So I bought a used vintage bike. I just love the bike and it's awesome. However it came with one problem: gears problems. First of all I have very little experience with bike, especially gears (currently watching youtube videos to learn more).

The problem that I have in the bike is three folds:

1- The shifter for the front gear is soft, so there is absolutely no tension when you move it. So if you move it, nothing actually changes in the front gear at all. My question regarding this problem: could it be the shifter itself that is broken or could there be something else wrong? (i.e. like cable problem, or front gear problem itself). I'm trying to troubleshoot the problem.

2- I have never seen such shifters ever before, so if the switchers themselves are broken, are there still old school switchers like these? If so, do they have specific names so I can look them up online? Because when I search for "shifters", I only get the new popular ones!

3- The last problem has to do with the rear gears, the switcher doesn't switch to all speeds and I have no idea what's the problem.

Here are pics for my cool bike :D (so happy about it):

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  • It's probably something to do with tension, see how the cables have lots of slack along the frame tube. But I just wanted to say that the bike is cool but the back mudguard construct is hard to fathom ! Ahh you are carrying an extra mudguard in the pannier ! OK ! Cool
    – gaurwraith
    Commented Aug 4, 2015 at 21:03
  • Those are called "stem mount" or "quill mount" shifters. I think if you search on the full name you'll find some. You might also be able to make a downtime shifter work. Suntour made a nice one that had a wraparound strap that I think could be shortened so that it would work on the stem.
    – dlu
    Commented Aug 5, 2015 at 6:00
  • @dlu downtime? downtube? Spell checker?
    – Chris H
    Commented Aug 5, 2015 at 9:59
  • Ack, right you are, it should be down tube. Silly spell checker…
    – dlu
    Commented Aug 5, 2015 at 20:45
  • That bike almost certainly needs new cables, and a tuneup. A bike shop can fix you up. Commented Sep 13, 2015 at 12:31

5 Answers 5


At first glance I see the problem you are having .

Those are NOT friction shifters . They are positron shifters .

Research Shimano Positron Shifters for a more definitive explanation

This was Shimano's earlier attempt at an indexed gear system. Also known as "Positive Pre-Select" or PPS.

The main differences are that the indexing is in the deraileur rather than in the shifter on the handlebar. As a result, the bowden cable is a full housing and has a thicker solid inner rather than a woven stranded cable.

Upshot - you can't just fit any old cables to the rear mech. However its possible the front deraileur is just a standard non-indexed friction shifter.

  • 1
    Gidday and welcome to SE Bicycles - that's an excellent lead. However we prefer the answers to be self-contained rather than "go search this term" so I am about to edit your answer with more details. If I mess up your meaning please feel free to re-edit or revert.
    – Criggie
    Commented Jan 26, 2016 at 20:11

There are two (or three) very specific issues that are causing this problem.

The first is the cable housing is not routed correctly. For both derailleurs, there should be an open run of exposed cable along the downtube; the rear derailleur should have an open run going out to the rear derailleur as well. It looks like the stop for this, which should be clamped near the top of the downtube is missing, so the previous owner zip tied/taped the continuous run housing. Long runs of housing like this, especially with plastic shifters, lead to poor shifting, which is causing the "soft" shifting. That little U-shaped bracket near the rear derailleur: cable stop.

Second is the shifter itself. If you shift, and the lever simply springs back into place, then the little bolt on the side of the lever needs to be tightened. If you shift and the lever stays in place, you need to loosen the bolt holding the cable into place, and make sure that there is no slack in the cable. If there is, pull the cable tight, and bolt it back into place.

Regarding the rear derailleur not working correctly in all speeds: That is a Shimano Positron derailleur, which used a solid wire rather than a twisted cable for shifting. It looks like the wire has been replaced with a cable, which will not work properly at all. Spare wires have not been available for 20+ years, as Positron was considered a failure and discontinued rather quickly. This is definitely the nexus of the poor rear shifting.

Although this is not my usual position on repairs, I would recommend replacing both derailleurs and shifters. When you do, make sure that you add a cable stop to the downtube, so that the cables can be routed correctly. A good shop should have the required parts, or be able to do the work correctly for you.


These are called friction shifters and you can still buy new ones. You should be able to get better performance from the ones you have though. Note the 2 black plastic wing nuts on the side of the shifter. It is very important to tighten these enough to get the right amount of friction to stop the derailleur slipping out of gear. It takes a bit of trail and error to get right.

As commented above with point 3), you need to set the right amount of tension to get the correct range of movement in the derailleur. You may also need to adjust the small limit screws (with Philips heads) to help set this range.

These type of shifters are tricky to use. You need to listen and look at the gears to see you have engaged the one you want.

  • You may also need to re-align the rear derailleur if it's been in a crash, or it won't shift well (even with friction shifters). Also, depending on how you flex the bottom bracket area, you may have sone bad shifting.
    – Batman
    Commented Aug 5, 2015 at 0:21

The derailleurs (aka switchers) are controlled by the cable that runs between the lever and the derailleur. On most bikes, increasing the tension in the cable will move the front from the inner chainring towards the outer chainring.

Here's what I'd do:

  • First, I'd look carefully at the front derailleur and put a bit of oil on all of the places that look like pivot points.

  • While you're there look for two screws that adjust the limit stops of the derailleur (this adjustment keeps the derailleur from shifting the chain off the chainrings). They are usually marked H and L and they are probably the only screws that are on the derailleur body (as opposed to the screw on the clamp around the seat tube). If you look at the bottom of the screws you should see a bit of metal set up to hit them as the derailleur moves. It may be hitting on screw but if it is there should be a big(ish) gap at the other screw. Might as well oil the screws too.

  • Oops, there will be another screw, it's the one that clamps the cable that actuates the derailleur. Find that screw and the lever it is attached to, it's the lever that will actually move the derailleur when the cable is pulled. Try moving the lever down towards the cable – as if the cable is pulling it. The derailleur should move towards the large chainring (or maybe the small one, a few front derailleurs are made that way, but they are not too common). If it moves freely and then moves back when you let go of the lever that's a good thing. If it doesn't check the lever and the cable and see if you can move the lever and if the cable follows it – if you can get some slack in the cable so that you can move the lever and confirm that the derailleur is moving freely.

  • At this point if the derailleur moves, you can assume that it can be made to work. So follow the cable, does it seem to move freely? If not a bit of oil may help. Once you have the cable moving, check its tension. When you move the lever to slack the cable (to shift onto the smaller chainring), the spring in the derailleur will pick up the slack and the cable will stay taut. If this doesn't happen you need to go back to that screw that clamps the shift cable and loosen it, then pull the cable tight and clamp it again.

That should get you close. If the cables are old they may need replacing, and you should probably replace the housings at the same time. They aren't too expensive.

Those shifters are pretty much bullet proof. It will take a lot to stop them from working. They are really simple. Pretty much all that can go wrong is rust or a loose adjuster (if this is the case you'll be able to pull on the cable, but as soon as you let go it will go right back to the original position). All you need to do this is to tighten the screw on the side of the shifter.

  • Ok, I'm too tired to rewrite this now, but after editing the question I realized that I think the OP was using switchers to mean shifters. I'd originally read switcher to mean derailleur. So this needs a major edit…
    – dlu
    Commented Aug 5, 2015 at 5:57

Unfortunately, you own a bicycle with Shimano PPS Positron rear derailleur, cable and shift lever. These things were pure garbage; they seemingly always failed, required unique parts that were ONLY made by Shimano ( nothing else would fit or work) and were not very good.

  • Option 1: remove any and all Shimano Positron parts (i.e. rear derailleur, cable, shift lever) and then replace those utterly useless parts with any 'conventional' rear derailleur, cable and shift lever. This is time consuming and might be expensive... perhaps not worth doing.

  • Option 2: give or throw this bicycle away, then get any other bicycle that does NOT have Shimano Positron... there must be a very large mountain in a landfill somewhere that all these monstrosities ended up.

  • 1
    Hi, welcome to bicycles. This seems a bit ranty; you might want to edit it a bit to remove unnecessary vitriol and make it less SHOUTY (tip: try _emphasis_). Also suggesting that OP call Shimano about a part they haven't made in 30 years seems a bit quixotic; I can't think of a single thing that would still be under warranty after that long.
    – DavidW
    Commented May 30, 2020 at 4:20
  • Other than the grumping, what does this add to Cary's answer from 2016?
    – Criggie
    Commented May 30, 2020 at 12:54

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