Turning Rotors

[macdude357]

For a track car, it seems like rotors end up cracking way before they get too thin. I came across this article on the ECS site that talks about turning the rotors to remove the surface cracks/crazing:

http://ebcbrakes.com/articles/surfac...n-brake-discs/

Seems like it would be a good way to get more life out of your rotors. Anyone ever tried this?

[///Mobbin]

It makes sense but you may have trouble finding a shop to turn slotted or drilled rotors as the cutting bit can get stuck on the slots and holes. I have turned regular flat rotors that were pad deposited before and they were perfect after turning, hadn't really thought of it for surface cracks though, nice.

On a related note, I have been using PFC08 pads which wear very flat (no visible grooves) but get super hot and cause a good amount of cracking as a result. I wanted to switch to more aggressive pads anyway and am trying Pagid Blacks next which claim to eat into the rotors and cause grooving (hoping they eat away the cracks). Would be interesting to use a combo of pads like this to maximize rotor life but I'll admit it's more of a theory and fun experiment than anything else.

[macdude357]

Originally Posted by ///Mobbin

It makes sense but you may have trouble finding a shop to turn slotted or drilled rotors as the cutting bit can get stuck on the slots and holes. I have turned regular flat rotors that were pad deposited before and they were perfect after turning, hadn't really thought of it for surface cracks though, nice.

On a related note, I have been using PFC08 pads which wear very flat (no visible grooves) but get super hot and cause a good amount of cracking as a result. I wanted to switch to more aggressive pads anyway and am trying Pagid Blacks next which claim to eat into the rotors and cause grooving (hoping they eat away the cracks). Would be interesting to use a combo of pads like this to maximize rotor life but I'll admit it's more of a theory and fun experiment than anything else.

I'm using PFC08's as well. I put temp paint on my rotors and it hit well over 1200 degrees (I'm usiing the StopTech Aero Rotor OEM replacement rotors). Since ECS sells their drilled/slotted rotors and recommends the ProCut lathes, I would imagine those would be OK. There are a few shops nearby that have the ProCut lathe that charge around $80 per axle. So I might just give it a try.

[roastbeef]

No plans of a bbk?

[macdude357]

Originally Posted by roastbeef

No plans of a bbk?

Not until my existing rotors are toast. Even then I'm on the fence because it would put me in the B2 class for Bimmer Challenge. I don't really have any issues with brakes other than it takes longer to swap pads so hard to justify the expense.

[roastbeef]

Well what are you planning on if you keep oem brakes? Replace with new oem rotors? Slightly used rotors?

I will be replacing the rings on my bbk for the first time in a little bit. It's always talked about how a bbk can save money in the long run... it's now quite clear to me now that this is true- a set of rings is just a few hundred bucks more than a set of pads.

[macdude357]

Originally Posted by roastbeef

Well what are you planning on if you keep oem brakes? Replace with new oem rotors? Slightly used rotors?

I will be replacing the rings on my bbk for the first time in a little bit. It's always talked about how a bbk can save money in the long run... it's now quite clear to me now that this is true- a set of rings is just a few hundred bucks more than a set of pads.

I'm using the Stop Tech Aero rotors so I can get a new set of friction rings for those.

[roastbeef]

Oh, I see.

[macdude357]

Originally Posted by roastbeef

Well what are you planning on if you keep oem brakes? Replace with new oem rotors? Slightly used rotors?

I will be replacing the rings on my bbk for the first time in a little bit. It's always talked about how a bbk can save money in the long run... it's now quite clear to me now that this is true- a set of rings is just a few hundred bucks more than a set of pads.

How many track days did you get out of your rings/pads? Right now, I've got about 12 days on my rings and they look like they'll last a few more days at least. My PFC08 pads lasted about 12 days as well.

[roastbeef]

Originally Posted by macdude357

How many track days did you get out of your rings/pads? Right now, I've got about 12 days on my rings and they look like they'll last a few more days at least. My PFC08 pads lasted about 12 days as well.

Probably about 10 days or so... I've gone through one set of ds2500's and just about two sets of race pads. I'm using ferodo dsuno pads though, they are a bit more aggressive than the longer lasting ds1.11's which I will be sampling next.
Keep in mind, I say "a day", but when I make it up to Laguna, I do double run groups and every lap but the last lap is a hot lap. Two of those days were at Laguna. I might be putting these rotors through what would be some people's equivalent of 15+ days depending on the track and coordinator (track time and brake demand).

[admranger]

Originally Posted by macdude357

I'm using PFC08's as well. I put temp paint on my rotors and it hit well over 1200 degrees (I'm usiing the StopTech Aero Rotor OEM replacement rotors).

Great info.

[redpriest]

Originally Posted by macdude357

How many track days did you get out of your rings/pads? Right now, I've got about 12 days on my rings and they look like they'll last a few more days at least. My PFC08 pads lasted about 12 days as well.

25 days on mine using nothing but DS1.11

[scotty_miller]

Originally Posted by macdude357

I'm using PFC08's as well. I put temp paint on my rotors and it hit well over 1200 degrees (I'm usiing the StopTech Aero Rotor OEM replacement rotors). Since ECS sells their drilled/slotted rotors and recommends the ProCut lathes, I would imagine those would be OK. There are a few shops nearby that have the ProCut lathe that charge around $80 per axle. So I might just give it a try.

Good call on pro cut lathes. The pro cut lathe company makes an on car lathes and they can in fact cut slotted and drilled rotors no problem. I had them cut on my 135 when I had Stoptech slotted rotors and the PFC 08 heat cracked them. Any shop should charge you between $80-100 per axle. Anytime there is deep grooving I would recommend new rotors. If you are anywhere near the minimum discard thickness I would toss the rotors and buy new. Anytime you take a certain thousandths off a rotor they are prone to warping and might do so under the heat they face at the face at the track as-well-as crack even quicker than before. But it also depends on how much you have cut off the rotor too

[bigjae1976]

Originally Posted by roastbeef

Well what are you planning on if you keep oem brakes? Replace with new oem rotors? Slightly used rotors?

I will be replacing the rings on my bbk for the first time in a little bit. It's always talked about how a bbk can save money in the long run... it's now quite clear to me now that this is true- a set of rings is just a few hundred bucks more than a set of pads.

Are you replacing due to cracking or min run out? I've ran through 5 sets of track pads on my ST 380mm drilled rotors and they are still above the min run out. They do have a lot of cracking but nothing that would make them unserviceable.

[roastbeef]

Originally Posted by bigjae1976

Are you replacing due to cracking or min run out? I've ran through 5 sets of track pads on my ST 380mm drilled rotors and they are still above the min run out. They do have a lot of cracking but nothing that would make them unserviceable.

Cracking. I don't have a caliper to measure, but the j-hooks appear to be a bit shallow just eyeballing them.

[macdude357]

Originally Posted by redpriest

25 days on mine using nothing but DS1.11

How close to min thickness were your rotors? I'm wondering if all your street miles might have worn the rotor down, effectively making the cracks shallower giving your rotor longer life.

[Bellwilliam]

edit:

btw. cracking often caused by no cool down lap (for brakes).

[redpriest]

Originally Posted by macdude357

How close to min thickness were your rotors? I'm wondering if all your street miles might have worn the rotor down, effectively making the cracks shallower giving your rotor longer life.

There isn't really a minimum thickness per se with the AP Racing rotor. What I was told, was that it would crack long before you got to it - but essentially, all the J hook slots would be gone when you were there. There was plenty of depth left in the slots when I decided to replace them.

[bigjae1976]

Originally Posted by roastbeef

Cracking. I don't have a caliper to measure, but the j-hooks appear to be a bit shallow just eyeballing them.

Not familiar with the Ferodo pads. I have observed some pads tend to cause more cracking and crazing than others. PFC pads seem to generally cause more heat stress cracks whereas a Pagid causes less cracking but wears down the rotors faster.

On my E46 M3, I've ran through 4 sets of pads (1 PF01 and 2 Stoptech SR34s and 1 SR33). My rotors were at 30.8mm (32mm new) but the heat cracks were getting to the point of making the rotors useless. Luckily, the rotors discs are the same size front and rear on the E46 so I just swapped the fronts to the rear.

[roastbeef]

Originally Posted by bigjae1976

Not familiar with the Ferodo pads. I have observed some pads tend to cause more cracking and crazing than others. PFC pads seem to generally cause more heat stress cracks whereas a Pagid causes less cracking but wears down the rotors faster.

On my E46 M3, I've ran through 4 sets of pads (1 PF01 and 2 Stoptech SR34s and 1 SR33). My rotors were at 30.8mm (32mm new) but the heat cracks were getting to the point of making the rotors useless. Luckily, the rotors discs are the same size front and rear on the E46 so I just swapped the fronts to the rear.

The dsuno is the most aggressive race pad they make (I think). I'm sure that translates into more heat...

[M3 Number 86]

Originally Posted by macdude357

I'm using the Stop Tech Aero rotors so I can get a new set of friction rings for those.

how do you like those compared to oem? do they cool better? lighter? last longer?

btw pfc08 was eating up my rotors and not providing great braking and feel for me personally. i like rotor friendly aggressive pads like carbotech and gloc pads. but then after a few events you need new pads but rotors last forever.

i was looking for pfc rings but apparently they don't make them for our chassis. didn't know stop tech had some.

but last sunday at button willow the weather was perfect and my oem brakes felt like bbk!

[roastbeef]

Originally Posted by Bellwilliam

edit:

btw. cracking often caused by no cool down lap (for brakes).

only time i don't get a proper cool down lap is at laguna seca. kinda sucks, but they do it this way to maximize run group times. if you see a checkered flag at turn 8, they want you off the track in three more turns... its maybe 1/2 mile of "cooling down" at the downhill portion of the track. what is customary, is guys doing huge circles in the large parking lot area behind the paddock for a cool down. other than that, i'm pretty good about getting everything cooled down before parking the car.