Or are they just bent?

The rings are not running straight, by about 3mm between 12 and 6 o clock. I noticed this as rubbing on the mech cage after a recent strip and clean, haven’t crashed or dropped the bike.

If I swap the cranks to another bike, the problem travels with the cranks. Likewise if I put different cranks on (using same cups), they run true.

Strange part is that if I fit just the DS crank, it runs true. Fit the NDS with the centre bolt (Hirth joint) finger tight, still true. Torque the bolt, and they go out of true. So I’m not sure they are simply bent. Have cleaned the teeth of the Hirth joint, fitted new bearings and tried different cups, but no better.

They are Chorus cranks, about a year old or so. Back to the shop with them , or have I missed something?

Back to the shop.

Thing is, I’m pretty sure they were running ok before I stripped and cleaned them (took them off to investigate a clicking noise – usually some grit under the dirt seal) – not sure what I could have done to cause the problem.

This sounds like the Hirth joint is damaged. It can happen, sometimes from being ridden with the fixing bolt loose, sometimes from a huge over-torque load being applied to the fixing bolt.

That of course sets us wondering about the “clicking” noise – maybe movement caused by an under-torqued bolt, or a bolt that had worked loose.

Send them to us at the Service Centre and we can have a look for you. The best address to use at present is the office:

Velotech Cycling Ltd
37 Dinglederry
Olney
Bucks
MK46 5ES

HTH
Graeme
Velotech Cycling Ltd
Campagnolo Main UK SC