vasuvius

The drive train on my bike is Ultegra 6600 with a 12-25 Ultegra 6600 cassette
Recently I replaced the chain with an Ultegra CN-6701 and it has been working fine for 500+ miles.

I just bought a new set of wheels and got a new cassette so that I could use the old wheel and cassette for the trainer.
I got an Ultegra CS-6700 - same spec as before : 12-25
The spacers are exactly the same and visually the space between the cogs look exactly the same as the old 6600 cassette.

But when I put the new wheel on bike, there are a couple shifting hitches.
The chain rings are 34-50
With the front on 34T, the rear does not like to stay on the 19T cog - it keeps trying to jump to the 21T cog occassionally
All other shifts work fine with the 34T front.

With the front on 50T, shifting from 25T to 12T is smooth and clean, but shifting from 12T to 13T requires 2 clicks. Then it shifts cleanly all the way up to 25T.

The only other difference between the old wheelset / cassette and the new one is that the new wheel is also 11 speed compatible and has a spacer for using 10sp cassettes. Could this be the problem? Maybe I don't need the spacer?

The wheelset is a Vuelta Corsa SLR (got it on sale from Nashbar last week for a little over 200 bucks)
These wheels are at least 400 grams lighter than the Shimano R500 that I had on the bike.

Any thoughts on what I could look at to fix this?

Thanks
V

copswithguns

Are the cassettes new? Only thing I can think of is a bent chain or some messed up teeth that are causing the skip. Not to be insulting but has the chain been cleaned and lubed recently? Also did you accidentally move a barrel adjuster?

bgrider

Try making some adjustments with the barrel adjuster. If you are worried about messing it up more than it is now - dont. Just keep track of exactly how many turns you make one way or the other and then you can go back to where you started. Turn it a half turn one way - chec how it shifts. Worse? go back where you started. Try the other direction. Worse again - go back . Try a quarter turn. etc. You should be able to figure out the effect of turning it each way and will most likely solve the problem.

Good Luck.

redlude97

cable tension and/or H/L limits are off. You can't expect when changing wheels for the cassette to fall in the exact alignment as the other cassette. Go through a full RD setup from the beginning starting with the high and low limit screws and then adjust the cable tension.

Homebrew01

When swapping wheels, often the limit screws are close enough and you just need a twist or 2 of the barrel adjuster.

However, the 2 different shifting problems you describe are opposites. Are you sure you described the 19-21 problem correctly ?

vasuvius

Yes. This is why I am very perplexed.

When I put the old wheel with the old cassette on the bike, the shifting is fine.

The chain was cleaned and lubed about 60 miles ago. The old cassette was removed and cleaned at the same time.
I checked markings and grooves on both cassettes and they match. The chain is pretty new. I didn't check for wear as I don't expect any. Will do that when I start tinkering again.

I can start with the RD setup from scratch for the new wheel/cassette but I need both wheels to work as I'm still riding outside as well when there is no snow on the roads.

The wheel spacing is the same on both wheels - 130mm.

This noreaster in NJ brought us 8" of snow yesterday so I''ll use the trainer for the next couple days with the old wheel.
I want to fix any possible issues with the new wheel before I ride outside. A couple weeks ago I had a flat at 6am when it was 26 degrees and standing in the snow on the side of the road in the dark and cold to change the tube was no fun. Don't want any mechanical issues when I ride out with the new wheel

Homebrew01

When I swap wheels, it's usually just 3/4 turn or so and it's good.

vasuvius

thanks. I'll try that

fstshrk

+1 on this. I have to do the same when I swap wheels.

rpenmanparker 

Of course the alignment of different wheels with the derailleur is different. What others said about small adjustments of the barrel adjuster. Seems to me the 11-speed capability of the new hub is the main culprit. You have to expect a difference in cog positioning with that kind of change.

The complex behavior, needing more tension at the small cog end and less tension at the large cog end, suggests to me an interaction between the H limit and the chain tension. First get your H limit precisely right, chain perfectly centered on the small cog. Couldn't hurt to do the L stop too. Then get your barrel adjustment right for the center of the cassette, chain perfect on the 5th or 6th cog, and you should be okay all up and down.

As for going back and forth between wheels, I bet you only use three, maybe four gears on the trainer. Once you are set for the road, I suspect only a small barrel adjustment would set up the few trainer gears you use. You shouldn't have to change the H/L setup every time you switch back and forth, because you aren't likely sweeping across the whole cassette. At least I know I don't. Anyway, that is reasonable to hope for.

Robert

coffeehaus

I recently went from 5600 to 5700. One thing that could cause an issue is that the chains have an inside and an outside. If I remember correctly, the plates with the Shimano go on the outside. The cassettes and chainrings are supposed to work with the new shapes. The shapes are definitely different. I adjust my derailleurs whenever I change a chain and recommend that, too.