Soft pedal after almost every track day

[nrubenstein]

Interesting. Certainly what you guys are saying about braking technique could apply. While I knew that braking is what generated the heat, I had not considered that it's only while braking that heat can be effectively transferred to the pad. So while the same amount of energy gets soaked up by the brake system, less of it would end up in the pads and calipers, and would instead stay in the rotor. I'd guess the rotor does a better job of shedding that heat too?

So everyone thinks you can cook the pads and brake fluid without ever losing the majority of your breaks? This really breaks my understanding of brakes. I thought when one exceeds the temp limit that most pads would drop down to something closer to 30% or 40%, not stay closer to 70%-80%. At least the one time I've experienced brake fade it acted that way.

I don't think I'll have the money before my last track day for new pads, but I can certainly adjust my breaking and see if that changes how they act over the course of the day.

The problem with the HP+ is that they go from 100%-0% with next no warning. Brake torque just falls off a cliff.

Track pads will provide both meaningfully more brake torque, and meaningfully more heat resistance. That said, obviously you haven't exceeded the heat limit of the HP+ because you aren't terrified.

Be aware that proper braking technique may well result in higher peak temperatures, even though you aren't cooking your fluid.

See what happens when you run heavy and overpowered:

http://www.r3vlimited.com/board/showthread.php?t=253149

After one flush, no more fade (and the fluid from the first flush literally came out gooey).

[Earendil]

- You definitely need to commit. That is no half braking. You're either hard on the brakes, or not using them. Nothing in between. When approaching a corner, brake with a certain force at a certain marker. Then see what happens.

Thanks for the tip. I'm still quite the noob on track, which has only been exaggerated by moving and taking advantage of a few "opportunities". I've been "on track" 6 times, but that's been spread out over 3 tracks and 2 full rain days! On my new home track I finally feel like I have the hang of it enough to focus on my braking technique, where in the past I didn't have that in the top three things to focus on for each day. The lack of antilock brakes has made me hesitant to threshold brake too, as I like my tired to be moderately round ;)

[Earendil]

Interesting. Certainly what you guys are saying about braking technique could apply. While I knew that braking is what generated the heat, I had not considered that it's only while braking that heat can be effectively transferred to the pad. So while the same amount of energy gets soaked up by the brake system, less of it would end up in the pads and calipers, and would instead stay in the rotor. I'd guess the rotor does a better job of shedding that heat too?

So everyone thinks you can cook the pads and brake fluid without ever losing the majority of your breaks? This really breaks my understanding of brakes. I thought when one exceeds the temp limit that most pads would drop down to something closer to 30% or 40%, not stay closer to 70%-80%. At least the one time I've experienced brake fade it acted that way.

I don't think I'll have the money before my last track day for new pads, but I can certainly adjust my breaking and see if that changes how they act over the course of the day.

[Massive Lee]

Hey OP, after you have fitted better brake pads, here's a tip about braking.

- You definitely need to commit. That is no half braking. You're either hard on the brakes, or not using them. Nothing in between. When approcahing a corner, brake with a certain force at a certain marker. Then see what happens. Do you need to reaccelerate before the apex? If so, you're going too slow as you have braked too early. Please notice I didn't say you braked too hard. On the next lap, delay your braking by half a marker, using the exact same braking force. Again check if you need to give some gaz before the apex. If not, you have braked at the right marker. Repeat lap after lap. Every lap shall be done the same way. Do NOT reinvent the line or the braking markers. When you nailed a corner, then perfect the next one.

With time, you will go faster, and faster. Then you'll see if you need to adjust your braking marker, or just learn how to hold your car in corners. The e30 is a momentum car. Great handling and no power compared to a modern car. So do the best with it. Slowing down less also means you don't need to accelerate as much out of a corner, meaning you don't need 300hp to go fast.

[nrubenstein]

Agreed. Crappy pads are forcing you to spend too much time on the brakes, which puts far too much heat into your calipers.

After an initial bleed to get the goo out (apparently heating up the brakes really helped clean them out in a way that just flushing won't), my pedal was very solid. In spite of using up an entire set of pads in a couple session and completely trashing my rotors.

Constantly cooking the fluid like this is a pad choice/technique issue. Braking too conservatively is very hard on brakes. I learned that in my first ever track day when I kept cooking my pads even though I was going really slowly.

[E30_Pare]

So solution is to brake harder later. Aka your not going fast enough

[Bimmerman325i]

First, HP+ pads suck. They do. They are autocross pads, and they do not work well at track temps. I've had the exact problem you're having, and the issue is twofold.

First: your pads suck. Get something that doesn't outright give up above 600F, i.e. a real track pad. Lee's suggestion of HT10 is an excellent one, PFC pads are also good.

your fluid is good enough for now. What you mention consistently is that you're not braking hard, abut you're going slow in fast out, and that means you're braking LONG. Braking harder over a shorter distance does not transmit as much heat into the pad and the fluid as a long drawn out braking at less intensity. Heat flow is a function of time.

Ducting is good, and changing pads and fluid will help improve the time before heat gets in, but your technique sounds like you could use more braking intensity over a shorter distance, meaning less time for the same amount of released heat energy to go into your system.

You're an engineer. Mechanical? Heat flow and flux is a differential equation wrt time. While you are converting the same amount of kinetic energy into heat via the brakes regardless of the distance(aka time) spent, you are drastically reducing the amount of time over which that released energy will be able to go into the pad and the fluid and boil things.

My take. I was doing this exactly, braking too long and cooking the brake fluid. Braking harder (much) over less distance solved it right up, changing absolutely nothing. I still use ATE Blue or Typ200 fluid without problems. Still haven't added ducting, still using stock rotors and calipers. Had the same problem on an E30 and my current E36 M3, same solution.

[Earendil]

well, the hawks are clearly NOT working for you. you are cooking them. the compound is not designed to operate at the temps you are getting them to. soft pedal is because they are in a downward spiral. overheated, glazed, you push pedal farther, generate more heat, vaporize any moisture in fluid, pedal goes down more, etc.

There is a word I haven't seen associated with brake pads before, "Glazed". Perhaps my lack of understanding of what that term implies is where I'm going wrong here.
My assertion that my brake pads weren't failing was based on two things

1. Brakes exhibit a slow progression towards not working over the course of four 20 minute sessions. Slowing down or the start of a new session (reducing or eliminating heat) does not improve the characteristic.
2. By all accounts the HP+ pads when overheated fall off a very scary cliff leaving the driver with little or no stopping power, which I haven't experienced yet.

Perhaps if someone can explain the characteristics of a glazed brake pad to me I could identify that as an issue. For example, can the pad be de-glazed and function again normally after using it on the street? I'm still perplexed by why driving it home, changing the fluid, and driving it back to the track gives me better brakes.

you have two very experienced racers, and lee is also a brake expert, telling you the same thing.

And I mean no disrespect to yours, or anyone else's experience. The last 20 years on the internet has taught me to not blindly believe everything I read, and my engineering brain flat out won't let me. It's probably a handicap so please forgive me :)
Owning an E30 has also taught me not to throw parts at a problem, and r3v has taught me that you can find an opinionated person to tell you just about anything. I only seek to understand exactly what is going on at whatever detailed level people are able or willing to explain.

As I said, ducting will be done as the next project. A set of PF08 were going to be my next pad, so perhaps I'll pick them up early. What about ATE 200? The first guy told me it wasn't good enough and to use Motul, and you said you use it in your race car. From what I've read from the Pro3 guys out here, they tend to use both, with a few people swearing by one or the other.

Get better pads and more cooling. keep the HP+'s on the street where they belong.

Heh. I'd never use HP+ as a regular street pad, and I wouldn't suggest it to anyone either. Head turning noisy when cold, and while acceptable, their cold bite isn't confidence inducing. By going with PF08 I'm probably looking at buying a set of street pads and a second set of rotors just for track days. Oh well.

Thank you everyone for your time :)

[mlytle64]

well, the hawks are clearly NOT working for you. you are cooking them. the compound is not designed to operate at the temps you are getting them to. soft pedal is because they are in a downward spiral. overheated, glazed, you push pedal farther, generate more heat, vaporize any moisture in fluid, pedal goes down more, etc.

you have two very experienced racers, and lee is also a brake expert, telling you the same thing. get better pads and more cooling. keep the HP+'s on the street where they belong.

[Earendil]

yes, it is because of the rules, but that does not mean the stock brakes suck. I race an E30 in SCCA. stock brake system with PF01 pads, blank stock rotors, ATE Blue and cooling ducts. I push the brakes WAY harder than any HPDE car. ZERO issues. no fade, no problem hauling car down from 120+ lap after lap after lap. all weekend. same situation in my lap record holding E36 race car. the stock brake systems on E30's and E36's are more than capable of handling a racing environment.

IF

you run pads that can handle the heat and keep the rotors cool. that is the key.

in OP's case, your Hawk +'s suck on track. get real pads. and add cooling to the rotors. you will be amazed at the difference.

They may suck on track for some (or most) but they work for me likely because I push the brakes way less that you do :)

Given my description, you'd say that my brake fluid is being destroyed, yes?
But I'm also not experiencing brake fade.
So how am I cooking my brake fluid and not fading my hawk "suck" pads?
If I was getting brake fade and then afterwards my fluid was shot, I might understand.

I'll add cooling, but this still baffles me.

[mlytle64]

And they only do that because of rules. Everyone has the same handicap. The day the rules allow that brakes are free, within a year nobody will run stock brakes... ;-)

yes, it is because of the rules, but that does not mean the stock brakes suck. I race an E30 in SCCA. stock brake system with PF01 pads, blank stock rotors, ATE Blue and cooling ducts. I push the brakes WAY harder than any HPDE car. ZERO issues. no fade, no problem hauling car down from 120+ lap after lap after lap. all weekend. same situation in my lap record holding E36 race car. the stock brake systems on E30's and E36's are more than capable of handling a racing environment.

IF

you run pads that can handle the heat and keep the rotors cool. that is the key. as Lee said, containing the heat matters.

in OP's case, your Hawk +'s suck on track. get real pads. and add cooling to the rotors. you will be amazed at the difference.


i am not saying you can't improve on a stock system, just saying that the stock system can run very well with no issues in conditions far harsher than a HPDE driver could ever subject it to.

[Massive Lee]

Duct to the center of the rotors, so air air is equally spread out, and it will cool the bearings. Don't just direct air at one face. That would be counter-productive.

Cooler rotors means cooler brake pads means not as much heat gets to the brake fluid. Containing heat matters.

[Earendil]

And they only do that because of rules. Everyone has the same handicap. The day the rules allow that brakes are free, within a year nobody will run stock brakes... ;-)

While I do not doubt that many would choose to upgrade, I've also crewed and watched enough races to know their brakes don't function as poorly as mine, and certainly not on a downhill sliding scale over time. I'll try the ducting and leave the BBK for individuals that feel they need them.

[Massive Lee]

And I would have pointed to the SpecE30 and Pro3 guys that run stock rotors and calipers ;-)

And they only do that because of rules. Everyone has the same handicap. The day the rules allow that brakes are free, within a year nobody will run stock brakes... ;-)

[Earendil]

The problem on the e30 is twofold. Flexy calipers and tiny rotors. Improving anything costs. Sure, I could have told you to get a BBK with 11.75"x1.25" discs and stiff calipers. But before you get there, perhaps you could improve what you have.

And I would have pointed to the SpecE30 and Pro3 guys that run stock rotors and calipers ;-)
They do however use proper race pads and some (most?) use good ducting. I was going to make that bump when I started out driving my current setup. I suppose I'm just not convinced that I'm overheating my pads.

BTW If you drive hard, you will NEVER keep your brake pedal stiff more than half a session. Unless you bleed your brakes every session. ;-)

Well, it's more than just a lack of stiff pedal, as I don't think in at least one of the session I could locked the wheels if I tried ;)

Since I'm not experiencing brake pad fade, I'll hole off on getting something higher class until after I'm done with the HP+. I'll look into good brake ducting though in hopes that protects my brake fluid. I'm still not sure I understand that though...