bluehills3149

I have Campagnolo Centaur UltraTorque cranks (10spd) with a KMC 10spd chain. Cranks were bought 2nd hand but were near new. Fr Der is Centaur, levers Veloce Ultrashift (they have multiple clicks not the powershift mech). On some downshifts the chain slips between the 2 chainrings so the cranks spin and I need to upshift again then downshift again. Note I checked chainring screws and they are tight and every part is not that old at perhaps 1000 miles of use. The limit screws are set to minimize rubbing over the full range.

Andrew R Stewart 

Perhaps try loosening the inward limit screw a tad? Just guessing.


We use to see a lot of this problem decades ago. With the current ring spacing and contouring this shift into "neutral" is a lot less an issue. The release speed of many ft ders is so quick that the chain derails to the inside far more commonly too.


Are you in the cassette's small cogs when this happens? How fast a cadence are you typically doing want to down shift a lot (from large ring to...)? Andy.

bluehills3149

I haven't paid too much attention to the gears but I typically use the middle gears only. Cadence is usually low and low load on pedals. I just had it on the stand and looked at the downshifts and think I see some issues. As it is ultra shift, each click is very small so it only nudges the chain off the large sprocket so it just drops down and nests between the gears. I've given it slightly more range by adjusting the inner stop and adjusted the cable length a bit so hopefully it has enough momentum now to get over the dead spot. Looks OK on the stand but only a few rides will tell.

mbusky

Someone once told me that he put one of his chainrings on BACKWARDS and he would drop the chain in between his rings and could not figure out why till he visited the shop. I never saw it but hey why not?

bluehills3149

I remember reversing my chainrings when I was an impoverished student to give them another lease of life and this worked when the chainrings were not dished which was probably not the case in your example. But on Centaur cranks the outer big ring is def not reversible and the inner looks symmetrical so I don't see it being an issue even if it was able to be reversed as usually the screw holes are countersunk on one side.

Brian25

As bikes have more cogs, the chains become thinner. This is the exact reason why manufacturers and mechanics at stores do not recommend using a crank for for less gears with a narrower chain/ more cogs. I would highly suspect that the crank is a 9 speed crank (I know that the O.P. said it's a 10 speed crank). A solution would be to machine off a little bit of the aluminum on the spider to have the chain rings closer together. (Yes I have done this a few times)

Leisesturm

I am with you on this OR the inner ring is indeed reversed, as another poster wondered, and if in fact the screw holes were countersunk, being reversed might(?) widen the space between rings allowing the chain to get trapped.

Brian25

Yep.

bluehills3149

OK - I checked. The inner gear has the words campagnolo stamped on it and "36" for teeth count. Both should face OUT (I'm pretty sure of this) and as they are it's not on backwards. As to 9 spd? It's Ultratorque as I stated earlier. And the holes are NOT countersunk so it looks like you could reverse it easy enough although I did not check the hole alignment.

oldbobcat

I agree with loosing the low limit screw a tad. While youi're looking at the front derialleur, check the clearance between the outer plate and the big ring. If it's more than 2mm, lower it to 1-2mm.

Also consider your technique. Higher cadence always helps, and be sure to press the thumb tab sharply and all the way.