Ducksoup_SD

I purchased a recumbent touring bicycle with factory installed Shimano bar ends (SL-BS77 9-spd) and Deore XT (RD-M771 SGS). After a recent overhaul, I noticed that the system skips my #8 cog and goes straight to the #9 on my SRAM cassette (SRAM chain, too). Because of the position on the recumbent, I couldn't see this until I put the bike up for repairs, and since it was new to me, I didn't have a feel for what I was missing (I got a low gear going up a hill, so I didn't question it).

I have yet to find a cable tension that allows the #8 cog to be used. It appears that the bar end & XT combo is the problem -- can anyone confirm this? If it is the problem, can anyone recommend a wide capacity rear derailleur that will operate all 9 cogs in my cassette with the bar ends? The bar ends seem the best way to go on this recumbent because it is an under seat steering (USS) model and so twist grips can add handling issues.

Yes, I could go retro and switch to friction, but I'm spoiled now that I've been riding indexed drivetrains for 18 years...

Thanks in advance!

Metaluna

I can confirm that those barcons should work perfectly with XT rear derailleurs and not skip any gears. I've used them with the RD-M770 (low normal version of your RD) and it shifted very well with both Shimano and SRAM cassettes.

It sounds like you may have a derailleur hangar alignment problem, which you will need to have checked at a shop.

kycycler

+1 on what Metaluna said. Sound like a bent derailleur hanger. This may not be visible to the naked eye. Any good shop should have the tool to check and repair.

joejack951

Or possibly just too much cable tension and/or improperly adjusted high stop screw. Before worrying about the derailler hanger, I'd run through the RD setup at www.parktool.com and see how it works after that. If no luck, then start suspecting other areas.

mzeffex 

Incorrect.

joejack951

Thanks for sharing.

zzyzx_xyzzy

deraillleur hanger alignment is good to check. i have also seen this happen when the cog is slightly bent.

desertdork

I could easily be overspeaking my level of experience, but I would think a bent derailleur hanger would result in more shifting issues throughout the cassette...particularly on the smaller cogs...and not just on one cog.

I'd switch it to friction to inspect the shifting both on a stand and while riding. If I still couldn't get it to shift to and remain on the #8 cog while in friction, then a visible inspection may reveal a defect or flaw in that cog. I am assuming that this has always been an issue (in your recently acquired bike), but you have only recently discovered the problem.

If you haven't done so already, joejack's suggestion to correct the cable tension is the best starting point IMO.

helicomatic

This is by far the most error-prone combo of Shimano parts that claim to be compatible that I have encountered. If you have very long housing (which you probably do, on a recumbent,) the play in the bar-end shifter, the play in the derailleur (even when new), and the compressibility of normal shift housing, can combine in an unstoppable combo of frustration. I've seen this problem twice when building up bikes from parts here in the shop, and the quick fix for me was to just swap the RD-M771 for the RD-M772 "Shadow" derailleur, which seems to be more precise. There's probably some other solution that I haven't tried, like better cable housing, that might be more convenient for you since you've already paid for the derailleur.

This was never a problem with older XT top-normal derailleurs, and I have not tried the RD-M770 low-normal in this situation, but it seems to work for Metaluna.

rogerstg

FWIW, IME with conventional bikes, bent hangers usually present themselves as shifting problems in one or two cogs. Tension issues usually affect more cogs.

well biked

Interesting. I've not had anything but good luck with my Shimano 9 speed bar end shifters and RD-M771 derailleur on my Surly. I did use Shimano shift cable and housing, but I wouldn't think that would make that much difference. We've had occasional problems with the Shadow derailleurs, though.

roberth33tiger

it sounds like a cable/housing/friction problem to me, or stickyness in the RD, or combination of the two.

helicomatic

This was a while back now, but I believe the shifter was mounted on Nitto Albatross bars or mustache bars in both cases, leading to the most massively long cable housing, and a tandem shift cable.

I haven't heard complaints of any issue from assemblers or owners of recent LHTs either though, which come with those parts as complete bikes, so that's a good point.

operator

Which recumbent touring bicycle?

We had a bunch of those with sram 9s cassettes that would not shift well no matter what you did. Replacing it with a shimano cassette instantly solved the problem.

Ducksoup_SD

Thanks for all of your insights. It is possible that the hanger is bent; I had to bail or hit a noiseless hybrid car that I didn't see or hear and the bike landed on the right side. I have a new hanger on order (two, actually -- one for now, one for later). The bike is an HP Velotechnik Grasshopper FX, in case a switch to another cassette would help.

I recently purchased another SRAM cassette -- no change, so I don't think it's the cog. I seem to be able to get all of the gears in friction mode.

I guess I wasn't clear when I said I had yet to find the correct cable tension to reach gear #8 in index mode. I tried adjusting the tension many times while on gear #7, from almost downshifting to almost upshifting, and then, after each adjustment, using the lever to shift to #8 (several tries) -- none of the tension adjustments seemed to come close to hitting #8 instead of #9. The lever throw seems to be such that it can't hit #8 using the indexing and that's what has me thinking that I've never hit it before.

The shifter cable and housing is actually much shorter and has fewer bends than most bikes with bar ends or STI, since the handlebars are under the seat (under seat steering or USS). Perhaps Shimano is counting on a long housing that would move the derailleur less, due to the extra slop in the longer housing, and designed in a longer shift to counter the slop? Just food for thought...

Because of the suspension and drive train, the chain can wrap around the cassette much more than a diamond frame bike. I know from past experience that this can cause shifting issues, so I've backed it off as far as the adjustment screw will go. It still doesn't seem as open as the Surly that was pictured above.

There were several issues following delivery of the bike, so it's possible that something else was overlooked that I'm unaware of. I'm not a long-time Shimano fan, so I'm not up on all of the latest and greatest Shimano gear and interoperability info...

Thanks again for all of your help. Take a look at a Grasshopper FX at https://www.hpvelotechnik.com/index_e.html

Jeff Wills

OK- that's a better description of the issue. I'd bet that it's a cable tension/friction issue. I've been adjusting indexing on my 'bents for 18 years, and here's what I do make them work:

1. Put the bike on a workstand- you want a close look at the derailleur's action.
2. With the cable completely disconnected, verify that the chain shifts smoothly to the #1 and #9 cogs. Pay close attention to the 1-2 and 8-9 shifts. Adjust the high and low stops if needed.
3. Reconnect the cable with the shift lever in friction mode. Again, verify that the chain hits all the cogs, especially the problem 7-8-9 cogs.
4. Switch the shift lever back into index mode, and shift the chain to the #8 cog.
5. Without turning the cranks, shift the shift lever into high (#9). There should be a little slack in the cable.
6. Again, without turning the cranks, carefully remove the slack from the cable. Use the barrel adjuster for fine adjustments, but I often find I can make the correct adjustment by loosening the clamp screw and tugging on the cable with pliers.
7. Crank normally, allowing the chain to move to the #9 cog. There should be a little tension on the cable when the shifter and rear derailleur are in high gear.
8. Verify that the indexing works correctly for all gears, especially the 7-8-9 cogs. Use the barrel adjuster to center the derailleur under the cogs as needed.

Also verify that the center screw on the shift lever is very tight, and the loop that switches it from friction to index is all the way one way or the other. I've had occasions that the screw backs off a bit and it allows the shifter to miss-index. If this continues, the indexing mechanism can break.

Long ago I lived in Sandy Eggo- I used to ride from home (Rancho Bernardo) to work (west side of Mira Mesa). Lots of good hill riding.

Ducksoup_SD

Thanks, Jeff, for your comments. I used the Shimano cog designations in my descriptions of the problems and they number the cogs smallest = 1, largest = 9 for a 9-speed cassette (from their installation instructions). This appears to be different from your description where 9 = highest speed (their cog #1?). Shimano emphasized the shift for the #2 to #3 cogs as the key to adjusting the index shifting. When I get that right, my shift from #7 to #8 is what is completely missed as the chain goes to #9 (largest cog).

Yeah, that route will get some hill miles on the legs...

Jeff Wills

Yeah, those hills are part of the reason why I broke my old Lightning in half...

Still, something's fishy about the adjustment. I've had times when the shift has skipped over the next-to-last cog. It always comes down to carefully setting up the cable tension to get that cog.

operator

This was the exact model we were having issues with - if you're going to try another cass - don't get sram.

Metaluna

Actually I need to correct myself. I have the RD-M760, not the 770. So I can't speak to any issues with tolerances or play in the newer RD. Sorry about the confusion.

mo_feezy

I need to give my LHT a bath. Nice bike.

Jeff Wills

Really doesn't make a difference in terms of adjustment.