Nuts ‘n’ Bolts – Clean and Lube Rear Derailleur
[[image:harv_dr_mini.jpg::inline:1]]Another of those long-suffering bicycle components is that hundred year old French invention, the rear derailleur (RD).
Published February 19, 2008 by C.I.C.L.E.
By Harv :: Photos: Harv
[[image:harv_rd1_web.jpg::inline:1]]Another of those long-suffering bicycle components is that hundred year old French invention, the rear derailleur (RD). Over the years its design has undergone much improvement and an increase in capacity, from three to ten cogs. Being a retro-grouch, I think the zenith of design and practicality occurred with the five or six speed Shimano SIS. So for the purpose of this discussion, we will look at a six speed short cage Shimano unit.
Our low-end basic RD's life is actually pretty simple. All it has to do is tension and position the drive chain and move it into engagement with the freewheel (or cassette) cogs. But it has to do it smoothly, reliably, with minimal friction, and with accurate and repeatable indexing. What can go wrong (other than damage)? Well, the many articulation pivots can wear or get rough, the non-metallic jockey wheels can get dirty, wear, break, or become harder to spin. Any of these conditions can result in drive train failure or inefficiency. We'll look at the routine maintenance necessary to mitigate these problems.
OK, so we must remove the subject lump from its residence on the bicycle frame so that we can freshen up the various moving parts. We reach for the chain tool to break the chain so that it can be withdrawn from the jockey wheels, right? Wrong! Of course this will work, but I don't like to be pushing out chain pins un-necessarily. Just remove the lower jockey wheel and loosen the upper one so that one carrier plate can swing out of the way of the chain. See top photo.
Now strip off all the parts that will come off the RD. Not too many will as it is assembled at the factory by staking the main pivots or incorporating C-clips. Removing the main pivots is beyond the scope of this discussion. But you can remove the jockey wheels and one carrier plate as shown. Remove the claw anchor bolt (if any) and the cable adjusting barrel. Inspect and clean these. Chase the threads if need be and set aside for reassembly. Disassemble the jockey wheels into their components as shown in the photo. Clean everything with mineral spirits and allow to dry.
[[image:harv_oil2_web.jpg::inline:1]]Note that the RD moves in three modes. It moves in and out (perpendicular to the chain stay) to shift the chain onto the cogs. It pivots toward the rear of the frame to tension the chain. And it pivots down to clear the increasing diameter of the lower cogs. Each of these pivots needs to be lubricated at each end. A drop or two of light machine oil will do the trick. Apply the lube and work the unit manually to move the pivots and distribute the oil. Then wipe off the excess oil. If too much shake (free play) is detected in the pivots, the whole unit should be replaced if accurate and quiet cog swapping is desired. How much is too much? As with other bicycle bearings, any perceptible shake is too much.
Going back to the jockey wheels, we see that it consists of a usually black Bakelite type material which spins on a metal bushing and is held together with end plates through which pass a bolt. The bolt keeps the assembly held in the carrier. [[image:harv_lubjok2_web.jpg::inline:1]]Using a cotton swab, apply a dab of light grease to the bearing surface of the wheel. I use white lithium grease for this application. Factory assembly was probably done dry, no lubricant. That dab of grease should give you the 'racing option', so go for it.
Now assemble the upper jockey wheel and the carrier plate into the main body of the RD, but don't tighten down the bolt fully. Leave the lower jockey wheel off until you reinstall the RD into the bike, so that the unbroken chain can be threaded into it. Check that the upper and lower jockey wheels are in their respective positions. The RD shown here uses the same size wheels for both positions. Then install the lower jockey wheel and tighten both bolts. Your RD limit screws should be undisturbed, so a brief check will do here. Re tension the cable, check the shifting action and you are done.
I recommend you go through this RD overhaul every few thousand miles. The jockeys can be removed and lubed without removing the RD from the bike, and almost all of the pivots can be oiled in situ. This rigorous treatment is for the more fanatical rider/wrench with lots of time. Don't expect your local bike shop to do this, they won't. They would just charge you for a new RD and replace it. The old one would be tossed into a pile of junk never to see the light of day again. Unless, of course, they donated that pile to the Bike Oven where it could replace an even junkier part on a bottom-feeder bike. But at least it would get cleaned and lubed and maybe go another twenty years.