Rotors for Occasional Track Use

3-4 events per year is enough to potentially justify a BBK. I'm at about that many events or fewer and I needed an upgrade to a BBK.

What I was experiencing was inconsistent braking performance with PFC pads and fresh Motul RBF 660 fluid. It wasn't any one part overheating, just the whole system not being able to handle it. The result was increasing braking distance with each passing lap.

This also raised a safety concern because once or twice, I didn't brake soon enough. While I only had very late apex, it could have been much worse if it was part of the track with closer barriers.

I upgraded to an ST60 kit for the front and kept the stock rear rotor and caliper. No issues so far and I have plenty of confidence going late into a heavy braking zone late a session. It's more expensive than trying to bankrupt FCP Euro on warranty returns, but overall a more enjoyable experience when at the track.

former 240 s14 wrote

This is what I saw when I ordered:

"Ready for a re-ring? ECS offers discounts on pairs of replacement rotors to the original customer or customers showing proof of ownership. Please contact the Sales Department for additional information."

And this is what I got when I asked them about it:

"Hello,
Thank you for your email. We no longer sell re ring kits for the 2 piece rotors. I can sell a replacement set at $699.00. Please contact me to place your order."

But that was in 2018, so things may have changed.

Just a quick bump as my front OEM rotors are done after a couple recent events at TMP and WGI.

I am on the fence between the FCP lifetime deal and the cheap blanks on rockauto (which aren't that cheap anymore). Leaning towards FCP since the cheap Bendix's are almost $400 shipped for the whole car and will probably wear more quickly than the OEM stuff due to worse heat dissipation.

Some of my rotor issues are due to lack of cooling which I am remedying separately. I only do about 3-4 events a year so it doesn't make sense for me to spring for a spendy BBK.

Thoughts?

You can do the freaky brakes Brembo caliper upgrade as I mentioned in another thread. Paired with OEM rotors, it adds significant cooling ability. At under $1k, it is a good budget upgrade.

Z K wrote

You can do the freaky brakes Brembo caliper upgrade as I mentioned in another thread. Paired with OEM rotors, it adds significant cooling ability. At under $1k, it is a good budget upgrade.

Can I ask how a caliper upgrade adds cooling? All of the cooling is done by the rotor which isn't changing.

nsogiba wrote

Can I ask how a caliper upgrade adds cooling? All of the cooling is done by the rotor which isn't changing.

Heat capacity is your friend too, my friend. max 20-30min for a HPED section the brembos and stock rotors can take it all . You can also upgrade to tge f80 rotors

Girodisc rotors with oem calipers is a better upgrade.

nsogiba wrote

Can I ask how a caliper upgrade adds cooling? All of the cooling is done by the rotor which isn't changing.

nsogiba wrote

Can I ask how a caliper upgrade adds cooling? All of the cooling is done by the rotor which isn't changing.

The rotor does most of it for sure, but not all of it. Some heat rejection is done through the caliper. Pads get hot, too, and some of that heat ends up in the caliper. Bigger caliper means more mass to absorb heat (less temp variation in the pads) and/or more surface area to reject heat.

AFAIK, heat capacity/rejection is the main reason optional carbon ceramic brakes often have bigger calipers than non-ceramics; the rotor doesn't absorb as much heat as a metal one would, so the caliper has to pick up some of the slack. It's also why brake fluid heat tolerance matters; if all the heat rejection were done by the rotor, it's hard to imagine why anyone would need more than DOT3.

Can't imagine swapping in bigger calipers on the same brakes would be a game changer heat-wise, but it ought to help a little.

nsogiba wrote

Can I ask how a caliper upgrade adds cooling? All of the cooling is done by the rotor which isn't changing.

As others have said, heat is dissipated by the caliper as well. Pads get hot which transfer to the pistons and into the caliper body. Pads and brake fluid overheat which causes brake pad deposits, warp rotors and brake fade on track. The caliper acts as a giant heatsink. That is why a lot of high performance brake calipers are so big while the actual pads and pistons are not as big.

The stock rotors last for years of track use with proper pads and cooling. I only need to replace them once every dozen track days or so even with stock calipers. I don't know what you're doing to fry rotors as much as you are.

Z K wrote

As others have said, heat is dissipated by the caliper as well. Pads get hot which transfer to the pistons and into the caliper body. Pads and brake fluid overheat which causes brake pad deposits, warp rotors and brake fade on track. The caliper acts as a giant heatsink. That is why a lot of high performance brake calipers are so big while the actual pads and pistons are not as big.

The stock rotors last for years of track use with proper pads and cooling. I only need to replace them once every dozen track days or so even with stock calipers. I don't know what you're doing to fry rotors as much as you are.

I guess my original was statement was a bit wrongly worded, anything touching the pad/rotor interface will ultimately help reject heat (caliper, knuckle, etc), so I follow the team there.

I think a combination of very high rotor temps due to a lack of airflow (no ducting) and long straights (140+mph on back straight at WGI) contributes to degradation of pad and rotor.

My next iteration of the setup is going to be dedicated 2.5" silicone ducts plumbed directly to the dust shield, fresh OEM rotors (aluminum hat), and Hawk DTC 70 pads. I would have bought the DTC 60s via FCP but they seem to be on backorder.

Not a big fan of DTC pads as the dust they produce is corrosive. It will eat into your wheels and paint and can not be removed if it gets wet. It is not as bad if you wash the car immediately after driving but will still cause damage if you let it sit. But if this is a track only car, you may not care.

Stupid question, but bumping this up. My rotors are having a bad time (read: warped) (E92 M3 6MT ZCP)-- dad and I did 2 track days in this car at Road America when it was his but under my new ownership I don't have real plans to track; I have an E46 which is better setup for track (bucket seats, Brembo 4 pot). With that said, I wouldn't mind having it more capable at track just 'in case' if there is a 'no compromise' solution.

Given that the Girodisc upgrade is likely to last longer than stock/FCP and I don't put a ton of miles on the car, it seems like good value. Although FCP has the warranty deal, I would expect Girodisc to last some 7-10+ years (daily driver but I WFH-- maybe 5k miles a year?). Would there by any downside to the Girodisc solution with a more street-biased/OE pad? I'm sure in the near term I would be happy with new OE for some aggressive street driving, but I don't want to regret it down the road. Brakes were BAD last year at RA but they were shuttering from the beginning, it was not good timing for a track day

TIA

BTB wrote

Stupid question, but bumping this up. My rotors are having a bad time (read: warped) (E92 M3 6MT ZCP)-- dad and I did 2 track days in this car at Road America when it was his but under my new ownership I don't have real plans to track; I have an E46 which is better setup for track (bucket seats, Brembo 4 pot). With that said, I wouldn't mind having it more capable at track just 'in case' if there is a 'no compromise' solution.

Given that the Girodisc upgrade is likely to last longer than stock/FCP and I don't put a ton of miles on the car, it seems like good value. Although FCP has the warranty deal, I would expect Girodisc to last some 7-10+ years (daily driver but I WFH-- maybe 5k miles a year?). Would there by any downside to the Girodisc solution with a more street-biased/OE pad? I'm sure in the near term I would be happy with new OE for some aggressive street driving, but I don't want to regret it down the road. Brakes were BAD last year at RA but they were shuttering from the beginning, it was not good timing for a track day

TIA

The vibration you are experiencing is due to uneven pad deposits/transfer layer. The rotors are not warped. Did you use stock pads at RA?

No issues with stock or aftermarket performance street pads.

M3SQRD wrote

The vibration you are experiencing is due to uneven pad deposits/transfer layer. The rotors are not warped. Did you use stock pads at RA?

No issues with stock or aftermarket performance street pads.

Ah yes, I recall this is as a classic misnomer-- thanks for the correction. Yes, the car is/was bone stock. I had thought that some track driving and higher temps might 'clean' them off but if anything they got worse, it was probably the worst track driving experience I've had as far as brakes are concerned.

My records show that the front rotors and front/rear pads were replaced in March of 2019, about 27k miles ago. Perhaps resurfacing is an option (pads have tons of life, rotors don't look the best though given the miles I imagine they are not running thin), though my lazy self is leaning towards full replacement. It seems like the Girodisc rotor is the most accepted 'OEM+' option for street + light track driving

BTB wrote

Ah yes, I recall this is as a classic misnomer-- thanks for the correction. Yes, the car is/was bone stock. I had thought that some track driving and higher temps might 'clean' them off but if anything they got worse, it was probably the worst track driving experience I've had as far as brakes are concerned.

For brakes to self-clean, the pads have to be abrasive. That usually requires them to be cold. For street pads, even that often isn't enough because they just aren't that abrasive no matter how cold they are.


I've also heard that hard use can sometimes even out a pad transfer layer, but IDK how that works and I don't think I've ever had it happen. I've certainly had the opposite, though – hard use making uneven pad deposits worse, as you described in your case.

BTB wrote

Ah yes, I recall this is as a classic misnomer-- thanks for the correction. Yes, the car is/was bone stock. I had thought that some track driving and higher temps might 'clean' them off but if anything they got worse, it was probably the worst track driving experience I've had as far as brakes are concerned.

My records show that the front rotors and front/rear pads were replaced in March of 2019, about 27k miles ago. Perhaps resurfacing is an option (pads have tons of life, rotors don't look the best though given the miles I imagine they are not running thin), though my lazy self is leaning towards full replacement. It seems like the Girodisc rotor is the most accepted 'OEM+' option for street + light track driving

You would need a race compound to clear off the rotor surface. When cold, race compounds will act like a brake lathe and machine the rotor surfaces, removing stock pad material in the process. This is called abrasive braking. When you’ve properly transferred a layer of pad material onto the rotor surface and the pad is up to its operating temperature range then it’s called ablative braking - pad is wearing away the transfer layer and its pad material. You want to brake aggressively at times to keep the pad transfer layer on the rotor surfaces. OEM brakes will squeal loudly without a pad transfer layer.

IamFODI wrote

For brakes to self-clean, the pads have to be abrasive. That usually requires them to be cold. For street pads, even that often isn't enough because they just aren't that abrasive no matter how cold they are.


I've also heard that hard use can sometimes even out a pad transfer layer, but IDK how that works and I don't think I've ever had it happen. I've certainly had the opposite, though – hard use making uneven pad deposits worse, as you described in your case.

M3SQRD wrote

You would need a race compound to clear off the rotor surface. When cold, race compounds will act like a brake lathe and machine the rotor surfaces, removing stock pad material in the process. This is called abrasive braking. When you’ve properly transferred a layer of pad material onto the rotor surface and the pad is up to its operating temperature range then it’s called ablative braking - pad is wearing away the transfer layer and its pad material. You want to brake aggressively at times to keep the pad transfer layer on the rotor surfaces. OEM brakes will squeal loudly without a pad transfer layer.

I appreciate the feedback on this. It looks to be generally unadvisable to resurface BMW rotors, though I don't know that running an aggressive pad could really be considered resurfacing. Though there may be some life left, at 27k miles I'm leaning towards replacement with the Girodisc

BTB wrote

It looks to be generally unadvisable to resurface BMW rotors, though I don't know that running an aggressive pad could really be considered resurfacing.

If track pads = resurfacing, I've definitely resurfaced some OE rotors and they seem fine...

On a serious note, I agree that running track pads is very different from resurfacing. It's abrasive enough to degrade or get rid of the transfer layer, but I'd never expect it to fix excessive runout or something.

AFAIK, plenty of people have run OE rotors with track pads. No issues AFAIK. Maybe a little cracking around the holes, but not until the rotors were done from wear anyway.

GTBrandon wrote

I'm looking to upgrade/replace my rotors, and will be doing 3-4 DE events a year on the car. I have PFC08 pads and motul fluid already, but seeing now that the rotors might be the biggest limiting factor.

Question is: Do you go with FCP OE rotors for unlimited replacement, PFC DD V3, Girodisc, the new Tuner rotors, or something else.

Was thinking about a BBK but I don't think it's worth the money just yet, and think doing some sort of rotor replacement is the best option, let me know if I'm wrong though.

If you do decide to go the BBK route, we have our Road and Competition Brake Kits for the e90 M3 on sale at 20% off starting next week on 11/10. Based on the way things are going with tariffs, our costs, etc., they will never be less expensive in the future. If you bought one of our front brake kits at 20% off, you'd be much further ahead than if you bought 2-piece discs in the stock sizes at all four corners. It's still not going to be cheap, but brake kits also hold their value much better than just discs. Most of our owners pound on them for several years and when they sell their car they sell our brake kit for 65-70% of what they paid new. Just something to consider.

IamFODI wrote

If track pads = resurfacing, I've definitely resurfaced some OE rotors and they seem fine...

On a serious note, I agree that running track pads is very different from resurfacing. It's abrasive enough to degrade or get rid of the transfer layer, but I'd never expect it to fix excessive runout or something.

AFAIK, plenty of people have run OE rotors with track pads. No issues AFAIK. Maybe a little cracking around the holes, but not until the rotors were done from wear anyway.

You should read up on the differences between abrasive and ablative braking because it’s obvious you don’t know about them. Abrasive braking of race pads absolutely machine away a poor transfer layer and significantly increase rotor wear rate.

Did I say you can’t run race pad compounds on stock rotors? I certainly would not recommend running stock pads on stock rotors for track use even if it’s the first track day due to braking early and over slowing the car.

M3SQRD wrote

You should read up on the differences between abrasive and ablative braking because it’s obvious you don’t know about them. Abrasive braking of race pads absolutely machine away a poor transfer layer and significantly increase rotor wear rate.

Did I say you can’t run race pad compounds on stock rotors? I certainly would not recommend running stock pads on stock rotors for track use even if it’s the first track day due to braking early and over slowing the car.

Maybe I'm misreading your response but I'm pretty sure everything I said lines up with what you said here. I did say race pads can be run on stock rotors and that they can get rid of a bad transfer layer, which... I think are your main points? Please correct me if I'm wrong.