Vented rotors stop better or just run cooler?

[Christian]

My Z3 1.9 has the same non-vented front rotors as the early 318ti. It's time to replace the brakes and I'm considering installing new calipers to accommodate the vented rotors like 6 cylinder Z3's and E36 sedan/coupes have. I'm not sure if it's worth it though.

The only time I really use the brakes hard is when i autocross my car. The car doesn't get driven hard on the street, and my area doesn't have any hills, twisties, or any roads that really requires hard braking. The autocross runs are usually around 75 seconds, which isn't enough time for the brakes to get the brakes overheat.

Since the brakes don't get really hot when autocrossing, is there a benefit to upgrading to vented rotors? Will the car actually stop better during autocrossing? Or would they just keep the brakes cooler during repeated hard braking, such as driving mountain roads, etc.

[spidertri]

Vented rotors are most helpful for hard, repeated stops, such as track days and "canyon runs" (if you're into that).

At autox, I'd rather have the lower unsprung and rotational weight of the solid rotors. You'll also want to keep as much heat in the rotors as possible at autox.

[Christian]

Originally Posted by spidertri

At autox, I'd rather have the lower unsprung and rotational weight of the solid rotors. You'll also want to keep as much heat in the rotors as possible at autox.

That's certainly something to consider, although I'm sure the difference is negligible. Every little bit helps though.

[1996 328ti]

Do vented rotors change your autocross class?

[MINIz guy]

If they came stock on your car, then no. I believe the later model ti's, such as 99's, had vented front rotors. You'd still run in the same class as a 95 ti with solid front rotors.

Not sure about the update/backdate rule, but I think for street touring, you are allowed to switch to vented rotors if your car had solid rotors and vice versa. For street class, I think you're stuck with what you have.

[Christian]

Originally Posted by 1996 328ti

Do vented rotors change your autocross class?

In my case, no, it wouldn't change the class. I currently classed in SSM due to my DASC.