kirke

So I just bought a set of very nice Suntour Sprint cranks from the late 1980s. They are almost identical to the Superbe Pro, I suppose just not finished as nicely.

According to VeloBase.com these cranks require a bottom bracket with a 108mm JIS-tapered spindle:

https://velobase.com/ViewSingleCompon...m=115&AbsPos=4

I dont really feel like tracking down a matching Sprint bottom bracket in really good shape (unless someone out there has one, in which case: get in touch!) so I have two options.

One is to buy a really nice, but really expensive Phil Wood bottom bracket with a 108mm JIS spindle.

Or I found these IRD bottom brackets made by Tange with a JIS taper. The only problem is the closest spindle lenth they come in is 107mm:
https://store.somafab.com/irdqbjissqta.html

My question is: Will the 107mm spindle work on the Sprint cranks will supposedly need a 108mm spindle? Will that 1mm make a difference in my chainline? Should I put a spacer on the fixed cup to space it out that 1mm?

Any suggestions would be much appreciated!!

sideshow_bob

a couple of mm either way and your chainline will be fine. if you go 107 just check you've got sufficient clearance crank/spider and stay. thats going to depend on the frame you have.

there are a ton of 108mm jis bb's out there. sugino for one, i think also 7400 DA did 108mm track bb's

dperreno

You'll never notice 1mm, I doubt many (vintage) frames were built to that close of a tolerance

operator

107mm shimano lx/105 cart bb = $25. Thread over.

A 1mm difference in spindle length, assuming assymetrical is a .5mm difference in chainline where it matters (drive side). Non-issue.

kirke

Thanks everyone. I just worry about every little thing sometimes!

kirke

Well, one other thing...
I could techincally use a ISO spindle on the JIS cranks, correct?
The ISO spindle would just need to be longer to compensate for the taper?
So, I could use a 113mm or so ISO spindle?

HillRider

No, don't. An ISO spindle has a smaller end dimension than a JIS spindle and a JIS crank will go further up it as you surmise. The problem is the crank arm can go too far up the taper and either bottom out without getting tight or, worse, distort and damage the square hole in the crank arm. Use the right taper.

DannoXYZ 

Yeah, there's no way to predict the fit of JIS cranks on ISO taper. It would be a waste of time and money to try unless you can do a test-fit at a shop to see how much room you have to tighten the bolt without having the end of spindle be flush with the outside of the crank (bottom).

kirke

Well, I will forget the ISO thing then.

I can get my hands on a decent and cheap JIS bottom bracket with a 110mm spindle and that should do the trick.

Thanks to all for the information!