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My Cervelo P2 has Dura Ace front/rear derailleurs, the ear wheel has Shimano 6600 10 speed cassette, it runs well.

Now I want to use a pair of old Corima carbon wheels. The rear wheel, a 4-spoke, has Shimano CS-HG70-9 9 speed cassette.

I did two experiments:

  1. I put on the 9 speed carbon wheel directly, it seems to run well, chain can be shifted from smallest ring to largest without skipping a ring. 10 speed shifter misses 1 gear of course: shifting from the smallest ring to the largest, the first shift has no effect.

  2. I replaced the cassette of 9 speed carbon wheel with Shimano 6600 10 speed cassette. I did some search, all say it's fine to put 10 speed cassette onto 9 speed hub. Put the wheel back on bike, the chain can only go from the smallest ring to second largest ring. 10 speed shifter misses 1 gear still: shifting from the smallest ring to the largest, the first shift has no effect.

Two questions:

Q1: can I just use the 9 speed carbon wheel on my 10 speed bike? will it cause damage to the chain set? I think the 10 speed chain is thinner, no?

Q2: how come I'm missing 1 speed after replacing the 9 speed carbon wheel with a 10 speed cassette? do i need to adjust the rear derailleur?

update: I figured out the cause: when I moved the 10 speed cassette I left a 1mm spacer on the hub, as described here: http://www.bikeforums.net/bicycle-mechanics/781234-shimano-10-speed-cassette-washer-shim.html because of missing this 1mm spacer, the whole cassette is 1mm closer to the spokes, 1mm further from derailleur. as advised, I adjusted the rear derailleur and managed to get shifting back, but by putting that 1mm spacer back on, the derailleur is off again... though I wasted some time due to this rookie mistake, I actually learned a lot. thanks for all who helped

  • Are you going to be swapping wheels regularly? If so, find an adjustment that is good-enough for both and leave it there. If you miss one gear at the top or bottom, too bad. If its a permanent change of wheel, then get it right for how you want to ride it. – Criggie Apr 20 '16 at 3:30
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You probably need to adjust the 'top stop' screw on the rear mech, and also tighten the rear gear cable. The rear mech has two small screws. One of these adjusts how far up/inward the mech will move and the other screw adjusts how far down/outward it will move. They are used to prevent the chain dropping off the top and bottom of the cassette. Work out which one needs adjusted (trial and error should be ok) until the mech has the right range of movement to go from the biggest sprocket to the smallest sprocket (but no more).

Also, you might need to adjust the cable tension, esp if the mech is not moving from the smallest sprocket when you push the shifter. You can do this normally by simply adjusting the screw mechanism where the cable attaches to the rear mech, and screwing it outward, so as to tighten the cable. Again trial and error with this should work. Putting the bike on a work stand where the rear wheel is suspended off the floor, and you can spin the pedals and wheels while shifting the gears makes this job much easier. Dont be scared to experiment a bit to figure out how things work.

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