Ribble R872 and campy compact cranks

[Stewche]

Hi,

I recently ordered a r872 with full chorus group set with 50/34 chain rings from ribble. Today I got this email "Unfortunately we have come across a problem with your build, unfortunately the compact 34/50 does not fit efficiently onto the frame, the mechanics have tried to make it work but have had no luck, we can fit a standard 39/53 and this will run without any problems"

I found this odd so asked them if they could fit a mid compact which they told me they couldn't. Is there any reason why this could be? They even offer it here with mid compact ultegra... http://www.ribblecycles.co.uk/ribble-r8 ... l-edition/

Thanks

[Trkorb]

It might be something to do with the 110BCD (if 5 arm), hence they cant do mid compact or compact, and it must be something to do with the campag cranks, where the design differs to shimano.

Doing a quick google search it seems the bottom bracket area is wide and as it spreads out it keeps quite wide for some time. I assume the inside of the smaller BCD crank arm is fouling the frame or too close to be comfortable.

Is it one of the four arm campag cranksets or an older 5 arm?

If you asked them for a picture they would probably sort that for you.

Edit: It is very hard to find photos of the inside of campag drive side arms, however I did a search and it does seem that on both the 52-36 and 50-34 chainring combos for the 4 arms cranks, there is a small lip of metal extending beyond the hole for the chainring bolt towards the crank axle. On the 53-39 chainring combo that lip does not extend down as far. So i assume that that slightly longer metal lip is what is causing clearance issues on the frame.

Disclaimer here that I might be barking up the wrong tree.

[Stewche]

Ah I see cheers. That's a shame think a 53 will be a little too hard for me. I'll probably have to look for something else.

[Calnago]

It could also be that the brazeon for the front deraileur is too high and won't allow the front derailleur to sit low enough for the smaller front rings. I say this might be the reason because if it was chainring related it's usually the larger chain rings that might present clearance issues due to the chainstay angle towards the dropout, as opposed to the smaller ones. But if the derailleur cant go low enough, then that would certainly explain being able to use the larger rings but not the smaller. You should ask them specifically what it was. Would be interesting to know. I suspect it's one of those things they didn't really test out so well for All groupsets.

[Stewche]

I'll be sure to ask them tomorrow, thanks very much for your help. Now I'm just wondering whether I'll get away with the 53 with a 12-29 cassette.

[Trkorb]

I think Calnagos hypothesis is more likely!