Do disk brakes resist being pulled out?

[carlfogel]

When two pads squeeze a moving rotor with thousands of pounds of force in a disk brake, the friction resists the rotation of the disk enough to slow a car.

How much resistance (if any) does the squeezing of the pads provide if you try to pull the moving rotor out at roughly 90 degrees?

Imagine a rotor that is spinning steadily and powerfully on an axle in front of you, while a pair of pads on its far side steadily squeeze and brake it.

How hard do you have to pull the axle toward you to pull the rotor out from between the pads?

Will a tiny tug gradually pull the rotor out from between the pads?

If so, will it take an appreciably long time for the minute force to pull the rotor free?

Or is a powerful pull required, a force above some lower limit?

Or does it depend on how powerfully the pads are squeezing the rotor? That is, can the rotor be easy to pull out under light braking, but much harder under heavy braking?

Please feel free to use whatever figures are most convenient.

(The question came up in a weird disk brake thread in a bicycle forum. The well-meant replies did not inspire confidence.)

Thanks,

Carl Fogel

 

[Machinus]

The force of friction between the disc and the pad will increase, linearly as the speed, as the pads are moved toward the outside of the disc. If the wheel is driven and moving at a constant angular velocity, then it sort of depends on where the pads are relative to the force being used to pull the wheel. The pads will not just slow down the wheel, but exert a vector force on the chassis that they are attached to. So the answer is that yes they might, depending on their position.

 

[GSXR750]

In general, disk brakes are designed to resist being pulled out due to the friction created by the pads squeezing the rotor. The amount of resistance will depend on a few factors, including the force applied by the pads, the speed and rotation of the rotor, and the material and design of the brake system.

If you were to try and pull the rotor out at a 90 degree angle while it is spinning, you would likely encounter a significant amount of resistance. This is because the pads are exerting a strong force to slow down the rotation of the rotor, and pulling it out would require overcoming that force. The exact amount of force needed would depend on the specific brake system and its settings, but it would likely be more than a "tiny tug" and could potentially require a powerful pull.

Furthermore, the amount of resistance may vary depending on the level of braking being applied. As you mentioned, the rotor may be easier to pull out under light braking, but more difficult under heavy braking. This is because under heavy braking, the pads are applying a greater force to the rotor, creating more friction and resistance.

In terms of time, it would likely take some time for a minute force to pull the rotor out, especially if the brake system is properly functioning. This is because the friction created by the pads would need to be overcome, and the rotor may also be spinning at a high speed. However, if the brake system is not functioning properly or the pads are worn, it may be easier to pull the rotor out with a smaller force.

Overall, disk brakes are designed to resist being pulled out due to the friction created by the pads. While the exact amount of force needed to pull the rotor out will depend on various factors, it is safe to say that it would require a significant amount of force and would not be an easy task.