Bicycle Mechanics - New crank arm fit_BB compatability

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tmh657
03-09-09, 05:31 PM
I have a Suntour BB with Suntour Sprint cranks.
Just got a Shimano 600 Crank, (I wanted longer arms).

They are both square taper but the Suntour cranks go about 7/8 of the way on the spindle and then get tightened.

The Shimano crank goes almost all the way onto the spindle to the BB shell.

I am guessing the BB is not the correct taper for the Shimano crank since if tightened it would be against the BB shell.

Any ideas?
Thanks.

Panthers007
03-09-09, 06:34 PM
Get another bottom-bracket for the Shimano. Shimano and Suntour rarely get along.
DOS
03-09-09, 07:32 PM
Suntour on some BBs used a slightly different taper than JIS or ISO so fit between a Suntour and either JIS or ISO components will be slightly off. I don't know about your set up, but I have Suntour cranks on a Campy BB and they work fine. Sounds like your cranks will stay on snug but your chainline will be off. FWIW, My Suntour Superbe cranks are fantastic and I got em for next to nothing on EBAY so in addition to considering Panther007 suggestion of replacing your BB, you might look into new cranks to match your BB (although replacing the BB will be the cheaper option).

Grand Bois
03-09-09, 07:54 PM
They all have the same 2 degree taper. JIS spindles are "stubbier".
tmh657
03-09-09, 08:19 PM
FWIW, My Suntour Superbe cranks are fantastic and I got em for next to nothing on EBAY so in addition to considering Panther007 suggestion of replacing your BB, you might look into new cranks to match your BB (although replacing the BB will be the cheaper option).

Just got the Shimano cranks today in the mail from ebay purchase for a good price so a $24 Shimano UN54 w/ 118mm length will be purchased tomorrow.
Kinda sucks since that's more than I paid for the crank.

Oh well, the Suntour BB and Sprint crank will go in a drawer for now. It's a 170mm. Not sure why they outfitted the bike with 170's in 1988.
Schwinn put 165mm cranks on smaller frames.
The cranks are great just too short for me.

Thanks for the help guys.
DOS
03-09-09, 08:44 PM
They all have the same 2 degree taper. JIS spindles are "stubbier".

When determining whether my campy BB would work with ST superbe cranks, I had read in several places that Superbe used a different taper; with one cite indicating 1.8 degree vice 2.0. I never botherd to do any measurement myself but nor did I have any reason to question the assertion.