Brake shoe - coefficient of friction & Area

In summary: Additionally, a wider shoe will create more drag which could affect vehicle performance in a negative way.
  • #1
k.udhay
160
10
Hi,

Will I have a higher slipping force / torque by increasing the width of my brake shoe and drum? Though my instinct says it is possible, textbook says it's only the coefficient of friction that controls the slipping force. Can you pl help me understanding this? Thanks.
 
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  • #2
The friction force is determined by the coefficient of friction and how hard the brake shoe is pressed against the drum. A brake shoe with larger area squeezing the drum with the same force will not give a larger friction force.

However, since the brake shoe has a larger area, there will be a smaller force per unit area on the brake shoe, so it will not wear out as quickly.
 
  • #3
With a lot of material combinations the coefficient of friction is not constant and depends on the pressure. Often a reduction in pressure will increase the coefficient of friction.

Another separate effect is that, as mentioned, it will not wear out as quickly, so you could also use a different (softer) material to get a higher coefficient of friction with the same wear rate as previously.
 
  • #4
With a wider drum there will be a greater area to dissipate heat, so peak temperatures will be lower.
 
  • #5
Thank you all. Sorry for a late acknowledgment!
 
  • #6
As said earlier, a wider shoe/drum will absorb and dissipate more heat. Heat affects the friction coefficient of the shoe. Depending on the material, an optimal temperature exists to get the peak friction coefficient. If it is too low or too high, the friction coefficient goes down and if its high enough it can go down to practically zero (brake fade).

Shoe compounds for street vehicles are usually of the 'cold' type, meaning they work well with relatively cold parts. Racing compounds are usually of the 'hot' type, because the brakes are always relatively hot due their frequent use. On the other end, racing compounds can have friction coefficient lower than street compound at lower temperatures. How to Choose the Best Street and Track Brake Pads

So with the same shoe compound, a wider shoe absorbs and dissipates more heat and thus will exhibit brake fade later.
 

What is the coefficient of friction for a brake shoe?

The coefficient of friction for a brake shoe is a measure of how much friction is generated between the brake shoe and the surface it is in contact with. It is typically represented by the Greek letter mu (μ) and is a dimensionless quantity.

How is the coefficient of friction determined for a brake shoe?

The coefficient of friction for a brake shoe is determined through experimentation and testing. Factors such as the material of the brake shoe, the surface it is in contact with, and the amount of force applied are taken into consideration when calculating the coefficient of friction.

What is the relationship between coefficient of friction and braking performance?

The coefficient of friction plays a critical role in the braking performance of a vehicle. A higher coefficient of friction means that more friction is generated between the brake shoe and the surface, resulting in a stronger braking force and shorter stopping distance.

How does the area of a brake shoe affect its coefficient of friction?

The area of a brake shoe does not directly affect its coefficient of friction. However, a larger surface area can distribute the braking force over a larger area, resulting in a lower pressure and potentially reducing the coefficient of friction. Conversely, a smaller surface area can increase the pressure and potentially increase the coefficient of friction.

What factors can impact the coefficient of friction for a brake shoe?

Several factors can impact the coefficient of friction for a brake shoe, including the type of material used, the condition of the surface it is in contact with, the temperature, and the amount of force applied. Additionally, factors such as moisture, oil, and debris on the surface can also affect the coefficient of friction.

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