fit. The smallest cog does not contact the grooves on the freehub.  Is it possible to simply get a newer freehub body from Shimano to put on the older hub? It sure would be nice to continue using these excellent wheels.
— Jonathan

Dear Jonathan,
No, it’s not. Shimano does not offer 11-speed freehub bodies for that wheel. You have three possible solutions to be able to use your 11-speed shifter and derailleur with that wheel (with the rim, at least):

1. Replace the hub with a (20-spoke) 11-speed one, if you can find one.

2. Remove material from the freehub body (and possibly also from the largest cog carrier) until it fits.

3. Remove a cog from your 11-speed cassette and use it as a 10-speed one with 11-speed spacing.

You need a total of 1.85mm more space, and here’s a description of solution No. 2 that I’ve done, namely filing off that much of the stops at the feet of the splines. The tricky part is that you’re getting down to very little stop left, and you don’t want the cog carrier to drag on the hub body, so great care is required. If you have a lathe, you can instead remove some of the material off of the aluminum cog carrier on the largest cog. It has a 0.5mm inboard lip on it, for instance, which it could still engage enough without. You could instead machine that lip off, and then you’d file only 1.35mm off of the spline stops. In either case, be aware that your rear derailleur is now 1.85mm closer to the spokes, and the inner limit screw adjustment is extra critical. So is avoiding starting up hard from a standstill in low gear.

I’ve also described option No. 3 here in the past. You remove one of the small, free cogs and its spacer from the 11-speed cassette. Probably the largest one before those integrated with aluminum cog carriers. Then you put a 1mm spacer behind the entire cassette; you need this so that when the lockring is tightened down, the cogs will also be tight. Now load on your unconventional 10-speed cassette and tighten the lockring. Tighten the rear derailleur inner limit screw and cable tension appropriately. You will simply not be using the last click in the shifter, and your derailleur will be very safe from harm, being further from the spokes. If you have other 11-speed wheels you switch back and forth with, however, this solution will be untenable.
― Lennard

Feedback on SRAM 10-, 11-speed compatibility

Dear Lennard,
With regards to your response to Fabio from Brazil about using SRAM 11-speed rear derailleurs on his 10-speed SRAM shifter-equipped bike, you may want to clarify to him that only 11-speed road derailleurs from SRAM will work. SRAM’s 11-speed MTB rear derailleurs (unlike their 10-speed MTB rear derailleurs) no longer have Exact-Actuation.
— Ed

Feedback on stuck Campy shifters

Dear Lennard,
Coincidentally, I just addressed this same issue on my Super Record-equipped Colnago EPS. I intermittently experienced the same stuck shifter problem this past summer and fall. It caught me off guard on each occasion while I was in the middle of either a fast decent or as I was trying to practice sprints. Each time on the second shift all was fine. It bothered me so much that at the end of the outdoor season, I decided to do my best to find what was causing it. I was able to replicate the issue while riding indoor on the trainer. I tried to use the other shift lever to shift up on the cog. It felt slack. No shift. I stopped riding and found that there was a lot of tension in the rear shift cable. It’s as if that when I had shifted up on the cog prior to the down shift before the decent/sprint, the upshift had not completed properly. I disconnected the cable and then set about setting up the rear derailleur. During the setup I also found that the B screw adjustment was off quite a bit and the hanger was out of alignment. After the setting up and testing literally hundreds of up-down shifts, it shifts better than I have ever experienced. So your mention of putting a slight side pressure on the big lever seems to jive (in a way) with my cable tension being too high. I think I had been adjusting tension too high to compensate for the hanger alignment and B-Screw adjustment being incorrect. Long winded sorry!
— Glenn