Campag Chorus Triple C'Set. Front Mech problem

dave42

I bought a Chorus triple, square-taper chainset and a bb with the recommended 110mm width. But because the chainset has the same 'low-profile' crankarms as the Chorus double, the resulting Q-factor with a 110 bb seems too wide.

So I had the idea of using my existing chorus double bb (102mm) with the triple crankset. It very nearly works. Q-factor is the same as the double, chain-line works really well and there's bags of clearance between the inner ring and the chain-stay. There's just one annoying problem - the front mech won't go 'in' far enough to shift onto the granny ring. Front mech is a Record triple but the design of the parallelogram means the lower pivot point on the mech butts up against the seat tube (std 27 diam).

Does anyone know of a way I can get this setup (with the narrow 102mm bb) to work? Is there a front mech with a different design that would move in further, maybe an MTB or a shimano one? I've look at sheldonbrown and the Parker web-site and I don't think there's anything there, but I may have missed something. Guess I'm just trying to go beyond design limits?

TIA

Backpedaler

Dave42,
I had a similar problem, caused by the design of the frame- I got around it by spacing the driveside BB cup out with a washer or two. You have to watch that the LH crank doesn't get pulled over too far and catch the LH chainstay though. Not a guaranteed fix, but it might work!!

Best of luck!!

Monty Dog

Your LBS can probably supply suitable spacers for your BB - typically used on external BBs like Truvativ GXP, however the design of the Campagnolo BB might make this tricky as it relies on tapers to locate the spindle and bearings - depends on how far you need to move the driveside outboard. Happy medium might be a 107mm BB?

tenor

I am about to try a similar thing, but using a standard 110 bb in conjunction with a left hand crank from a Veloce double chainset.
From what I understand, the Record/Chorus triple bb was 110, but offset to the drive side. My reasoning is that the symetricall 110bb will pull the chainline in a bit (a good thing), but not so much that the front mech will struggle with. Using the Veloce/Centaur LH crank from a double will maintain correct the overall Q value and I hope to have a Record Triple with a better chainline and lower overall Q factor - both good imho.
I bought the spare LH cank off e-bay for about 10 pounds so should be a cheap way out.