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I have a folding bike with v-brakes and I noticed that when I pull on the rear brake lever, one arm of the v-brake doesn't go back to its original position. I tried adjusting the screws but it still doesn't go back. Although I'm not entirely sure if, when it stays in place, it hits the rim.

What could be the likely cause of this? The spring? Lubrication? Thank you.

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    They do need to be lubed occasionally. I generally use whatever chain oil I have on hand. Also make sure that the cable isn't sticking and that the rubber boot isn't restricting things. – Daniel R Hicks Oct 11 '16 at 2:45
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    You might also need to take the rim brake off the pivot and clean it as in this answer as well. I have to do this a few times every winter. – Batman Oct 11 '16 at 4:22
  • @Batman thanks! I tried cleaning it but apparently the faulty arm has a spring that has a lower tension compared to the working arm. I guess that's the culprit. – dork Oct 12 '16 at 3:18
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There are a few possibilities but its fairly easy to isolate the likely problem.

Unclip the noodle (where the cable comes out) and check if the problem is in the V brakes or the cable.

If its the V brakes, it could be a broken spring, or the brakes need oiling.

If the brakes are free to move and spring back firmly, its likely a problem with the cable or the brake lever. Without pulling the cable out of the housings, slide the cable back and forward - it should be free to move. If not, check the brake lever is free, or it could be a corroded or kinked cable. If its the cable, a replace is only a few dollars and is the best option (I almost always put in new outers as well). You can try adding some lube to the cable and working it, its usually successful but never as good as new cables. If the cable is kinked, you may have luck straightening it, but again, a new cable is always a better option.

  • All right. Thanks! I'll check it when I get home and post an update! I replaced the brake cables over the weekend but I noticed the problem even before I replaced them. – dork Oct 11 '16 at 2:59
  • @dork did you replace both inner wire and outers? Does the brake lever move freely when no wire was attached? Its probably the brake arms. – Criggie Oct 11 '16 at 6:31
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    @Criggie, yes, I did. I think it's the spring under the arm. I removed the cable from both arms. The arm that isn't going back to position, I can remove the spring easily. As for the other one, it's really hard to remove. So I'm guessing the faulty arm's spring has lower tension. – dork Oct 12 '16 at 3:17
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Daniel's comment is right, in addition check the brake lever for stiffness.

You should be able to undo the noodle from the noodle-holder, the brake arms should extend out to the sides, and each should have about the same hand-pressure required to close up.

There should be a "tension" adjust screw in the base of each arm, although I have bikes with just one and another bike with none.

Each brake arm has a spring which can normally slot into one of three positions too.

It could be one of your springs has got really weak, they don't tend to get stronger with age.

Its a lot of trial and error and tweaking.

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    All right. Thanks! I'll check it when I get home and post an update! – dork Oct 11 '16 at 2:59
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Another crude (but often effective) hack / adjustment for older or ineffectual springs is as follows: the springs - which are essentially just a long piece of heavy gauge wire that gets tucked behind a protruding peg to hold them in place - can be "untucked" (for lack of a better technical term) and then you can manually bend them out slightly by using a screwdriver, e.g. behind the curvature of the spring arm, for leverage.

This is an admittedly rather crude but yet still often very effective "hack" to bring them back to life, provided you don't overdo it to the point of causing more harm than good. This would be a hack to employ after other more "proper" ways of adjustment (e.g. tension screws or what not) have been attempted first.

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I had a similar problem in the front brake of a Schwinn Loop folding bike, but the arm wasn't moving at all. It seems like it's all rusted inside, because I couldn't even take it off even after soaking it in WD-40. I did manage to move it a bit side to side, but with a lot of force. I'll try heat from a hairdryer in a couple of days when the new brakes arrive. But if it's stuck like that, you might need to change the brakes.

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