Bicycle Mechanics - One gear off 10 speed Ultegra cassette - Mavic ES's

I just swapped my 10 speed Ultegra cassette from the stock rear wheel that came with my bike (Shimano Ultegra WH-6600's) to a set of Mavic Ksyrium ES's. I followed all the directions on the park tool site for removal and attachment of a cassette like mine, even torqued the lockring down to the 40 Nm spec. After going for my first ride this morning on these wheels I noticed that the rear shifting is off. Looks like the rear derailleur thinks the second to largest cog is the final gear, and when I'm shifted into any of the three largest cogs the chain leaps down 1 gear. Is there a spacer or something I need to install for a 10 speed Ultegra cassette for Mavic ES's? I don't think that's necessary for this size cassette, but I could be wrong. Or is it just a matter of re-adjusting my rear derailleur by tightening the barel adjuster or messing with the limit screws? I'd hate to mess with the screws if I don't have to - the derailleur was shifting smooth as silk on this same cassette when it was attached to the Shimano wheel, and there was no spacer for that cassette on that wheel. My brifters are 10 speed Shimano Ultegras too just so you know. Any help on the easiest way for me to fix this would be greatly appreciated! :)

Did you use the Mavic spacer and the Shimano 10 speed spacer? You need to use both.

Did you use the Mavic spacer and the Shimano 10 speed spacer? You need to use both.

Are either of these spacers that go between the cassette and the hub? If so there were no spacers there when the cassette was mounted to my Shimano wheels, and no Mavic spacer came with the ES's, only bags, tools, magnet and instructions.

Are either of these spacers that go between the cassette and the hub? If so there were no spacers there when the cassette was mounted to my Shimano wheels, and no Mavic spacer came with the ES's, only bags, tools, magnet and instructions.

You should have got the spacer with the wheelset. Call Mavic customer service (800-GOMAVIC) and they'll very likely just send you one. Or, your local Mavic dealer may very well have one for you. Normally, when you get a Mavic M10 wheel (i.e. Shimano/SRAM compatible), it should have the spacer right on the freehub, held on by a black o-ring.

yes they go between the cassette and the hub body. I guess call up mavic for a spacer and an lbs should have a 10speed spacer somewhere

Aren't your cogs loose? Usually. the lock ring bottoms out before the cassette is tight if the spacer isn't present.

I took the cassette off again and now I notice the Shimano spacer, however there was never a Mavic spacer included with these wheels. Guess I'll call Mavic - the shops around town I called didn't have a Mavic spacer they could let go. Thanks for all the help!

Well, after doing lots more research and talking to a couple of bike shops in town, I found out that I in fact have the Mavic supplied spacer that came with the ES wheels. My Shimano 10 speed 12-25 cassette did not have the spacer that normally comes with it installed when it was mounted to my older Ultegra WH-6600 wheels (from what I can gather, the hubs on these wheels don't require the Shimano spacer). So, when I went to swap the cassette over to my Mavic ES wheels, the only spacer I ever had was the Mavic one.

The thing is, when I have just the Mavic spacer installed, I get no free play from the cassette. There's not a bit of movement along the axel and seems tight as could be with the lockring torqued to 40 Nm. I was under the impression that without the Shimano cassette spacer installed in addition to the Mavic one the cassette would not be fitted tight enough to the freehub. Once I adjusted the limit screws on my derailleurs the shifting is working properly again, even though I only have the Mavic spacer installed (though I'm still getting a bit of chain rub on my FR).

This thread was really helpful too:
http://bikeforums.net/showthread.php?t=385144&highlight=spacer+mavic

My question is, considering my situation described above, do I really need the Shimano spacer installed in addition to the Mavic spacer with a Kysrium ES wheel hub and Shimano 10 speed 12-25 cassette?

My question is, considering my situation described above, do I really need the Shimano spacer installed in addition to the Mavic spacer with a Kysrium ES wheel hub and Shimano 10 speed 12-25 cassette?

Yes. Your Shimano wheel uses a 10 speed specific hub which does not require the 10 speed spacer.

Yes. Your Shimano wheel uses a 10 speed specific hub which does not require the 10 speed spacer.

Even though I get no free movement of the cassette along the wheel axle with just the Mavic spacer installed? Is there still some chance of damage I'm not aware of without the Shimano one installed? Thanks for the info in advance!

Well if your lockring tightens down just fine w/o the shimano spacer, it really doesn't matter. You'll just adjust the limits and shifting as is. But if you do a wheel swap, you'll have to readjust the limits and shifting because the whole cassette is off by 1mm.