Dirt and rear derailleur getting slow
 

After an hour or so in heavy dirt, grit, rain, mud, heavy gravel dust... my rear derailleur starts getting a little slow and I have to start double shifting to get a gear change, like 2 up and it will jump 2 gears and then 1 to get back down. I suspect it is the last piece of cable housing that is getting gummed up (my routing is top tube then down the upper chain stay) but it may be the rear der itself. I replace the end housing piece far more often than the rest and it seems to help a little long term. I have a RD592 and Jagwire LEX housings if that matters. I have a few of the Jagwire cable ends but I've never used them, where are these used and would they prevent junk from working its way into the housing? I will say that once the water/wetness stops and dries or I get back out on the road, my shifting eventually returns to normal so its not really just the dirt, it is the dirt and moisture. Any suggestions or just live with it.

https://cimg9.ibsrv.net/gimg/bikefor...5910c45cd8.jpg



https://cimg9.ibsrv.net/gimg/bikefor...8ccfb5eb5e.jpg

Those ferrules you have pictured are used with cable liners. They work really well. You could install that ferrule, run the shifter cable through, slide a piece of cable liner over the cable and then over the tiny end of the ferrule. That should keep gunk from working its way up into the housing. But with all that said that may not be the problem, like you said. It's just an easy thing to try.

I find that if I slacken everything, I can usually pull the cable out of the frame bosses. Then I can run that final bit (before he derailer) up high and check the condition of the cable and/or lube the cable in that final bit. You might want to put some WD-40 in there to clean everything out. You could add some water repellant lube back in there next, but that is probably more likely to get gunked up than anything.

Make sure the pivot points on the derailer are clean and lubed.

Is it slow in both directions? That would generally help diagnose a spring tension issue as opposed to a cable tension issue. Smearing a dab of grease on the cable ferrule ends prior to a rain/mud ride keeps water out of the housing or as shoota suggests, running cable liner. On the end that terminates at the RD this trick still works and is what a lot of cyclocross racers use. Then wipe and clean after the ride and reapply before the next race

do you Clean your bike after every ride ? it's a good practice if not sticking to the pavements ...

Yes, clean and lube my RD before most rides. I scrub/wash it and spray either teflon or silicone with teflon all over the der and wipe it off (in theory neither of those leave a sticky grease behind) and then put it through a few cycles. Same with the front. That specific instance above in the picture was after 4 straight days of dirt and dust but the trouble didn't start until the 5th day when it rained. I stopped and put some white lightning I had on the der eventually and I can't say if it helped or not but I was not in a position to actually clean it. The day before that trip, I replaced the end piece of housing that goes to the rear der knowing this happens to me :)
It is typical, any day in the dirt with lot of splashing dirt will eventually cause the problem. No mud/dirt, no problem. It is mostly on the upshifts when it happens. When it is clean or dry, I have no problems. I have about 8K miles on that Deore and a lot on trails/dirt/gravel, maybe it's getting a little old? I have a Tiagra der I could throw on but I don't like that compared to the Deore.

As for trying the cable liner. From the frame boss up to the upper frame boss effectively protecting the run down the chainstay? I think that might help. The housings I have are LEX-SL and have a liner already. I see this below but a comment in the reviews mentions that it specifically does not fit over the Jagwire sealed ferrules I have laying around. hmmm.. Maybe that is wrong. Any suggestion on cable liner and/or ferrules? I am willing to try even if that is not the root cause. It certainly won't hurt and dirt will almost always be in my route.

https://www.jensonusa.com/Jagwire-Black-Housing-Liner

Thats the liner I have, I fit it over shimano and jagwire ferrules by stretching the end with a pick tool and/or applying a small section of adhesive heat shrink

Great, I have both and I'll give it a go.

I'm going to question the efficacy of this approach.

Aggressive spraying and scrubbing can drive lube out of the pivot points.

Saturating the entire derailleur with lube of any kind isn't how it should be lubricated. There is no need to douse the entire thing with lube. Only specific points need to be lubricated.

My parts get total coverage in dirt and grit on most of my rides that involve any off road. There is no way there wasn't already dirt everywhere anyway. That ship sailed. I am not picking out individual dirt or grits from specific areas with a pick or a pair of tweezers. A scrub brush and soap on my derailleur (and other parts) and then a rinse with a hose and than when dry a quick spray from a can of silicone, chain lube or similar with a red straw "concentrating" on the pivot points but it goes everywhere (except my disc because I hold a piece of cardboard I have standing by behind my cassette). Cycle the der through the range and wipe off excess and runs. The whole lubing takes me 10 seconds. Sure, I could get a small bottle of fluid and drop individual micro drops in just prime locations but that ends up running everywhere too and takes more time than needed. Look at my picture above, you can see on the der near and under the pivot points that the dirt is not light brown but looks wet. Those are not "wet" areas from water, that is what dripped and ran over when I put a few small drips of lube on the pivot points about 50 miles earlier in the day as a stop gap after the fact and it ran out and covered the dirt. That targeted approach of lube application is no different in the end. Maybe I put 1 or 5 drops too many sitting on the side of the trail but is 1 or 5 drops really a source of inefficiency and contention? I'm not metering it. It is what it is. Stuff is going to get dirty, if there is an obvious way to keep some dirt out of some areas like cables I'll try it. If the cable liner doesnt help, next time I'll dump some water on my rear der and get some dirt off. If I had to treat my bike like a wind up watch with the back opened up or a Jenga stack on the edge, I would have given up riding years ago.

I change the whole cable and probably guides when it sticks like that. Its easy and not too expensive.

To be clear, I believe too much spraying, scrubbing and lubing is the problem. I never said anything about picking out individual pieces of dirt or treating it like the internals of a wrist watch. On the contrary.

I'd overhaul the rear derailleur - disassemble, clean and lube with the correct lubricants in the right places once, and then leave it alone.

A rear derailleur doesn't need to be scrubbed with brushes and soap every use. That's too much.


-Tim-