I could feel and hear the "kerChunk" with each revolution -- every time the pedal rounded the 6 o'clock position. It was a little disconcerting, but I knew exactly what was happening. The curse of Ultra-Torque. I've spent lots of time talking about the problems associated with press-fit bottom brackets, I thought today I'd share another bottom bracket issue, but this time, one which even crops up on threaded systems.
|The Ultra-Torque crank spindle is comprised of two half-shafts|
that are joined together in the middle with a Hirth joint.
|Here's the non-drive half shaft. It's really a beautifully machined|
piece of equipment, but there may be a problem in the application.
|Joined together, the two halves of the Hirth joint look like this,|
held together in the middle with a large diameter bolt.
|To accommodate slight variations in BB shell width, the|
Ultra-Torque system uses this "wave washer." It is less than
ideal for the task. (photo from Park Tool)
I suppose that washer is supposed to act almost like a spring to keep the system under proper load laterally. In practice, it doesn't seem to be up to the task. When installed into most frames, even those conforming to Campagnolo's defined specifications (their installation instructions listed an acceptable range from 67.2 mm to 68.8 mm for British/ISO frames), one can physically move the crank laterally in the frame. When pedaling, sometimes this movement can present itself, resulting in a "knock" or that kerChunk that I described earlier. Apparently, Campagnolo's engineers say that this lateral movement is not a problem and that it should not present itself when pedaling. Many rabid Campagnolo fans echo that sentiment, and deny there is any issue. "It's Campagnolo," they'll say -- "how could there possibly be anything wrong?" Some will point to the strength of the Hirth joint, and hail it for its high-tech turbine applications, which is actually irrelevant to this issue. It would be hard to find anybody who is a bigger Campy fan than I am, but realistically, I think there is an engineering problem here.
The issue was first brought to light in 2008 by John Satory, the bicycle mechanic and blogger known as "RogueMechanic." This guy has been on a one-man crusade about the Ultra-Torque issue, has had several conflicts with Campagnolo over it, and has even received hate mail about it.
The thing is, it's quite possible that some people would never notice a problem when riding. If a frame's actual width measures at the wider end of the acceptable specifications, it's possible that the lateral movement would be negated. Maybe some people have such unbelievably smooth pedal strokes that it never presents itself on the road. It's also possible that some people aren't as sensitive to the knocking and therefore don't notice it. Or perhaps some notice it, but don't know to what to attribute it (I've seen where people have attributed the problem to bad bearings, pedals, shoes/cleats, and more).
I installed the Ultra-Torque crank and bottom bracket onto one of my bikes some time back. I was impressed by the engineering, and what seemed to be an unbelievably simple installation (no bearing adjustment whatsoever). After a couple thousand miles, I started to detect that kerChunk. I asked a local mechanic about it, and learned that Campy was aware that some people might have that issue (though apparently, they still consider it a non-issue) and suggested using a second wave washer to solve it. We tried that, and it seemed to settle the problem. I could still produce the lateral movement of the crank when the bike was on the stand, but it did not seem to present itself when riding -- for a while, that is. A couple more thousand miles, and I started to notice it again. Faintly at first. Gradually, it got worse. Pedal, kerChunk, pedal, kerChunk.
|The Ultra-Torque shim kit, from RogueMechanic.|
|It's a little tough to see, but that's the left-side Ultra-Torque|
cup with about 1.2 mm of shims.
It's worth pointing out that press-fit bottom brackets aren't the only ones that present problems that shouldn't be problems, though it's also notable that Shimano's Hollowtech BB system has more adjustment designed into it. But luckily, with the threaded frame and cups, it seems to me that fixing the problem is at least fairly straightforward. I can also say that I'm glad I don't have the press-fit version of the Ultra-Torque. Perhaps one could still make adjustments for width using shims, but I can only imagine that press-fit would only compound the issues. Still, when I think about the fact that I've got a Phil Wood bottom bracket on my Rivendell with about 15 years and I-don't-even-know-how-many miles on it (still feels as slick as butter), could somebody remind me exactly what was wrong with a good old fashioned square-taper bottom bracket?