TCR Rider

I'm considering switching from a standard crank (52-36) to a compact (50-32) on one of my bikes. I'm assuming that a slightly shorter chain would be in order. Am I correct? Also Would the front derailleur have to be adjusted?
Thanks

Retro Grouch 

Since you are changing cranksets, I'd resize the chain just on general principles. It doesn't take very much time or effort to do. I use the big/big method. Run the chain around the biggest front chainring and the biggest rear cog bypassing the rear derailleur. Figure out the shortest place that you could connect the chain. Now add 2 links (1 inch) onto that. That s the shortest chain that you can safely use with that gear combination. If it was my bike, I'd start a brand new chain with the new chain rings.

Going from a 52 to a 50 isn't much of a big ring change. Your front derailleur might work just fine as it is. If it was my bike, however, I'd lower the derailleur a skosh to match the new smaller ring.

redlude97

Are you actually running 50/32 or 50/34? Depends how your chain was originally sized, I prefer using the small/small sizing method so as long as it will run the 34x11 combo without slack I'd leave it

HillRider

Going from a 52T to a 50T will, assuming the chain is now sized correctly, allow you to shorten the chain by a one "half-link" or 1/2" as you only change it by 1/2 of the tooth count difference. Since chains have to be shortened or lengthened in full-link (1") increments, you can't change it.

TCR Rider

That sounds right to me. A slightly shorter chain should make the shifting crisper and a new chain is definetly in order.
That's what I was thinking as far as the front derailleur is concerned.
Thanks

redlude97

A shorter chain makes no difference in the crispness of the shifting

TCR Rider

My bad - it would actually be a 50/34. Initially I'll be running a 12/28 cassette since that is what is on the bike now. I rarely use the 12 now so if I find I need the 11 once the compact crank is on I'll consider going to the 11/28. I do like having the extra gear in the middle of the cassette but that's another story.
I'll go with the chain at the current length and see how it works out. That's actually what I was hoping to find out. Easier to leave it alone.

TCR Rider

I find that surprising. I would think that if there is too much slack in the chain it would tend to jump around and skip over the teeth of the gears.

speedy25

If there is too much slack, the upper jockey wheel rubs the chain. Yes I have seen this out in the real world!

-SP

redlude97

the RD takes in all the extra slack unless the chain is too long, but a longer chain within spec never has slack

HillRider

This can only happen if your derailleur "wrap" capacity is marginal and you try to ride in small-small.

TCR Rider

That is a plausible explanation. The difference in length is still within the specs for both cranks. Good to know makes the swap that much easier.