I’ve had some brake fade issues in my V70 T5M following a Corvette down hills with lots of switchbacks. The Shenandoah Mountains are my favorite place to play (safely), because the speeds remain reasonable. Descending on twisty roads is of course hard on brakes; “effective” motor power and acceleration is increased, “effective” mass/momemtum of car is increased as you fight the additional effects of gravity pulling your car down the hill, repeatedly decelerating hard into swithbacks/corners. Our time down the hill is limited by brakes overheating / fading more than any other factor.
My question is about how to best address the brake fading issue.
At first I thought, bigger rotors is what I need. But recently somewhere online I saw a list of the weights of various size rotors that can be fitted to the P2 cars (I’ve lost where that list is… can anyone help me find it?). Now I wonder if the more massive rotors are better, due to the increased thermal capacity or inertia. I’m running the 305mm rotors, and I noticed on the list that numerous larger rotors were actually less weight (e.g. the 316s). Only the R rotors showed significantly greater weight than the 305s. Can anyone here confirm these observations?
I’m leery of going with the relatively massive R rotors, because theory suggests then I’ll get less grip on uneven road surfaces – more unsprung mass makes the suspension less compliant. Rotational inertia (and thereby acceleration) also takes a hit, both because of heavier rotors and because of the larger wheels required. (That can be its own topic: the advantages/disadvantages of larger wheels w.r.t. acceleration, cornering, etc.) Besides which I don’t know how hard it will be to fit the R-rotors and calipers to my car (and I’d have to get bigger wheels… running OEM 16″ Metis presently).
Then there’s the variable in rotor type or brand. Assuming the same size and weight, which rotors are better at dissipating heat? I read somewhere else that the shape or angle of the vanes (vented front rotors) can affect cooling, or slotting or drilling the brake surface? From the pictures online, I see some rotors have vanes that go all the way to the “hat” and others have the vanes only under the braking surface. I expect these details to make some difference.
The other factor to consider is the brake pads… I gather that ceramic pads are less likely to fade because they run cooler? I don’t understand quite why that would be. On any given downhill run, the energy absorbed in the brakes would remain the same, and the way that energy is stored and ultimately dissipated also remains the same: thermal. How is it possible that one kind of brake pad would run cooler than another? Or is it that ceramic pads function better at higher temperatures? If so, then I have to worry more about brake fluid boiling?
Maybe I’ll just have to slow down.
Looking forward to any comments on this, focussing on the brake fade problem.
Thanks,
Boris