I am not much of a mechanic but have just replaced the cassette and chain on my bikes. When the chain was off I thought it would be a good opportunity to clean everything else up.
I noticed the two wheels (jockey and tension) on the rear derail are quite different. One seems to have no axial play and spins very smoothly when pulled round. The other has a little bit of play but does not spin freely. It turns ok, but does not spin freely like the other (as in it stops when you let go when the other one continues to spin after being turned)
I know one of them should have axial play to allow for the chain but should it spin?
It is an Ultegra rear derail. If the wheels need replacing do I simply undo the screw, let it drop out and replace with the new one?
How long should they last? I am on 7,000km, nearly 100% good weather and probably around 2km or more indoors.
Sounds fine unless it actually seems gummed up. Different derailleurs I’ve had seem to have different feels to the jockey wheels.
Seems normal to me. Pretty sure it’s on a bushing rather than a bearing so it’s not gonna spin that easily. They do get gummed up sometimes, though (cyclocross is infamous for consuming RD pulley assemblies), so if it actually takes work to turn it then it’s a fairly easy/inexpensive replacement. You could opt for aftermarket ‘upgrades’ with sealed bearings, but the ones I’ve tried in the past ran more noisy because they didn’t seem to center as freely in terms of the lateral play that Shimano designs into the originals. Could be some better ones out there, however.
Might wan to remove them, clean them, then repack them with grease. From past experience with Shimano rear derailleur, one pulley wheel should have some axial play and the other none. Both should spin without major binding.
Ultegra actually has one bearing and one bushing jockey if I’m not mistaken so thats why theres a difference. It goes back to the idea that a load may change the efficiency of things.
Anyways, if you really are curious about these questions friction-facts.com does tests on things like this.
Both should spin without major binding.
That;s what I thought, one is pretty gummed up though and requires about three times more force to turn than my speedplay pedal. Called the LBS, they have one in stock so am getting a new one today.
Thanks everyone for your help.
Ultegra actually has one bearing and one bushing jockey if I’m not mistaken so thats why theres a difference. It goes back to the idea that a load may change the efficiency of things.
Anyways, if you really are curious about these questions friction-facts.com does tests on things like this.
The top pulley runs on a bushing (allows for a bit more play for chain alignment, and costs less). It spins freely when clean, but gums up easily, and has more drag than bearings when under load. You can replace this one with a sealed bearing assembly, no problem. The lower pulley is a sealed bearing. There is some drag from the seal, but these last many years under normal (non-cx/mtb) conditions.