mikew968

At what minimum thickness do you change out your front pads?



Thanks,

mark kibort

I pulll them at 4-5 mm

ProCoach

ExMB

Most event forms require a minimum of 50% pad thickness to start an event.

ProCoach

Typical new thickness of the front pad friction material for a Seventies 911 is .595", a Boxster is .610"

So, a little more than a quarter inch is 50% wear, so about .300" thickness, or about 7-7.5mm, which is the thickness of the typical backing plate.

Gary R.

After 50-70% my pedal travel told me it was time to change them. I like the nice high brake pedal new pads and fresh fluid gives..

ExMB

I just changed PFC11s on my car and the backing plate is 5mm with pad material being 12mm F and 13mm R. The total thickness is reflected in the PFC PN as 17 and 18.

IAW with Clark's reference chart your numbers come in approximately 3/16" thicker overall.

Bill Lehman

If after an event they measure 50%, I leave them in for another event.

bgiere

IME it depends on the pads...PFC pads I can run down to fairly thin limits and they do just fine...Hawk and Pagid got cruddy at 50%

fatbillybob

I think it depends on the brake system. Every system has a weakest link. Full pad is better like new tires but how low can you go? Around 2010 in scca T1 a c5 vette racer was airlifted out at Runoffs from an exploding rotor with brake failure. We complained earlier and often for an aftermarket brake allowance for safety. We got it after someone got hurt. Stoptech knew our problem and designed and tested their SCCA T1 brake kit on my c5 vette racecar. It is so over engineered that I can and have raced my pads down to a millimeter of the pad backing with no percievable loss of braking ability while rotors last at least 1 1/2 years. And I don't bed in pads or cryo rotors nor season them.

so you have to track your system and log some data or you will probably spend more on consumables

HenryPcar

Your brake system is hydraulic and pedal height and firmness stay the same regardless of the wear on the pads.

Matt Romanowski

System compliance and caliper stiffness change in practice.

Brake performance at the top level is a very deep rabbit hole. Things like caliper stiffness, age fatigue (hardness changing), seal performance, seal material, seal aging, assembly oil, all make big differences. Then in the pads themselves, some compounds oxidize over time after they are heated, so their performance changes with just time (not use). Some are very stable in regards to oxidation, but can have other problems. Depending on the brake pad material, pads have different thermal conductivity. This thermal conductivity changes how much heat gets to the caliper and then you start the whole seal, stiffness, flex problems. You also have different alloys in calipers where some deal with high temps better than others.

When you don't have control over most of those items, like in a street car, look at the overall wear rate for the track your going to decide from there.

Gary R.

Well thank you for the intelligent insight but you are wrong. Thanks for the comment, but maybe don't comment when someone speaks from fact until you have a clue...

HenryPcar

Your original comment stated :
After 50-70% my pedal travel told me it was time to change them. I like the nice high brake pedal new pads and fresh fluid gives..

Surely there are other variables, but you did not specify as such. I'm merely commenting on your post which might seem highly intelligent to you, but not to other readers having to guess where you are coming from.

mark kibort

pedal travel has little to do with brake pad wear at levels of 50 to 70% the travel has to do with how much fluid push it takes the pads to contact and create friction on the discs. this doesnt change with pad wear by design. however, if you do observe a correlation, it could be due to air in the system as the pads have worn to those levels (50-70%)

this is true. PFC seem to handle extreme temps very well. pagid oranges were the worst. i remember pulling off 5mm pads to have pieces of the pads fall out as they were removed.

that is by design, yes.

observation doesnt mean correlation. Im a firm believer if you are going to claim someone wrong you better bring your data and reasoning.

50 to 70% wear shouldnt effect pedal travel. the design of a modern master cylinder creates a mechanism where pad wear (piston extension) to not effect pedal height or feel