Blackdays

I swapped my 7800 crank out for a SRAM Quarq crank about a month ago. It has the Red chainrings.

My question is - is it possible to get the crank to mesh well with my 7800 group? I've been tweaking it for the past week, and it seems like the two just don't like each other. The chain wants to jump off the small ring if I'm cross chained (not that I would be in an ideal situation - but this shouldn't happen).

JonnyV

There shouldn't be an issue getting this to work. New chain and new crank rings? If one of these is used and worn and the other new you could run into these meshing problems.

Blackdays

I did buy a new chain as well - and a new cassette to make sure that it wouldn't wear down the chain early.

I cannot figure this out. I might just take it to the LBS to see if they can come up with something.

BarracksSi

Would the chain be getting picked up by the big ring when you're cross-chaining?

Maybe the big ring is just that good at forcing shifts, or maybe it's further inboard than the 7800 was...

R900

No problems for me. I would just start from scratch and set everything up again. Likely something simple.

fastbub

Something like this. pedal it cross chained in a stand and see if the chain is catching on something or grabbing the chain ring somewhere.

Is your bike a small size or does it have really short chainstays? This creates a greater angle on the chain when crossed than something with longer stays. There might be just enough difference in how far in or out the chain rings are with your new crank to cause a problem. Longer chainstays can generally accomodate cross chaining a little better.

ericm979

I run Sram chainrings on a 7800 drivetrain. They work fine, even with the short R3 chainstays.
I suspect that you have an adjustment problem.

BarracksSi

Chainstays are usually just as short on any size of bike these days, so I don't think that's a problem. Besides, it didn't do this with the 7800 crank he had before.

Don't GXP BBs use spacers depending on the BB shell width? Or was that Campy?

topflightpro

Are the front derailleur limits set properly. The different crankset could require adjusting the front derailleur to match.