Pelotoner

Hi Everyone:

I am playing with the idea of going to a compact crank from a standard double 53/39 Ultegra on my 2002 Lemond Buenos Aries. I believe the crank length right now is 175mm. It is a 9 speed running an Ultegra 12/27. The bike is full Ultegra with a 105 bb.

The bottom bracket is currently a Shimano BB-5500 which is 109.5mm and a shell width of 68mm.

I have been looking at the Shimano FC-R700 or possibly at Sram Force or maybe even a Red. I guess my concern is going from a 9 speed to 10 speed as I can not find any 9 speed compact crank options. I am not even sure which bb I would get if I went the Sram route. Have read that the FC-R700 will work, but it requires a different bb.

I guess I am looking for opinions and perhaps advise from anyone else who has done this switch.

Thanks in advance for your replies.

-Pelotoner

TriEngineer

change the chainrings, keep everything else equal.
it's a 130BCD, get 50t 130BCD rings from FSA, and whatever ring you want for the inner one.
sourcing compact cranksets plus all accessories is too much money.

umd

10sp cranks work with 9sp as well.


That won't help the OP if he wants a smaller inner ring. 130BCD only goes down to 38T, most compacts are 34T or 36T.

hammond9705

As umd says, you can run a 10spd compact with your 9 speed drive train. You are going to need a new BB but they are cheap. The length of your existing crank is stamped on the inside of the arm near the pedal.

Pelotoner

Thanks for the input. I started to check around and can see where I can get the 50, but the lowest FSA 130 I am seeing so far is 39.

All the newer model BB's do not give dimensions so I am concerned that I will not be able to find one that will fit. is 68mm and 109.5 a standard size for a bb?

umd

English bottom brackets are pretty much standard. Italian BBs are less common. FSA and some others make a 38, but they aren't very common and you aren't going to find any smaller than that, it just isn't physically possibly.

Pelotoner

checked and they are 175's so thanks for telling me where to look, sometimes in my old age I miss these things.

as for the bb, it looks like a lot of them are 68mm to 72mm with a spacer so the 68mm english is the correct size. None of the new ones show the 109.5mm width, is this standard for the double cranks?

Thanks again everyone.

umd

A lot of the newer cranks use external bearings, so there is no spindle width to deal with.

Pelotoner

ok that answers that question... reading I was unable to find that answer anywhere, but it makes sense and I am sure you could tell I was thinking it... just wanted to make sure before I drop cash on parts. Thanks again.

achoo

The FC-R700 could very well come with a bottom bracket - when I got one when Jenson was dumping them a few months ago it came with an Ultegra 6600 bottom bracket.