OK, what you are asking (I think) is if you can install a new 10 speed cogset onto your rented race wheels that are 9 speed compatible. If they are Shimano brand cogsets, the answer is: Yes.

Shimano 9 speed and 10 speed cogsets fit onto the same the freehub body (the round cylinder on the hub you slide the cogs onto). Be mindful of the lockrings as they are different and always be careful threading them onto the freehub body.

If your current drivetrain is 10 speed, adjusted to shift a 10 speed pattern, and is working OK then you need not make any derailleur/shifter adjustments. Simply install a 10-speed cogset onto your rental wheels, be sure everything is correctly installed on the wheel, put the wheels on the bike double checking your quick release skewers and then test the shifting.

I think you'll be just fine. Best of luck.

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Tom Demerly
The Tri Shop.com

I'm sure someone will correct me if I am wrong, but use your 10sp cassette. You will have to use a 1mm spacer on the freehub body (slide it on before the cassette). All of my hubs are 9sp and I run 10 on them.

yup. Is that spacer 1mm? I can't remember. I seem to have some recollection of it being some weird size.

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Tom Demerly
The Tri Shop.com

Tom -

Thanks for the quick reply.

Drivetrain is a 10spd shimano, and rental wheel hub is 9 speed shimano. So, if I understand you correctly, I can simply take my 10 speed cassette, and swap it over to the rental wheel.

Phew...big relief. One of those last minute IMAZ worries off the last.

Thanks!

The spacer is the same as a bottom bracket spacer. The size?? I don't know but it must be 1mm or less.

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Yes, take the 10 sp cassette and install it on your rentals, but make sure you have that spacer behind the cassette.