ISIS Bottom Bracket Help needed Please.

[Bullpup]

I have a 72mm wide frame to which I wish to fit some Race Race Cranks.

I had a 119mm Axel but it was too long - the front mech wouldn't reach the outside ring. A bit of measurement later I calculate I need the outer chain ring to come in by 5mm so by my calculation I need a 109mm axle.

More internet research: The manufacturer - Specialized specifies a 108mm Axle. Raceface specifies a 113mm Axle. So it should be about right.

So I buy one of each - all FSA Pro' s and they are still too long!

I decide to measure the Bottom Brackets themselves and check the distance on the drive side from the end of the axle to the inside face of the cup flange and get the following results:

119mm Axle. 22.20mm

114mm Axle. 22.30mm

109mm Axle. 20.00mm

Surely the reduction in Axle length should be split evenly between drive and non-drive sides and come down in 2.50mm per side? per 5mm size drop.

i.e. the 109mm Axle should measure 17.50mm?


What should I do next?

Many thanks

 

[FluffyChicken]

Raceface are 113, so fit a 113. Remember you bolt the cranks on until they hit the chain line stop.

 

[Bullpup]

Thanks for the reply Fluffy. Could you please clarify what you mean by a "chain line Stop" - I have tightened the Cranks as tight as they will go on the 109mm axle and they still stick out too much.

 

[Bullpup]

I have now found this
http://www.raceface.com/instructions/CR ... _crank.pdf
and this:
http://www.bike-components.de/bedienung ... ctions.pdf

I hink I just need to get the cranks to seat properly.

Thank you

 

[FluffyChicken]

RaceFace manuals are in the archive as well.

But on the ISIS bottom bracket (like on some square taper shimano bottom brackets) there is a metal stop, it looks like a spacer and the reason you need the large holed tool
The crank should hit that and be tightened up.

I don't know your FSA's but the RaceFace Signatures you could then play with the alignment by moving both cups in or out 1mm at a time (one full turn iirc).

 

[Bullpup]

Great thank you-I will give it a go tomorrow.