Originally posted by brad
I traded some thoughts with Mark L. on this forum regarding chain wear a few weeks ago.
Chain wear on tandems (and most bikes) is a wild card; some teams tear through chains in 1,500 mi whereas others can go for more than 3,000 mi without needing a replacement. Interestingly, it's the folks who spend more time in the middle and granny rings and/or who don't routinely clean and lube their drive train that see the shortest chain life.
Therefore, it's a prudent move to routinely check chain wear on your tandem's drive and sync chains instead of waiting until you experience balky shifting to replace the chains. After all, chains are a lot cheaper to replace than cassettes and chainrings.
... which chain has the most stress? The timing chain or the drive chain?
Drive chain, by several orders of magnitude:
- The sync chain only transmits power from the Captain to the Stoker using a 1:1 ratio with loads distributed over a pair of matched chain rings with 34 - 42t in a continuous, straight line.
- The drive chain transmits the Captain's plus the Stoker's power (2x) using gear ratios ranging from .8:1 through 5:1 with loads distributed over cogs with far fewer teeth than the timing rings, e.g., 11-12-13-14-15...34t. Add to that, the constant changes that the chain line moves through -- including left-to-right (little/little) and right-to-left (big/big) cross-over conditions -- and the side loads that the chain plates and rivets must deal with from both the front and rear derailleurs.
In regard to the latter -- derailleur shifting -- this is still a violent, "brute-force" type of gear shifting that no one would tolerate in any other form of vehicle transmission. To Shimano's credit, they pioneered the IG/HG chain and cog interface using ramps, pins and shaped chain sideplates that made indexed shifting feasible for the masses and that allows shifting under loads which is nearly a regular occurance for off-road riding. Does this make Shimano chains "better" than the rest? Perhaps, but not necessarily. The biggest factor in chain performance is proper maintenance and cleaning and this is where Shimano chains really "shine" -- if you will -- in comparison to the other chains on the market. Assuming you have one bike with a reasonably clean and properly lubricated Shimano Ultegra HG chain and another with a SRAM PC-89R chain, both will perform about the same. Now, let 1,000 mi of grime collect on both chains and you'll find the Shimano chain shifts a bit better than the SRAM model. Clean and lube both chains and parity returns. Just something to keep in mind. Me, I keep my chains pretty clean. I've got DuraAce HGs, Ultegra HGs, SRAM PC-59s, 69s, 89Rs, 91s and Campy C9s and they all work pretty well; although Campy's are the most noisy and least durable of the bunch. How do I decide which chain to buy? I buy what's on sale -- after all, they're chains and the only thing that wears out faster on a bicycle are its tires.
Final Note: For anyone who would like to use Shimano's chains but isn't a fan of the one-time-use pins, you can puchase an excellent, re-useable link from Licktons called the "Superlink": http://www.lickbike.com/i0338150.htm
These things are durable, even stronger than the chain itself and while I've busted one of the orignial SACHs PowerLinks (none of the newer ones), I'd be surprised if one of the SuperLinks has ever failed.