I know these cars have wear sensors but whats the minimum thickness of the pads before they need replacing?

 

Depends on usage. If it is a street car driven conservatively you can run them pretty thin. The whole issue is one of heat transfer. You don't want the pad so thin that the backing plate will transfer excess heat to the piston faces and their seals. That can cause damage. If you have 3mm of pad left and it's the conservatively-driven street car then you won't ever build much heat. On the other hand, if it is a track car and you are planning on doing a day at a track that is hard on brakes, it would not be wise to go out with 3mm remaining.

 

Track car pads should be replaced when the pads are the same thickness as the backing plate.

 

As per Porsche manual the minimum thickness before replacement is 2mm (.08in). But it is better to change them (2.5 to 3mm) before the pad wear warning sensor touch the disk. You won't have to replace it and save $20.00... A new pad thickness is about 12mm. An please correct me if I am wrong but if the sensor touch the disc you need a reset with a Durametric or PIWIS tool...

 

Agaiin, I think that depends on usage. If I went on track with 3-4mm of pad thickness, they would be in the danger zone before the day was through. I run paint on my rotors and stickers on my calipers so I can know how hot things are getting. If everything is at upper limits for caliper temp, which directly relates to pad temps then 2-3mm would probably put me in danger of transferring too much heat. My car runs pretty fast at some tracks and therefore requires more and longer periods of friction/torque to bring it down than on slower cars. Depends on usage. PFC-01 compound on Brembo GT kits.

 

Al, you are way ahead of me.I'm just going by what the tech inspectors in my club are telling me. I upgraded to GT3 6 piston calipers and 350mm discs that have ceramic piston inserts. I use Pagid yellows front, Pagid blacks on the rears.
When you change your pads, how thick are they?

 

In the past I wouldn't go to a weekend with less than 6mm on the high side of the taper. For this season I have just switched over to PFC-06 which supposedly has nearly as much torque as the -01 but is designed as an endurance racing pad. Damn, I sure hope so. I have no data on those pads thus far.

Historically a set of -01 front pads with Brembos 4 corners was lasting 3 days. Before I changed to rear Brembo GT's from the 997 rear rotors with 996 calipers and Pagid Blacks, the front 01's were lasting 2 days.

This is my experience and doesn't necessarily translate to straightaway speeds and braking habits of others; only mine.

That's my roundabout answer to your question. My change would occur at anything under 6mm if I were preparing for a 2-day event, i.e. slightly more than 50% pad remaining.

 

all Al's info is spot on. you can run to 2-3mm on the street before replacement and I think that is what the OP wanted to know. for track work I would never go to the track with pads at or below 50% due to the increased heat transfer and increased fluid temps even with my brake set up.

 

mine is going in next week to have the pads replaced. if i find out any more info i'll post it up. i'll post up some pics of the pads they are replacing as well. my brakes just started squeaking a bit now, but my warning light has yet to come on.