I've had my S-40 about 18 months and the shifting has always seemed a little off. Having a factory built bike I soon discovered the Sram cassette had 2-3 mm of wobble. Replaced with a XT 10 speed cassette and upgraded the Sram chain to a one piece KMC 10 speed chain. Better shifting but still some noise and drag. I accepted the situation until I read an article in Velo News about how 11 speed chains will work on 10 speed systems and add some needed tolerance back into the system. It was time to replace my current 10 speed chain so I ordered a Sram PC1130 120 link chain for about $22. Great, the chain came in my length, 120 links, so no splicing or two master links, and priced right at Worldwide Cycles. I've only used the chain for 100 miles, but have to say most of the chain noise and any shifting problems are gone, I didn't adjust either front or rear derail before putting on the 11 speed chain and it works better than the 10 speed chain. I'll have to wait to see if the 11 speed will last as many miles as a 10 speed chain, but for now it seems a better choice. I ordered two more 11speed chains today just in case.