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Campagnolo chainring won't fit Campag crankset
Posted: Fri Apr 05, 2013 6:13 am
by idler
I have just tried to fit a Campag 36t chainring to a Campag ultra torque compact crankset - and it didn't work.
It appeared to fit on the spider okay except for where it attaches behind the crank arm - the hole there was a little off-centre (towards the crank axle) and would not allow the nut to be tightened.
Does anyone know if the is a mismatch between the various Campagnolo compact chainrings and cranksets (the chainring was described as Chorus 10spd for compacts and the cranks are Centaur ultra torque compact).
Campagnolo chainring won't fit Campag crankset
Posted: Fri Apr 05, 2013 6:13 am
by Weenie
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Re: Campagnolo chainring won't fit Campag crankset
Posted: Fri Apr 05, 2013 6:44 am
by idler
Bit of research indicates that the 36t that I have does not have the CT standard configuration of holes (4 at 110mm and 1 at 112mm distance from centre). I don't know what this chainring is designed to fit but I guess I will have to try again.
Re: Campagnolo chainring won't fit Campag crankset
Posted: Fri Apr 05, 2013 1:47 pm
by bikerjulio
Yes Campy has had at least 2 styles of CT chainrings. On an circa 2004 square taper centaur CT crankset the 110 BCD was completely conventional. It may be the only occasion when Campy chainrings were made to a common standard! On the later hidden arm cranksets, the BCD is not conventional with the hidden bolt being off line, and as you have discovered, not compatible. Look in the spares catalogs online for more info.
Re: Campagnolo chainring won't fit Campag crankset
Posted: Sat Apr 06, 2013 4:14 pm
by graeme_f_k
It is also worth noting that Campagnolo chainrings are not of common thickness, so there can be an issue with fitting chainrings not specified for a given crank set - the "hidden" bolt means that the chainring has to have the appropriate thickness for the cranks and spacer that you are aiming to attach it to.
The offset bolt is there so that users can't make a mistake with regard to the relative positioning of the two rings, in order that the ramps and pins and tooth profiles are correctly placed to lift & drop the chain.
Re: Campagnolo chainring won't fit Campag crankset
Posted: Sun Apr 07, 2013 5:50 am
by idler
graeme_f_k wrote:It is also worth noting that Campagnolo chainrings are not of common thickness, so there can be an issue with fitting chainrings not specified for a given crank set - the "hidden" bolt means that the chainring has to have the appropriate thickness for the cranks and spacer that you are aiming to attach it to.
The offset bolt is there so that users can't make a mistake with regard to the relative positioning of the two rings, in order that the ramps and pins and tooth profiles are correctly placed to lift & drop the chain.
Thanks for that.
Looking at my chainsets though it appears that differences in thickness of the chainrings is more of an issue with the outer rather than the inner ring. A slightly thicker inner ring should still sit at the same distance from the outer ring at the offset point and the same spacer could be used (and bolt should still be long enough to be tightened). However, a thicker or thinner outer ring (which attaches directly to the crank arm) would cause problems as the distance between it and the inner ring would therefore vary.