Originally Posted by
mr9iron
This RD is the torx bolt type, so I'd have to see a dealer if the o-rings are worn. Is there a relative way to tell if those o-rings are shot by moving the RD say with some rocking motion by hand? -guessing like half MM of play is probably good, more is probably not so good?
Broadly yes, we use the vertical distance from end of the bolt that secures the jockey cage to the lower pivot as the datum, to the surface table at 0, 120 and 240 degrees of rotation around the boss that is vertical relative to the table. Max variation allowed is +/-0.25mm. Very hard to quantify any other way. A "waggle test" isn't really reliable enough.
You also mentioned "horizontal alignment" - does this mean bending of the hanger? It is a steel frame, so there is no hanger, the mount is the actual dropout itself. I was not aware of any horizontal adjustment on the RD itself so I am guessing cold bending of the drop out would be needed if this were the case?
Yes. Lots of mechs don't like adjusting the fore-aft true as it throws the up-down alignment out - but the face of the hanger that the RD bolts up against does need to be, within boundaries, co-planar with the sprockets / wheel.
The problem is the repeated bending of the hanger to adjust both "x" and "y" alignment. This can weaken or, in extreme cases, cause failure in the hanger. There's a trick to doing both with a minimal amount of adjustment that a lot of mechanics never quite acquire!
Again appreciate the reply,
Jeff
No problem!