[El Scorcho]

Here is the conundrum.

Brand new Record 10 Chain

Brand new Record 10 chain rings

Brand new Record 10 cassette.

Everything is golden and it shifts like a champ, except under power the 12T skips on every pedal stroke. Been working on this for 4 hours and I am losing my mind.

Checked the limit screws- lines up perfectly.
Checked the torque on the cassette- exact.

What am I missing?

 

[Undecided]

Does it skip off toward the 13, or toward the outside? What's the chain line look like and is the front derailleur right against the chain?

 

[El Scorcho]

Hard to see which way it is jumping as I cannot duplicate the problem in the stand, only when I am putting the power down.

The chainline is smooth and direct with a small 1/16+- gap between the front derailleur.

 

[Pirx]

Hard to see which way it is jumping as I cannot duplicate the problem in the stand, only when I am putting the power down.

How much power? Does your frame flex a lot? Do you get the skipping both on the left-leg and the right-leg stroke?

 

[El Scorcho]

At cruising speed there is no problem. Hard effort or standing and it is every pedal stroke with the right leg.

Bike is a Pinarello Paris. Not a lot of flex.

To answer an earlier question, it looks to jump slightly toward the 13t.

 

[BlueMasi1]

B Screw Adjustment?

I had a similar problem and solved it by adjusting the B screw.

 

[C-40]

Don't rule out a defective part. It could be something as simple as a stiff chain link that will disappear with a little more use.

I assume that you know how to set the chain length properly, using the little/little method.

I also assume that you've tried some minor adjustment to the shift cable tension and/or the small cog limit screw.

I also assume that you're not using the little ring with the 12T cog when this happens. If so, then it's a chain-line issue.

The B screw only affects the clearance with the upper jockey pulley, when the chain is on the larger cogs.

 

[Pirx]

At cruising speed there is no problem. Hard effort or standing and it is every pedal stroke with the right leg.

Bike is a Pinarello Paris. Not a lot of flex.

Probably not but, if you get skipping only on one leg, there's definitely flexing involved.

I also assume that you're not using the little ring with the 12T cog when this happens. If so, then it's a chain-line issue.

Excellent point. According to the OP, we have the chain trying to move towards the inside. Might well be an issue of a borderline viable small-small gear combination. In that case the answer is simple: Don't do that. Regardless of anything else, you really should avoid hammering it in one of those extreme combinations (small-small or big-big). Things depend a lot on your specific geometry. On my Felt F1 (56cm) frame, fully crossed combinations work fine, on a different frame they may not. On the OP's frame, if that is the issue, the combination almost works, but not quite.

 

[Undecided]

And are you sure the rear wheel is clamped correctly?

 

[El Scorcho]

C-40 FTW!! LBS had a new Centaur cassette, I installed it and shazam! Problem solved.

Must be a defective part in some small way.

Thanks for all the input, I tried everything you recommended.

 

[kgbianchi]

Shift issue possibility

C-40 FTW!! LBS had a new Centaur cassette, I installed it and shazam! Problem solved.

Must be a defective part in some small way.

Thanks for all the input, I tried everything you recommended.

If you are not careful, it is possible to put the last cog on the cassette body incorrectly. This may be why the new cassette worked?

 

[El Scorcho]

I removed and reinstalled that cassette 4 times. I am not perfect but I will bet I didn't do it wrong 4 times.