Compact crank conversion

jwb_onz said:

I am about to convert my Ultegra 53/39 (10 speed) crankset to a Shimano 50/34 compact. I'm expecting to have to lower the front derailleur and will I need to shorten the chain?

Any experience out there will be appreciated

Probably won't have to shorten the chain. Loosing three teeth on your chainring doesn't correspond to 3 less spaces in your chain.

jwb_onz said:

I am about to convert my Ultegra 53/39 (10 speed) crankset to a Shimano 50/34 compact. I'm expecting to have to lower the front derailleur and will I need to shorten the chain?

Any experience out there will be appreciated

shift to the small-small and if there is some sagging or slack in the chain then you need to shorten.

hd reynolds said:

shift to the small-small and if there is some sagging or slack in the chain then you need to shorten.

(Please someone correct me if I am wrong)

I adjust the chain length by big front big back with as little slack as possible. If there are any reasons why I should vary this method please post?

Edit:- I guess the thoery is with this chain length, regardless of stuff ups with cross over, the drive train can not be damaged due to force from a chain which is to short.

Al R 1955 said:

(Please someone correct me if I am wrong)

I adjust the chain length by big front big back with as little slack as possible. If there are any reasons why I should vary this method please post?

Edit:- I guess the thoery is with this chain length, regardless of stuff ups with cross over, the drive train can not be damaged due to force from a chain which is to short.

This is a no brainer...normally I would check both big/big and small/small for chain length. Since you're switching to a compact (using the same chain from your previous normal chainset), the small/small is the one to check for chain length and you can be sure it will clear the big/big.

thanks for the help.

the Shimano technical doc I've just found has you set up the derailleur cogs in a vertical line when the chain is on the 'big - big' combination. I'll check for slackness on the smaller combinations.

cheers

hd reynolds said:

shift to the small-small and if there is some sagging or slack in the chain then you need to shorten.

I understand (now) after reading your other posts on this thread that you were refering directly to the question & not as a general method of chain adjustment. My appoligies.

I still think that an inexperianced person may look only at this response from you & take out more links than necessary.

Did you also change the rear cassette? My friend just made the crank switch you describe but he also changed his 12-23 to an 11-23. He definitely had to shorten chain a tad.

I have always gone the small sprocket front and small sprocket rear to check chain length. I then try to get 1 to 2 cm between the chain and the top cog on the derailleur. This usually gives you plenty of chain for the big front to big rear combination.

park said:

Did you also change the rear cassette? My friend just made the crank switch you describe but he also changed his 12-23 to an 11-23. He definitely had to shorten chain a tad.

I've alreadly got 11-23. And will stick with that. Thanks everyone for your advice. I'm hoping I don't have to do anything with the chain length as I hear the Shimano 10 speed chain can be a bit tricky to join.

jwb_onz said:

I am about to convert my Ultegra 53/39 (10 speed) crankset to a Shimano 50/34 compact. I'm expecting to have to lower the front derailleur and will I need to shorten the chain?

Any experience out there will be appreciated

There is a specific setup for optimal shifting. On Campy with a triple you use big to big and a normal double bigCR to littlecog and have the idler wheels perfectly vertical. Not sure with Shimano but, I am sure there is an optimal setup. As far as the FD you need to set it correctly for the large CR with the suggested spacing for the best shifting. Normally with the compact double the cage length is longer than a normal double. You may need to play around with the FD to get it to work. Why would one put a compact double on an 12-23 or an 11-23???? Why not just go to a 12-25 (or 27)?