Derailleur adjustment with compact crank

[aicabsolut]

Yeah, the spacing can be different between wheels meaning you might need some derailleur adjustments to make shifting optimal when switching. Are you running the same cassette spread on the two sets? That's another factor, though mostly has to do with the B-screw.

[HillSlugger]

Yeah, the spacing can be different between wheels meaning you might need some derailleur adjustments to make shifting optimal when switching. Are you running the same cassette spread on the two sets? That's another factor, though mostly has to do with the B-screw.

Yes, same cassette on both (12-27). Didn't have this problem on my road bike with the triple/long rear cage.

I have discovered that my chain length *will* allow me to get onto the big-big combination. At the other extreme on the small-small (or next to smallest cog) the jockey wheels start to rub on each other.

I suppose I'd be much better off if I could HTFU and learn to ride a 12-25!

btw I made some adjustments to the tension using the barrel adjuster and the shifting was better behaved today, but not perfect. Instead of skipping past the 3rd cog (or was it 4th?) it was reluctant to get up onto it, but only when I was in the small chain ring. I suppose I should be switching to the large chain ring instead of going to this combo.

[aicabsolut]

Whether you have to make adjustments when switching between wheels seems to be bike geometry and individual derailleur dependent...so I'm not surprised you were ok switching with the triple but are now having problems.

When you say "get up into it" are you shifting harder or easier? If harder (which is what I'm thinking when you say you shouldn't be using that combo in the small ring), then loosen the cable by turning the barrel clockwise and see how that goes. The cable tension isn't as finicky as the limit screws so you can play with it more. Or you can start from scratch and loosen it a lot then start to re-tighten until it shifts properly.

If you're only having problems when in the small ring, then it probably isn't your limit screw on the RD. More likely a cable tension thing.

What do you mean that the jockey wheels start to rub on each other? Do you mean the chain is rubbing on the underside of the derailleur cage? That's not a big problem. That's what that part of the cage over the bottom pulley is for. Plus, you've got a fair amount of slack on the underside of the chain a lot of the time when in harder gears. It'd be worse for your derailleur and shifting if the pulleys/cage were rubbing on the large cog when in the small ring / big cog combo.

[lunacycles]

I always found my race wheels and training wheels were a bit different in terms of where the outer edge of the small cog sat in relation to the hub locknut, and shifting problems resulted. If this dimension is even .5mm different, you will have shifting problems when you switch from one wheelset to the other. It seems to me you need to have confidence about rear derailleur adjustment to deal with this regularly. You will probably have to re-adjust the high gear limit screw and the low gear limit screw to achieve precise shifting when you swap out wheels. Assuming you are using the same brand cassette on both wheels, you should NOT have to mess with the barrel adjuster. The barrel adjuster (cable tension) controls the distance the derailleur moves with each shift, and that should stay constant if you are using the same brand cassette on both wheels.

[aicabsolut]

Yeah, that's true, but she's having issues at the middle of the cassette for shifting when she switches wheelsets, so there the fix probably wouldn't be the limits. It's possible to be the B screw if the derailleur isn't aligned straight around the 3rd or 4th cog from the small end, but skipping over a cog sounds like cable problems or operator error.

[HillSlugger]

Yeah, that's true, but she's having issues at the middle of the cassette for shifting when she switches wheelsets, so there the fix probably wouldn't be the limits. It's possible to be the B screw if the derailleur isn't aligned straight around the 3rd or 4th cog from the small end, but skipping over a cog sounds like cable problems or operator error.

It feels to me like a cable tension issue. I can finesse it into place if I play with the lever.

I raced on the bike today, stayed in the big ring the whole time, and had no shifting issues. I love that bike!