I can recommend the 50/50's, but go with the XX instead of the X. The XX come with a bunch of replacement pins, so you can add more to make them grip better.

I'm guessing the 3900 comes with something like an Acera rear derailleur, or something close to that range. These arn't the highest end derailleurs, and I've had a lot of problems adjusting my brother's 4100 acera derailleur well. You might not be able to do much upgrading though. If you have a 7 speed hub, I doubt you can find a higher end derailleur that will work properly with the 7 speed setup (correct me if I'm wrong) and I doubt that hub would be able to make the switch to an 8 speed, or even 9 speed hub to work properly with the higher end derailleurs.

So it might be very costly to upgrade the R.D.


Oh and Brad, what trials bike do you have?