Chorus compatibility

[merckx]

Kind of an odd-ball question. Does anyone know if this 1991 Chorus 7spd rear derailleur will index with 9v Ergo shifters and 9v cassette? Maybe Peter?

[oliver1850]

I have one here I could put on a C9 bike and try it. Early or late 9 speed levers?

[Columbus SLX]

Not likely. It's designed for 126 rear spacing (6 & 7 speed) so I believe you'll be hard pressed to get the extra 4mm travel needed for 9 speed.

That, BTW, is an awesome derailleur. It has two parallelogram angle settings (A & B) which allow the thing better chain gap depending on the range of your freewheel.

[merckx]

I have late 9 spd mechs and ergos. Interesting thought about the length of travel. I was just considering the actuation ratio.

[merckx]

I have one here I could put on a C9 bike and try it. Early or late 9 speed levers?

Could you?

[Columbus SLX]

I have late 9 spd mechs and ergos. Interesting thought about the length of travel. I was just considering the actuation ratio.

Anything pre-10 speed uses the same pull ratio (they only changed it for 10 speed around 2000 or so). Good luck and report results - would love to know if it has enough travel to work.

[cnighbor1]

For RD compatibility I have filed the flat were limit screw hit to allow more travel

[oldpotatoe]

Kind of an odd-ball question. Does anyone know if this 1991 Chorus 7spd rear derailleur will index with 9v Ergo shifters and 9v cassette? Maybe Peter?

No spring in the top bolt. First gen attempt at indexing, slant parallogram RD...not floating top pulley either..it 'may' work. Works much better with big barrel friction shifters.

As for pre/post 1999..that doesn't really matter. As for 126mm spacing..yes, 126-130 is 4mm but 7s freewheels weren't 4mm narrower than a 9s cogset.

[oliver1850]

I put one on my Atlanta with Daytona 9 levers for my evening ride. I think I have a 13-23 cassette on it, and left the Chorus in the A position. With the cable clamped in the intended position, there was not nearly enough derailleur travel. With it clamped on the other side of the bolt, it was much better, but couldn't be adjusted to totally eliminate 2 cog shifts. I rode it 65 miles and I could get all the gears, but sometimes had to shift 2 clicks in one direction and 1 in the other to get the gear I wanted. A floating top pulley might help. I had a similar situation with a 2nd gen. Chorus RD on an 8 speed bike. I ended up drilling through the clamp bolt so the cable could pass through it. After that, it shifted perfectly.

I think the combination could be made to work pretty well. It may require a floating top pulley, a drilled cable clamp bolt, or some messing with the cassette spacer widths.

[merckx]

I put one on my Atlanta with Daytona 9 levers for my evening ride. I think I have a 13-23 cassette on it, and left the Chorus in the A position. With the cable clamped in the intended position, there was not nearly enough derailleur travel. With it clamped on the other side of the bolt, it was much better, but couldn't be adjusted to totally eliminate 2 cog shifts. I rode it 65 miles and I could get all the gears, but sometimes had to shift 2 clicks in one direction and 1 in the other to get the gear I wanted. A floating top pulley might help. I had a similar situation with a 2nd gen. Chorus RD on an 8 speed bike. I ended up drilling through the clamp bolt so the cable could pass through it. After that, it shifted perfectly.

I think the combination could be made to work pretty well. It may require a floating top pulley, a drilled cable clamp bolt, or some messing with the cassette spacer widths.

Boy, that rear mech sure looks handsome hanging off that Serotta. I was hopeful that the combination would shift with aplomb. I guess the collision of new(ish) and old world technology doesn't always bring the results that we desire, at least in this case. Thank you for taking the time to educate me on this project. You are a good man.

[Hindmost]

Kind of an odd-ball question. Does anyone know if this 1991 Chorus 7spd rear derailleur will index with 9v Ergo shifters and 9v cassette? Maybe Peter?

Good question. Months ago, I was going to try the same derailer with 10v and decided not to. So consensus is it won't work.