Advice needed re XTR M951 Rear Mech

[Thorpie]

Advice needed! My 97 Explosif came with a XTR M951 rear mech. It is in good condition and I have replaced both jockey wheels as the originals were knackered. I have noticed today that the mech does not have a barrel adjuster. It does have a device which I think is a tension wheel(allows the cable to route to the mech vertically and around a small wheel, simular to a jockey wheel, before meeting the pinch bolt). The barrel adjuster is either missing or, what I think is a tension wheel, has replaced it. Can anyone advise me if what I have described is a tension wheel and is the barrel adjuster missing or is it not needed with a tension wheel :????????????????

Thanks in advance,

Trevor.

 

[one-eyed_jim]

Advice needed! My 97 Explosif came with a XTR M951 rear mech. It is in good condition and I have replaced both jockey wheels as the originals were knackered. I have noticed today that the mech does not have a barrel adjuster. It does have a device which I think is a tension wheel(allows the cable to route to the mech vertically and around a small wheel, simular to a jockey wheel, before meeting the pinch bolt). The barrel adjuster is either missing or, what I think is a tension wheel, has replaced it. Can anyone advise me if what I have described is a tension wheel and is the barrel adjuster missing or is it not needed with a tension wheel.

The barrel adjuster isn't needed, full stop. There's one on the shifter, and one is enough. This is XTR after all. It's a bit more of a faff to tweak the indexing while eyeballing the cassette, but that's what race mechanics are for, right?

The "tension wheel" is Shimano's take on the Avid Rollamajig. It makes the cable housing loop shorter and straighter, and should make shifting a teeny bit lighter. You can take it off easily if you don't like it.

You probably noticed that the RD-M952

a) has a barrel adjuster

and

b) dispenses with the Rollamajig

I don't know whether Shimano had legal problems with Avid, but obviously they didn't think the idea worth persevering with.

 

[Carsten]

the RD-M951 doesn't have a barrel adjuster

 

[Thorpie]

Cheers guys, this forum is a font of all knowledge!

I think the tension wheel looks kind of retro so I will leave it on. Thanks again,

Trevor.

 

[BG]

I'm using a Jagwire inline barrel adjuster LBS gave me one for free that was floating around in their workshop) on the cable stop on the seatstay of my bike that has this derailleur. Yes I know there is one on the shifter, but relying only on that adjuster just proved quite costly:

The barrel adjuster in my shifter (an XT M739 8 speed STI) is (sorry... was) made of aluminium and it threaded into the plastic body of the shifter with a thin steel shim (a helicoil?). after years of faithful service (using the adjuster on an M739 rear derailleur) I decided up upgrade to XTR and fitted an M951 rapid rise unit like you've got. So I used the adjuster on the shifter to adjust it, only to have the thin steel shim disintegrate and fall into the body of the shifter destroying all the internal ratchet mechanisms. Resulting in one dead shifter.

Not happy!

Got a new 8 speed shifter M748 from CRC, but it just isn't the same as the old unit.

I now use the cheep (free in my case) Jagwire inline unit to do my adjustments to save this from happening again - ugly solution, but once bitten as they say.