RS7's and Shimano b/b - Cotic Soul

[Denis99]

Not quite retro, but worth mentioning as a few here may ride Cotic's.

Just bought a new 2010 Cotic Soul frame,fitted Middleburn RS7 cranks to a Shimano square taper UN52 113 x 73.

The b/b is too short, despite what Middleburn say about 113mm being the correct b/b width.

The driveside crank arm fouls the serrated splines on the inner diameter (the bit where you insert the b/b tool).

Fitted another UN52 73 x118 and all is fine - could very possibly get away with a 115 width, but didn't have one on hand to try.

Chain line is good also.

Selling the 113 x 73 in the classifieds if anyone is interested - like new , fitted once, less the 5 minutes use.

 

[Scrat]

Ha Ha someone else with this problem

113/73 IS the correct BB, 118 will screw up you're chainline royally.

You need a flangeless BB or an older shimano with a pressed on cup (these had a much thinner flange than the one piece cast ones)

I currently have them on my CX bike which is running a 107/68 twin ring setup

 

[Denis99]

Scrat, chain line looks ok (not perfect, but acceptable), fitted by local bike shop.

When you say a flangeless BB, do you mean something like the Phil Wood b/b?

 

[Scrat]

I'm not sure who does current flangeless:

but the likes of Raceface taperlock, Zero, early Hope etc

If at the end of the day you're happy and IT WORKS, why fiddle any further?

 

[Dr S]

mmmmm

The Cotic website quoted 113 is only the right width (for 99% of crank apps) if you are using a ISIS bottom bracket only. For square taper cranks you need to look at a specific width for the particular crank you are about to use. Middleburn square taper will need a 115 onwards.

 

[Denis99]

I'm using square taper, so it's a little bit more re assuring to know that 115mm is closer to the "right" width.

As I said chain line looks good - its not absolutely perrfect, but pretty close.

 

[jimmy5willy]

I'm removing an isis BB that was 112.5mm and need to put in a square taper. Is it just a straight swap or do I need to go a bit shorter/longer with the sq taper? If it's a straight swap I'll have your square one off ya.

 

[Dr S]

I'm removing an isis BB that was 112.5mm and need to put in a square taper. Is it just a straight swap or do I need to go a bit shorter/longer with the sq taper? If it's a straight swap I'll have your square one off ya.

it depends on which cranks and to a certain degree what frame you are using.

 

[Denis99]

I don't know for certain if you can do this - contact someone in your local bike shop for some advice, or perhaps others can help from this forum.

 

[Denis99]

Just had an email from Cotic concerning the b/b widths used with Middleburn square taper cranks.

Cotic have confirmed that you need a longer axle than 113mm for the square taper M'burns.

115mm could fit......but it looks like it might be a tad too short.

118mm looks to be the width.