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Old 12-31-10, 12:38 PM   #1
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Long-running index shifting problem....

Hi, I've posted a lot about issues getting my Surly to have index shifting.

Surly LHT - Shimano 44/32/22 SLX crankset, 7 speed cassette, 7 speed chain, 2 sets of shimano 7 speed downtube shifters.

I've worked on bikes for years -- read all Sheldon's stuff, etc.

Basically, I've always been able to set it up to where it seems fine in the stand, and maybe for a day or two commuting....but then I'll stop at a traffic light, and when I start up again the chain will "pop" or "clunk" right when I start pedaling again.

Then it goes for maybe another 2 days with completely normal shifting, then does it again....really annoying.

I tried aligning the derailleur hanger -- which seems to have reduced but not eliminated it.

I've tried turning the RD barrel adjuster a bit tighter or looser to fix -- same result.

What the crap is going on with this? Are downtube shifters just not as precise on each individual shift as STI? My old 9-speed STI stuff never did this.

I mostly ride on the 44t chainring. Chain is relatively new (not stretched out). Cogs are relatively new also (not wore out).

Thanks,
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Old 12-31-10, 12:51 PM   #2
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Chain is relatively new (not stretched out). Cogs are relatively new also (not wore out).
there may lie your problem .. they are not worn in together,
buy new parts, chain and cogs.. and start over ..
dont get attached to chains replace them more often...


and that top pulley slop sideways helps make up for index alignment,
see that there is that motion going on.

Last edited by fietsbob; 12-31-10 at 12:56 PM.
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Old 12-31-10, 12:55 PM   #3
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Should have clarified -- purchased from Niagara at the same time -- installed together. So they are indeed worn together.
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Old 12-31-10, 12:58 PM   #4
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Take a look at your chain. Modern index chains have lots of bevel on the inside of the plates so if trimmed a bit off they can still pick up the sprocket teeth. Likewise the teeth of modern cassette are more pointed so as to better slip into a chain.

It's kind of like the way ferry slips are shaped like funnels to catch a slightly mis-aimed boat and guide it into the slip.

Older chains tend to have squarer plate profiles and therefore more likely to catch the edge of sprocket teeth and ride up, then go over the side.
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Old 12-31-10, 12:58 PM   #5
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Got a friction mode? how does that work?

I liked full height teeth better, new hyperghide profiles are very unsettled in the gear ..
once you are there, it wants to be somewhere else.

Last edited by fietsbob; 12-31-10 at 01:04 PM.
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Old 12-31-10, 02:07 PM   #6
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Had a similar problem on our tandem. Discovered a few problems. If you have barrell cable adjusters, make sure they aren't turning on their own. Some will work themselves loose and get things out of adjustment. However, the thing that I think was really the problem was the "B" adjustment on the R/D. Our long, rather loose, chain would tend to half-way derail on the rear cassette from our back pedal action just before starting up. We dismount with the right pedal down, then bring it up to the 12:00 position to start. When we tightened up the chain with the "B" adjuster, the problem went away until the barrel adjuster lost position. The chain is the correct length, but is longer because it's a tandem. Now I need to replace the stupid cable adjuster with one that stays put...

P.S. Love my LHT. I used pure friction. It served me well on my trip across the U.S.

Last edited by Old Hammer Boy; 12-31-10 at 02:12 PM.
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Old 12-31-10, 03:28 PM   #7
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That pop or clunk may be your freewheel mechanism failing to engage. Shimano mechanisms aren't really intended to be taken apart for repair, but a flush with WD-40 may often get them working.
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Old 12-31-10, 03:48 PM   #8
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No, it's a freehub and I can actually discern that it has something to do with the chain not engaging properly with the cogs for whatever reason. Maybe the 9-speed stuff just meshes better....maybe the 7-speed chain I'm using isn't the greatest...who knows?
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Old 12-31-10, 03:57 PM   #9
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what kind of shifters and what kind of RD? if you somehow mixed 7spd DA shifters and other RDs or vice/versa that could be the issue.

also what is the gearing on your cassette? a 13-28 7spd while indexing will not seem as smooth as a 12 24 9spd since you are jumping more teeth.

you are using indexed housing yes? the housing isn't getting chewed up somewhere is it? on the IGH I set up last year I had a similar issue until I discovered the housing was pulling through one of the stops.
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Old 12-31-10, 04:01 PM   #10
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About that "pop or clunk": do you mean that, when the pop or clunk occurs, the chain jumps from one sprocket onto another? Or do you mean that the chain stays on the same sprocket but slips? If the chain slips on the same sprocket, you may have used that particular gear combination enough so that the sprocket has worn out. Look for "shark fin" profiles on the teeth of that sprocket. Seems unlikely, since you say that the chain and sprockets are relatively new, but it's worth checking.

If you mean that the chain ghost shifts (i.e., tries to move to a different sprocket without the shift lever being moved), you should check the "B" screw adjustment, as suggested earlier; also, check that the cable housing at the rear derailleur is long enough and is not kinked. Lubricate the cable where it passes under the bottom bracket and where it passes through the rear housing.

Given how cheap gear cables and housing are, consider replacing them, at least for the rear derailleur. If you do it yourself, be sure to use a high-quality cutter for the housing (or have the bike shop cut it for you). Before inserting the cable into the new housing, use a sharpened spoke end to ream the hole in the housing to eliminate burrs and attach the correct metal housing ends.
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Old 12-31-10, 04:02 PM   #11
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BG, you may have hit the proverbial nail on the noggin. I'd re-cable and re-house with Shimano Stainless cables and Jagwire lined housing, then follow the Park Tool procedure to adjust and align. 7 speed Shimano stuff is very forgiving, probably the easiest and most rock solid systems around. Assuming you are using all Shimano and all compatible stuff, and not mix N' matching.
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Old 12-31-10, 04:08 PM   #12
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Originally Posted by Bianchigirll View Post
you are using indexed housing yes? the housing isn't getting chewed up somewhere is it?
This is an important thing to check. From your description it sounds like it could be a cable issue. Remove the shift cable all the way and inspect each section of housing. Also make sure your cable routing isn't causing kinks which will degrade shifting.

Are you SURE the RD is sitting straight? You mentioned straightening the hanger. If it's not straight it could cause the jumping you describe.
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Old 12-31-10, 04:46 PM   #13
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Originally Posted by TurbineBlade View Post
No, it's a freehub and I can actually discern that it has something to do with the chain not engaging properly with the cogs for whatever reason. Maybe the 9-speed stuff just meshes better....maybe the 7-speed chain I'm using isn't the greatest...who knows?
A freehub still has a freewheel mechanism - that's what allows you to coast without pedaling.
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Old 12-31-10, 06:03 PM   #14
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you are using indexed housing yes? the housing isn't getting chewed up somewhere is it?
This is an important thing to check. From your description it sounds like it could be a cable issue. Remove the shift cable all the way and inspect each section of housing. Also make sure your cable routing isn't causing kinks which will degrade shifting.

Are you SURE the RD is sitting straight? You mentioned straightening the hanger. If it's not straight it could cause the jumping you describe.
Yes, it's shimano SIS housing - cut with good cutters, burrs removed, opened with a sharpened spoke. Ferrules on both ends - seated properly.

The housing loop is plenty long to avoid the sharp bend that 90% of peoples' bikes seem to leave the shop with ....at least that I notice.

One thing I noticed in the work stand is that in each gear, I can still move the shifter a little and the RD does actually move to a noticeable degree....meaning that each time I shift it there's probably some latitude in where exactly the shifter stops. Maybe this can cause the chain to occasionally try to "pop" over onto the next cog while still shifting pretty well and seeming OK a lot of the time. I guess I need to figure out the best cable tension adjustment (even though it seems to index pretty well over a fairly wide range of barrel-turning).
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Old 12-31-10, 06:07 PM   #15
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also what is the gearing on your cassette? a 13-28 7spd while indexing will not seem as smooth as a 12 24 9spd since you are jumping more teeth.
Shifting isn't the problem, it's that the chain seems to want to "hop" onto other cogs every once in a while for some reason. Usually I notice it after stopping at a traffic light and possibly back-pedaling a turn or two.

Quote:
If you mean that the chain ghost shifts (i.e., tries to move to a different sprocket without the shift lever being moved), you should check the "B" screw adjustment, as suggested earlier; also, check that the cable housing at the rear derailleur is long enough and is not kinked. Lubricate the cable where it passes under the bottom bracket and where it passes through the rear housing.
Rechecked this earlier in the stand -- it's at the optimal position. Thanks for the reminder .

Quote:
what kind of shifters and what kind of RD? if you somehow mixed 7spd DA shifters and other RDs or vice/versa that could be the issue.
Not DA stuff...I know about that. The shifters are Shimano "exage" 7 speed currently, the other are older 105 ones. Both seem to do the same thing.
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Old 01-01-11, 04:16 AM   #16
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You mentioned that bit of movement of the shifter and derailer you can make while engaged in one gear. That's called overshift, but it should always spring back to the same position after you make that slight movement of the lever as if trying to downshift to a bigger cog.
If the derailer can hang at more than one position for each indexed position of the lever, then there is too much friction in the shifter or the cabling. The overshift is meant to be only momentary during downshifts, and if the derailer doesn't freely spring back to the exact indexed position then this will happen when the frame sees the highest pedaling force, as when accelerating from a stop as you described. That can cause at least a partial, momentary ghost-shift that sounds just like what you've described.
I would first tug on the exposed cable wire along the downtube to check for cable friction and smooth derailer movement and return. If that seems smooth, I would remove the lever and blast it out with aerosol (foaming) Tri-Flow (look for a tiny spring-end opening on the lever's back side), then re-mount and check shifter movement before and as the mounting bolt is secured. The overshift movement should now easily be overcome by the cable's tension alone so that the derailer always returns to a precise location for each indexed position, and frame flex can't tug the cable enough to make the lever move.
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Old 01-01-11, 06:51 AM   #17
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I'd try replacing the Centeron with a normal pulley; I'm not sure it's warranted on 5mm spacing. That float you noticed in the levers should be taken up by cable tension.

Also, if it's a fresh cable, you might find there's a little bit of springiness introduced to the system where the cable passes under the BB guide - a fresh one will often want to bow out slightly around the guide cause the derailleur's return spring isn't strong enough to pull it straight until it's developed a bend. I put a bit of a bend into a new rear cable when I install it.
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Old 01-01-11, 10:33 AM   #18
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Thanks for all the ideas you've given me! I'm going to check under the bb at the cable guide -- though it seems unlikely to be the issue as the cables are new and I can't eye ball any issues from friction coming from that area. I also use full-coverage fenders with huge, pavement-dragging flaps so I don't tend to get a lot of debris under there.

dddd: I see what you're talking about. The shifter does indeed spring back into the...well, I guess the correct position, what I meant is that I can physically grab the lever and pull it slightly to get some cable movement. I don't think it tends to move by itself, but I could be wrong. I guess this little bit of movement is something designed into the shifters to facilitate down shifting - like you mentioned. I didn't know that.

I'm going to try it out, and make very minor adjustments to cable tension and see how it goes. I'll update after this week of commuting.

Thanks,
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