Brakes fade under track usage

[jhadler]

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

[Dan (almaden)]

you need these hubs and calipers and rotors for the front

[Dan (almaden)]

these on the rear.....sorry Eric.

[Joe Ricard]

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.

[jhadler]

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

[Kart54]

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

[Acox914]

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




http://www.ajusa.com/cgi-bin/pb/view_product?prod_id=0000000047&sub_loc=1&part_number=AJR%20600%20911&model_id=0248&session_id=b1de615ce6131fc27d8b08f6a321c05e

[trekkor]

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

[Brant]

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.

[trekkor]

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

[Eric_Shea]

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

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???

[Acox914]

thanks skipper

AA

[trekkor]

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

[Brant]

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

[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:

[trekkor]

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

[Joe Ricard]

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.

[Don Wohlfarth]

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.
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.

[Joe Ricard]

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.

[degreeoff1]

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