afrowheels

That point in the tour when problems are accumulating... Hit a bump a week or so back that completely messed up my rear gear indexing. Couldn't figure out why but fortunately had the Gevenalle friction option so switching to that kept me on the road. Took the bike into a mechanic who said the issue was the derailleur cage is bent and he couldn't do anything about it. He re-indexed it which lost me my lowest gear - no trivial thing given the mountains here in Ecuador - and only lasted about 5km before I had to switch to friction again.

So, I think I need to replace the derailleur asap and the best 9spd I am likely to find here is an Alivio (https://www.bicis.ec/products/tensor...89e8536d&_ss=r). Officially it covers my range (11-34). So it should be good enough to keep me on the road? Any possible problems I am not thinking about?

MarcusT

If the gearing is the same as well as for the shifter, you should be good to go.
Unfortunately, Shimano has cut the 9 sp line up from the higher end. Alivio and Acera I believe are the last ones to offer 9 sp

csport

It should be good. If you want something that is not shadow, they have this one: https://www.bicis.ec/products/tensor...ltus-rd-m370-l (says limited quantity).
Also check that the derailleur hanger is not bent.

Tourist in MSN

That should work. I googled SHIMANO ALIVIO RD-M3100-SGS and that told me it is sold as a 9 speed.

I did not check to see if that has a long enough cage to match your cassette because I do not know your cassette. If it does not take up slack for your cassette and chainring sizes, you might lose a few gears on smaller sprockets when on the smallest chainring.

Keep using the same amount of chain on the new derailleur, do not remove any links. It should work but test it on the big and big ring and sprocket before riding.

Alternatives would be any long cage derailleur including used derailleurs that are a Shimano 7, 8 or 9 speed. A Shimano 10 speed from a road system (not mountain) might work too.

If you buy used, I would suggest you re-lube the jockey wheels first. If you remove them to re-lube them, do that one at a time to make sure that you do not accidently mix up any of the parts from the upper and lower. And if you remove them, make sure you get the bolts tight on reassembly.

As noted by Csport, derailleur hanger may need adjustment. If that is a replaceable one, be careful you do not overstress it, it might break. If it was me, I would not try to adjust a replaceable one that could break.

Good luck.

And, one more option, try to adjust (bend) the bent cage. Sounds like you are already going to buy another derailleur, so if you break it, sounds like you already plan to get a replacement anyway.

A few years ago I saw a nice derailleur for cheap at a swap meet that matched some of the ones I use. I bought it, re-greased the jockey wheels and installed it. And shifting was not very good. I could ride it, but it was not playing well with the rest of my parts. So, inspection told me the cage was bent. I suspected that the prior owner ran it into a rock or something while riding. Removed it from the bike and adjusted (bent) it using a really big vice and a really big crescent wrench. Works fine after that. But I knew that I might break it when I did that, and I was willing to risk breakage. I would NOT try to bend it on the bike, only off of the bike. I have now been using this one that I bent for at least a year.

afrowheels

Thanks. What would be the downside of the shadow version?

Apparently the hanger is straight: they checked it while I was there. Had been straightened out previously as well.

veganbikes

It should work fine. If you can find an old M737 derailleur that would be my ultimate choice but those are old and haven't been in production since the early/mid 90s but they are pretty bomb proof. I have had mine since 2015 and I got it used from someone who mountain biked with it and thrashed it about and it has gone from 8 to 7 speed and now is running a 9 speed with zero issues and little maintenance aside from chain cleaning and lubing once and a while.

Tourist in MSN

He is not going to be lucky enough to find one of those.

I am not sure if the one in the photo is an M735, M737 or M739, but I have several of those on different bikes. But I am slowly changing the jockey wheels to sealed bearing, such as in the photo.



My 2017 Lynskey in the photo. Photo is three years old.

Previously in this thread I mentioned that I straightened the cage on one of mine that I bought used, that also was one of these.

Tourist in MSN

I can't speak for Csport, but it is my understanding that you need a rear derailleur for a 7, 8 or 9 speed Shimano system. And as I mentioned in a previous thread a 10 speed road derailleur might work. But the mountain bike 10 speed likely does not work. I am assuming that a 7 speed would have enough range, but those all likely went into in the scrap heap decades ago, but if you found one it might have too little range. Best to look for an 8 or 9 speed derailleur.

It is my understanding that some Shadow derailleurs would not have the right amount of cable pull per shift, some might. The key is getting one for the right number of sprockets on the cassette.

A 9 speed shifter like you have has 2.5mm of cable pull per gear shift. Thus, you want the derailleur that needs that amount of cable pull per shift to work with that shifter.

afrowheels

That looks pretty bombproof, but yeah probably would not find one. Did find an Alivio 9sp M3100 new. Full update below.

afrowheels

Short version: took the bike to a new bikestore/workshop and they got the old derailleur working again but I bought an Alivio 9spd anyway just in case.

Long version:

Not much of this is making sense to me. The original issue happened when I hit a bump going uphill and the indexing went completely out of whack for no apparent reason.

The first mechanic I took it to blamed the bent derailleur cage - and it does look bent even to my untrained eye. His re-indexing barely lasted 5km and other things started feeling 'not right' - but again couldn't see anything. Though I did notice the rear wheel 'skidding' when I pushed hard in lower gear and couldn't figure out why until a few kilometres before the end of a day I saw the rear skewer halfway out!

So after 3 days of difficult cycling I took it to a new bikeshop sure that I just needed a new derailleur. They sensibly wanted to look at the bike first. That mechanic diagnosed the problem as being with the skewer and the hub (to the extent I understood - Spanish, etc): said the skewer thread was stripped and the wheel was not aligning properly as a result. The previous workshop may have been responsible since they did service the hubs. (But then what was the original problem??) He replaced the skewer and reconfigured the derailleur. Took the view that a new one was not necessary despite the cage being bent.

I was not entirely convinced and facing 1,000km+ in more remote Peruvian mountains decided to buy the Alivio 9spd anyway just in case. What's another 300gms

After a day of riding the good news is that I can use my lowest gear again. However, it still occasionally starts trying to jump up to 2nd. And does not stay reliably on the largest rear cog when on the middle chainring. That's in friction mode. I haven't tried switching to indexed mode...fills me with dread tbh. I had asked the guy to reconfigure with indexing but I guess he didn't understand.

Next few days are going to be some very tough riding: tomorrow supposedly 3,000m+ climbing - hoping the app is wrong but suspect not then some gravel road. So I reckon whatever problems still exist should be brought to the fore pretty quickly. My gut says I'll have to replace the derailleur, but my priority at the moment is to get across the border before my visa expires so if I can postpone the job until then I will.

afrowheels

For anyone who's wondering how this turned out. The XT kept giving problems, so I eventually did replace it. Surprised to have managed to install the Alivio successfully myself. It was a little tricky initially because the mount is not quite the same as the XT. presumably because of the 'shadow' profile. But it seems to be working smoothly and no problems with the gear range that I have.

Trakhak

I went through over a dozen rear derailleurs back in the late '80s and '90s, thanks to the low ground clearance of my Cannondale 26"/24" MTB's rear derailleur, which kept picking up bits of broken branches from the trails I was riding. Started with expensive replacements and eventually worked down to the cheapest Shimano rear derailleurs. They all worked equally flawlessly.

robow

Remember too, Shimano's trickle down technology. Often last year's XT is this year's LX (when it was available) and last year's LX is this year's Deore and so on. Often the current Deore or Alivio is very similar to XT from many years ago but a few grams heavier. Glad it all worked out for you.

afrowheels

I wasn't aware of that trickle down approach. But yeah, when I put together my first touring bike I was caught up in the hype about XT being so much better. Having experienced both I am more likely to go for the cheaper components in the future: they seem good enough for my purposes.