I have friction shifters and for some reason the front one gives me a bit of trouble. It tends to return to its most untensioned state. So say I want to shift to a higher gear, it will try to drop me back down to my lower gear. My guess is I might need to lube up the cable and shifter. Any other known solutions?
With friction shifters this is usually caused by one of two problems:
- Loose Shifter Screw: Friction shift levers usually have a wing-nut-screew used to adjust the tension and friction of the lever against the mounting housing. Tighten this screw, but not too tight or else you can't move the shift lever. You can also take the shifter apart (noting carefully the order of the parts) and clean everything with degreaser. DO NOT LUBE - you are trying to regain friction, not remove it.
Edit re. ʍǝɥʇɐɯ - After you adjust everything you may find that the shifter screw continues to come loose almost immediately - in that case you may want to use a little 'adjustable/removable' Loctite on the screw, assemble, and let it sit for a while before using. That should help hold everything together.
- Cable Friction: Often there will be one or more points of friction on the cable route. This could be in the housing, or in the routing channels under the bottom bracket. As you apply pressure to the pedals the frame flexes, pulling the cable one way, but then the friction stops it from sliding back. Check and clean your housings and routing points, especially at the bottom bracket.
I thought you might want to know the historical background to this particular problem and how to fix it so that it stays fixed...
Suntour 'Power Ratchet' friction shifters contain a spring and a ratchet, with the ratchet working one way, the idea being that it should be easy to shift gears with them. On most of their shifters of this era, e.g. the down tube, top-shifter and bar-end variants, there was a ratchet in both levers. However, with the stem-mounted shifters (as commonly found on more affordable bikes) they skimped on the ratchet for the left hand lever.
Here is a diagram for a down-tube lever, note the two ratchets (10):
Now here is what you have, note how parts (10) and (11) only feature on one side:
So the lever set is 'defective' from the start, no little ratchet like you have on the right lever. The consequence of this is that the lever is always trying to undo the screw. Plus, even if you do not actually use the gear, there is the small matter of road vibration, this too loosens the screw.
To remedy this problem you need to increase the friction on the screw (17), not the lever gubbins as a whole. Place a small dollop of Loctite on the screw thread, do up the screw to how it suits you and the job should be a good one.
Hope that helps!