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Idris
07-22-2012, 01:51 PM
I've been battling to get my front derailleur on my Highroller (http://forum.atomiczombie.com/showthread.php/6714-Full-suspension-High-Roller) to reach the big chainwheel and not drop the chain off the inside of the small chainwheel. I thought it was the deraliur, but having lined up 5 different ones the have almost the same seatpost to chainwheel spacing and throw.

I have big gaps down between the cranks and the BB, using and nice enough crank set. I tried my best crank set and found the same spacing. I then tried one of the many ugly pressed steel junk ones I have - BINGO - normal spacing resumed...but why.

I started looking at BB axle lengths, all the oldschool ones from which the nasty chainwheel/cranks came from and the ones I have welded up for use have long axles, the new type BB that needs a special tool to extract all have short axles

Looks like I'm going to have to borrow a BB extractor and see if they are swappable or cut up another frame and weld up another BB - the current one was off a suspension triangle, so very little work to make it nice to use NO hole filling.

Ticktock
07-23-2012, 05:09 AM
Hi,
I am going to assume that you can get the same parts in USA as we do here in China (can be dangerous-so If I am wrong--sorry)
There are two different length axles available , and both fit the same bottom bracket, and have the same (usually) tapered squares for the cranks.
The difference is mainly on the Chain side, where the length varies. You should only have to get the correct axle for the Chainrings you intend to use. By correct I mean the one that puts the chain ring in the right place for the derailer.
I had the same thing with my trike, and a new axle solved it.
If all else fails, rather than make a whole new bottom bracket assembly, simply reweld the derailer tube in the place that keeps the derailer happy!
Hope that helps,
Steve G
Beijing

Ticktock
07-23-2012, 05:26 AM
Hi Again,
Just a thought, could the axle be in backwards?
I doubt it because one of your cranks does work, but simply reversing it may work.
Steve g,
beijing

Idris
07-31-2012, 02:52 PM
Hi Again,
Just a thought, could the axle be in backwards?
I doubt it because one of your cranks does work, but simply reversing it may work.
Steve g,
beijing

The axle lengths were different by 2cm at least, so no cigar by reversing.

Modern cartridge BB does indeed fit in the oldschool BB, a bit of force and some screwing in and out was needed as the new style has threads for a greater distance.

Problem now solved, nice (or at least nicer) chainset now usable.