Originally Posted by RubeRad

Evan, I didn't see this possibility mentioned in the above posts; you say that "the pedals always just stop and won't go forward" -- it sounds to me like it might be possible that your chain is too short to reach all the way around the big front chainring and the big rear cog. As noted above, it is generally considered bad practice to use such a "crosschain" gear combination.

I have the same thing on my bike; I moved all the components (including chain, gears etc) from one bike to a larger frame, and now if I try to shift into the large-large combination it doesn't quite make it, and everything is totally frozen until I release the rear quick-release so the wheel can slide forward and provide slack to shift the chain away from the big/big combination. For me it's not a problem because (a) I don't ride cross-chained in general and (b) I hardly ever use the big front chainring anyways. The only time this ever happens to me is after I clean/tune my bike and I'm riding circles in the cul-de-sac to work it through all the gears, and forget to avoid the big/big combo.

Sheldon Brown says:


And I can't find it right now, but I seem to remember SB writing something about common practice for bike shop mechanics to install chains a little too short, because it is not expected for riders to shift into the big/big combination, but if they do...watch out!

Crosschaining is certainly suboptimal for the durability of your drivetrain components, so as advised above, you should probably avoid it. But if it's something you really want to do -- or something you expect to occasionally do accidentally -- you should make sure your chain is long enough for it.