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Sorry for question language. This is a phenomena that I observed. I was on a stationery bicycle and applied the rear brakes. When I tried to move backwards, the bike won't budge. But when I tried to move it forward, the wheel started to turn slightly. Please note that the wheel did not drag or spin. But moved forward. The bike has cantilever brakes. Does it have to do something with the angle of brakes mounted?

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  • Hard to say. Perhaps a photo might help.
    – jwh20
    Commented Sep 30, 2022 at 12:44
  • Thank you for your precious comments. BTW, the same phenomena can be observed in front wheels. When the front braked are applied, the wheels could move backwards, but not forward.
    – user18398875
    Commented Sep 30, 2022 at 15:30
  • Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.
    – Community
    Commented Sep 30, 2022 at 16:08
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    Check the axle nuts - they're probably loose
    – FreeMan
    Commented Sep 30, 2022 at 18:14
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    By "stationary bike" I presume you mean an ordinary bike that wasn't moving, not a stationary "exercise bike".
    – Daniel R Hicks
    Commented Sep 30, 2022 at 22:19

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I suspect you're discussing the difference between dragging the rear wheel when you have locked-up the brakes, vs pushing the opposite direction.

If so, this is more of a physics question - and the same-but-reverse effect happens with a bike's front brakes in that you pull the bike toward you far easier than push it away.

  • As you push the wheel away from you the locked-up brake prevents the wheel from rotating at all.
  • Due to vectors, your push on the bike and the pushback from the tyre on the ground are not exactly opposite, so this creates a torque or rotation.
  • When pushing, that rotation makes the front of the bike dive downward, increasing the pressure of the tyre on the ground and creating more friction, therefore grip.
  • In contrast when pulling the bike, the rotation imparted by braking makes the pulled-wheel (or the rear wheel in a normal bike) lift, decreasing the friction with the road and lowering the barrier to enter the "sliding friction" state instead of the "static friction" state.
    Vehicles can brake faster with controlled braking rather than going beyond into a state of skidding.

Upshot - what you have observed is normal, and part of your basic M check before riding a bike. A quick hard-squeeze on the brake levers, and a push/pull of the bike to confirm the brakes are working is a standard check before riding.

It doesn't matter where on the frame the brakes are - disk and rim, band or roller brakes all do exactly the same as long as they can lock the wheel.

Incidentally, the physics described above is exactly why the front brake does 90+% of the braking on a normal bike, and the rear is there as a backup. The best braking effect you can get on any bicycle is when the front is doing almost 100% of the work, and the rear is just about-but-not-quite breaking traction with the road

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    Just about the only time I use the rear brake is to avoid rolling backward when I'm stopped on a steep incline (and for exactly the reasons you've given).
    – Ray Butterworth
    Commented Oct 1, 2022 at 0:48

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