[roku.g9]

For my track guys! What do you think about my front rotors? I feel like my last couple of track days have been producing these micro cracks at an exponential rate. Getting faster maybe?!

My initial reaction is that these are almost done. But curious on everyone's perspective: would you run these for a few more events or start ordering a new pair?

[Rich.Wolfson]

Originally Posted by roku.g9

For my track guys! What do you think about my front rotors? I feel like my last couple of track days have been producing these micro cracks at an exponential rate. Getting faster maybe?!

My initial reaction is that these are almost done. But curious on everyone's perspective: would you run these for a few more events or start ordering a new pair?

Running track days costs brakes and tires. I never go to the track without new bedded pads and rotors ready to go.

That's just me.

///Rich

[msendit]

Originally Posted by roku.g9

For my track guys! What do you think about my front rotors? I feel like my last couple of track days have been producing these micro cracks at an exponential rate. Getting faster maybe?!

My initial reaction is that these are almost done. But curious on everyone's perspective: would you run these for a few more events or start ordering a new pair?

They're perfectly fine :-) Micro cracks on our heavy cars are pretty common -- one rule of thumb is to change the rotors when the cracks make it all the way from the hat to the outer edge. To give you an idea, once you start leaning on the brakes, it can take as little as a session to have them looking like yours. For the next set, stay away from the dimpled / drilled ones -- it exacerbates cracking.

Congrats, you've gotten faster!

[dradernh]

Originally Posted by roku.g9

For my track guys! What do you think about my front rotors? I feel like my last couple of track days have been producing these micro cracks at an exponential rate. Getting faster maybe?!

My initial reaction is that these are almost done. But curious on everyone's perspective: would you run these for a few more events or start ordering a new pair?

The color of your calipers indicates that you've significantly overheated your braking components. But what choice did you have, as they're not really up to the task of not overheating when slowing our cars as they're being run hard on a race track.

My calipers are still the same color of blue that they were when the car was new. However, they're also in need a rebuild. The dust boots are cracked, and while I've yet to look at the piston seals, I'm pretty sure they need replacement as well. The last thing we want on the track is to have a piston seal fail, allowing brake fluid to leak out onto a rotor that's going to set the fluid on fire.

My take is that the stock calipers' pistons should have their dust boots and piston seals examined at whatever an appropriate interval is to ensure that they're still doing the job they're designed for. I don't know what that interval is, but if I was tracking my car regularly I'd certainly want to find out and have boots and seals handy when replacement was necessary.

The general rule of thumb on cracks is that as long as they're not wide enough to catch a fingernail as it's dragged across the rotor at a fairly sharp angle, you're still okay.

I'm going to disagree with my good friend msendit here. While I do agree that drilled rotors are to be avoided as far as track duty goes, you've got dimpled rotors, and I don't see your dimples having anything to do with the still-beginning cracks you've got. Nevertheless, his point is well-taken: look carefully at where your cracks are beginning, so if it matters, you're aware of it. My take is that slotted-only rotors are the best choice for track or street/track duty.

When I was going to the track a lot, I followed the approach described by Rich.Wolfson. That way, I was never left high and dry when I needed fresh parts in the middle of an event. Practicing replacement away from the track makes doing that work at the track go quite a bit easier. Of course, at a BMW event (as well as many others) there's frequently help at hand if you're not sure how to proceed. Still, self-sufficiency is generally the best way to deal with this hobby's inevitable hiccups.

BTW, my experience with brake components overheating (detailed here: https://www.2addicts.com/forums/show....php?t=1670372) indicated that a brake upgrade would be a wise investment if regular track duty is on an owner's calendar. In that regard, StopTech's kits are popular. I haven't used them, but I have used AP Racing's kits on another BMW, and my judgement is that they're as good as it gets. Unfortunately, Essex Parts, AP's representative in the US, apparently isn't ever going to make a kit for our cars. However, this source has done the work to make an AP kit available to us: https://www.tomwrigleyperformance.co...vpf-ymm-search.

The principal fact I can share about AP's calipers and rotors is that they guarantee a first-time, every-time braking experience. During the years I ran a pro-built, pro-am championship-winning BMW race car in HPDEs and TTs, I never, ever had to think about how my brakes were going to behave. They were like the transmission – they simply worked, doing the same thing every time I asked them to, and I asked a lot of them. If you're serious about getting better at the track, I believe the value of that quality of experience cannot be overstated.

Alternatively, upgrades to the stock Brembo calipers include stainless steel pistons and high-temperature boots and seals. The former was mentioned here recently by another member, but I can't find the post now. For the latter, I found this source: https://www.ohioperformancesolutions.com/. I'd also recommend doing what I had done: find a way to get however much air you can flowing through the small opening into the center of the front rotors. It won't be much, but here we're talking about every little bit helps.

Coming at this another way, I'd like to mention that the better you are as a driver, the less you use the brakes. I know that's counter-intuitive (and that you may already know this! ), but the better, faster drivers are using the brakes hard for very short intervals of time. Of course, each braking turn dictates the general braking profile that might be seen on a software channel trace, but the basic idea is: get on 'em smoothly and hard, get off 'em smoothly and easy, and have the car at the maximum speed at which it can still turn-in. Naturally, trail-braking/brake-steering is always turn-dependent.

Have fun as you get better and faster!

[roku.g9]

Originally Posted by dradernh

The color of your calipers indicates that you've significantly overheated your braking components. But what choice did you have, as they're not really up to the task of not overheating when slowing our cars as they're being run hard on a race track.

My calipers are still the same color of blue that they were when the car was new. However, they're also in need a rebuild. The dust boots are cracked, and while I've yet to look at the piston seals, I'm pretty sure they need replacement as well. The last thing we want on the track is to have a piston seal fail, allowing brake fluid to leak out onto a rotor that's going to set the fluid on fire.

My take is that the stock calipers' pistons should have their dust boots and piston seals examined at whatever an appropriate interval is to ensure that they're still doing the job they're designed for. I don't know what that interval is, but if I was tracking my car regularly I'd certainly want to find out and have boots and seals handy when replacement was necessary.

The general rule of thumb on cracks is that as long as they're not wide enough to catch a fingernail as it's dragged across the rotor at a fairly sharp angle, you're still okay.

I'm going to disagree with my good friend msendit here. While I do agree that drilled rotors are to be avoided as far as track duty goes, you've got dimpled rotors, and I don't see your dimples having anything to do with the still-beginning cracks you've got. Nevertheless, his point is well-taken: look carefully at where your cracks are beginning, so if it matters, you're aware of it. My take is that slotted-only rotors are the best choice for track or street/track duty.

When I was going to the track a lot, I followed the approach described by Rich.Wolfson. That way, I was never left high and dry when I needed fresh parts in the middle of an event. Practicing replacement away from the track makes doing that work at the track go quite a bit easier. Of course, at a BMW event (as well as many others) there's frequently help at hand if you're not sure how to proceed. Still, self-sufficiency is generally the best way to deal with this hobby's inevitable hiccups.

BTW, my experience with brake components overheating (detailed here: https://www.2addicts.com/forums/showthread.php?t=1670372) indicated that a brake upgrade would be a wise investment if regular track duty is on an owner's calendar. In that regard, StopTech's kits are popular. I haven't used them, but I have used AP Racing's kits on another BMW, and my judgement is that they're as good as it gets. Unfortunately, Essex Parts, AP's representative in the US, apparently isn't ever going to make a kit for our cars. However, this source has done the work to make an AP kit available to us: https://www.tomwrigleyperformance.com/?year_id=118&make=159&category=23&s=&post_type=pro duct&action=vpf-ymm-search.

The principal fact I can share about AP's calipers and rotors is that they guarantee a first-time, every-time braking experience. During the years I ran a pro-built, pro-am championship-winning BMW race car in HPDEs and TTs, I never, ever had to think about how my brakes were going to behave. They were like the transmission – they simply worked, doing the same thing every time I asked them to, and I asked a lot of them. If you're serious about getting better at the track, I believe the value of that quality of experience cannot be overstated.

Alternatively, upgrades to the stock Brembo calipers include stainless steel pistons and high-temperature boots and seals. The former was mentioned here recently by another member, but I can't find the post now. For the latter, I found this source: https://www.ohioperformancesolutions.com/. I'd also recommend doing what I had done: find a way to get however much air you can flowing through the small opening into the center of the front rotors. It won't be much, but here we're talking about every little bit helps.

Coming at this another way, I'd like to mention that the better you are as a driver, the less you use the brakes. I know that's counter-intuitive (and that you may already know this! ), but the better, faster drivers are using the brakes hard for very short intervals of time. Of course, each braking turn dictates the general braking profile that might be seen on a software channel trace, but the basic idea is: get on 'em smoothly and hard, get off 'em smoothly and easy, and have the car at the maximum speed at which it can still turn-in. Naturally, trail-braking/brake-steering is always turn-dependent.

Have fun as you get better and faster!

Incredible response! Thank you for the time. I wasn't at all worried about the caliper color(although I kinda like the dark green it's turned into lol), as I knew from many friends on these calipers that it just comes with seat time. Nonetheless, I agree with everything you've laid out. I don't cut corners on safety , and prior to my most recent track day I did have my calipers inspected(thanks to bmw for damaging a rotor I had to replace out of pocket).

Overall, I'm very happy with the stock system after upgraded fluid and pads. The car has handled 100+ degree days at Thunderhill just fine, and I actually mostly track at Laguna Seca due to such nice weather a majority of the year. I think I'm going to call it a season and swap back in my street pads, before cautiously hitting some more days next year on these rotors again.

[edycol]

I would agree with everyone here, but personally I would go solid rotors or at most slotted if possible.
The structural integrity is higher, they are cheaper. Also, when I go to the track I bring in my box brake tools and set of front and rear pads and front rotors. Just in case. Practice at home. With Brembo calipers, changing pads is super easy and if something goes wrong you can quickly change rotors too.