rear derailleur problem

[Tom]

XTR "rapid-rise" rear derailleur:

Shifts up no problem (largest cog to smallest) but won't shift down properly. It's like the derailleur is stuck, it will shift if I push on the derailleur body with my hand. When I shift by pulling the cable, it moves fine in both directions. Any suggestions?

[tacklebox]

Dry,dirty cable housing.

[schoenrock]

does it move freely in your hand or can you feel a bind?

[M_Dub]

get new cable and housing, wd40 and triflow your shifter internals and lube all your derailluer joints.
if it doesnt work then...something is seriously wrong

[stillgoing]

Any chance the spring is worn out and weak? I'd imagine the spring has to work a little harder on a rapid rise as compared to a traditional shifter.

And, of course, as others have suggested - cable and housing, but I imagine you've checked that.

[M_Dub]

Originally Posted by stillgoing

Any chance the spring is worn out and weak? I'd imagine the spring has to work a little harder on a rapid rise as compared to a traditional shifter.

why?
its releasing and pulling just like any other derailluer
just backward

[peachy-B]

Originally Posted by derwood

Dry,dirty cable housing.

chi-ching!

[stillgoing]

Originally Posted by M_Dub

why?
its releasing and pulling just like any other derailluer
just backward

I'm just theorizing, but..

On a derailleur, there's more than one srping - a spring that moves the mechanism to the more relaxed position and I've referred to above (call it spring "A"), and another spring "B" that keeps the chain tensioned by pulling the idler pulleys toward the back of the bike. When shifting to a smaller cog, this latter spring is returning to a relaxed position - pulling.

So - in a traditional derailleur, when spring A returns to a relaxed position, it is not fighting spring B, as it is also returning to a more relaxed position.

However, in rapid rise, the two springs fight each other. Spring A is stronger and wins, but it has to be in general a stronger spring that what would be used in a 'normal' derailleur.

At least - that's my take on it.

[connor]

SRAM that shit off your bike.

[M_Dub]

Originally Posted by connor

SRAM that shit off your bike.

true that

[DrewM]

Sliding it by hand watch the cable-bolt arm (where your derailleur cable is held in place) and see if it rubs or contacts anywhere on the derailleur body.

Often said arm will bend upwords slightly when it sustains a downward impact (I've had this problem a couple times and the symptoms are exactly what you describe).

If the cable-bolt arm rub, take some vice grips or pliers or whatever and just bend the little arm down a bit. Retension your derailleur cable and go to town.