Brake Fade at The Track?

Black Cobra '99

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Hello every one, So I finally went to my first open track event :cool: (more on this later) and I think I experienced brake fade.

Two days before the event I changed my old pads to Hawk HPS and brake fluid to Motul DOT 5.1 (rated to 522*). The new pads had a great initial bite and didn't need much pedal travel.

So, just before starting the final session the initial bite was gone and I needed to push the pedal quite a bit. Its not that nothing happens, its more like, more pedal travel for more stopping power. The car still stopped great and it actually still feels like this right now. So I'm a bit confused on what happened.

Rotor temp after the final session was 646*, Hawk's website says the HPS optimal range is 300-500* and max is 700*
The brake fluid reservoir was 169*
 

RedVenom48

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Its possible you cooked em. Even though you didnt record max temp doesnt mean they werent over that on the track. I think you might have wanted the HPS 5.0 or even the next step up. Even a few laps on a road course will still super heat the brakes far hotter than street and spirited street driving.

Still, check bleeders on all corners. Might have had a tiny amount of air trapped somewhere too
 

barspen

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+1 on checking for trapped air after flushing the lines...Pump the brakes a lot to get any air forced out and look for leaks & drips.

However, you are using the wrong pad for HPDE, IMHO. the HPS 5.0 (I run them too) are great for the street, twisty mountain roads and very light novice-level track use, but they will not perform well in heavy braking situations, especially with no brake cooling kit. You need to step up to racing pad. Hawk has many and there are also several other good manufactures out there that make racing pads. I run Carbotects XP-10 (F) and XP-8 (R) and they do not fade at all. I swap the fronts the night before an event. Most race pads will dust and squeal much more that HPS 5.0, which is why I swap them.
 

Black Cobra '99

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Thanks for the replies guys.
I was afraid that this is the case, from what I read people were recommending the HPS for light track duty. But the track I went to has fast corners so you're really hard on the brakes.

So, I'm gonna have to step up my pad choice and will get cooling ducts but for now are the cooked Hawks fine for the street?
 
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RedVenom48

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This is what I would do:

1: Reflush brake fluid

2: Get your rotors recut, fresh meat

3: Remove and lightly scuff the pad surface to get the glaze off. Easiest way to do that is to get some Maroon 3m Scotch-brite and tape to something flat. With even pressure, lightly scuff the pad surface until it looks dull. Wipe with a clean dry rag to removed fine dust. Ensure pad surface is flat.

4:Reassemble brakes and road test with light braking for about 10 miles. Return, park and let the brakes cold soak (sitting overnight is perfect).

Brakes should be good to go after that.

3m style scuff scotch-brite:
https://www.amazon.com/3M-Scotch-Brite-General-Purpose-6-Inch/dp/B000LPN3WQ
 

Coz

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If you are just experiencing longer or spongier pedal travel this is due to air in your lines, probably caused by your fluid in the caliper overheating and boiling. If your pads were fading you would experience longer stopping distances which you indicate you did not experience.

I would recommend you switch to a DOT4 fluid like Motul RBF600. It has a higher dry boiling point of 593 vs 522 and also a higher wet boiling point of 421 vs. 365.

Better pads may be a good idea in any case since you are driving aggresively enough to boil fluid. But your current pads may be ok since you are still stopping great. They should definitely be ok for the street. To be on the safe side, slide out your pads and take a look to make sure they are not cracked or have chunks missing from the surface.
 

barspen

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So, I'm gonna have to step up my pad choice and will get cooling ducts but for now are the cooked Hawks fine for the street?

+1 on cooling ducts. They are a bit of pain to install, but worth every cent for HPDE.

As far a brake fluid, fresh Motul 5.1 should be fine in most cases, but you do get a better dry boiling point with Motul 600 or 660. Doubt you are anywhere near the upper limits of the fluid yet. Getting air trapped in the system from the bleeding process is a different issue than boiling. If you are boiling fluid, you will feel it (little-to-no brake pedal) and hear it (bubbling in the reservoir). Cooling ducts will go a long way in brining temp down. Some also run titanium shims between the pad backing and caliper piston to disperse heat.

If you have 5mm or more of the Hawk 5.0 pad left, Ed's step-by-step to resurfacing the rotors and pads is great advice. Anything less than 5mm or uneven wear, major crack, groves, etc. on the pad, toss them and get a new set.
 

Coz

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If his pedal was firm until the final session I think he properly bled the lines initially. He probably had some overheating. His rotor temp was 646° and I'm guessing with that type of non-round number it was taken with a heat gun or thermal imager in the paddock area. Before the cool down lap and transit to the paddock, his temps were probably 200-300° higher. While rotor temp does not = caliper temp, it is not inconceivable that it approached or exceeded 500° and if the 5.1 attracted any moisture in those 2 days it's boiling point would be a bit less than 522°
 

Black Cobra '99

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If you are just experiencing longer or spongier pedal travel this is due to air in your lines, probably caused by your fluid in the caliper overheating and boiling. If your pads were fading you would experience longer stopping distances which you indicate you did not experience.

Well, I wasn't exactly pushing the limits of my brakes so I can't say for sure if the braking distance was effected.

As far a brake fluid, fresh Motul 5.1 should be fine in most cases, but you do get a better dry boiling point with Motul 600 or 660. Doubt you are anywhere near the upper limits of the fluid yet. Getting air trapped in the system from the bleeding process is a different issue than boiling. If you are boiling fluid, you will feel it (little-to-no brake pedal) and hear it (bubbling in the reservoir). Cooling ducts will go a long way in brining temp down. Some also run titanium shims between the pad backing and caliper piston to disperse heat.

I'd love to get the 600 or 660 but unfortunatley it isn't available around here. I was lucky enuogh to find the 5.1
I've seen the titanum plates but not sure if they work. If they do make a difference I'll defintley get them.

If his pedal was firm until the final session I think he properly bled the lines initially. He probably had some overheating. His rotor temp was 646° and I'm guessing with that type of non-round number it was taken with a heat gun or thermal imager in the paddock area. Before the cool down lap and transit to the paddock, his temps were probably 200-300° higher. While rotor temp does not = caliper temp, it is not inconceivable that it approached or exceeded 500° and if the 5.1 attracted any moisture in those 2 days it's boiling point would be a bit less than 522°

You're right, rotor temp was taken with a heat gun after the cool down lap.
I did bleead the brakes so I'm sure its not air in the system.

Either way, I'll get a better pad because I'll probably be more aggressive the next time. I'm hoping the 5.1 will be enough if not I'll have to find a way to get better fluid.
 

barspen

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You can buy just about any fluid you want on Amazon.

I believe Girodisc and a company called Hard Brakes makes the shims, but I haven't tried them myself.

Don't forget to look at a brake cooling kit :)

Best of luck!
 

Coz

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Black Cobra '99

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Well I really appreciate the help. Cooling ducts are defintley happening.

It'll be a while before the next event but I'll update this thread when I get the chance.
 

Imatk

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I've read that ducts can possibly crack the rotor at high temps due to the rapid heat cycling. No personal experience, but I'd be interested to see what you guys think of this.
 

Coz

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Ducts will reduce the possibility of cracking.

What typically happens in hi-temp scenarios, even without ducts is that cross-drilled rotors will develop cracks between the holes.

If you are going to be driving aggressively then I recommend you get solid rotors or ones that are only slotted.

When using steel rotors, professional racers overwhelmingly use slotted (including the curlicue variety) or solid rotors. Do a search for images for "NASCAR Brakes" or "IMSA Brakes", etc. and you'll see what I mean. The only ones that are cross-drilled are the Carbon-Ceramic rotors which have totally different properties than steel.

Also, make sure your duct directs the air into the hub of the rotor and not mostly on the face of the inner side. By going into the hub, the air is pumped thru the center and out through the vanes to the outer edges. This cools the rotor evenly. If you only cool the face of one side, it could warp or maybe even crack the rotor.

Some companies make the brake backing plates with oval ducts to avoid the top edge of the duct directing air right on to the face of the rotor.
 

Black Cobra '99

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UPDATE: I finally got around to work on this, and there was more damage than I expected. The left front rotor had a sizable step at the outer edge(more weight on that side?), and all rotors had bumps when you run your finger across them.
So I turned the rotors and scuffed the pads and put everythoing back together. Unfortunatley nothing changed and pedal feel was the same. I took the front pads again and they looked glazed just like before, so I got a rougher sand paper and did them again but nothing changed.

Next event is on 23 DEC so I decided to go with new rotors and pads. I already have the Carbotech XP10's and a friend suggested that I try them and see if they'll work, but I wasn't sure how the cut rotors will effect the pads.
 

tomshep

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You really got your rotors hot and they are junk. Based on your description, you had a lot more heat on your brakes than you believe. You need better pads than what you were running. I would also get the Motul 600. Get it mail order.

Tom
 

Coz

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Unless you are are REALLY serious when tracking your car and want to go with uber-expensive 2-pc rotors, I would recommend StopTech (by Centric) slotted rotors. RockAuto has the best prices:

https://www.rockauto.com/en/catalog...rcharged,1442746,brake+&+wheel+hub,rotor,1896

They are the:
12661089SL (left)
12661089SR (right)

If you want to go a little extra you can get the cryo treated versions with a "CSL" or "CSR" at the end of the p/n.

TireRack also has them:
https://www.tirerack.com/brakes/bra...p=Sport+Slotted+Cryo-Treated+Rotor&cat=Rotors
 

Black Cobra '99

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How did your fluid look?

Fluid looks fine but I'll do a flush anyways.

Unless you are are REALLY serious when tracking your car and want to go with uber-expensive 2-pc rotors, I would recommend StopTech (by Centric) slotted rotors. RockAuto has the best prices:

https://www.rockauto.com/en/catalog...rcharged,1442746,brake+&+wheel+hub,rotor,1896

They are the:
12661089SL (left)
12661089SR (right)

If you want to go a little extra you can get the cryo treated versions with a "CSL" or "CSR" at the end of the p/n.

TireRack also has them:
https://www.tirerack.com/brakes/bra...p=Sport+Slotted+Cryo-Treated+Rotor&cat=Rotors

I do plan on going with a big brake kit eventually but for now I got the StopTech rotors you mentioned.
 

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