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Campy chainline/BB troubles(13 posts)

Campy chainline/BB troublesdawgcatchr
Aug 16, 2003 10:33 PM
My Chorus BB wasn't giving my drivetrain a good chainline-it was off to the non-drive side by 1.5mm. So, I bought a 1.5mm spacer, put it to the inside of the drive-side BB assembly, and tightened down. As I tightened the BB, the aluminum ring that says "Campagnolo, 36x24" popped off for some reason. Now, both cups essentially look like non-drive side cups-that is, they have no limit to how far they can move inside the BB shell (except for the preload against the opposing cup).

Well, I still tightened down the drive-side cup, then backed it off 1.5mm. I then took the non drive-side cup in by 1.5mm to bring it up to torque. Will this setup be okay, or will it likely come unthreaded? Do I need a new BB now that I lost that aluminum ring that keeps the drive-side cup fixed against the frame? How can I correctly adjust the chainline next time, if this setup won't work?
re: Campy chainline/BB troublesJuanmoretime
Aug 17, 2003 3:09 AM
I would definitely keep my eye on it. Did you teflon tape the cups? I also would make sure that you torque the one cup with a torque wrench as I would think that between the teflon tape and proper torque, it shouldn't go anywhere.
re: Campy chainline/BB troublesRusty Coggs
Aug 17, 2003 5:05 AM
Some things may not be worth worry about.
Doesn't sound good to me.Spoke Wrench
Aug 17, 2003 9:09 AM
I'm thinking that if you have an English threaded bottom bracket, it's going to tighten up. If it's Italian, it's likely to come loose.
Answer: Phil WoodLeroy
Aug 17, 2003 4:23 PM
Check out Phil's bottom brackets. You'll never have to post a bottom bracket question again.
Two adjustable cupsKerry Irons
Aug 17, 2003 4:44 PM
It's sort of a problem, in that you will have a harder time defining the right chain line (BTW, it sounds like the spacer wasn't a great fit, if it really did cause this failure). However, the torque of the left cup will apply an equal force on the right cup (check it with a torque wrench to be sure) and so should keep it from spontaneously unthreading. Another poster mentioned concerns about IT vs US thread - no way can you swap these two and not know it. IT would never fit in the smaller BSA threaded BB, while trying to torque a BSA thread cup in an IT BB would strip things out immediately.
Two adjustable cupsSpoke Wrench
Aug 17, 2003 5:28 PM
As I understand the problem, he has neither a flange on the cup anymore nor a lock ring to anchor the right side cup. As a result, the bearing procession is likely to cause the cup to rotate in the bottom bracket shell. That's why the threading style matters. If it's Italian the bearing procession will cause it to loosen. If it's English it will be threaded the other way and will tighten the bearings.
sure about the chainline...C-40
Aug 17, 2003 8:01 PM
a properly built frame should not have a chainline problem, unless you have a crankarm that was also over tightened and damaged.

How did you make this measure measurement, and are you absolutely sure that it's correct?

To answer your question, see if you can get a replacement right side cup from campy. If not get another BB. Also don't try that spacer again, it's surely what caused the problem. If you really need a adjustable chainline, you could get a Phil Wood BB, but they are pricey.
How I measured the chainline...dawgcatchr
Aug 17, 2003 11:14 PM
Here is how I measured the chainling (as best I could)-the distance from NON drive side crankarm to chainstay was 9.5mm; the distance from drive-side crankarm to chainstay was 6.5mm. I then used this logic-if the chainline is perfect, then the angle from the small ring up front to the 5th cog in back will be the same as the large ring up front to the 6th ring in back (slightly outward at the same angle for both). I then eyeballed the chainline (I have 12-20 vision, so I can usually pick up small differences visually)-reality was that small chainring to 5th had an angle, but big chainrinng to 6th had the chain perfectly straight front to rear. When I backed that cup out approximately 1.5mm (drive-side) the chain angle appears identical in both of the combinations I described above, plus it is shifting slightly better throughout the range. FWIW, this is a Colnago CT1, 2001 model-I have 800 miles on the bike and noticed the chainline being out when I built it up, but didn't really get around to trying to remedy the problem until now.

To answer another question-I no longer have the drive-side flange for the BB-it popped off. Campy BB's don't have a separate lock ring, do they? This BB never did, neither does my other Chorus.

Where can I find a Phil Wood BB?
imaginary problem...C-40
Aug 18, 2003 4:31 AM
I think you're wasting time and money on a nonexistent problem, myself. Your method is not correct. Campy's instructions show how to measure the distance (43.5mm) from the center of the bottom bracket to the center of the crank (between the two rings).

The angle from the little chainring to the middle 6th cog should be straighter than the angle to the 5th cog, since the little chainring is to the left of the crank centerline and the 6th cog is also left of the cassette center.

I'd try to get the replacement right cup or just get a new Chorus BB, since they are cheap. Phil Wood BBs are expensive and require more special tools to install. But if you insist on wasting money, Colorado Cyclist sells them.
The other thing...dawgcatchr
Aug 18, 2003 7:08 AM
With the BB backed out 1.5mm, my knees plumb exactly the same on both feet. Tje way it had previously been set up, the Q-factor on one foot was larger than the other (pretty noticeable if you plumb both knees). Since I have terrible knees, I really need to have the BB centered as much as possible-I can feel the differenece on my right knee (bad) if the Q factor is higher than it should be (that is part of the reason I went to Campy and Speedplay, to minimize the Q-factor). - for phil wood bbLeroy
Aug 19, 2003 4:30 AM
I've bought 3 there - good to deal with. Stop wasting your time trying to rig up a broken campy bb and get the part you need.
Aug 19, 2003 5:09 AM
There is no way that you can measure to an accuracy of 1-2mm from your knee to the pedal with a plumb bob. You need an education in precision measurement.

If moving the crank to the right makes your knee feel better, fine, but you'll never convince me that your crank is truly off center, unless you measure it at the bottom bracket. Even then a precision machinists scale is required to make the measurement accurately. Don't get out a ruler or tape measure and eyeball it from a distance.

By adding a spacer to the right side of the BB you have INCREASED the "Q-factor". Seems like this would make things worse on your right knee.