So I've pieced together a new drivetrain to replace the 52/36 - 11/27 on my Felt F3. I just finished installing an Exogram standard crankset along with a 7900 11/27 cassette and Ti X10SL chain... but for some reason the chain keeps trying to climb off the lower RD pulley.
I ran the crank for ~150 miles on my 11/25 cassette and old chain before I got the new cassette in - then installed the DA cassette and KMC chain at once. It's as if the chain line is at such an angle that it's pulling the chain off the lower pulley when in 53/27 - which surprises me considering the Shimano cassette is actually further outboard than the SRAM. Also, this problem persists randomly throughout the rear cogs - so it's not simply a result of chain line (I presume).

I've also checked the links on the chain and none appear to be stiff. Is there something else I'm missing?

Bent cage maybe?

It worked fine an hour before with the old chain and cassette.

It sounds like you need to adjust the inner and outer limits on your rd.

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So you mentioned first the largest cog and large chainring......first reply to that is generally it's a no go - while you may be able to shift to it you should not plan to ride it.

My guess with a new chain would be that possibly the Ti chain when assembled has (purposely or not) tighter tolerances between side plates - therefore it's not as flexible side to side as others. But you did mention the problem sometimes happening in other gears. Should it be the tolerances they should loosen up over time.....but with such a $$$$ chain and some good riding to be had, who wants to mess with it.....

My personal opinion - I go for reasonably light. And there are so many steel chains that are oh so close to Ti chains in weight that the $$$$ spent for the Ti is money being thrown away. Just my opinon.

Sounds like an adjustment problem. The red RD can be a pain to get just right. Does it skip when down or up shifting?

Hanger alignment can cause this since the position of the pulleys is always relative to it's mounting point.
Regardless of the "it worked before" the above statements about tighter chain tolerance etc will make this misalignment stand out.
And it is probably twisted and not bent in or out.

@Nifty - I've messed with the limits a bunch and I've seen no change in the chain riding up the pulley. I won't say that I'm a master tech and I've set it "perfectly" and it's still amiss.. but I'd expect that if it were a symptom of the limit adjustment that running through the range would produce a different reaction - which is not the case.

@tommasini - while I didn't install a 11-27 so I could stay in the big ring, I'd still appreciate my equipment functioning properly. The Ti is just a coating and has more effect on wear than weight.

@Dave67 - I can get the cassette to shift very well through the gears but it won't eliminate the skipping on the pulley.

@timzcat - my first suspicion was the hanger... how can I go about alleviating a misalignment?


Thanks for the feedback, fellas. I'm going to try anything that's mentioned - that's why I ask!



Edit: Tomorrow I'll try to eliminate some variables by changing out the cassette and chain one and at time to see what works with old components. If any piece just won't play well - I hope it's the chain... I need more gearing!

stick a 5mm allen wrench in the rear derailleur mounting bolt, brace the back of it around the cable housing, and push the allen wrench toward the back of the bike. i'd go with a couple firm nudges. you may not even feel like you bent (straightened?) anything and that it all sprung back to place, but test it anyway.
edit- on red rear derailleurs, and others that have both pulley cage sides made of carbon, they can sometimes hold a twist with the clamping force of the pulley bolts. you may even be able to grab the lower pulley with two fingers and twist it in the direction you want it to aim, and it may stay there. doublecheck the pulley bolt tightness after.

I wish I had brought my bike to work so I could try that!