Retrobike Forum Index

It is currently Sat Dec 10, 2016 4:10 am

* Login   * Register * Search  * FAQ



Post new topic Reply to topic  [ 15 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Crank question..
PostPosted: Sun Jan 25, 2009 7:21 pm 
Old School Hero

Joined: Sat Jun 09, 2007 2:35 pm
Posts: 179
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


Top
 Profile  
 
 Post subject:
PostPosted: Sun Jan 25, 2009 8:07 pm 
Retro Guru

Joined: Sun Dec 14, 2008 2:11 pm
Posts: 303
Square taper axles are a standard size.

Have you bought the axle length to suit the chainset you are using?


Top
 Profile  
 
 Post subject:
PostPosted: Sun Jan 25, 2009 8:22 pm 
Old School Grand Master
User avatar

Joined: Wed Feb 20, 2008 12:21 pm
Posts: 5785
Location: Lost in Translation
GarethPJ wrote:
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.


Last edited by one-eyed_jim on Sun Jan 25, 2009 8:24 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject:
PostPosted: Sun Jan 25, 2009 8:24 pm 
Old School Hero

Joined: Sat Jun 09, 2007 2:35 pm
Posts: 179
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.


Top
 Profile  
 
 Post subject:
PostPosted: Sun Jan 25, 2009 8:29 pm 
Old School Grand Master
User avatar

Joined: Wed Feb 20, 2008 12:21 pm
Posts: 5785
Location: Lost in Translation
martin_b wrote:
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.


Top
 Profile  
 
 Post subject:
PostPosted: Sun Jan 25, 2009 8:43 pm 
Old School Hero

Joined: Sat Jun 09, 2007 2:35 pm
Posts: 179
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.


Top
 Profile  
 
 Post subject:
PostPosted: Sun Jan 25, 2009 9:00 pm 
Old School Grand Master
User avatar

Joined: Wed Feb 20, 2008 12:21 pm
Posts: 5785
Location: Lost in Translation
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.


Top
 Profile  
 
 Post subject:
PostPosted: Sun Jan 25, 2009 9:06 pm 
Old School Grand Master
User avatar

Joined: Wed Feb 20, 2008 12:21 pm
Posts: 5785
Location: Lost in Translation
http://sheldonbrown.com/gloss_bo-z.html#bottom

http://sheldonbrown.com/bbsize.html

http://sheldonbrown.com/bbtaper.html


Top
 Profile  
 
 Post subject:
PostPosted: Sun Jan 25, 2009 9:36 pm 
Old School Hero

Joined: Sat Jun 09, 2007 2:35 pm
Posts: 179
frame is a Donnay, Well thats whats its badged as see it here
http://www.retrobike.co.uk/forum/viewto ... highlight=


chainset is here http://www.retrobike.co.uk/forum/viewto ... highlight=


Its an Italian bottom bracket. i may try to refub the supplied bracket bearings and use the original axle.


Top
 Profile  
 
 Post subject:
PostPosted: Mon Jan 26, 2009 7:10 pm 
Old School Grand Master
User avatar

Joined: Wed Feb 20, 2008 12:21 pm
Posts: 5785
Location: Lost in Translation
martin_b wrote:
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.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 15 posts ]  Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: Google [Bot] and 11 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  

About Us

Follow Retrobike

Other cool stuff

All content © 2005-2015 Retrobike unless otherwise stated.
Cookies Policy.
bikedeals - the best bike deals in one place
FatCOGS - Fat Chance Owner's Group

Powered by phpBB® Forum Software © phpBB Group