I received an email from someone last week or so that impressed the heck out of me because of how thorough and logical approach was addressing this issue. This is too good not to share. He was experiencing the dreaded non-issue with his Campagnolo Ultra Torque System. I must say that his theory of the clicking coming from the Hirth joint is interesting and not unrealistic. This being said, I still think that the majority of the noises (knocking and clicking) is more related to the axial movement. Usually movement usually and eventually developes into noise. Nevertheless, below are exerps (i.e. the meat) of the correspondence... I excluded identies to protect the inocent from the rabid Campy loyalists...
Here is an account of my experience with this problem, as related to the person I sold my bike to:
As you might have guessed from our conversation, I try to be thorough when confronting a mechanical problem. So I can tell you that I did research the web for postings of similar problems and did find a few, including an earlier--and much shorter--report from the "Rogue Mechanic." Here we are, approximately 2 years later, and the reports seem to be everywhere. This is what I expected, given the nature of Campy's new design.
I had already tried pretty much everything you will find in the list of "fixes" attempted, including:
1) sending the crank back to Campy for replacement--they said the crank was fine but that they "found sand in the bearings." This lie confounded me at the time--the crank had been used for perhaps 20 miles only on clean, dry pavement--but now makes sense if they were trying to avoid an avalanche of complaints for which they had no solution.
2) replaced the bearings (with ceramic ones), which--of course--made no difference
3) refaced the bottom bracket, to make sure it was dimensionally accurate, and that the opposing bearing shells were completely parallel
4) replaced the bearing shells themselves---just in case
5) got rid of the stupid wave washer, and shimmed up the non-drive side with shims ordered from McMaster Carr in L.A. (still have all the shims, if you're interested)
6) Then, as I mentioned, I hooked up the Chassis Ear to try to determine exactly just where within the bottom bracket this click was originating. I used several microphones, and by switching between them was able to determine that the noise was as loud on the non-drive side as the chain ring side. By inference, my suspicion is that the joint itself makes this clicking noise. Now, one wonders, how is this possible?
Well, look at the size of the coupling bolt which secures the two crank halves. Its diameter is constrained by the inside bore diameter of the bored-out (and consequently weakened) crank. In addition, this bolt is countersunk to a depth of a couple of centimeters, which results in reduced weight of the crank, but also reduces strength and leaves a shallow coupling for Campy's ill-advised choice of a short coupling bolt with very few threads. This combination, in my view, most likely allows movement in the Hirth joint itself and the resulting noise. Using Loctite to secure those threads made no difference.
Now, it occurred to me that one method of confirming this conclusion would be to apply machinist's blue dye to the Hirth joint itself, and then ride the bike, take it apart, examine the dye pattern, etc. This is the method for determining exactness of gear occlusion in critical applications such as automotive differential ring and pinion gears. Suspecting this would confirm my suspicion (and having the knowledge and experience to do this), I brought home some machinist's dye. At this point, however, I reflected on how much time I had already spent, and what--if any--benefit would come from further testing. Campagnolo had not only showed no interest in the problem, it had lied to one of its best and most faithful dealers about it. There weren't enough failures showing up in the field yet for this relatively new part to cause market flashback. And I had moved on, as, evidently, had the engineers at Campagnolo.
I hope that this message finds you well and thank you very much for sharing your experience and technical expertise. I really appreciate the process that you went through because it was thorough and logical. I also understand your frustration, not only with the design but also with the company completely turning it's back on an obvious design flaw/issue. I'm sure that you saw all of the flack that I caught bringing this to light...that was and still is interesting. Recently I was told by Tom K., the national sales manager, that they designed the axial movement into the system. I politely threw up the BS flag...
Anyway, I find your theory of the Hirth joint to be very interesting as the Ducati gear example. I agree that it's not the best choice for this application and can certainly lead to creating a noise. As you are probably well aware, movement will eventually manifest into a noise. It would have been interesting to see the results of you using the machinist's dye... In fact, if I get a chance and have the time, I just might do it... I'll let you know.
For what it's worth, the complaints that I have heard regarding the noise fall in the knock and click range. From what I can tell, the knock seems to be from the loading and unloading of the wave washer. I find that this is more prevalent on bikes with BB shell widths on the low end of the tolerance spec. It seems to me that the clicks happen when the bearing and/or cups are worn and or dry (very little grease). I actually have examples of cups with the finish rubbed off from the axial bearing movement. All of this being said, after reading your theory, it certainly very reasonable that the clicking can also be coming from the Hirth joint. I certainly wouldn't rule it out. This in fact is going to bug the crap out of me until I try the machinist's dye... stay tuned.
In closing, thanks again for sharing this with me. I always like getting different prospectives from those who have hands on experience and not form those who for one reason or another cannot remove themselves from the theoretical world.
...and his reply:
Thanks for the comments, which I'm also passing along to the owner of the bike with which I had this UltraTorque problem.
I also can see why the wave-washer approach might cause a knocking sound, but the "click" that I had was really elusive. It only happened when standing off the saddle and climbing grades above 12% or so, but was unnerving on those occasions. A Shimano crank with square-profile axle (like the previous Centaur crank) solved the problem.
Keep up the good work.