1

When I have my back brake fully on my rear wheel rocks about an an 1" back and forth? My other bikes have no play.

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  • Likely this is because the brake arms flex that much. This is just the way this particular bike works. Sep 27, 2021 at 15:03
  • 5
    Disk or rim brakes?
    – mattnz
    Sep 27, 2021 at 18:24
  • A whole inch, really? That's a lot, I can't see how any of the standard-suspect issues could cause that much play. Sep 27, 2021 at 22:50
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    Where does the movement/looseness come from? Is the axle moving? Is the brake moving? Is the hub moving relative to the axle? Is the rim rotating/moving relative to the axle?
    – Michael
    Sep 28, 2021 at 5:57

1 Answer 1

2

There are a few possible reasons:

  • Flex in the brake arms, as mentioned in the comments. Obviously not for disc brakes which are stiffer and mounted closer to the axis of rotation. It's also possible for the arms to be stiff enough but mounted loosely.
  • Some unusual brakes built into hubs seem prone to a dead zone that feels like this.
  • Fat soft tyres deform more easily than hard skinny ones, and there's more rubber to deform, so this movement will be far more noticeable on an MTB than a road bike.
  • A loose wheel. If all the spokes are a little loose, especially with low spoke counts and/or radial spoking, they'll flex enough to display this effect (note that radial spoking isn't a good idea with disc wheels, because of this torque, and also shouldn't be used on the back, so shouldn't be your problem).

A loose hub or QR skewer is more likely to cause a partly side-to-side movement, at least with disc brakes, and is easy to check - but do check the wheel is in securely (especially at the front, as front wheel failures are bad news)

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  • 1
    A radially spoked wheel isn't a good idea for rear wheels, disc or rim brakes. So I don't believe it could be a radially spoked wheel.
    – juhist
    Sep 27, 2021 at 15:41
  • @juhist - you're right, I forgot to go back and mention then when I checked and saw it was the rear. but the main bit of that point holds (loose, or low count)
    – Chris H
    Sep 27, 2021 at 15:43
  • 2
    Loose caliper mounting bolt will also cause this.
    – mattnz
    Sep 27, 2021 at 18:25

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