matt33

I have an odd situation with my rotor and pad wear. 997 GT3 running Girodisc rotors and Pagid RS29 pads (which I like a lot).

380mm front rotors show cracks after 10 days (pads last around 8 days)
350mm rear rotors dont crack at all and wear out (!) after 30 days (yet pads only last 5-6 days)

Would better cooling to the fronts improve the rotor life? (perhaps go with the cup lip with air cut-outs?)
Would a better bedding-in procedure help the rotor life?

One other data point.. several of these driving days were 100F+ and the rears were well worn before these really hot days.

Any thoughts?

Matty

Tim the Engineer

I had a friend who had the same issue when he installed 380 mm Girodisc front rotors and 997.2 GT3 calipers on his 987.1 Cayman race car.

The theory put forward was that the discs were too big, and that they were over-cooling on the straights, thus introducing too wide a range of heat cycling.

fnel1771

+1^

TRAKCAR

Cool down gently.. Not much else to do?

Frank 993 C4S

Interesting theory. I've never heard that one before. Been running the same rotors for 6 years without issue provided you bed pads properly and you manage cool down.

Tim the Engineer

Well, there is a certain logic to it. My discs seems to last, too. Running 350/325 on the Cayman.

matt33

I've never heard of this either. It would almost imply a cool down lap (with all that airflow) is detrimental to rotor life and coming straight into the pits would allow a more gradual cool down.

Not a crazy thought.. I have just always thought more cooling the better as a general rule, but that is probably rooted in helping the brakes function better, not necessarily to extend rotor life.

Matty

Tim the Engineer

I think it was more the idea of repeated hot-cold cycling inducing repeated heat stressing, rather then a single cycle such as a cool down lap. Also, coming to a standstill in the pits after a race or track session causes the temperature of everything to shoot up, as there is no longer any cooling.

As I said, it was just a theory.

However, I am somewhat curious as to why we all insist on putting on the biggest everything on our cars. Is there really a point in putting on brakes or tires that are bigger than required? Does it does is all cost, weight and rotational inertia...

matt33

Ok got it.

In this case these are OEM rotor sizes

85Gold

Because this is “The Super Size it country” I will say the stock CS 987.2 brakes are marginal when pushed but I never felt the 350mm brakes on my 6GT3’s weren’t up to the task.

Peter