Crank question..

martin_b

Retro Guru
Hi Guys,

I resecntly got a frame on here, it came with a 110 "loose bearing" BB. It wasnt in great nick so I've changed it for a Campag sealed unit. ( Ive tried 2)

Trouble is that the square tapper on the axle isnt big enough for the 3 sets of chainrings I've tried, ( one road two mtb). When you torque up bolts the axle slips on so far that the chain rings foul the frame. Do camag use a different size axle tapper?

cheers

Martin
 
Square taper axles are a standard size.

Have you bought the axle length to suit the chainset you are using?
 
GarethPJ":vz18jqvv said:
Square taper axles are a standard size.
Oh no they're not!

The slim Campag taper axle will draw much further into the crank than the relatively fat Shimano/JIS taper. To confuse matters, not all Japanese cranks use JIS (Suntour Superbe Pro and older Dura Ace are two exceptions I'm aware of) and not all European cranks are made in the Campag mould, but if the old axle was JIS and the new one is Campag, the difference in taper engagement is going to be about 3mm per side.

Chainring clearance (and chainline) is one problem, but the bolt can also bottom out on the axle before the full press-fit is acheived. That can mean mangled tapers in the future as the crank squirms and frets under load.
 
I'd assumed the one that came with the bike was correct?

Is there a way to work out what axle length you need?

The bike has 64X54 stamped on the shell, and the width of the BB when installed is apx 75mm including locking rings.
 
martin_b":1pg3sg74 said:
I'd assumed the one that came with the bike was correct?

Is there a way to work out what axle length you need?

The bike has 64X54 stamped on the shell, and the width of the BB when installed is apx 75mm including locking rings.
The bottom bracket needs to match the frame and the cranks. The shell width and thread type are determined by the frame. Just measure across the shell of the frame. 68mm is common for British frames, 70mm for Italian, 73mm for oversized mtbs, and there are a few other standards around. The thread dimensions may be indicated on the old BB cups.

The axle length is specific to the cranks you want to fit, and can vary between 102mm and 130mm or more. You need to know, or make an educated guess, what length is required for a given pair of cranks. Some cranks use asymmetric axles. You can sometimes use a thin spacer under one cup of the bottom bracket to shift things from side to side as necessary.

Give us more information, and we can be more helpful.
 
Thanks Guys .. got the calipers out and this is what Ive found..

The shell is 70mm across.

I've tried to fit a 2 ring road chain set ( bought a while ago here) and a 38t single speed crooks Bros crank set.

with the road bike set the inner chainring bubs the stays, and with the single speed setup the crank rubs against the BB locking ring itself.
 
You need to be more precise about things if you want reasonable answers. It's hard to help when your information is kinda vague. For example, who made the frame? When were your Cook cranks made? What brand is your road crankset, and how big are the rings? What is it you're trying to acheive?

Look closely at the cups you took out of the frame. If one has a reversed thread, they're British threaded. If they're both threaded the same way, they're probably Italian, but again, this is likely to be marked on the cups.

It's not clear from what you write whether the problem is the Campag taper, the axle length, or a combination of the two. Cook Bros made several series of crank, some of which need long axles, and some of which don't, but all of which will want a JIS taper, not a Campag one.

Your road cranks may or may not need a JIS taper, but again it could be a question of axle length as well. Take the rings off, and mount the right crank on the axle. Now take the bolt out and check how close the axle comes to the end of the taper. If you've got 1mm or more, you're safe - but you'll obviously need a longer axle if you plan to run these cranks with the current inner ring.
 
martin_b":s6b1svfn said:
Its an Italian bottom bracket. i may try to refub the supplied bracket bearings and use the original axle.
If your cranks foul with the modern Campag axle, they'll foul with the old one. I don't know the specs for the correct axle for your Stronglight cranks, but you'll clearly need a longer axle for them to work on your frame with the rings you have.

Most of the Campag road double cranks manufactured from the late eighties until the mid noughties will work on a 111mm Campag axle, the exceptions being 9- and 10-speed Record and Chorus, which want 102mm. There are plenty of nice NOS mid-level Campag cranks around for not too much money. I think if it were my bike I'd be looking for one of those.
 
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