AlanHK

I've got these SIS shifters on an old bike with a triple crankset. The front lever moves up to "3" (large ring), but then falls back. Is there a way to adjust the tension in the lever so it stays on 3? Other levers have a screw in the middle, but can't see one here or an obvious way to open it.

Andrew R Stewart 

Not sure what "screw in the middle" you're talking about...

First think I think of is too much cable tension for where the high limit screw is (needs to be?) set. Andy

AlanHK

Yes, my point was, I can't see one. Thought there might be a concealed one.
Or is the tension just not adjustable?

First think I think of is too much cable tension for where the high limit screw is (needs to be?) set. Andy[/QUOTE]

When adjusting the cable I just pulled the cable taut for the low limit (just enough to take the slack out). If I pull the lever to shift to high gear, it shifts smoothly but then slips back. The high limit doesn't seem relevant.


Googled and found this: https://bicycles.stackexchange.com/q...shift-into-3rd
which suggests the shifter grease is too sticky, needs fresh lube.
So still need a way to open the thing to clean and lube it?

Andrew R Stewart 

Let me be less obtuse, what do you mean by "screw in the middle"? That's not a common bike component reference. Do you mean a cable length (usually said as tension) adjuster?

Remove the cable from the ft der. Holding the now free end of the cable move the lever through it's range. Do all three "click" points engage? If so then the shifter is not likely to be a problem. Check to make sure that the cable moves freely as a hinderance or kink at the wrong point could upset things.

As I tried to suggest a common reason for your issue is that the der reaches it's travel limit (as set by the high limit screw) before the lever has fully engaged the 3rd click point. Your photos show a shifter with an adjusting barrel. Have you attached the cable slack enough to need to slightly turn the adjuster to get 1st and 2nd "positions" to work friendly? If so the use it to try to get the 3rd position to stick. Andy

AlanHK

Not cable tension, tension inside the lever body. Maybe should say how much resistance against the cable tension.
I used to have downtube shifters with a tension screw or adjuster dongle in the middle. Like below. Maybe that's only on friction shifters, not index ones?






I'll test the shifter as you suggest later.

Andrew R Stewart 

Ah, now I see. Most indexed shifters have little or no real cable spool friction. In fact reducing any friction within the shifter is a goal. This is a separate aspect then the spool rotation springs. The springs usually are fairly weak and only serve to rotate the spool as the pawl is released, augmenting the der's parallelogram return spring.

With friction levers one needs enough lever pivot friction to hold it's position against the der's return spring (and other forces like frame flex). With an indexed lever the pawl and catch serve to hold the lever/cable/der in position. When shifting into the larger sprockets (for most ders, ft and rr) the lever has to overcome the der's return spring. If the lever is friction then the friction setting is also added to the effort to move the lever. With an indexed lever there's no extra friction to overcome.

But indexed levers bring into the picture the inability to move off of the index click point by an amount less then the next click point and stay there. So the lever will just rotate back until the last pawl/catch and stop there. If the cable is too short/tight then the lever might never reach that third point. If the lever once did reach the 3rd point/click and no cable adjusting has been done then the limit screw might have been turned in a tad and now doesn't allow the cable to move as far as before.

It is these various possibilities (and that we can only write and not touch/see) that make me take a step by step method to assess. When I adjust a der I don't only use the lever to move the der. I pull on an exposed cable or use my fingers to shift, checking on the der's function without another device (the lever) in play. One device at a time gets checked. When I install a cable and before attaching it to the anchor bolt I will pull on the cable and cycle through the lever's travel, to confirm the lever's function. Only after confirming each end's function can you assume that pairing the ends will be able to be coordinated properly. Andy

dedhed

Ratchet pawl likely sticking.
Give it a good flush with WD40 while working it back & forth. Once it starts catching, flush it some more. Finally give it a spray of lube like Tri flow.

Or replace https://www.ebay.com/itm/NOS-Shimano...MAAOSwfhtdNzKD

mitchmellow62

A history might help. Newly acquired? In the stable a long time? Working fine until recently? Never worked right? Etc.

+1 on too much cable tension. I'd follow Andy's great description and methodology: release the cable at the derailleur, check and/or reset limits by moving the derailleur with your hand, check shifter function while the cable is still detached, screw out the barrel adjuster at the shifter a little (it looks to be screwed all the way in and won't allow one to reduce tension when fine tuning; perhaps another clue), attach the cable and see what you've got.

By the way, indexed 3x7 thumb shifters are pretty cheap if replacement is needed. Even cheaper used at a coop.

stanman13

Is the front shifter even indexed? Frequently they are not. Honestly if it were mine I'd just source a set of cheap friction shifters and be done. Or at least just a left/front one. Ten bucks:

https://smile.amazon.com/Sunrace-SLM...y&sr=8-1-fkmr2



EDIT: Or, if you want the original style, twelve bucks:

https://www.ebay.com/p/Shimano-SL-TY...F-R/1932731278

AlanHK

So releasing the cable, the shifter will lock into "3".
But even unscrewing the H limit screw on the derailleur all the way, it can't go that far.

So, the derailleur and lever are a mismatch. Either the builder didn't care it didn't work or it's a replacement.
Both parts work, but not together.
Also, the cable rubs on the body of the derailleur, and the spring on low gear. Not going to wear it out, but it surely cannot be designed to do that.





So I'll look for new shifters and/or derailleurs.

-- This bike is a "rescue", i.e. I picked it up from the roadside with a torn up tube and seat and generally grubby. But parts show very little wear, no chain skip, brakes and rear gears are fine. So far invested about $10 in fixing it. So can't complain too much.

JoeTBM 

First try routing that cable over the tab on the anchor bolt, not through it. This will fix your rubbing problem and also may clear up your popping out of high gear issue.

dsbrantjr

+1 Having the wire go under the tab instead of over shortens the lever arm, which will increase the force needed and also throw off the indexing, moving the derailleur too far per lever click.

AlanHK

?? I don't understand what you mean.

Andrew R Stewart 

The cable anchor bolt has a tabbed washer under it's head. The cable is trapped between this tabbed washer and the der arm. By running the cable to the outside of the tab you change the amount the der moves per lever click point. The effective lever arm the cable is working with changes by how the cable is run around the tab.

Having said all that it looks to my eyes that the tabbed washer is not OEM to that der anyway, it looks to be for a different der and you can see the end of the tabbed washer's cable groove just to the left of the obvious tab. There's a less obvious tab behind the cable and that groove extends past that tab to the washer's other side. I seriously wonder if this ft der is designed to work with the levers shown. Andy

JoeTBM 

Look at this article, about 1/2 way down there are pictures of incorrect and correct routing at the front derailleur anchor bolt.

https://bikerumor.com/2013/01/09/new...install-notes/

The one on the right is correct

AlanHK

Yeah, it just bumps on the H limit long before the lever reaches its "3" lock point.

mitchmellow62

If the front derailleur is Shimano I have a hard time believing it is not compatible with the shifter. Especially in the 7 speed era. However, I prove my ignorance almost every day! I've never totally liked indexed front/left shifters and would probably go for a cheap friction replacement. Inexpensive and you can easily trim the derailleur.

You haven't said how the shift to the 2/intermediate ring is. If that is perfect I'm at a loss and perhaps they are incompatible. Otherwise I would look at alternate cable attachment (shortening the lever arm so the same cable pull moves the derailleur less) or maybe play with some slack in the cable when the shifter and derailleur are in the 1/smallest ring (relying on the low limit stop). However, either approach would also change the derailleur position in the 2/intermediate ring.

AlanHK

I was sceptical, but gave it a try.
And it works.
Cable is now not rubbing on the body and most importantly, the lever now goes to 3 and clicks, so the chain stays on the big ring.
Kudos Joe!
Problem was at the opposite end I had first thought.

Andrew R Stewart 

Glad this is figured out. Andy

JoeTBM 

Glad it worked out for you, now get on it and go riding.

mitchmellow62

Wonderful! A lengthened lever arm; further proving my ignorance. lol!