Opinion on Big Brake Kits & Tracking

[MasterP]

Originally Posted by M3SQRD

On my e46 M3 track car I had used CT race, PFC 01 race, CT race (finished off an old set) and then PFC 05 race pads all on the same set of rotors. I didn't have any issues mixing CT and PFC compounds on the same rotor.

PFC race compounds will easily clean off the CT 1521 street compound.

I'm sure you can get away with it. But CT says you can't/shouldn't.

http://www.ctbrakes.com/faqs.asp#troubleshooting5

[F3IGHTY]

Originally Posted by M3SQRD

On my e46 M3 track car I had used CT race, PFC 01 race, CT race (finished off an old set) and then PFC 05 race pads all on the same set of rotors. I didn't have any issues mixing CT and PFC compounds on the same rotor.

PFC race compounds will easily clean off the CT 1521 street compound.

Same, I’ve mixed pads with CT, P Mu, Ferodo, Stoptech, never had an issue.

[SEAT TIME RULES]

Originally Posted by jacobe92

Stay clear of Carbotech brake pads, they're garbage. BBK rotors are pricey and they'll eat your rotors alive. Spend a little more to get quality ones. Not making that mistake twice. I like the Endless ME20. Moreover, I also hear good things about the Brembo RE10.

CT's are garbage? Why? I've run them for years now using DBA rotors.
The pads are pricey but they don't eat rotors when cold, but still can handle 1300 degree temps...

[ashmostro]

Originally Posted by M3SQRD

There's a decent amount of your front rotor face not being used. ST, or other pad manufacturers, doesn't offer a pad with a larger radial depth for the ST60 caliper so all of the rotor is used? Using all of the rotor face with a larger pad will decrease pad wear, increase the area to transfer kinetic energy to thermal energy, and decrease rotor temps. I'm just surprised to see this much of the rotor not being used - why does ST offer such a large rotor ring if they had no plans to offer a pad to use the increased rotor radial depth?

So I emailed the man himself, Dave Zeckhausen, about this issue of there being very few full radial depth race pds for the ST-60 and he had a very interesting answer for me that I wasn’t expecting, but makes a lot of sense to me:

The reason StopTech went with wide annulus rotors for the F80 was not to increase pad surface area. Rather, it was to increase thermal mass and heat-shedding ability via radiation. The former is a function of weight. The latter is a function of surface area (not necessarily swept). Thus, the wide annulus rotors don't reach temperatures as high and they cool down significantly faster than the standard annulus rotors.

Finally, the use of standard annulus pads slightly increases brake torque over using the taller pads. Intuition might be that it would reduce brake torque, because of reduced surface area. But intuition is wrong. Brake torque is a function of pad Cf (a constant, regardless of swept area), clamping force, and effective radius. The key here is that effective radius equals the distance from the center of the hub to the center of the brake pad. If the pad doesn't hang down as close to the hub, then the center of that pad is actually further away from the hub than the taller pad. That INCREASES torque.

[FlyingLow78]

Originally Posted by ashmostro

So I emailed the man himself, Dave Zeckhausen, about this issue of there being very few full radial depth race pds for the ST-60 and he had a very interesting answer for me that I wasn’t expecting, but makes a lot of sense to me:

The reason StopTech went with wide annulus rotors for the F80 was not to increase pad surface area. Rather, it was to increase thermal mass and heat-shedding ability via radiation. The former is a function of weight. The latter is a function of surface area (not necessarily swept). Thus, the wide annulus rotors don't reach temperatures as high and they cool down significantly faster than the standard annulus rotors.

Finally, the use of standard annulus pads slightly increases brake torque over using the taller pads. Intuition might be that it would reduce brake torque, because of reduced surface area. But intuition is wrong. Brake torque is a function of pad Cf (a constant, regardless of swept area), clamping force, and effective radius. The key here is that effective radius equals the distance from the center of the hub to the center of the brake pad. If the pad doesn't hang down as close to the hub, then the center of that pad is actually further away from the hub than the taller pad. That INCREASES torque.

What's applicable to my situation (and my crash) is that using a narrow annulus pad concentrates the friction in a smaller area, so the pad gets hotter for the same amount of friction than a wide annulus pad. I came so close to melting my front pads that they turned rainbow colors and adopted a flakey appearance. They got so hot they just wouldn't stop the car.

Dave is super knowledgeable and he really helped me sort out my issues after another vendor failed me twice.

Next time out at Monza (if there is a next time...) I will use a pad that doesn't lose friction until a much higher temperature. Dave has already found me a set of pads that should do the job.

[ashmostro]

How's the car doing friend?

[FlyingLow78]

Originally Posted by ashmostro

How's the car doing friend?

The '15 is totaled and I've cannibalized as much as I dare without it looking obvious. The '18 is being built as we type.

[ashmostro]

Godspeed. Glad things appear to be working out.

[M3SQRD]

Originally Posted by ashmostro

So I emailed the man himself, Dave Zeckhausen, about this issue of there being very few full radial depth race pds for the ST-60 and he had a very interesting answer for me that I wasn’t expecting, but makes a lot of sense to me:

The reason StopTech went with wide annulus rotors for the F80 was not to increase pad surface area. Rather, it was to increase thermal mass and heat-shedding ability via radiation. The former is a function of weight. The latter is a function of surface area (not necessarily swept). Thus, the wide annulus rotors don't reach temperatures as high and they cool down significantly faster than the standard annulus rotors.

Finally, the use of standard annulus pads slightly increases brake torque over using the taller pads. Intuition might be that it would reduce brake torque, because of reduced surface area. But intuition is wrong. Brake torque is a function of pad Cf (a constant, regardless of swept area), clamping force, and effective radius. The key here is that effective radius equals the distance from the center of the hub to the center of the brake pad. If the pad doesn't hang down as close to the hub, then the center of that pad is actually further away from the hub than the taller pad. That INCREASES torque.

Ok. However, I'd be surprised if a 380 mm narrow annulus rotor has insufficient thermal mass compared to a wide annulus rotor and the additional radiative heat transfer area likely does little to help rotor temps (view factors aren't very good). Also, I doubt the change in effective friction radius of a narrow vs. large pad is significant and, therefore, results in a very noticeable increase in brake torque. The one critical thing not addressed is the large temp gradient between the rotor surface under the pad and free rotor surface where there's no pad touching - this exists near the floating interface with the hat and, therefore, bending in the rotor will exist due to the temp gradient . Surface cracking on the rotors will occur more easily as a result.

[ashmostro]

This is one of those assessments where, without actually doing the math and collecting the real data you can't say for sure whether the advantages of one approach outweighs its inherent disadvantages to the point of being clearly the wrong choice.

I can hope that Stoptech's decision to use this approach was intentional and a consequence of analyzing a multitude of tests. Unfortunately I can't prove that they did, but hey that's true of any consumer product.

I'm comfortable accepting the explanation and the risk it bears. Others might not and that's just as valid.

[FlyingLow78]

Originally Posted by ashmostro

This is one of those assessments where, without actually doing the math and collecting the real data you can't say for sure whether the advantages of one approach outweighs its inherent disadvantages to the point of being clearly the wrong choice.

I can hope that Stoptech's decision to use this approach was intentional and a consequence of analyzing a multitude of tests. Unfortunately I can't prove that they did, but hey that's true of any consumer product.

I'm comfortable accepting the explanation and the risk it bears. Others might not and that's just as valid.

If you compare the StopTech pads, though, you'll see they're sized for the wider annulus rotor and the ST60 caliper, whereas nearly all of the ST60 pads out there are sized only for narrow annulus applications. Prior to the discovery of the AP19 pad shape being about 3mm deeper radially, all we had were a bunch of aftermarket pads that didn't use the full rotor width.

Note the difference between the Pagid RSL29 pad on top and the StopTech pad underneath.

[ashmostro]

But not the stoptech race pads

[M3SQRD]

Originally Posted by ashmostro

This is one of those assessments where, without actually doing the math and collecting the real data you can't say for sure whether the advantages of one approach outweighs its inherent disadvantages to the point of being clearly the wrong choice.

I can hope that Stoptech's decision to use this approach was intentional and a consequence of analyzing a multitude of tests. Unfortunately I can't prove that they did, but hey that's true of any consumer product.

I'm comfortable accepting the explanation and the risk it bears. Others might not and that's just as valid.

I've previously discussed this exact topic with PFC race engineers and have direct experience. Cracking decreased, and longevity increased, on AP rotors on my e46 M3 once I switched to a PFC pad that fully covered the rotor surface.

[MasterP]

Stoptech ST60 Track pad on the right. AP19 Track pad on the left. Both are same manufacturer Cobalt friction. Same compound XR1. Same thickness, 20mm.

[M3SQRD]

Originally Posted by MasterP

Stoptech ST60 Track pad on the right. AP19 Track pad on the left. Both are same manufacturer Cobalt friction. Same compound XR1. Same thickness, 20mm.

The pad on the left looks like it has a 54 mm radial depth vs. a 51 mm radial depth on the right? The left pad would cover more rotor surface area.

[MasterP]

Originally Posted by M3SQRD

The pad on the left looks like it has a 54 mm radial depth vs. a 51 mm radial depth on the right? The left pad would cover more rotor surface area.

That is correct.

[Caliboy951]

Originally Posted by awbmw

Noticed your running the APR wing and front splitter...looks great, but did it make any difference to traction/lap times or slow you down on the straight?

Sorry for the delayed response just realized I never replied.

With the full aero the car is way more stable especially in the high bank high speed turns and yes I'm sacrificing a bit of speed but then I added more power to hopefully make up for the speed that I'm losing.

[sly1types]

Is there any brake duct kits out? Anyone run them?

[JustAnothaM4]

Originally Posted by Caliboy951

BBK should be the first thing you purchase if you plan on doing track days, the second is a good suspension! These cars make enough powder but stopping and turning is where it's at!
Then I'd do a set of rims and good track tires I also run Apex 18" and Nittos.

The wheels in the picture are BW TA16 or Apex EC-7s?

[4Y_stack_acceleration]

Originally Posted by Bruce AaLee

I searched the forums for this caliper discoloration issue when it first started happening and if I remember correctly everyone that has complained has pretty much been blown off. I asked my service advisor and the GM and they both said that BMW wouldn't replace it since the brakes still function normally and there is no defect. My argument that the defect is in the paint or finish didn't go anywhere. I'm sure BMW is aware of this issue but seeing how they keep painting brake calipers Blue I don't think its a large enough issue for them to care.

Sorry to revive an extremely old thread, but I had the same issues with the blue OEM calipers discoloring to green. I had to rebuild them and decided to recoat them in BMW Performance Yellow, which not only looked a lot better for a black F82 - they have not discolored at all after 6 events so far. My shop owner also runs this same coating, did 30 events this year without any discoloration.

[Theruleslawyer]

Originally Posted by 4Y_stack_acceleration

Sorry to revive an extremely old thread, but I had the same issues with the blue OEM calipers discoloring to green. I had to rebuild them and decided to recoat them in BMW Performance Yellow, which not only looked a lot better for a black F82 - they have not discolored at all after 6 events so far. My shop owner also runs this same coating, did 30 events this year without any discoloration.

What brand coating?

[4Y_stack_acceleration]

Originally Posted by Theruleslawyer

What brand coating?

Color is Hot Yellow from company called Prismatic.