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Bottom bracket swap out

Old 06-19-14, 06:24 AM
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Rickalodeon
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Bottom bracket swap out

I've been all over the Sheldon Brown site as well as forum posts without success. I was hoping that someone here might have the specs comparison to help me determine if I can remove my current Sugino VP double crankset (and bottom bracket) and replace it with a Shimano double 6700 setup for my Univega Supra Sport frame.

Any help would be greatly appreciated. Thanks.

Last edited by Rickalodeon; 06-19-14 at 06:52 AM.
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Old 06-19-14, 08:26 AM
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Univega = English threading 68mm width + 1.37"*24tpi threading
Sugino = square taper BB
6700 = external
So you'd have to swap out the BB as well (which you indicated). But make sure you get a standard English threaded crank/BB setup, not one of the BB30, BB86, or whatever the newest solution in search of a problem is.
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Old 06-19-14, 10:14 AM
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Originally Posted by Ex Pres View Post
Univega = English threading 68mm width + 1.37"*24tpi threading
Sugino = square taper BB
6700 = external
So you'd have to swap out the BB as well (which you indicated). But make sure you get a standard English threaded crank/BB setup, not one of the BB30, BB86, or whatever the newest solution in search of a problem is.
Do you think that there would be any chainline, chainring clearance or crank clearance issues? I.e. Do you know if the specs are the same for both models? Thanks.
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Old 06-19-14, 11:53 AM
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Originally Posted by Rickalodeon View Post
Do you think that there would be any chainline, chainring clearance or crank clearance issues? I.e. Do you know if the specs are the same for both models? Thanks.
Chainline is set by the crank/BB and the frame would not affect this - excepting some oddball [no-dish] frames and the like. You're putting a road bike crank into a road bike. Clearance should almost never be an issue with an external-type crankset, as there are not multiple spindle lengths to choose from. The spindle is part of the crank itself.

I've put external style cranks on a couple of bikes that were from the square taper days. Admittedly a small sample of 2, but ran into zero issues - besides needing new tools.
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Old 06-19-14, 12:40 PM
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Originally Posted by Ex Pres View Post
Chainline is set by the crank/BB and the frame would not affect this - excepting some oddball [no-dish] frames and the like. You're putting a road bike crank into a road bike. Clearance should almost never be an issue with an external-type crankset, as there are not multiple spindle lengths to choose from. The spindle is part of the crank itself.

I've put external style cranks on a couple of bikes that were from the square taper days. Admittedly a small sample of 2, but ran into zero issues - besides needing new tools.
Since I couldn't find any of the specs on either crankset/BB, I was concerned that a change in the distance between chain rings and frame center might also be indicative of a change in their orientation (chainline) with the cogs. I was ultimately concerned about compatibility between the new crankset/BB and vintage frame. But you made several key points...road bike crank into road bike, limited available spindle lengths, and you've done the conversion yourself.

Ex Pres....That was exactly the insight that I was looking for....Many thanks.
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Old 07-03-14, 05:08 AM
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...Just a follow up note in hopes that this might help another newbie like myself. The new crankset fit perfectly. So far, this was the easiest upgrade I've made. Had a bit of a challenge readjusting the front derailleur, but all is well.
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Old 07-03-14, 03:53 PM
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I was getting ready to reply, to mention that these new cranksets are all designed for 130mm rear spacing, but likely your freewheel isn't quite as wide as the intended modern cassette, so won't cause noticeable cross-chaining noise/friction.

I tend to prefer minimal "chainline" (as it is called, the distance from chainring/chainset center to seat tube center).

I like to make use of the big/big cog sprocket combination with frequency, as when cresting our many rolling hills.

So I usually prefer older bottom bracket designs that give me the freedom to select the chainline dimension at the chainrings.

Very glad to hear your new crankset works well on your older bike though.

How does it look?
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