[roku.g9]

Has anyone come off the stock rotors? If so, at what point? I'm running a 2017 m240i at 31k miles. Few track days and am wondering if I can get my warranty to replace the rotors before expiration or just flat out upgrading them for the track period. Running PF 08 pads which are great, but worried they're eating the rotors.

[dradernh]

Originally Posted by roku.g9

Running PF 08 pads which are great, but worried they're eating the rotors.

You can measure your rotors to see how close they are to needing replacement.

https://www.newtis.info/tisv2/a/en/f...rakes/JWrOrgzU

This is the tool '34 1 280' shown for measuring rotor thickness: https://parts.germainbmw.com/oem-par...10-83300495451.

[HP Autosport]

Originally Posted by roku.g9

Has anyone come off the stock rotors? If so, at what point? I'm running a 2017 m240i at 31k miles. Few track days and am wondering if I can get my warranty to replace the rotors before expiration or just flat out upgrading them for the track period. Running PF 08 pads which are great, but worried they're eating the rotors.

Most track pads can cause accelerated rotor wear at lower temperatures...meaning during your day to day street driving. After the pads reach operating temperature they are not as abrasive.

[roku.g9]

Originally Posted by HP Autosport

Most track pads can cause accelerated rotor wear at lower temperatures...meaning during your day to day street driving. After the pads reach operating temperature they are not as abrasive.

I don't understand how some people will leave track pads on for daily driving. I couldn't do it. I might even consider changing them at the track. I can confirm the abrasive ness is way tougher on street use. On track, very minimal once at operating temps.

[dradernh]

Originally Posted by roku.g9

I don't understand how some people will leave track pads on for daily driving. I couldn't do it. I might even consider changing them at the track. I can confirm the abrasive ness is way tougher on street use. On track, very minimal once at operating temps.

Well, some drivers are not only too lazy, they don't care about rotor wear, seeing rotors as fairly inexpensive wear items on a street/track car.

Ask me how I know, running DTC-70s daily as I do!

[roku.g9]

Originally Posted by dradernh

You can measure your rotors to see how close they are to needing replacement.

https://www.newtis.info/tisv2/a/en/f22-m240i-cou/repair-manuals/34-brakes/34-11-front-wheel-brakes/JWrOrgzU

This is the tool '34 1 280' shown for measuring rotor thickness: https://parts.germainbmw.com/oem-parts/bmw-template-813010-83300495451.

Thank you for sharing this!!

[Maynard]

I got new rotors under warranty, but they also will 'resurface' them if they aren't scored or warped (won't do that for regular customers, for them they give you the 'not designed to be turned down' speech). My dealership is fairly 'tracking-friendly' in this (I'd worn thru Hawks, and then basically melted down my factory pads/rotors during an HPDE and they didn't even question replacing them); yours may not be so agreeable, so you may want to swap back to stock pads before you go in to ask for this.

[roku.g9]

What aftermarket rotors have people ran? I'm wondering if I stick with OEM m performance or go aftermarket. My warranty ends in October and I don't think I'll be able to reach minimum thickness for BMW to replace under warranty. I'll be very damn close although. Oh well, stainless steel lines and rotors were on my wishlist anyways.

[dradernh]

Originally Posted by roku.g9

What aftermarket rotors have people ran? I'm wondering if I stick with OEM m performance or go aftermarket. My warranty ends in October and I don't think I'll be able to reach minimum thickness for BMW to replace under warranty. I'll be very damn close although. Oh well, stainless steel lines and rotors were on my wishlist anyways.

What is it you're trying to achieve?

[roku.g9]

Originally Posted by dradernh

What is it you're trying to achieve?

Better braking performance. 4-6 more track days lined up this year and although I have had no issues with the brakes yet, I'd rather play it safe. Saw a car run into a tire wall and get totaled after frying their brakes and trying to stop on the longest straight at Laguna Seca. Bad bad day.

[dradernh]

Originally Posted by roku.g9

Better braking performance. 4-6 more track days lined up this year and although I have had no issues with the brakes yet, I'd rather play it safe. Saw a car run into a tire wall and get totaled after frying their brakes and trying to stop on the longest straight at Laguna Seca. Bad bad day.

I don't think aftermarket rotors are going to help much unless you get units with a larger diameter. And even then I'm not sure they're going to solve the problem of heat. If you're serious about dealing with heat, you want to consider a semi-race caliper/rotor set like Stoptech makes. Or even the M Performance BBK which offers 370mm front rotors.

If you've read my temperature readings of the OEM rotors and calipers, our cars are majorly challenged due to it being difficult to channel air into the center of the rotors so that they can be cooled in-between stops. This thread details what I did to try to deal with it: https://www.2addicts.com/forums/show....php?t=1670372. With the knuckles filling the openings into the rotors, I didn't really have much success.

My opinion is that if a driver is beating on his brakes (like the one you described wrecking at Laguna Seca) or he's running at a heavy-braking track (no idea if Laguna qualifies in that regard), any brakes on our cars are going to get hotter than you want them to get. Think: checking dust boots after every event to see if they need replacement. My brakes regularly got much too hot at Mid-Ohio, a track with exactly one heavy-braking zone in a 1:44 lap; and I'm pretty easy on the brakes.

The solution is brake ducts, but there's no place to run them. I'm not sure, but msendit may have come up with something as he's developing his car seriously. Also, I believe capt_and solved the problem, but at great expense; his sale thread will give you an idea: https://www.2addicts.com/forums/show....php?t=1607481. I think his widebody kit may have given him an opportunity to get air into the center of his rotors, but I'm not sure.

[msendit]

Originally Posted by dradernh

I don't think aftermarket rotors are going to help much unless you get units with a larger diameter.

What Doug said. Aftermarket rotors won't give you better braking -- you can't fit larger ones for better cooling under the stock calipers, and your track pads should be enough to get you into ABS braking. Rotors could give you slightly better pedal feel -- I quite enjoy the feel of a fresh set of Stoptech-s for example -- but that disappears pretty fast, so definitely not worth it just for that.

And yes, Laguna is notoriously heavy on brakes.

In terms of brake ducts, I haven't done anything recently. I'm currently running 355x35 mm rotors on 275 tires and that has eliminated the worst of the brake fade.

A couple of weeks ago, I spied on the M235iRs, when they came to Sonoma for the TC America race (I run the same fenders and similar tire sizes). They had ducts in the most obvious place -- on the inside of the wheel well. Looked like the tire still caught them occasionally though -- they were plastered with electrical tape (?). Maybe I'll just do that if I need better cooling, it's a pretty minor consumable if they last 2-3 days.