drewfio

I've been trying to tune the rear shifting on my wife's bike for some time now, and can't get it dialed in. The problem is when I shift from lower to higher (larger to smaller) gears I can get it indexed properly, but if I shift from high to low gears across the cassette it will grind slightly and slightly touch the neighboring cog.

I've observed the following behavior in the shifter. When I push forward to upshift it fully seats against the index stop (not sure the exact word, but the "notch" that determines its index position). But if I shift in the other direction it does not return all the way to the stop. But if I push on it, only then will it fully seat. This means that the cable is pulled slightly too taught when shifting in that direction, and the pulley wheel is slightly misaligned with the cog. This shifter behavior is also present when there is no cable attached, and just shifting the lever on the frame.

I've now tried 3 different downtube shifters—2 older but in nice condition 7s Light Action shifters, and a brand new Shimano SL-R400 set I bought new—all with the same result. I have 10s dura ace downtube shifters on my own bike, and they do not exhibit this behavior. So I'm wondering, is this expected behavior for these shifters? Is it compensated for somehow in the rest of the drivetrain and that isn't working? Is there something else I need to do to make sure it indexes to the exact same place for a given cog, regardless of the direction I shifted from?

I's appreciate any help. Thanks!

dedhed

https://www.bikeforums.net/classic-v...er-horror.html

dedhed

Check the bosses for broken tabs

https://www.bikeforums.net/classic-v...er-horror.html

70sSanO

I have a similar issue but only on the 2nd position. But it happens more on the upshift (3rd to 2nd). It doesn’t grind but can be a bit noisy. It would go away if I put pressure in the opposite direction on the lever; which wasn’t acceptable. New set of Ultegra 6401’s.

Since you have the same issue with 3 different sets shifters, I would check the rear derailleur to make sure the pivots and cage are tight. I’m not betting there is a problem here, but at least rule it out.

When you set everything up can you turn the cable barrel adjuster and get it to quiet down on the downshifts? Shift from first position to fourth and turn the adjuster, probably left (out) to tighten the cable.

If it shifts fine downshifting, you might be able to fudge the limit setting and spacing on one of the cogs. It may mean finding a workable compromise. Since all indexing starts from the 1st position cog, (top normal), that is where I would begin.

I know my stock 8 speed Shimano cassette has a spacer that measured 3.09mm instead of the typical 3.0mm for 8 speeds between the 2nd and 3rd cog positions. I ended up using an even thicker 3.2mm spacer and that helped.

Over the years I have read accounts of Shimano’s cog spacing not being a consistent amount throughout the cassette, but never tried to verify it or if that is just for the older downtube/thumb shifters.

Good luck!

John

Edit Added: If you get it pretty good, a slightly narrower 9 speed might help to quiet it a bit more.

drewfio

Thanks for the replies!

They are tight

Yes

It really does seem to be related to the shifter(s) or their setup. I mean, they definitely have the behavior I described, which doesn't seem desirable as far as I can tell. So either the shifters are supposed to be that way, all three I've tried are defective, or I'm setting something up wrong (though I've installed shifters a bunch of times, I haven't encountered this issue before).

Here is a video of what is happening with the lever, needing to be push into place after downshifting:
https://drive.google.com/file/d/1K41...ew?usp=sharing

70sSanO

Couldn’t anything tell from the video. Obviously make sure the shifter selector is clicked into Index and the M5 shifter attach bolt is as tight as possible.

John

drewfio

I do have an extra 9 speed chain. I'll probably give this a shot too.

70sSanO

Just curious, are you running the Shimano Centeron/guide pulley?

John

drewfio

Yeah, right now it has a Shimano 105 derailleur with a Centeron/G pulley. But in my efforts have also tried an Ultegra derailleur, an old Exage derailleur, as well as swapping out for some cartridge bearing pulley wheels from Velo Orange I had lying around. The guide pulley on those doesn't have any float though like the Shimano ones, and whether that is the reason or not, they worsened the issues (though the wheels spin very smoothly).

drewfio

I double checked, and the M5 bolt is tightened. I made sure the 7 speed levers I tried were fully clicked into index mode. And the shifter on there now has no friction mode, only index.

trailangel

I can't tell what is going on here. Op mentions 7 sp, but Shimano SL-R400 is 8 sp. The spacing is different. No mention of exactly which DR is being used.
For 8 sp I had to read the shimano DR setup instructions to the letter to get it to work right.

drewfio

Sorry should have mentioned what other parts were in the mix. But I have tried a bunch of different combos—appropriately paired (and some not...) derailleurs, cassettes, and shifters. Initially was all 500EX 7 speed shifters and derailleur and Shimano 7 speed cassette. Then tried Shimano Light Action & speed shifters and derailleur. Tried that with three different 7 speed cassettes. Then I tried A new SL-R400 8s shifter with a new 8 speed cassette, using 7 of 8 cogs on the 7 speed freehub. I didn't have an 8 speed specific derailleur, but I tried that setup in combination with the initial Exage derailleur, the Light Action derailleur, as well as a 9 speed Ultegra 6500 derailleur, and a 9 speed 105 5501 derailleur. I also checked that the derailleur hanger was straight (with a Park hanger tool). Was never able to get it shifting totally problem free. The closest I've gotten it is with the SL-R400 and Ultegra derailleur though.

In most combos I can get it to index properly in one direction (upshifting), but in the other it does not, unless when I downshift I then push the shifter lever back into place, since it does not settle into the correct position on its own. I would probably live with it if I had no other choice, pushing the lever back after each shift, but I know my wife will not always do that, and will then have gears slip (this is what happened when she took it out for a test ride).

So I'm still curious about this shifter behavior, if it is normal, and usually just works anyway. I have a Schwinn Voyageur with 7s Light Action shifters, and it all seems to work fine. It's in storage, but I want to check when I get a chance if the shifters on that bike have this behavior as well. Perhaps some of you can tell me if this happens on your bikes, but still works fine anyway.

70sSanO

As a direct answer, no that is not how the index shifter should work.

John

rccardr 

ALL of those parts mentioned should work well with each other. And in many years of working with Shimano down tube shifting components, have never (with the exception of 6208’s) had any go bad or do what you describe.
There’s something very basically wrong here, and it may well be in the cable and housing setup. Shifting up (small to large) means you are putting positive pressure on the cable. Shifting down (large to small) means you are releasing pressure on the cable and the RD spring is providing the cog change. Different RD’s tried means it’s not a bum RD spring so it has to be somewhere else kn the system.

Good Shimano stainless drawn cables of good Jagwire housing would be one suggestion.

drewfio

An update:

I seem to have gotten it working pretty well on the stand. She'll have to give it a test ride to really tell, but it's pretty smooth and reasonably quiet in the stand.

I tried the suggestion from 70sSanO to try a 9 speed chain. I put the 7 speed cassette and 7 speed Light Action shifters back on, with the Ultegra 6500 derailleur. The shifter still has the issue of not seating in place when going from harder gear to easier (without being manually pushed back into place), but the combination of the wider 7 speed cassette spacing and the narrower 9 speed chain seems to compensate for the variation in shift position caused by the shifter, and keep the chain from touching the neighboring cogs. Fingers crossed it works on the road!

The bike in question, in its current state, if you are curious:

ShannonM

If a narrower chain helps, by adding additional play into the system, that's a useful thing to know. Clearly, there's an underlying issue, and I think it's in the frame. The symptoms are classic for a bent hanger, but yours is straight, so... misalignment in the rear triangle? The hanger being square to the dropout won't help if the dropout itself is crooked.

Just a thought,

--Shannon

drewfio

Yeah, I was thinking there could be an underlying issue with the frame, given how hard it has been to get dialed in compared to almost every other bike I've worked on. But nothing looks wrong with the frame as far as I can tell. The main difference I can think of between this and my bikes is just how much smaller it is. It has 26 inch wheels on a road bike. The chain stays are very short, causing a sharper angle when the chain is not in the center of the cassette. Some of the issues persisted across the full range of the cassette though, so I don't think that can be blamed for everything. But it has added another wrinkle.

ThermionicScott 

Would it be correct to say that the indexing works correctly in one direction, but you need to overshift a bit for it to complete the shift in the other direction? If so, that is one thing, but it's not the shifter's responsibility to settle back into the detent where you wanted it to go, you have to move it back there yourself. It can't read your mind.

onitsuka_luv

this finnicky behavior can also be a result of chain and/or cassette wear in just the most used gears, changing a chain but not cassette or both of them just being worn too far together.