Brakes fade under track usage
 

OK not just another brake upgrade thing.

the Red Neck Racer had it's 1st track day Friday.

each session was 7 laps give or take. ended up with 60 total laps for the day. some times there was less than 15 minutes between sessions.

Stock 17mm MC Stock front and rear calipers and good fluid Pagid black pads.

Really a great Autocross set up. Easily modulated and serious stopping power cold.

So get things warmed up, or should I say smokin hot. rotors are now Blue and there is ash like deposits around the pads.

Contibuting factors which I never seen coming (sometimes I am such a rookie) Front cow catcher air dam blocked air to brakes, not the best pad choice. Regular supplier of Castrol LMA was out. so I got Valvoline synthetic brake fluid. (NOT worth a damn).


Plan to fix before next track event goes like this:
make cooling ducts for front. Get better brake fluid, and what are the best pads for track use. 1900 pounds of car capable of serious speed on R3SO4 Hoosiers 225/45-15. Might even have Slicks for next DE.

http://forums.pelicanparts.com/uploa...1147713955.jpg

I'd certainly start with pads and fluid. You might pick up some heat-indicating paint and place some on the edges of the rotors to see how effective your ducting is, when you get there. Put some on the rear rotors, too. It would be interesting to see the temp difference between the front/rear rotors.

The next escalation step I'd try would be slotting (not drilling) the rotors. The benefits may be marginal, but it's pretty cheap to do.

After that, the next step I'd try would be vented front rotors, using a pair of Mueller's hubs. Talk to Eric Shea about widening spacers for your stock front calipers to use with the vented rotors. I personally think this is the best low-buck solution, since it involves changing the fewest parts, and as you note, the stock 17mm MC and stock calipers with good pads provide plenty of stopping power. You just need to find a way to shed the extra heat generated by track abuse.

Hey Joe,

Told ya your brakes would take a beatin'. :)

Good pads, good fluid are important. But brake ducts are KEY. It doesn't matter if you're running Full blown super pads and racing fluid, if you can't get air to the brakes, they WILL get too hot.

Get some air to those brakes. Even dryer hose from Home depot wrapped on there with zip ties will make a huge difference.

I like Porterfield R4 or R4s pads, and Ate Super Blue fluid. Motul 600 is pretty good fluid too.

-Josh2

Thats what I used when I had 4 lug too with great results.

Do the things you listed and you won't have a problem.

Well, I mean you'll still have problems but not with your brakes:D

Josh my contact pyrometer showed 550 degree rotors after running half a lap staying off the brakes being easy on the car and then tooling around the parking lot @ 25 MPH for 10 minutes. Rears were 300 ish.

Made sure NOT to engage parking brake. Just parked in gear.

Going to get some ducting going soon. Thanks

Yeah, those temps would be expected. You should try and get someone to shoot a couple high speed photographs from the side while you're under heavy braking. I'll -bet- good money that your rotors are incandescant. And if they aren't then you're not braking hard enough. Yes, your brakes will get that hot. 1400 degrees is not uncommon for rotors while under load. That's why _air_ is critical in keeping temps under control. Even the best brake pads in the world won't survive without cooling.

A good primer for brakes in on our SCCA Time Trials website. Great shot of glowing brakes on an Integra.

http://www.sccatimetrials.org/requirements/brakes.html

-Josh2

I will add that I have _punnished_ the Porterfield R4 pads and still had the ability to slow the car. Smoke pouring from the wheel wells, quite literally, and still had brakes. Not to say they didn't fade, they did. But they didn't go away either.

Yes, it was deliberate.

And I've run high performance street pads on the track (with no ducting) and they went AWAY after one or two laps. yes, they were GONE. :eek:

I won't ever do that again... Not fun...

-Josh2

Joe, nice pic of the car by the way. Very good action shot. :)

joe, mueller hubs and m calipers.... :)



you could always ziptie an elbow onto the a arm.. ala trekkor :)

Keep in mind that your front rotors also house your front wheel bearings. Different metals, grease in there... More to think about when saying "cooling is key".

Iffin your rotors are bluuoooooo from heat, check 'em for cracking too!

If you're going to do more of these track days then you need to move up to M-Calipers and Vented Rotors.

You are a text book study in what we see with 914 calipers. They are awesome for even the most agressive autocross but... get agressive on a track and you'll experience fade.

Also... brake less :D

So, Eric, why new calipers? Spaced stock calipers should work great with vented rotors, and you don't mess up the brake balance by fitting front calipers with larger pucks.

Are you not still working on adding spacers to the stock calipers?

If properly setup , meaning good pads, fluid and **COOLING**, stock 914 brakes can work reasonably well, even under track conditions. Not STELLAR, but pretty good.

Bigger calipers won't do much until you get them wrapped around vented discs. Yes, going to vented discs and calipers can make good gains in brake longevity for track use. But that also adds unsprung weight to the car as well.

Joe, if you're planning on running a lot of track events, then maybe upgrading the brakes might be the way to go. But if it's only the occasional track event, and mostly autox, I'd keep what you've got and just run a separate set of track pads with FRESH fluid for the track. The rears may be a bit of a PITA to swap out (venting clearance setting), but the knowledge that your brakes won't leave you when you need 'em the most is well worth it IMO.

Air is key. After that, fresh high temp fluid and good race pads.

A note about fluids. Generally speaking, the high temp fluids tend to be hydrophilic, meaning they like to absorb water. This is fine, as long as the fluid is fresh. But the high temp stuff will need to be flushed more frequently. The specs on the fluids will list both a dry boiling point, and a wet boiling point. As water creeps into the fluid, the boiling point drops. This is because the water boils at a much lower temperature than the fluid. Once the water boils, it becomes vapor, which is compressible. This mens the brake pedal will hit the floor board at the most innoportune time (like braking for turn 1 at the end of the front straight). Flush before a track event to make sure you've got good, dry fluid in there.

Pads: The better race pads will use ceramic backing plates. This helps keep the heat from going throuhg the pad, through the piston to the fluid. A stainless steel shim between the pad and the piston is not a bad idea either. Stainless steel is a lousy thermal conductor, which is good in this case.

-Josh2

James, I'm not spacing the fronts. Not enough call for it. Excellent idea though. Mike should engineer some spacers to sell with the Mueller hubs (ooooooooooops, is Brad reading this?). They should be 7mm I believe.

Josh has nailed it from what I can see. If you're going to do more of these then the M-Caliper would be the ticket. The pad size is the same. The only advantage is the vented rotors in my book.

There's a guy here on the PP 911 boards that makes -6 shrouds. He also makes some very nice A-arm ducts. The ARJ kit may be all that's needed (along with the nice pads and fluid). No need to cut the front.

I'd say the bottom line is based upon how many track days vs. autocross days this car will be seeing. Air, pads and fluid will probably get you by for now.

I'll throw in my comment that I use when someone says they need bigger brakes. I ask them this "Can you lock up your brakes right now?". If the answer is yes, then they have enough brake, and need to work on the modulator instead.

Yes, bigger brakes are worth it for track stuff. The M calipers and vented rotors are a good step. But retaining the same pad size will not make you stop any harder, it'll just keep the brakes a little cooler, which in many cases is enough.

The key with brake upgrades is swept area. Longer, wider pads are the key to more stopping power. That's why the monster brembos are 4 or six pot monsters. So they can apply even pressure on those really long pads. More swept area. And larger diameter brakes mean more braking torque applied by the brakes.

Anyway, just a little more rambling...

Around the cones, tires suffer the abuse. Around the track, it's the brakes that take the beating.

-Josh2

M calipers on the front with Billet 4 bolt hubs and vented SC rotors, Porterfield R4SE pads.
Rear:stock 914-4 front calipers on the rear with stock textar or mintex pads
Proportioning valve removed.
Pentosin DOT 4 fluid.

It works great....good modulation, good pedal feel, firm pedal, no fade, stop with the best newer Porsches on the track


None of this set up is guess work....it is on the car and working as advertised.

If you have blue rotors check to see if you have a frozen piston on that caliper. Even under very heavy use it shouldn't be blue.:(

I agree with Dan, if your brakes have blued, you might be dragging a pad.

-Josh2

Strictly speaking, Joe didn't really say anything about needing "bigger" brakes, just more fade resistance.

As for the swept area comment, I disagree, to a point.

As you say, pad area helps with fade resistance (or can, anyway). By itself, however, pad area does nothing to improve braking torque. Brakes follow the "classic" friction model, in which area of contact is NOT a factor. Only force of contact and the coefficient of friction between the two materials (pad and rotor) matters. If you pressed a pencil point made of brake pad material against a rotor with the same force, you'd get the same amount of braking torque, as you would with a huge pad. The difference is the pencil point would wear very rapidly. I've seen some racers attempting to solve a brake balance problem by milling away some amount of pad material to "reduce the braking". All they end up doing is wearing out those pads faster, and often causing fade by heating up the remaining material too fast. This does end up reducing the braking, but is obviously not the ideal way to do this.

Now, there are also leverage effects at play here. If you apply the force farther from the axis of rotation, you get more braking torque for the same amount of braking force. Look at any recent sportbike front brakes and you see an excellent application of this idea: a thin, annular ring of brake rotor well away from the hub, held there with a spidery "hat". This ring requires a long, thin pad to get adequate (for wear and fade resistance) area, so you need a long, thin multi-piston caliper to squeeze that pad, or you need a thick, rigid (and heavy) backplate for the pad to spread the load for you.

Joe's problem is just one of shedding heat, so there's no need for bigger calipers and/or bigger caliper pistons. Bigger pads would help some, ducting air will likely help a lot, vented rotors would help a great deal.

Yup. The longer pads are good for heat dissapation. The larger diamter is for more braking torque. Must have missspoke there.

As for the bigger brake thing, I just threw that in. I know the topic is heat management, not more clamping force.

-Josh2

you need these hubs and calipers and rotors for the fronthttp://forums.pelicanparts.com/uploa...1147732271.jpg

these on the rear.....sorry Eric.;) http://forums.pelicanparts.com/uploa...1147732378.jpg

Well to answer the questions posed. I Autocross at least twice a month in the Summer and 3 times a month in the winter.
This was my 1st track day and aside from shaking of adreniine ovedose for the whole next day. I will probaby only do 2 or 3 track lapping days. Been approached by some buddies to do a PCA DE. But I don't EVER hold my pinky up while driving and my hot rod has embarrassed all those real P cars that dare race me in AX.

Can I lock up the wheels? Yea you got to be kiding me right? even with just a warm up lap to get some heat in the tires. nice cool brakes you just are not going to slide a 225/45-15 R3SO4 Hoosier. Unless you screw up bad.

Autocross is run on 22 x 9.5 x 15 R25 Hoosier slicks They don't slide once warm either. I now have new front rotors and Porterfield R4S front pads. We will see how that goes for Autocross. need to make up a set of front race rotors and pads keep the just for track.

Oh and NO there is no dragging pads. just alot of laps without much cool down. Wide open throttle and drop the anchor at the last possible minute.

Could use some pictures for ideas on brake ducting.

Hey Joe,

Welcome to the club!! Tracks are fun aren't they? Heh... You're hooked now!

Don't turn your nose up at PCA. yeah, there's the occasional pinker lifter in the PCA, but they tend not to be the ones that show up at the track. They are a GREAT resource for extra track time. Oh yeah, you'll love this one: Being an active SCCA autoxer, you'll rapidly find yourself -lapping- the occasional Sunday DE 911 driver. Lot's of fun! :)

You may want to go over your brakes, as I had more than enough brake to lock up the fronts with the same setup (225/45-15 Hoosiers). Not that you -should- lock up the brakes, but you should at least be -able- to. If not, then you need to look at the brakes, as there is likely a problem in there. Might also explain the overcooked rotors.

edit: At the track, you have a lot more momentum in the wheels that will resist locking up more than at an autox.

As for the Porterfields? I gotta warn you against using them for autox with slicks or Hoosier DOT tires. Porterfields have -bite-. And that makes lockup on corner entry a very easy thing to do. Slicks are very light, and coupled with lightweight wheels, the reduced rotational intertia means that it's easy to lock 'em up. Flatspotted Hoosiers suck. I lost a pair of Hoosier DOT tires in one second when a course worker ran in front of me at an autox. I had to make a split second decision, hit 'em (which would dent the car, and mean a TON of paperwork), or brake as hard as I could. I got on 'em just a tad to hard, and POOF!! $350 worth of tires up in smoke. I was soooooo pissed.

My recommendation would be to run Porterfields for track, and something nice and soft for autox. Carbotech chealated pads are very nice for autox.

As for ductuing? Browse the pegasus catalog for preformed duct openings that you can mount into the cow-catcher if it doesn't already have ports. Then run the hose back and in along the A-arm. Get the outlet of the hose as close as you can to the rotor. And if the dust shields are still on there, toss 'em! Hose is easilly obtained from multiple vendors. They've got some nice high temp hoses, but they ain't cheap. I ran the vinyl home depot dryer hose up to a metal nozzle that I mounted at the rotor interface. Didn't melt the hose, and spent a lot less. Gotta watch for tears though as any road debris, especially cones, can tear 'em up or off.

-Josh2

Brakes
 

Hi Joe,
Welcome to the club.
Stock M calipers front and rear. Stock rotors redrilled to 5 lug with Eric Shea's cryotreatment on the front. Goodyear 23x9.5x15 soft compund race slicks and Porterfield R4s pads all around with cockpit adjustable brake bias. Full race SCCA G prod 914. No noticeable brake fade in 100 plus laps. No discoloration, Eric Shea's rotors still look like new.
Results? 1 second place finish, 3 first place finishes and new lap record at Buttonwillow last time out. And yes, I can lock up the brakes with the slicks warm going into the Mazda turn at Buttonwillow with a Super Production Corvette on my tail.
I was concerned because of alot of what I had read here previously and the fact I am required by the SCCA rules to run stock rotors and calipers. Now having run many many practice laps (over 100) plus the above races my comment is if your using up stock rotors and calipers with or without ducting your doing to much braking. I'm on my brakes hard and often and have not been able to use them up yet on the 13 turn track at Buttonwillow.
Just my .02 worth
Randy
"Car 54 Here I Am" Currently leading G prod points in Cal Club SCCA

JOE. HERE IS WHAT YOU SEEK
 

AJR
scoops mount to bottom of A arm, and divert air to the backing plates......

http://images.ajusa.com/products/000....full_size.jpg


http://www.ajusa.com/cgi-bin/pb/view_product?prod_id=0000000047&sub_loc=1&part_num ber=AJR%20600%20911&model_id=0248&session_id=b1de6 15ce6131fc27d8b08f6a321c05e

My cheapo Depot set-up actually works pretty good I must say.

I check temps on the front calipers and they are nowhere near the boiling point of Motul fluid.

I'm trying to remember the temps. Seems like under 300° in the front and 250° in the rears.

My ducting goes through 1 1/2 inch ABS openings fitted in my air dam and the air is directed at the calipers and rotors .

I run rebuilt stock calipers, solid rotors, Porterfield r-4's around and stainless lines.
I bleed the system before every track day. Speedbleeders.

No shortage of brakes after 30 minute sessions.

I plan on refining my cooling this week. I'll post pics.

KT

http://forums.pelicanparts.com/uploa...1147745403.jpg

Joe,

if you can't lock up into a corner then something is wrong with your calipers

trust me..
stock brakes are adequate for a stockish 914 (even with big tires)
the fastest stock teener I know is running stock brakes with big hoosiers

dump some air on them and try not to use the brakes

the ONLY teener drivers I know that are cooking the brakes do so because they are OVER braking and need to learn how to drive correctly.

you are over braking
you definitely need the correct fluid
but you are over braking
work on momentum and you will be 5 seconds faster and not cooking your brakes.

Yep!

Short firm stabs at the brakes, late.

Not loooong braking early, off and than on again.
i'm still working on it...

It will take repeated visits to the same track to find the limits.

KT

Over b-r-a-k-i-n-g Tia Brant! Glad you weighed in... I thought of you when I typed my first reply... brake less :D

Aaron's got the right setup there Joe... except it forces air to the center of the rotor. With a solid rotor I'm not sure that's the best idea. A different backing plate that forces air right at the caliper would be cool (in more ways than one).

Why do our little cars always need a custom solution???

thanks skipper

AA

Aaron, are you running those coolers?

I wonder what is most important, cooling the rotors or the calipers?
I've seen both set-ups on race cars.



KT

B-r-a-k-i-n-g...
ahhhhh.... too many glasses of wine (or is that Whine) to spell correctly.

Trekkor, I run those on vented rotors.
cooling the mass of the rotors is the normal solution.
you would be proud of me, I have some new scoops (uninstalled) that came straight outta the big box

Eric,
teeners may be custom.
but they are easy too.
same racer I mention above just dumps air onto the caliper opening
so simplier on a teener to route air

signed affectionately...
aunt brant

Here is a mounted pic...
you will find that the stainless screen is absolutely necessary in wheel to wheel...

otherwise the inside of the rotor vents packs with tire rubber and the actual vents and vanes become plugged:

http://forums.pelicanparts.com/uploa...1147755878.jpg

We have an average speed generator for the local tracks based on lap times on the GGR PCA web site.


mph calc

A blast of air at 75 miles per hour average airspeed will do wonders.


KT

Ya'll may have a point about over braking.
The most brake fade happened when Hassan was driving. He is damn fast and a heck of a car handler. However when I drove the car I had no sense of fade.
I was accused of over driving most of the corners and not steering a clean line.

Well 1st time I have done something like this and seriously need more instruction. Wish I had a good 914 driver show me how it is done. As we all know these cars are different to drive that most all others.

Couple thoughts...sounds like 2 people were driving your car. Brakes may not have had enough time to cool between sessions. Rotor temp ~550 after 20 min driving around the paddock says the rotors were pretty damn hot coming in from the track.
Something is wrong with your brakes if you can't lock them up. ATE blue/gold is a good CHEAP brake fluid. If you don't remember when the fluid was changed flush the system with the better brake fluid.
Blue rotors and you're overheating the rotors. White ash around the pad shows you're overheating the pads.
Driving a track is different than running ax. Wide open throttle til the last minute before dropping the anchor doesn't help (except at ax. ;)) You are trying to hard and overdriving the car. :o
You want to cool the rotor, then the caliper. Cooling will also be helped if you have full depth pads, change them when they get half way worn. Pads absorb some of the heat from the rotor and keep it away from the caliper.

Thanks all good points. I will try to apply most of the stuff recommended as driving technique.

I just love the parts about my brakes not working correctly. I GOT THEM HOT THATS ALL.
Yes two drivers Hassan got in and drove the car with less than 15 minutes in between sessions.
Brand new pads which are well suited to street AX not track.

no cooling ducting, I'll fix that before next track day.

big ass air dam and dust shields on rotors Just didn't realize so my bust.

I am not going to prove I can lock up Hoosiers just to screw them up. But the general consesus and comments are "holy crap your cars stops quick" I think the system works damn good.

So all ya'll excuse me while I go change oil and figure out how to mount the RX-7 oil cooler. and continue to whip ass at Autocross.

I don't think anyone said this......YET!! HA!

19mm MC will also help I lock mine up with 245/40's all day long

Josh