28 sprockets to 32 - how many extra links?

gingermagician

I'm switching the set up on my girlfriend's Genesis Equilibrium to an 11-32 on the back (compact chainrings, 105 5700).

I have the medium cage derailleur, cassette and a new KMC chain ready to go, but was hoping someone might know how many additional full links I'll need in the chain? Any info would be appreciated.

drlodge

Depends on the chain length now. With a compact and 11-32 you'll have no room for error. What's the rear derailleur position with the chain on small-small and big-big?

StillGoing

GingerMagician wrote:

I'm switching the set up on my girlfriend's Genesis Equilibrium to an 11-32 on the back (compact chainrings, 105 5700).

I have the medium cage derailleur, cassette and a new KMC chain ready to go, but was hoping someone might know how many additional full links I'll need in the chain? Any info would be appreciated.

For a quick and easy method, jut wrap the chain around big/big missing out the rear derailleur, add 2 links plus the split link and fit.

gingermagician

drlodge wrote:

Depends on the chain length now. With a compact and 11-32 you'll have no room for error. What's the rear derailleur position with the chain on small-small and big-big?

Sorry, slightly confused - why would I have 'no room for error' if I'm fitting a new chain (and therefore shortening it)?

drlodge

GingerMagician wrote:

drlodge wrote:

Depends on the chain length now. With a compact and 11-32 you'll have no room for error. What's the rear derailleur position with the chain on small-small and big-big?

Sorry, slightly confused - why would I have 'no room for error' if I'm fitting a new chain (and therefore shortening it)?

With a tooth difference of (50-34)+(32-11)=37, the rear derailleur will be at the limit of the amount of chain slack it can take up. Therefore the chain needs to be a specific length - not one link shorter or longer than the "correct" length. Too short and the rear derailleur will get yanked out of its mount and god knows what else when in big-big. Too long and the chain will still be slack when in small-small which could cause you similar problems.

Suggest you try the new chain for length and check both in big-big and small-small to see what the correct length is, any advice offered here has some guess work involved although philthy3 offers sound advice as a starting point.

gingermagician

Ok, sounds like a reasonable plan. Thanks for the guidance.

eaglejackson

Park Tool has a detailed article on determining proper chain length, including a formula that you might find useful. http://www.parktool.com/blog/repair-help/chain-length-sizing

venster

I went from 28->32T on my Ultegra and didn't need to change the chain length - may be I was just lucky, but I don't ride 50-32 rings....

cycleclinic

1" of extra chain 1 outer link and one inner assuming the chain is of corect length to begin with. Every tooth added requires ~1/4" extra chain

matt-h

venster wrote:

I went from 28->32T on my Ultegra and didn't need to change the chain length - may be I was just lucky, but I don't ride 50-32 rings....

Exactly this.
No need to change the length unless you plan on being silly