For the combination of crank, frame and BB to work, several conditions must be met.
1) Cups are correct threading for frame.
2) Distance between races on spindle is correct for wall thickness of cups. Once the BB is assembled, if the lockring isnt nearly flush with the face of the adjustable cup, and assuming theres nothing wrong with your BB shell*, youve got a problem with the race spacing. (* English and French = 68mm, Ital = 70 mm . usually)
3) Taper is correct for arms. A lot of fuss is made about this issue, perhaps a bit too much. Virtually all BB spindles and arms have the same taper angle. As you pointed out, different spindles have different dimensions on the outboard end. It is also true that different spindles have different dimensions at the inboard end. While these dimensions have implications for how far inboard or outboard you crank will ultimately sit, it is best to first determine if the crank and spindle can be correctly joined. Before you install the BB, try fitting the spindle to the arm. Tighten it as though you were assembling it for use. Remove the bolt. The spindle end should not come all the way to the washer seat in the arm and the arm should not bottom on the inboard end of the spindle. The arm should press on far enough that the outboard end is less than 4 mm or so of the washer seat.
4) The right side dimensions of the spindle are correct for the crank. This means that the rings are centered relative to the rear cluster, that the chainline is correct. Naturally, neither the inner ring nor the arm should contact the frame, but with good equipment, this shouldnt be an issue once proper chainline is established. (Assumptions: your rear hub is correctly spaced, you arent using some weird inner ring like a 51 T double or 42 T triple .). Note that I referred to right side dimensions. Ive stated things this way because the distance from the race to the right end of the spindle is not the only determinant of where the crank will ultimately sit. As stated above, some spindles start out skinny and some start out fat. A skinny spindle allows a given crank to move further inboard, so the effective length is shorter. Remember to establish that condition 3 is achievable before worrying about 4. 3 is not usually a problem, but if it is forget about 4 and start again with a different parts.
5) The left side dimensions of the spindle are correct for the crank. Ideally, the left arm will sit just as far outboard as the right. Lots of older cranks require very asymmetrical spindles to get proper arm alignment, and newer symmetrical BBs throw this off. Even if everything is perfect, some frames have out-of-square BBs and the cranks dont clear the stays equally when using the factory spec BB
Tom Dalton
Bethlehem, PA
rhawks@lmi.net wrote:
All I can say about the $900 bid for those cranks is wow. On my Cinelli, I have a set of cranks that are identical including the condition. I have no intention of parting that bike out though, as it has way to much meaning to me in it's current condition. About the only thing I might ever do is get some other crank set as a user because I do plan to ride this bike.
I have a question though related to cranks. How do I determine that the taper on a spindle is appropriate or not for a crank? I checked Sheldon's web site but couldn't find a discussion of spindle tapers that I thought I had read there before. My hazy memory is that there are two more common tapers but that there are others as well. One taper is one commonly used on on-topic campy cranks, and the other would be the standard found on most japanese parts. However, would some Japanese components have the same taper as campy? The reason I ask this is that a bike I bought (specifically to part out. Nothing was 'original' on this bike anyway) had a campy bottom bracket set, but Sugino(?) Super Mighty.
I was playing around with different spindles I have and different cranks and it appears that some Shimano spindles might have the same taper angle but start out with a wider end. I found I could fit some cranks onto the campy spindle much farther than the campy crank would go on the campy spindle, and the campy crank would not fit nearly as far on the shimano spindle as the newer SR or Sugino crank would. In all cases though it appeared as though there was contact both fore and aft along the taper. Can someone enlighten? Thanks.
rob _______________________________________________
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