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From a few days now, when trying to pedal standing, my pedals become very rigid and it sounds like if the brakes are dragging. If I sit down again, the noise goes away and it's easy to pedal again. In fact, if I just try to apply more pressure to the pedals to go faster, the problem happens again.

I thought that the brakes were the problem so I adjusted them and I know they are not dragging. The chain and gears are well lubricated. I'm trying to fix this by myself so I can learn. Can you help me to figure out what the problem is?

  • What kind of bike is it? Does it have a derailleur? Single Speed? Fixie? etc. – Batman Aug 18 '15 at 19:01
  • I would guess that either you have bad bearings somewhere or the chain is getting jammed (due to loose bearings or a misaligned derailer) when you do this. Or the chain could be worn out. – Daniel R Hicks Aug 18 '15 at 19:05
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    More information may be needed. What happens if you put the bike on a stand and try to pedal? Can you feel the friction or the pedals/wheel hanging up on something? – Gary.Ray Aug 18 '15 at 19:08
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    How is your rear wheel attached to the bike? Specifically do you have a quick release or are there nuts on each side? It sounds to me like you have nuts and the one on the right side might be loose. If this were the case, when you put more pressure on the chain it could be pulling the wheel forward on the right causing it to drag on the left chain stay. Then as you ease up on the pedals the tight left nut would serve as an anchor point letting the axle move back to its original centered position. You can probably see this happen if you are comfortable looking down while you are peddling hard. – dlu Aug 18 '15 at 19:20
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    Another possibility I've seen more than once is a broken frame. Plus I've seen similar symptoms when the rear sprockets are badly hooked. – Daniel R Hicks Aug 19 '15 at 2:25
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Something is dragging as you pedal harder. The most likely thing is that your rear wheel is moving so that the tire drags against the chain stay when you apply power.

This is something that you'll probably need to troubleshoot when you're riding because it isn't likely to show up with the bike on a work stand. You might be able to make it happen by applying a standing load to the pedals while holding the front brake. To do this I'd want somebody holding the bars to stabilize the bike (and to help me look for what moves when I load the chain).

The interesting thing about what's happening is that you say the problem goes away when you ease up. If the problem is due to the tire rubbing on the chain stay then there must be some mechanism to return the wheel to its neutral location. The only thing that I can think of right now that might do this is a nutted rear axle where the nut on the right (drive) side is loose enough to allow the axle to move under load and then move back when the load eases up.

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    Loose bearing will also do this, that's pretty much the entire point of the bearing races/cups. – Móż Aug 19 '15 at 2:04
  • Do you know how loose the bearing would have to be to permit the tire to rub on the stay? Seems like it would be quite a bit. – dlu Aug 19 '15 at 8:05
  • I've seen track and racing bikes with only a couple of millimetres between the tyre and frame, so the wheel bearings don't have to be very loose at all for that to rub. – Móż Aug 19 '15 at 8:29
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My guess is that your rear end is flexing and either:

  • Rear rim is touching the brake pad, or
  • Tire is rubbing the chainstay

With the former, try checking your wheel alignment and loosing your brakes a bit (safely) and testing.

With the latter, look for tire rub marks in your chainstay area where the chainstay meets the bottom bracket.

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