Proper chain length makes a big difference with shifting. It’s not intuitive — that’s for sure — but lots of front shifting problems are solved by setting chain length (and tension) correctly.
Do a simple check on your bike by shifting the chain to the big chainring and the biggest cassette cog; then, push on the end of the derailleur cage (pushing forward) to see how much it will move forward. If it moves just a little, then you’re good. If it moves a lot, then you’ve got too much chain. If it’s really tight on the chain, you probably don’t have enough.
When changing the chain (or setting up a new bike) follow this video technique:
The process is simple and straightforward . . . and it’s basically the same for Road Bikes (as shown in the video), Mountain Bikes and Cyclocross bikes. (See note below about suspension.)
Chain Length Specifics:
Here are a few key points for setting chain length:
1. Minimize the chain — less chain means less mass (less moving mass) and less chain to get caught in or around things. On the other hand, make sure there is enough chain so that things don’t bind up.
2. Assure proper tension — too much chain can cause things to get sloppy in the small ring and smaller cassette cogs. Rear derailleurs are made to take up chain when moving from larger to smaller cogs, and from bigger to smaller chainrings. If there is too much chain, the rear derailleur is not able to take up sufficient slack; and, at some point, there will be no tension on the chain — allowing it to “droop” — with undesirable side effects.
3. Proper chain length gives proper chain tension when cross chaining (big ring to big cassette cog) so that the chain stays on the gear teeth even when the alignment (caused by cross chaining) is not correct.
A chain that’s too long (loose) may cause dropped chains and/or inconsistent shifting — front and back shifting.
A chain that’s too short (tight) can cause even bigger problems. Hopefully the bike just won’t shift into the largest cog or to the big ring … BUT, things can go really bad … if it does shift and rips the derailleur off, damages the chain or bends gear teeth.
Too long – can cause annoyance. Too short – can be very expensive. Like Goldilocks, we want it “Just Right“!
1. If you use a master link (power link, extra link, snap link — or whatever) make sure you break the chain at a point that allows the extra link to be inserted properly.
2. For bikes with rear suspension, the chain length measurement should include (or at least compensate for) “Chain Growth” that occurs with suspension compression. Basically, that means the chain needs to be a little longer to allow motion of the suspension because the back wheel usually moves away from the crank as the suspension is compressed. Measure with the suspension compressed. (Typically, a couple links will do the job.)
– For more info, check out this page from Park Tool.
I love the featured image at the top of this post. At first glance it looks awesome, but look closer . . . the chain is too long by about 6 links. Unfortunately, this is very common — even on brand new bikes in the shop.