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I recently got an old bicycle for the sole purpose of using it on a trainer. It has old non-indexed levers for gear changing and they don't seem to work OK. The front one slips into lower after a while, and the rear one is now "locked" since it's plastic, I don't want to force it and break it.

I don't want to invest much into this bike, it was already more than I was planning to spend on it.

I was thinking to remove them and fix the derailleurs on a specific gear ratio. I would like to be able to adjust the rear one, but wouldn't mind if the process is somewhat cumbersome (ie: requires tools).

Is this possible? What would be the best path to do it?

Some pictures for clarification:

Shifters: Shifters

Front derailleur: Front derailleur

Rear derailleur: Rear derailleur

There doesn't seem to be any barrel adjuster on the derailleur side, just on the shifters.

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    First picture: If you just break away the two 'wings' of the bolt you have a metal six sided head that you can unscrew with a standard wrench for maintenance.
    – Carel
    Aug 28 '18 at 20:04
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    See the wing nuts on the side of the old levers? Those are tension adjusters. The lever that slips needs to have its tightened. The one that's stuck needs to have its loosened. It looks like it's only the wings that are plastic, so just take it apart and replace them with $0.20 wing bolts from the hardware store. Clean the mechanism while you're in there, dust and grit might be the other reason they're not working right.
    – Perkins
    Aug 28 '18 at 20:42
  • To physically remove the levers, simply unbolt them. You might then be able to use the "limit" screws on the derailers to force them to the desired gear (or there might not be enough range in the gears to permit this). If the limit screws don't do it you'd have to somehow clamp the cable in an appropriate position.
    – Daniel R Hicks
    Aug 29 '18 at 12:03
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    A side comment, if you take off any parts, then clean them and bag them, and store them away or donate to a local bike fixup cooperative. Someone might want to restore the bike someday. And "Simplex" is a good 60~70s brand name for those into authenticity.
    – Criggie ♦
    Aug 30 '18 at 10:07
  • @Criggie, yup, I always do this, I'm kind of a hoarder
    – Sorin
    Aug 30 '18 at 11:54
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The simplest method I can think of is to put the shifters into the position with the least cable tension (normally the small ring at the front as well as the rear) and then undo the cable from the derailleur. Next, move the derailleur into the gear you want and tighten the cable in this new position.

A bit more detail:

It might need two people. With the bike off the ground turn the pedals and push the rear derailleur into position and have it held there. Be careful with your fingers near the moving parts! Stop the wheel and tighten the cable. Finally use the barrel adjuster to index the gear.

Make sure the lower limit screw will prevent the chain ever going into the spokes, but it already should be doing that job.

The other tweak for the rear derailleur is to remove the inner cable and insert it directly into the derailleur and tighten it off in the gear you want. It would be very short and doesn't need to go through any housing. That would be locked in, but you could change the gear without shortening the chain, by adjusting the cable again. This would work better if the shifter proves not to be reliable for the above method.

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  • This seems like the right path, thanks I will have a look and maybe get back with a few questions!
    – Sorin
    Aug 28 '18 at 14:45
  • I don't get the second approach, if I cut the cable there isn't a way to make it fixed. I'm assuming that the gear will be selected by adjusting the length of cable visible in the last picture. However there doesn't seem to be anything preventing the cable from slipping through the upper hole. Should I make a knot or put a cable crimp on it ?
    – Sorin
    Aug 28 '18 at 15:04
  • @Sorin the Head of the cable that keeps it in the shifter would normally be sufficient to keep it in the upper hole. It’s something you can try without needing to cut the cable. But it’s worth trying the first approach first if not too late
    – Swifty
    Aug 28 '18 at 15:29
  • Yea, I was jut about to comment, I finally understood your first suggestion, and that's what I'm going to try first, If I can unstick the rear level (come to think of it, it isn't even necessary, if it sticks it should remain there). If it doesn't work (but I don't see why), I think I have some old cable arround from my other bike, I'm going to dismantle this one and and use a short length of that to try the second approach. Thanks!
    – Sorin
    Aug 28 '18 at 15:34
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If I understand correctly you have slipping shifting levers that let the derailleurs move without your intervening. A non-indexed shifter slips because the friction setting is too low.

Friction of the lever is easily adjusted by a screw at the side of the lever. If it still slips after tightening you'll unscrew the thing taking care to remember the correct order of items when is comes apart. (Take a photo maybe to assist your memory.) Then clean the bits to remove any grease and reassemble. It usually helps. At least it did in the old days before indexed gears.

Friction adjustment

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  • You are probably right, however, the parts you are pointing out on my bike are a sort of plastic cover and are cracked and turning freely. I would probably need to rip them off and use a wrench to turn the screws, but I'm not ready to do that yet, but I'm going to keep your suggestion in mind!
    – Sorin
    Aug 28 '18 at 14:37
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Yes, it is possible. The actions needed would be:

  • remove rear wheel (you need suitable wrench unless you have quick-release axle)
  • remove chain (you need a chain breaker unless you can find a master link and disengage it)
  • remove both front and rear derailleurs (most likely Phillips head screwdriver is the tool you need, perhaps suitable allen key or a wrench)
  • remove derailleur cables and shifters (again, Phillips head screwdriver, allen key or a wrench, depending on how the shifters were mounted)
  • put back the rear wheel
  • put the chain back on the desired chainring (front) and sprocket (rear), measure how long it needs to be, using the chain breaker set the correct length and affix the chain
  • tension the chain by readjusting the rear wheel

This way you have converted your bike into a semi-single speed the cheapest way possible. And you won't be carrying the weight of the parts you are not using.

If you want to go further in reducing weight you may replace the freewheel/cassette with a single-speed freewheel (you need freewheel remover tool) and unused front chainrings (you need crank remover and most likely chainring nut wrench).

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  • saving weight won't be as important if the bike is only used on the trainer, but this would convert to single speed. might be dependent on the rear fork end type being horizontal, to tension the chain
    – Swifty
    Aug 28 '18 at 13:17
  • This will only work if the frame has slot dropouts to tension the chain. Also, makes the OP commit to one gear ratio. Retaining the derailleur would be a better approach.
    – Argenti Apparatus
    Aug 28 '18 at 14:00
  • Bikes with derailleurs usually don't have any way of adjusting the rear wheel's position. Chain tensioning is the only reason to move the back wheel, and a derailleur bike uses the derailleur for that.
    – David Richerby
    Aug 28 '18 at 14:04
  • Thanks for your answer, but I would rather keep the bike intact as much as possible. Your solution would be the last resort.
    – Sorin
    Aug 28 '18 at 14:42
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The really quick and dirty method (after removing the shift levers) would be to use a vise-grip plier and pinch the cable at the required position while it's routed through a cable brazing on the frame. That enables relatively quick gear changes although the cable will get mangled over time. Another disadvantage is that you have a plier hanging from the bike and it might get in the way if you can't find a suitable spot.

Another quick method would be to tie a knot in the cable instead of using a plier but this makes it a little more difficult to accurately set the derailleur.

These solutions are the ones where cost is nil. Considering the bike won't even move as it's on a trainer, the plier method isn't that out of place.

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  • Good idea - I'd suggest a jubilee clip / spiral hose clamp rather than vise-grips which will have more mass and will wiggle about more, maybe dropping off.
    – Criggie ♦
    Aug 29 '18 at 1:40
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Your rear derailleur has upper and lower limit screws (so does the front), which will usually be either on the "knuckle" at the back of the derailleur or on the outer side plate. These limit the derailleur's travel. Because the derailleur is sprung, you really only need to worry about the low-limit screw; the spring will hold it against the limit. Depending on what gear you want, you may not get enough range out of the limit screw, but that's where I'd start. All you'll need is a screwdriver.

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    The lower limit screws won't go to the outer chainring or larger sprockets. He'll still need some cable tension to get there even if he only needs one gear.
    – Gabriel
    Aug 28 '18 at 13:07
  • One can set a derailleur to a fixed position using one of the methods mentioned in this thread: bicycles.stackexchange.com/q/24920/34697
    – Mike
    Aug 28 '18 at 13:14

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