Tech FAQ: on front brake mounting

Published January 24, 2012 05:53PM

Dear Lennard,
Looking to put Campagnolo Chorus/Centaur mixed Group onto a 2010 Giant TCR Advanced. It came with SRAM Force, which has been moved over to a CX bike. All my wheels are Shimano/SRAM. What do I need to do to get the shifting correct and also install an Ultra Torque Crank into this frame, which is setup with a Press Fit BB? Please get back to me ASAP, this is my son’s bike and he need to start training for college road season in Madison, WI.
― Jeffrey

Dear Jeffrey,
Regarding the shifting, your best solution to make a Campy drivetrain work well is to use all Campy parts. In other words, get new freehub bodies for his wheels and use a Campy cogset and chain to go with his Campy cranks, derailleurs and shifters.

You don’t specify which parts in your mixed group are Chorus and which are Centaur. If the derailleurs and shifters are Chorus, you have 11-speed, and if the derailleurs and shifters are Centaur, you have 10-speed.

In either case, if you’re going to try to get away without getting new freehub bodies, then get Shimano cogsets adapted by Wheels Mfg. to be compatible with Campy drivetrains. I have never used the 11-speed conversions, but I’ve used the 10-speed conversions a lot.

Currently, one of my sets of cyclocross wheels is done that way, and both of my ’cross bikes have Campy 10-speed drivetrains, and it works fine on either bike, with a fair amount of readjustment of the cable tension and limit screws.

I raced Master’s Nationals in ’cross a few weeks ago in the same place your son is heading (Madison), and one of my bikes had this setup and worked fine, despite the mud. The red bike on the right has the Wheels-adapted Dura-Ace cogset, and the one on the left has a standard Campy Record 10-speed cogset.

BTW, you can see that I use KMC chains on both bikes, and they work just as well for me as the Campy Record chains I used to have on there.

If you’re trying to get away without getting any other parts, I do know people who just use a straight SRAM or Shimano cogset with a Campy 10-speed drivetrain and are happy with its performance. I’ve tried it for cyclocross, and no way does the chain line up well enough on every cog to work acceptably for that. But for road use, you could try it and see if he can get away with it.

As for the bottom bracket, you don’t specify whether you have a PF30 or a BB86, so I can’t be sure which adapter you will need for a Campy Ultra-Torque crank. Here’s the one for PF30 and here’s the one for BB86

I believe a 2010 Giant TCR Advanced comes with BB86. You can tell which it is by measuring the frame’s bottom bracket shell. A BB86 shell will have an inner diameter of 41mm, and a width (or length, depending on how you look at it) of 86.5mm from end to end. A PF30 shell will have a 46mm I.D. and a 68mm width. Other possibilities for other non-Trek, non-Cervelo bikes are BB30 (42mm I.D., 68mm width) and BB386 EVO (46mm I.D., 86.5mm width), and Campagnolo makes adaptors for its cranks for all of them.

As I said in the 2012 Velo Buyer’s Guide, which you should all have received in your mailboxes by now, adaptors are not always a perfect solution for press-fit bottom brackets. There are plenty of people out there who have had problems with creaking and movement of them. Press-fit bottom brackets have plastic sleeves surrounding the bearings that distort as needed if the bottom bracket shell internal diameter is not perfectly round and of the correct diameter.

Aluminum adaptors to fit 24mm-spindle cranks to PF30, BB86, BBRight PF, or BB386 EVO bottom bracket shells, however, are generally machined to tight tolerances and require correspondingly tight tolerances of the frame’s bottom bracket shell or they will move around and creak. But wait! The whole idea of press-fit bottom brackets, after all, is to fit into frames that are not made to exact tolerances so that they could be simply molded with cheap labor and not machined afterward. Now you see the problem. Adaptor problems are less common in BB30 frames, since they have metal bottom bracket shells machined after construction to fit the bearings and the snaprings.
― Lennard

Dear Lennard,
I just finished installing a Record 11 group on my Cannondale Cadd 8 frame. Everything went great and works great with the exception of the front brake mounting. The longest center mounting bolt that was included is 24mm and does not have the 6 thread engagement, but only about 2-3. This does mount the brake tight against the fork. The old front brake mounting bolt that came off had about the same. It seems a bit disconcerting does it not? Do you have any suggestions on this one?
― Zach

Dear Zach,
By current convention, it’s actually not the fault of Campagnolo or of whoever made your previous brake; it’s probably the fault of the person who mounted the first front brake on that fork and didn’t use the correct recessed nut.

Since carbon forks these days have such widely varying crown thickness, it’s unrealistic to expect a brake manufacturer to make different brake center bolts to fit every fork. Instead, there seems to be an unwritten agreement on a standard center bolt length that all brake makers adhere to (it’s based on what length worked with steel forks, whose crowns were generally within a few millimeters of being the same thickness). Rather than brakes coming with different center bolts (and perhaps requiring the consumer to disassemble and reassemble the brake—not a pretty sight from a liability perspective), each fork takes a unique nut. That’s why essentially all road forks these days come packaged with a recessed nut that is the proper length to ensure sufficient thread engagement on the front brake.

Of course, all brakes do also come with a nut, because to sell one without a nut is not really a complete brake, but, at least in our case at Zinn Cycles, we never use that nut and instead use the one that comes with the fork. We recycle lots of brake nuts each year, and they’re always the ones that come with the brakes, not the ones that come with the forks.

You need to find the right recessed nut for your fork, and your worries will be over.
― Lennard

Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.