OGRacing

iTrader: (1)

If i don't mention a chassis please assume i'm talking about a Race car, with slicks, and mild aero. I should have mentioned that it before, my bad...

Hoosiers can overwhelm a lot of braking components. the majority of people running a low TQ pad can run a Higher TQ pad without overwhelming the tire even on a r comp or no slick tire. You did hit on a good point. i ask people in braking classes "what stops a race car?" 9 times out of 10 i get "the brakes" to that i say "WRONG.. the tire stops the car". Allot of people think that the biggest brakes in the world will stop you better, when in fact you are 100% limited by the tires ability. Keep in mind horsepower is not the same as brake Tq. More brake torque is not better. You want have the correct amount of brake torque for your tires. In the cases of locking up your front tires there might still be some potential brake performance left in the chassis. If you are locking up your front tires, do notice what your rear tires are doing. the theory to get around the track quickly, is to use 100% of your tires 100% of the time. in a braking zone It's all about balance. chances are if you're locking the front tires and your rears are just rolling along almost without any temperature in them at all. if that is true you are leaving allot of time left on the table, and out on the track.

Pad compounds are not just about "this will lock up a tire". Finding the right compound relies heavily on factors like, tire compound, tire size, weight distribution, rotor size, rotor size(in general and front vs rear), the ratio of caliper piston diameter to master cylinder size. but before we start talking about that we need to cover pads. Brake pads can be broken up into the 3 phases of how they work. Initial bite, TQ output, and modulation.

number one Initial bite. this is the characteristic of a pad on first contact with the rotor. if you where to look at a brake dyno you would see a spike at initial contact followed by the Tq level and then how the pad modulates off. this is spike in the duno is considered "initial bite" Or "bite". Initial bite is purely driver preference. Manufacturers have a tendency to keep that characteristic throughout their pad offerings. hawk has a tendency to have a very high initial bite. PFC and pagid are a more mild initial bite. Allot of Club racers like a High initial bite. I hear things like "I want to get thrown into the harness". That sounds fun and all, but professional drivers (the really fast guys, not the pay to play guys) like a low or mild initial bite. the really fast guys like a mild initial bite because it helps the tire keep cohesion with the track. this will allow you to brake harder and deeper into the turn. giving you a few extra tenths. a lower initial bite is also easier to drive on. i recommend a full GT pad for beginners. because of the ease it engages the rotor. Drifters. I always recommend hawk to drifters as the initial bite is so high it helps them break the back tires loose to start a slide.


Torque output or "Mu". This is the part when guys get really excited.. i get requests for "i want the highest MU pad you got.." unless you have one of chip ganassi's old indy cars this would be a very bad idea. Pad Tq is not in any way like Horsepower-"more is good!". the Tq of a pad need to be matched to your application. Brake Tq in a pad has another characteristic, Consistency. General conception that a pad that a professional uses is harder to drive on. i mean they are professionals right? the pro cars are insanely hard to drive. when it comes to horsepower and crazy over steer that is true. it's not true when it comes to the brakes. in fact it's the opposite. a world class pad is insanely consistent throughout it's entire temperature range. this means when a driver is leaving the pits or diving into turn 10A at road atlanta the pedal will feel exactly the same. that cannot be said for a low price economy race pad. even the HP+ has a strange tq rise with heat. (i'm sure i'm getting some un huas from people that know the hp+). When i'm setting up a car for a beginner I encourage them to spend the extra $$ on a pro set of race pads. It makes the learning experience that much easier for them. When I say pro-pads i don't mean super high Tq pads (i'm talking about the pads pro's use, PFC & Pagid). The higher the Tq is, the less forgiving a pad becomes. If you have an insanely high tq pad on a car that isn't set up with slicks and downforce you're going to overload a tire easily. the Bite of the pads will become very hard to drive , the tq will overload the tires, you'll never get any heat , and you can forget about the transfer layer. the pad compound needs to be matched to the chassis. That key in difficult driving leads me on to modulation..

Modulation! modulation is also known as release characteristics. What it feels like to release the brake pedal. Modulation is generally linked between pad TQ and chassis set up. for example we will look at the PFC 07 compound. the 07 is a very high tq Compound. On a indy car (the chassis the 07 was made for) with huge slicks and tons of downforce. the 07 will feel normal, you'll be able to ease off the brakes. the brakes would still give you a good linear release. on a lemons car, 200qutg tire, no aero. The 07 will feel like a light switch, Linear Fell would be a dream with that setup. lets reverse it. if you where to install a 97 compound (good for a underpowered gt car or a rally racer) on to an indy car. The modulation would be wonderful, you could modulate all day. you would not have significant tq to adequately slow the vehicle down.


what should you take away from pads? have the correct pad for the chassis you're using. More brake Tq is not better brake Tq. When considering new pads rate your's on Bite, Tq and Modulation. More TQ is not always a good thing. having the highest Tq pads on the block doesn't mean your the fastest guy around. Chicks don't care about how much brake Tq you have... have i mentioned don't over do the Tq.

Dunning Kruger Affect

Well stock studs have never failed; therefore,

DeerHunter

Granted, but is it advisable to run 5 mm spacers with stock studs? Sorry for the off-topic question, but it's part of a holistic equation (rotor vs. wheel size).

m2cupcar

iTrader: (5)

I think few realize just how critical (and complicated) mastering the brake pedal is. Lack of this often sends a driver off shopping for big brakes when they've yet to realize the potential of stock brakes and good pads. Having beta tested traqmates on test days, it was very enlightening to see what a good G curve in a brake zone yielded in speed and reduced time. Add to that a more controlled load/car, less wear and happier brakes in the next braking zone.

Dunning Kruger Affect

You can probably fit 2 or 3 full threads on, so all good to go.

OGRacing

iTrader: (1)

I can tell you're getting allot of heat, that's clear. why, isn't so clear. i can tell you that allot of professional teams avoid carbotch due to short pad life, also a few years ago they had a high delamination rate AKA failure rate.
I do know of (and refuse to work with) a certain corvette shop likes to sell carbotechs. the only reason is because they don't last very long so, they can sell more pads, and make more money. highly unethical in my book when there are solutions to this.

I do want to know what your rears are doing. Your increased F pad temperatures might be as a result of an incorrect braking system ballance. IE too much front bias.
Answer me this:
What pads are you using in the rear
any rear upgrades? Ie.. larger rotor, changed caliper.
what calipers are you currently using on the front and the rear? wilwood,1.8, 1.6?
are you using the stock proportioning valve?

Sorry man, I think all the oem calipers are made in the people's republic. i'm not 100% sure, so looking deeper into the subject might yield some results. i would avoid any oem calipers for motor sports. they are simply not made for racing temperatures. they are engineered for being cheap to make and easy to install on an assembly line..

DeerHunter

Front calipers are the Wilwood Dynalites on 11" DBA5000 rotors. I'm using Carbotech XP-10s in the rear and wear has been entirely acceptable. I have a 4-wheel BBK, so the rears are 10.75" and use the stock sliding caliper. My '93 has ABS and I don't have a proportioning valve. I would hazard that there's a lot of stock rear bias, since if my ABS stops working (which has happened occasionally), I get instant rear lock-up under heavy braking.

I ended up using the Carbotech pads because I wanted a compound that would work on the street as well as the track. In the past, track-friendly pads didn't work well when cold and the transfer layers didn't play well together when I switched back and forth. I'm certainly open to suggestions in this respect.

OGRacing

iTrader: (1)

do you rely on the ABS for most braking events?

Leafy

iTrader: (1)

Does the 93 have 01+ abs with the electronic proportioning?

z31maniac

I understand balance is key, but you didn't really circle back to your initial assertion or my question.

Assuming with a lower tq pad you're getting everything you can out of the tire (ie stopping as efficiently as possible), how does a higher tq pad shorten your braking zone?

OGRacing

iTrader: (1)

it wont. you are right. If your tires are operating at 100% capacity then you won't gain any braking performance. i'm my experience almost no system is operating at 100% capacity with a low torq pad. The only exception to this would be operation in a low traction environment. I.E. rain or rally conditions. I do apologize for any confusion this might have caused.

kaisersoze

iTrader: (8)

Thanks for answering my PM
just a couple of other questions
Do you think titanium shims do anything? I suspect not much if they do but would like an unbiased opinion.

Any opinion on the sintered metallic pads like Cobalt or Carbonne Lorraine. They do seem to last a little longer in my experience but I am not really fast enough to probably see a huge difference.

DeerHunter

Probably less so on the track than on an autocross course. As mentioned before, the rear brake bias is horribly canted to the rear and pulling the fuse probably wouldn't be advisable.

My car still has the OEM ABS, which is a little old-tech. I don't believe it has EBD.

Leafy

iTrader: (1)

If you have such bad rear brake lockup with the abs disabled you probably should fix your bias setup since your abs doesnt have ebd.

OGRacing

iTrader: (1)

titanium shims is what i was talking about a few posts back, when i referred to them as "insulators". they separate the heat of the pad away from the pistons in the caliper. They are fairly cheap. if you're having issues boiling fluid, it would be worth a shot to try those. if you're not boiling the fluid, then you won't notice anything.

Carbonne lorraine, i've never heard of them. personally i would run :P i haven't had any feedback on cobalt. The only experience i've had with them is when turner motorsports was running them. The business behind that was turner got them for free. after that sponsorship expired turner switched to AP.

sounds like your have some real issues in your system. if it was my car i would do a small tear down. inspect the shocks, prop valve, and the calipers.

still more questions to try and answer your problem.

Are you getting rear lock up mid tun, as a result of trail braking, or are they locking in longitudinal G only?
Are the rears locking up after the front brakes have boiled the fluid?
when the rears do lock.. how long have you been on track? does the problem start at turn 1, or after 15 mins or so?

I ask because the way the factory prop valve works. it will cut the rear fluid pressure the harder you press on the pedal. your car is behaving backwards of the way a normal oem type Miata chassis should operate.

DeerHunter

That's my understanding of the way a non-ABS system works. I just assumed that the early non-EBD ABS set-ups had a static bias towards the rear and just let the ABS sort it all out under different braking loads. I could be completely off base, however.

With the ABS active, how do you determine where the lock up is occurring? The car is actually very stable under all kinds of braking, even trail-braking. No shenanigans that irk me. The soft pedal usually occurs about 15 minutes into a 20 minute session. It will recover before I go out again.

OGRacing

iTrader: (1)

As a practice i Always recommend not running factory ABS units. one is a reason like this. We have no idea where the issues are coming from and making fixing them that much harder. 2nd much like the calipers and everything else on a oem application it is not made for Motorsports. the pros use a Bosch ABS ($10K not counting the tuning costs). it works 10,000 times faster than the factory abs. the bosch will keep braking components from falling apart. as it has almost a linear operation. Imagine the rotor getting to thermal capacity (If it boiling the fluid yout very near thermal capacity of a rotor.) then start fluxuating the pressure 60 times a second. i've seen more rotor failures that were a result of a factory ABS.and by rotor failures i mean rotors exploding.


you can determine rear lock up when the rears will begin to slide around. when you're pulling into the pits i want to see the rears lock up just after the fronts do. next time you're at an autocross do a few hard brakes in a straight line (pull the abs fuse) and have someone watch. they should be able to tell you when the rears lock up in comparison the the fronts.

2manyhobyz

iTrader: (4)

Hi John,
I would appreciate it if you would weigh in on pads for your regular family car. Do you have a brand/model recommendation for over-the-counter compound that stands out over all the choices that are out there? I'm not so concerned so much about pad life as much as stopping power. Thanks
-Jeff

OGRacing

iTrader: (1)

Oh man that topic goes straight into my heart. i Have a jeep commander. not 1 single manufacturer makes a flippin performance street pad for my car. i'm using the hawk LTB right now. i can overheat those pads going to the store. i hate them.

in a family sedan you might be able to find the hawk HP+ for it. They dust like mad, but the stopping power is good.

Leafy

iTrader: (1)

What sort of family car? There's a lot of sedans that have some decently aggressive and high heat pads made for them, and depending on the manufacturer (like GM) there could be an easy and cheap parts bin swap to something more substantial with even better pad choice.