Anyone have experience running 10 spd chain with 9 spd cassette? Specifically, I have a 2x9 drivetrain, with a XX crank up front, and an XTR rear 9 spd cassette, X-0 9 spd derailleur.

On my road bike, I ran a 10 spd chain w/ 9spd cassette for a while with no issues.. but at my shop, they are saying I should not do that on a MTB. The Sram 991 chain is 300g!! That's 50g down the tubes over a 10spd chain.

Many people (myself included) run a 10 spd chain with 9 spd XTR rear cassettes. I've found the KMC X10SL chain to be the pick of the bunch. It outlasts 9spd XTR and SRAM 991 chains by a fair margin, is lighter, and the narrower chain allows you to tune the front derailleur for tighter shifting without worrying about chain rub. There is no discernible difference in shifting quality.

Super, that's what I figured! The guys at my LBS are very good - but when it comes to doing anything innovative, or not recommended, they have no experience. They were shocked that I used a 10spd chain on a 9spd road bike setup... as if I was putting diesel in a gas engine or something. I run the X10sl on my road bike, so I picked up another one of those on Ebay last night. Can't go wrong for $44.

Thanks

as above - using KMC X10SL on XTR and Sram X0 9 speed cassettes with no problems whatsoever. search for post on here and you will find people using 11 speed on 9 speed cassetters with no issues; there is a big jump in price from 10 to 11 sp chain.

and don't think narrower chains are weaker or wear quicker as they don't - the wear would be on the link indent - roller interface which is same regardles of chain width.

i use also x10sl on 9sp. works great!!!

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Happy Trails !!!
MTB / Giant Xtc '05 / 8.7Kg
ROAD / La Perla Negra - FM015 / 7.0Kg

Works fine - my wife and I have both run 10 sp chains on our 1x9 cross bikes and the shifting was perfect.