9spd Chainset and 7Spd Freewheel ? HELP

Quoted post said:

Originally posted by clarkythe1st
I have stripped an old GT frame and need some help ! I have two sets of wheels both with Shimano 7sp Freewheels. Im about to buy a new chainset and was wondering if I can use a 9speed chainset with a 7 speed Freewheel ? The front and rear mech are still 7 speed. Any help appreciated..

My experience has been with 8 speed but this is how things have worked for me.

A 9 speed chain with a 7/8 speed crankset and front derailleur will not shift as well as it is supposed to. The rear will shift just fine. If you go to a 9 speed crank and front derailleur and leave the back as a 7/8 speed, everything will work much better.

Unless you actually want to upgrade the crank and derailleur, I'd use a SRAM PC-68 chain on it. My Shimano chains have shifted quicker, but the SRAM chains have tolerated marginal chain lines and other anomalies better.

The "official" answer is likely no, but there have been weirder combinations that (anecdotally) have worked. The rings/cogs are somewhat thinner on most of the 9 speed stuff you will deal with and the chains allow for smaller widths in them. I have witnessed this translating into "sticky" shifting or crappy shifting altogether. You can easily find 7/8 speed chains out there at any LBS or any of the discount web places. They are cheaper as well, typically. If you are sticking with the 7 speed derailluers and such there is no need to buy a 9 speed chain, in my experience. Good luck.

K.

Quoted post said:

Originally posted by ireman_1
The "official" answer is likely no, but there have been weirder combinations that (anecdotally) have worked. The rings/cogs are somewhat thinner on most of the 9 speed stuff you will deal with and the chains allow for smaller widths in them. I have witnessed this translating into "sticky" shifting or crappy shifting altogether. You can easily find 7/8 speed chains out there at any LBS or any of the discount web places. They are cheaper as well, typically. If you are sticking with the 7 speed derailluers and such there is no need to buy a 9 speed chain, in my experience. Good luck.

K.

Whoops.. Being in the UK I've got my terminology wrong !! I meant buy a 9 speed Crankset and use it with a 7spd freewheel at the rear. I'm understanding you are right though that the 9spd crank set will use a narrow chain which wont be too happy on the standard width 7spd rear set up. Especially when down shifting under pressure I guess. Back to the drawing board..

Quoted post said:

Originally posted by clarkythe1st
I meant buy a 9 speed Crankset and use it with a 7spd freewheel at the rear. I'm understanding you are right though that the 9spd crank set will use a narrow chain which wont be too happy on the standard width 7spd rear set up. Especially when down shifting under pressure I guess. Back to the drawing board..

No, I think you got it wrong. At the front you shift by putting pressure on the outside of the chain, so a thinner (9spd) chain will perhaps not work as well with a wider (7spd) front derailleur). At the rear shifting is done by moving the chain from its centre line, you have the pulley wheels that "should" be able to keep a thinner chain reasonably centered even in a wider 7spd rear derailleur. As long as the shifter matches the frewheel/cassette there is a good chance that it will work.

Quoted post said:

Originally posted by dabac
No, I think you got it wrong. At the front you shift by putting pressure on the outside of the chain, so a thinner (9spd) chain will perhaps not work as well with a wider (7spd) front derailleur). At the rear shifting is done by moving the chain from its centre line, you have the pulley wheels that "should" be able to keep a thinner chain reasonably centered even in a wider 7spd rear derailleur. As long as the shifter matches the frewheel/cassette there is a good chance that it will work.

Correcto, a 9 speed chain works fine on a 7 speed rear. sometimes even ok on the front even with a 7 or 8 speed FD, depending on the shifters being used.