6 speed rear mechs

[Murk]

I had a catastrophic failure of my rear mech on the way home last night. Not sure exactly what
happened but it ended up embedded in the back wheel. Problem is, it was part of a 15 year old
Shimano 105 gear set - hence it's a 6-speed setup with indexed down-tube levers. Does anyone know
where I can get a suitable 6-speed Shimano-compatible rear mech? I'm assuming that the current
range, such as the Sora, would not be compatible, or am I wrong?

I'd also like to say a thank you to the cyclist who stopped to offer assistance on a quiet, unlit,
country road between Edinburgh and Falkirk. Without her light I wouldn't have known what had
happened at all. Hope she got home before her batteries gave out.

Mark

 

[Andy Welch]

On 23-Jan-2003, [email protected] (Murk) wrote:

> Problem is, it was part of a 15 year old Shimano 105 gear set - hence it's a 6-speed setup with
> indexed down-tube levers. Does anyone know where I can get a suitable 6-speed Shimano-compatible
> rear mech? I'm assuming that the current range, such as the Sora, would not be compatible, or am
> I wrong?

I'd wait for confirmation from others before plonking down real cash but I think you are wrong. I
don't think there is much (if any) functional difference between an older 6 speed rear mech and a
newer 9 speed one. That is the amount that it moves for a given cable pull is the same. The
difference is in the shifters. A 6 speed shifter will pull a larger amount of cable for each click
than a 9 speed but the mech is the same. I guess it's possible that a 9 speed mech has a greater
range of movement than a 6 speed (since the block is bigger) but you restrict the motion with the
stop screws anyway.

Cheers,

Andy

 

[Pete Biggs]

Murk wrote:
> Problem is, it was part of a 15 year old Shimano 105 gear set - hence it's a 6-speed setup with
> indexed down-tube levers. Does anyone know where I can get a suitable 6-speed Shimano-compatible
> rear mech? I'm assuming that the current range, such as the Sora, would not be compatible, or am
> I wrong?

I think you might be wrong. Not tried it myself (I've also got 105 6sp gears on my old tourer,
incidentally now indexing with a Campag 8sp cassette!), but I have read about new 8 and 9sp mechs
"working fine" with 6 & 7sp freewheels, eg: ..............

from http://www.sheldonbrown.com/harris/derailers.html : "Rear derailers often are referred to as
"7-speed", "8-speed" or "9-speed." This is not as important a distinction as it might appear.
Current model derailers are pretty much interchangeable within brands. A "7-speed" or "8-speed"
designation generall just indicates that the derailer is an older design, or a cheaper model.
They'll all work with all 3 systems, though the models marked "9-speed" will generally be slightly
better (whatever cluster you use.)"

I reckon it's well worth a try with a cheap modern mech. Could always save it for future or sell if
no joy, then track down a second-hand old mech, or maybe a 6 or 7sp one from
http://www.sjscycles.com/store/vIndex.htm (I don't know if these are suitable/good).

~PB

 

[Rudge]

If you do try a 9 speed rear deraileur and it does not shift correctly you could try clamping the
cable inner on the other side of the clamping bolt. It apparently changes the amount the deraileur
arm moves for each click of the STI levers. I have seen this suggestion previously on a cycling
newsgroups.

> Does anyone know where I can get a suitable 6-speed Shimano-compatible rear mech? I'm assuming
> that the current range, such as the Sora, would not be compatible, or am I wrong?