"You're missing a lot John..."

by John Satory October 09, 2009

The following is another post on a forum directed to me by someone who goes by the name C-40. My replies are in bold…

You're missing a lot, John.

I'm a mechanical engineer with over 30 years in the business of precision measurement, so I'll give you my explanation of how the system is supposed to work. I'll first say however, that I installed my first UT crank this spring. After 3500 miles, I've got no sideplay or creaking issues. My crank has worked perfectly all year, on two different frames.  Wow.  You have installed one UT system.  Congratulations.  Obviously this makes you an expert and thus more qualified with this situation.

Yes, there is a fixed distance between the bearings, but forget about the Hirth joint. It has nothing to do with the situation.  Actually, yes it does.  It's a part of the design.  No manufactured product is perfect and there is a chance that a crank could have been produced with a mistake in the overall bearing spacing.  True.  In fact Italian machinists are known to at some times machine their parts on the "long" side, i.e. not remove enough material... I wouldn't jump to the conclusion that this means that any, all or many cranks suffer from such a problem.  I actually said that some do, not many or all.  There also two bearing cups in the system and either one of those could have a dimensional error. Unless you have the factory drawings to know what each component should measure, you're not going to be able to say where the problem lies. The toughest thing to measure would be the distance between the bearings, to verify a problem, but a long internal micrometer would do the job. Measuring the cup thickness between the shell and bearing contact surfaces, is one simple check than anyone with a micrometer could do. If you have several cups around, you could at least compare them for deviations.

Campy specifies that the BB shell width must be 68mm +or - .8mm. If I read correctly, you measured a nearly perfect 68.1mm BB shell width. Did you also verify that the shell faces were square with the threads? Yes I did.  I chase and face EVERY bottom bracket shell.  Since I don't own expensive BB facing tools, Well C-40, I do own those expensive tools.   I screw both cups in until they contact a .010 inch feeler gage, then use .008-.012 inch feeler gages to search for high or low spots. Neither of my LOOK 585 frames needed facing to square the faces to the threads.

Another BB shell problem that can occur, but is nearly impossible to fix is misaligned threads.  This is very unlikely. If the threads on each side are not in alignment with each other, no amount of thread chasing or shell facing will fix the problem. Thread chasers merely follow the path of the orginal threads and usually do little but remove burrs, unless the original thread was cut under low limit on the pitch diameter.  I understand the function as well as the limitations of thread chasers.

One of the confusing issues with the BB cups is the use of Loctite 222 (or not). I've bought two sets of cups this year, for two different frames. Both sets came with a large amount of a yellow thread locker applied to the threads, from the factory. I personally decided to grease the threads of the BB shell and torque the cups in place, rather than use loctite 222. Loctite should only be used on threads that are free of foreign material, so using it without removing the yellow thread locker would not make sense. Also, the yellow thread locker produces so much intereference that it is impossible to hand tighten the cups. Mine required a substantial amount of torque, just to get the cup faces in contact with the BB shell. I would not use Loctite 222 unless I knew the BB faces were not square and also had no way to correct the problem. The loctite is intended to keep the cup faces aligned with the threads, even if faces are out of square, but it won't help if the threads are misaligned. I also think a BB installed with the loctite would be far more prone to creaking, particularly if little or no torque is applied. If the loctite doesn't hold adequately, any small movement of the cup will result in a creak.  I'm with you on this one C-40.  I use antiseize and torque both cups to spec.  In regards to the faces not being square, again, this is very unlikely.

The purpose of the wavy washer is simple. It's nothing but a spring to apply a preload force on the bearings and eliminate all freeplay. I understand.  If the BB width is not within the specified dimensions, then the washer would not produce the desired minimum pressure, or it would produce too much, resulting in binding and/or premature bearing failure. All of the shells that I have dealt with have been well within specified dimensions after facing the shell.  Of course, if there are errors in the dimensions of the crank or the bearing cups, then there could be a problem even with the proper BB shell width. Let's "assume" that that they got all of the dimensions right.  We're talking very high quality components from a respected and experienced manufacturer.  I don't think that that's asking too much here.  Of course, There should never be any actual "freeplay" in the system. I completely agree.  When you pushed on the crankarm and got movement, all you were doing is overcoming the spring force of the wavy washer - that's how it's supposed to work! I was doing that to replicate the noise.  You also mentioned a system that can't compensate for variations in the BB shell width. That's precisely what the wavy washer does. If all other dimensions are correct, then any BB shell in the specified range should produce an acceptable preload on the bearings. The reason that one spindle length can also accomodate a 70mm Italian BB is a no-brainer. I never questioned this C-40, but thanks for the enlightening me.  The thickness of the cups is just made 1mm thinner on each side, so the nominal distance between the cups faces is the same. Get out your micrometer and compare the two types.

It seems to me that installing any amount of shims merely defeats the intended function of the wavy washer, immediately increasing the preload tension. I'd start with trying a new wavy washer, or better yet a new pair of bearing cups, that includes the washer. Install those and see if it works any better. Of course, if the crank is dimensionally incorrect, the problem will remain.  If you review what I stated, adding shims internally was only a temporary fix.  I never intended it to be permanent.  After visually inspecting the cups, I didn't finds anything that caused concern.  If there was a dimensional error the cups and the wave washer needed to be replaced, I find that totally unacceptable.  Especially with less than 3k miles on it. How many cup sets do I have to stack to get a set that is dimensionally correct?  What ever happened to precise and repeatable manufacturing processes?

Be sure that all surfaces of the bearings that contact the cup are greased to prevent creaks. Also don't overlook another common source of creaks, the chainring and bolt area. If I think I've got a creak, the first thing I do is apply some thin lube, like Slick 50 1-lube to eliminate that area as the source.  Got it C-40.

Now that I've read even further into your posting on the subject, the more I realize you really don't understand the system and just guessed at a fix (adding shims). Sometimes when you're under the gun with time restrictions, etc., you have to come up with unique and unorthodox solutions quickly to make something that should work... work.  The technical name that I use for that is "Unassing".  If you really supected a wear problem with the bearing cups or bearing OD, you should have taken some precision measurements rather than take the shade tree mechanic approach of guessing.  Call it whatever you want to call it C-40.  I was brainstorming and theorizing.  Maybe I was wrong in assuming that the everything was dimensionally correct...  But I really don't think that I was wrong in making that assumption.  The real kicker is that I have experienced this issue of knocking coming from axial crank movement on several bikes... Your fix really defeats the system and is likely to ruin the bearings, if they aren't ruined already. The bearings were and still are fine C-40. 

There have been some reports of bearing failures on early model cranks, but changes were made at some point before '08 cranks came out. The latest bearings have plastic rather than metal cages around the balls.  Relevance of this?  Again, very atypical for Campagnolo...

Also, since you're dealing remotely with a customer, I never diagnose an issue remotely.  I do not come to ANY conclusions without some one-on-one time with the bike.   be sure the problem is not something totally unrelated like creaky cleats or a creaky saddle. I just put a new saddle on with no lube in the rail area and it's amazing how a creaky saddle clamp can sound just like the BB.  Thanks again for the insight C-40... 

Last, I'll say that you final conclusions are totally wrong, regarding both the Hirth joint and the loctite.  Perhaps you should just post your problem details and spare yourself the public display of ignorance (sorry, couldn't resist).  Thanks again for your input, insight, and for not offering up a single viable solution besides replacing parts that may or may not be dimensionally correct.

Leave a comment

Comments will be approved before showing up.