[MENTION=403744]plonz[/MENTION] It would help to know the make and model of the cranks in question plus the BB shell width. Some pictures would be even better.

A few years ago I was putting together a single speed beater using an old Gitane Interclub frame with a French BB.

I'd been down the road of matching cranks and BBs for ~40 years. I decided to document some of the steps that I went through on this project. Here's a link to my Flickr album that may give you some ideas:

https://www.flickr.com/photos/282672...57627678462359

Click on the pictures and read the descriptions below them...

EDITORIAL COMMENT:

All of the crap about ISO, JIS, Campy, French, Japanese spindle tapers is just that!!! In the 1970's Phil Wood made "one size taper works with all" cartridges. They worked fine most of the time!

1. Once a crank arm has been torqued onto the spindle, the soft aluminum alloy deforms to fit the spindle taper. More so with crank arms that have been removed and replaced a number of times. Factor in used cranks that have been run loose and that the magnifies the problem.


2. These are/were BICYCLE parts not Swiss watch movements! The manufacturing tolerances in the tapered square mounting holes in the crank arms plus the small end measurements and lengths of the tapers combined with the overall spindle lengths vary substantially within the same make and part number! I've known this for many years but never documented it.



I measured all of these BB spindles and cartridges in this box plus a lot more. They were various Campy, Ofmega, Avocet, Shimano, Suntour, SR, Sugino, TA, Stronglight, Phil Wood and other brands.


3. If it fits, it works! These views show the proper crankarm fit on the BB spindle taper




4. Fitting the spindle to the BB cups presents some additional issues. The balls should run in the center "ball track" - not too high or too low. The second picture shows the proper ball contact area.




5. So how do you determine what's going toi fit?

The easiest was is to get the correct BB and spindle that matches the crank arms - no guessing or trial and error!

When that's not practical, get a pair of 1/4" caged ball bearings. Clean ALL of the grease off. Get a pair of cups and a spindle and do the same with them. When all of the parts are clean and dry, take a magic marker and cover the ball track area on the spindle and both cups and let dry (you could use a product called ****m Layout Fluid too).

Assemble the BB with the dry components by hand tight enough to take up the slack. Rotate the spindle a few times and take the BB apart to check the ball contact areas on the parts. If everything looks good put it back together by hand again.

Slide the crank arms onto the spindle and check to see how well the fit -see drawing above in #3 . Keep in mind that when you torque the crank arms onto the spindle at 20 to 30 Foot Pounds, they will seat 1mm to 3mm further onto the spindle.


6. The small chainring should clear the chain stay by about 4 to 5mm, depending on small chainring diameter and any clearance flat on the chainstay.

Every time you remove and replace the crankarm it will seat a little further onto the spindle. Also the crank arm bolts should be re-torqued after 50-100 miles of riding depending on the rider's weight, strength and style of riding. That seats them further onto the spindle too.

If a bike gets used a lot the crank bolts or nuts should be frequently checked to make sure they haven't worked loose. Squeaking or creaking when honking up a hill is a good (bad) sign that the crankarms need to be retightened! Continued riding with that condition will end up trashing the taper in the crankarms. That's why used cranks should be carefully checked for damaged tapers.

The 4-5mm figure is a "WAG" (wild assed guess) but gives wiggle room for future crankarm re-seating on the spindle plus it allows for switching to a larger inner chainring.

Another point, a frame with short chainstays a 130mm rear hub and larger inner chainrings will run out of clearance a lot faster than one with 120mm or 126mm rear dropout spacing and longer chainstays.

If there's not enough clearance or if the crankarm sticks out too far you have to use a different spindle or BB.


7. Q-Factor like chain line is another throw back affectation... Q-Factor is a one size fits all fit fascist fantasy...

Chainline was a Brit obsession when they used SS and internal hub gears with stiff 1/8" chains. In mid 70's 3/32" bushing-less chains became the standard. They have a lot of lateral flexibility so chainline is much less of a concern!

verktyg

Chas. Breaker of hearts, destroyer of myths and seeker of truth!