Brake pad performance & wear vs. thickness

[wemorgan]

As per the title, does anyone know how the brake pad performance & wear changes vs. the thickness?

Thanks.

 

[Dieselman]

They do seem to overheat and sing nicely when getting worn down. Braking performance drops off when they overheat.

Having once parked at a customers and the car being completely engulfed in smoke assured me they had indeed overheated.

 

[wemorgan]

I'd imagine the temperature change is a function of the pad volume, but would it be linear? That seems a little drastic to me as I doubt a 4mm pad gets twice as hot as a 8mm pad, or does it?

 

[kth286]

it's about disapating the heat.

 

[wemorgan]

So I guess a thinner pad would disapate the heat quicker to the backing plate and caliper than a thicker one.

So are pad minimum thickness specifications given to stop the risk of owners wearing down to zero thickness, rather than the brakes not performing as well when at a reduced thickness?

 

[Dieselman]

So are pad minimum thickness specifications given to stop the risk of owners wearing down to zero thickness, rather than the brakes not performing as well when at a reduced thickness?

Yes, but thin friction material overheats more quickly in my experience.

 

[markjay]

I also believe that over time the actual mating surface area reduces compared to brand new pads and discs, due to deformation. This should also reduce braking efficiency.

The other problem is that when the brakes get hot, the brake fluid gets hot as well and may reach boiling point at the calliper. This actually happened to me some years ago, very eerie as the pedal just goes down like it was pushed into soft rubber with the car hardly slows down. All was back to normal as soon as the brakes cooled off.

 

[wemorgan]

Thanks guys. One for further research I feel

If it helps where I'm coming from is: My front brake pads have done 3 track days and are now ~60% worn. I have two more tracks days booked in quick succession. I'm basically wondering when to change my pads. I'll of course check the pads during and after each track day, but would rather start each track day knowing my pads/discs/tyres will last the full day.