Track Day: Front track pads and OEM Rear's

[MNm3]

So I have a dilema. I have an upcoming few track days and I may not be able to get rear pads in time to install them before hand. I will have the front pads, which are a full on track pad.

Given this scenario, is it okay to run track pads in the front and OEMs in the rear?????????? Most of the braking is done with the fronts, so I would assume so.

Also, the DSC will be off so the rears won't be getting over used by any means.

[lucid]

Depending on the pads you'll be putting on the front, you'll most likely end up shifting the braking bias even more forward (if they have a higher CoF vs temp curve than the stock pads). That's not the end of the world, but that means you won't be utilizing the grip that is available in the rear tires as much, and your braking performance will decrease somewhat. Also, your front rotors will run hotter than they would have as a consequence. My understanding is that most BBKs actually dial in slightly less front bias to increase performance for instance.

[JAJ]

Which pads are you running up front? Pagid? Performance Friction? Hawk? Someone else?

The exact pad you're running will determine the results.

If the rear pads overheat, the load moves to the front anyway as the rears become less effective. That would be a stable but undesireable outcome.

The scarier risk is that you overload the fronts if their initial mu is so high that the rears never actually do much stopping. Then, you're risking fluid problems in the front, and there's little margin of safety if it boils.

Originally Posted by MNm3

So I have a dilema. I have an upcoming few track days and I may not be able to get rear pads in time to install them before hand. I will have the front pads, which are a full on track pad.

Given this scenario, is it okay to run track pads in the front and OEMs in the rear?????????? Most of the braking is done with the fronts, so I would assume so.

Also, the DSC will be off so the rears won't be getting over used by any means.

[MNm3]

Originally Posted by lucid

Depending on the pads you'll be putting on the front, you'll most likely end up shifting the braking bias even more forward (if they have a higher CoF vs temp curve than the stock pads). That's not the end of the world, but that means you won't be utilizing the grip that is available in the rear tires as much, and your braking performance will decrease somewhat. Also, your front rotors will run hotter than they would have as a consequence. My understanding is that most BBKs actually dial in slightly less front bias to increase performance for instance.

I'm not sure I'm understanding this correctly. How does switching out pads alter the braking bias? Wouldn't it just mean that the fronts would be able to handle a higher temperature and thus not fade as easily? I guess theres bias as to how much temp the fronts can handle versus the rear.

I don't even know if fade is much of a result of the rear brakes, is it??? I honestly don't know.

[Gearhead999s]

I have done it before when I could not get track pads for the rear.It will be ok,just expect that you will wear the stock rear pads out very quick compared to the fronts.I never noticed a great difference in brake balance but then again I am not on a very aggressive track pad.(Hawk HP+'s).

[lucid]

Originally Posted by MNm3

I'm not sure I'm understanding this correctly. How does switching out pads alter the braking bias? Wouldn't it just mean that the fronts would be able to handle a higher temperature and thus not fade as easily? I guess theres bias as to how much temp the fronts can handle versus the rear.

I don't even know if fade is much of a result of the rear brakes, is it??? I honestly don't know.

Different pads have different friction characteristics and generate different braking torque as a result (everything else being equal). Brake bias is a function of several variables, and pad-rotor friction coefficient is just one of them.

Friction characteristics of any pad is a function of temperature. Technically, brake "fade" happens when the coefficient of friction starts to drop significantly with increasing pad-rotor temperature.

As JAJ is saying, if you boil the fluid, you can also run into issues; pedal travel will increase since you'd be compressing the gas and eventually won't be able to apply much pressure to the pads at all--regardless of what the pad-rotor temperatures are.

[lucid]

Originally Posted by Gearhead999s

I have done it before when I could not get track pads for the rear.It will be ok,just expect that you will wear the stock rear pads out very quick compared to the fronts.I never noticed a great difference in brake balance but then again I am not on a very aggressive track pad.(Hawk HP+'s).

I've seen a report of someone running Pagid RS19 F and OEM R on a E92 M3, and he didn't run into any "major" issues either.

I had to run a more aggressive pads up front myself a few times, and noticed that the front rotors were significantly hotter in the paddock, which made sense (I have a habit of measuring rotor surface temps at the end of a session).

[MNm3]

Originally Posted by JAJ

Which pads are you running up front? Pagid? Performance Friction? Hawk? Someone else?

The exact pad you're running will determine the results.

If the rear pads overheat, the load moves to the front anyway as the rears become less effective. That would be a stable but undesireable outcome.

The scarier risk is that you overload the fronts if their initial mu is so high that the rears never actually do much stopping. Then, you're risking fluid problems in the front, and there's little margin of safety if it boils.

Sorry. Should have clarified. They are Carbotechs. Their track pad. Can't remember the number for the life of me.

Do the rears ever get to a point where they are overheating anyway??? You would think that with a front wheel drive car, there is so much bias towards the front anyway, that the rears never really get close to their max temp, even with OE pads.

Maybe with track pads, that all changes though I guess.

[Gearhead999s]

Originally Posted by lucid

I've seen a report of someone running Pagid RS19 F and OEM R on a E92 M3, and he didn't run into any "major" issues either.

I had to run a more aggressive pads up front myself a few times, and noticed that the front rotors were significantly hotter in the paddock, which made sense (I have a habit of measuring rotor surface temps at the end of a session).

I can never measure the rotor temp in the paddock as I have made a point of cooling brakes well down on a cool down lap and since I became anal about that my pad deposit vibration is a thing of the past.

[MNm3]

I will be running ate Super Blue racing fluid with SS lines. So that may help the pedal travel, boil, pressure issue.

[lucid]

Originally Posted by Gearhead999s

I can never the rotor temp in the paddock as I have made a point of cooling brakes well down on a cool down lap and since I became anal about that my pad deposit vibration is a thing of the past.

Yep, paddock temps are not particularly accurate as the rotors probably cool off at different rates, but I still like to keep an eye on them to make sure something is not totally off... I've seen some pretty high temps at the paddock on the E92 and the Z4M, which prompted me to dial things back the next session, etc.

[Gearhead999s]

Originally Posted by lucid

Yep, paddock temps are not particularly accurate as the rotors probably cool off at different rates, but I still like to keep an eye on them to make sure something is not totally off... I've seen some pretty high temps at the paddock on the E92 and the Z4M, which prompted me to dial things back the next session, etc.

I have figured out they are too hot when I pull in the pits and the dust boots are on fireThat has happened on a few cars that I have raced.

[MNm3]

So the general consensus is that it could possibly be just fine or I could possibly get screwed by this setup from what I am understanding.

[lucid]

Originally Posted by Gearhead999s

I have figured out they are too hot when I pull in the pits and the dust boots are on fireThat has happened on a few cars that I have raced.

I've had a few pads smoke on me at the paddock pretty bad, but no fires!

I've been meaning to use some temp sensitive paint to see what the peak temps are like--mainly out of curiosity...

[Gearhead999s]

Originally Posted by MNm3

So the general consensus is that it could possibly be just fine or I could possibly get screwed by this setup from what I am understanding.

You will be fine!Just dont be standing on the brakes all the time!

[MNm3]

Sweet. Thanks for the input guys.

[RickyBobby]

I left stock rear pads in for my last track day (out of laziness) and it was fine. Towards the end of the session I felt a tiny amount of fade in the form of squirlyness under braking, but it wasn't that bad. In fact, I'm actually inclined to leave my stock rear brakes in for my less brake intensive tracks. Especially while I'm still under warranty

[JAJ]

Originally Posted by RickyBobby

...my less brake intensive tracks...

I280?

[RickyBobby]

Originally Posted by JAJ

I280?

Ha,

Infineon = less brake intensive track

[Radiation Joe]

I-280 used to be part of our unofficial test track. Big loop included highway 9, Skyline, and Highway 84. Those were the days about 30 years ago when it wasn't unusual to run up against some guy in a 930 Turbo coming out of a turn sideways on Skyline.

Try that today without hitting a cyclist, motorcyclist or CHP.

This was back when Steve Dinan was some goofball stuffing M30 engines into e30s on Evelyn Avenue in Sunnyvale when he wasn't working as at tech at A&E on Winchester.

Yup. I'm really old.

[lucid]

Originally Posted by Radiation Joe

I-280 used to be part of our unofficial test track. Big loop included highway 9, Skyline, and Highway 84. Those were the days about 30 years ago when it wasn't unusual to run up against some guy in a 930 Turbo coming out of a turn sideways on Skyline.

Try that today without hitting a cyclist, motorcyclist or CHP.

This was back when Steve Dinan was some goofball stuffing M30 engines into e30s on Evelyn Avenue in Sunnyvale when he wasn't working as at tech at A&E on Winchester.

Yup. I'm really old.

I'm familiar with the latter part of the story since that's when I lived around there--especially the CHP part--but come on Joe, you're not "old"...

[Radiation Joe]

I forgot you spent time there. 1990s?

I'm a few months away from half a century. Old happened at 30. Was hoping to mature before 50, but it looks like I'm going to miss that goal.