Question about brakes

[13726548]

I just came home from Road Atlanta after doing a PDX/track day for the first time in my life. I have to admit that I'm hooked and I plan on returning as soon as funds allow.
But before I do, I want to make sure my brakes are in good shape. I noticed that under heavy braking, like going in to turn 10A (downhill 120mph to 40-50mph) the steering wheel and the car itself starts to vibrate as if the rotors are warped. Is this just the nature of the OEM pads, or should I check my rotors for cracks?

 

[jayel579]

Check for cracks, buy new ones you do not need anything exotic for rotors. OE pads will not hold up to track days. Get better pads, Hawk, Carbotech, Cobalt... and replace your brake fluid with some sort of high temp fluid, i.e. ATe, Motul...

Brakes for track days should be considered consumibles just like tires and gas.

 

[13726548]

What do you think of the Hawk HT10s? Can those work with the oem rotors I have now with nothing else done to'em?

 

[DUFUS]

Observations from another novice...
I just installed new OEM rotors as a "just in case" thing after 10 or so track events along with HT10 front and HP+ rear (HT10's on order for rear also, but didn't arrive in time) and completed a track day 7/16. Seemed like a good combo. I haven't had a chance to check pad or rotor wear, but as mentioned, they're consumables and part of the price to play. Also, as mentioned, better brake fluid (along with frequent bleeding/flush) is a must.
What tires are you running? If you're leaning towards Hawk, perhaps DTC 70/60 (f/r) would be a good match the lower the treadwear rating of your tires. More $ though...
BTW, could your vibration be ABS kicking in?
Which also reminds me, turn advancetrac/stability control/whatever it's called, all the way OFF for the track.
Other less critical braking considerations: stainless steel lines and/or ducting.

 

[13726548]

I don't mind the fact that brake pads are considered as consumables. They can be pricey but I don't plan on doing track days more than twice a year, so theoretically they'll last me a while as long as I have separate pads for street driving.
I am running the stock BFGoodrich tires that have a wear rating of 400. I do not plan on running r-comp tires, at least not for the next track day. The brake fluid I used had a DOT4 rating.
I don't think the vibration was from my ABS, but I'm not sure. Would the steering wheel vibrate when ABS is engaged?
And yes, TCS was turned off.

 

[VTXFrank]

Did it do this right from the start or after you had already done some hard braking? I found that with my stock rotors and pads, after a lot of hard braking, heating everything up good, I would start to get some shimmying right before the brakes started to fade. Then I would go around some other corners that didn't require I slow down so much and by the time I got to the next hard corner, I could brake hard again yet still, towards the end of my braking for the corner, get that shimmy again.

 

[ct07gt]

Probably wouldn't cause steering wheel vibration, but make sure you don't set the parking brake after runs. It cooks the pad material onto the rotor and can cause it to warp from cooling slower than where the pad is not touching.

 

[13726548]

Did it do this right from the start or after you had already done some hard braking? I found that with my stock rotors and pads, after a lot of hard braking, heating everything up good, I would start to get some shimmying right before the brakes started to fade. Then I would go around some other corners that didn't require I slow down so much and by the time I got to the next hard corner, I could brake hard again yet still, towards the end of my braking for the corner, get that shimmy again.

The shimmying started after things were up to temperature. There was a smell in the air as well - I'm not sure if that was from the tires or the brakes. I knew the stock equipment wasn't quite up to the task so I didn't push it any harder than I already was. I was braking before the 300 marker on this particular turn.

Probably wouldn't cause steering wheel vibration, but make sure you don't set the parking brake after runs. It cooks the pad material onto the rotor and can cause it to warp from cooling slower than where the pad is not touching.

Yes, my PDX instructor said the same thing.

 

[Chris B.]

What do you think of the Hawk HT10s? Can those work with the oem rotors I have now with nothing else done to'em?

The HT-10's are good pads if you aren't doing a lot of high speed braking. I wore through a set in two days at VIR last year. Out cars are heavy and the brakes get very hot when slowing down form high speeds. The HT-10's wore out fast because my brake temperatures were at the top of their temperature rating. The next step up in the hawk pads are the DTC-60's. However, thy are a little harsh and grabby if you are using street tires, especially in the rain or even on a damp track

I've been really happy with the Carbotech pads I've used. I use to use Hawk pads, but made the switch last year. Last year I used the XP-12's up front and the XP-10's on the rear brakes. This year I'm tyring the XP-10's up front and the XP-8's in the rear. The XP-10's will handle 1650+ degrees and the XP-8's will handle 1350+ degrees. Both would be fine along with good fluid such as Motul RBF 600.

Stock OEM Ford rotors hold up amazingly well. In 2500+ track miles in my previous 2008 Mustang GT I used 2 sets of front rotors and one set of rear rotors before they started to get mroe than small cracks.

 

[Cone Sweeper]

Like Chris said.. i've been running a set of stock rotor's but using hawk dtc-60's front and rear and race brake fluid along with a cooling kit I had made.. those things will help regardless of the brake setup you use..

 

[13726548]

I appreciate the responses.

And as far as brake fluid goes, are all DOT4s created equally? I'm running off-the-shelf Valvoline DOT4 and didn't have issues with boiling fluid of any sort. But then again I wasn't braking too hard.

 

[jayel579]

Get ATe super blue, its cheap but very good. My brother flips between ATe super blue and their red (TYP 200, I think) on his E30. Makes it very easy to know when you have flushed out the old fluid. Motul 600 is way better but very expensive and wont last any longer.

 

[Sleeper_08]

+1 For ATE Super Blue/ATE TYP 200

 

[DUFUS]

http://members.rennlist.org/911pcars/brakefluid.htm

 

[argonaut]

The vibration and shimmy you felt is probably due to inconsistent pad deposits on the rotors. As you know by now, the stock pads are designed to last a long time and be quiet on the street, they are not capable of handling the elevated temperatures seen on a race track. In effect what happend was you started to melt the pads and the pad material got smeared all over the rotors. This caused the material to build up more in some spots than others and the result can be bad vibration.

Do you still have the problem now...on the street? Sometimes it will clear itself up - the rotors cool down and the pads just scrape off the high spots. Other times you have to take more drastic action like sanding the rotors, street driving with very abrasive pads or worst case getting them turned at a machine shop.

Personally I don't care for the Super Blue fluid. I use to run it but found that it stains everything, like plastic master cylinder reservoirs and the clear tubing I use to bleed the brakes with. Now I use Motul. Although it would be overkill for the OPs use, next year I think I'll switch to Castrol SRF. Its insanely expensive but (and its a big BUT for me) you never need to bleed. All season long without bleeding. I use to mess with brakes constantly, every day at least and sometimes in between sessions - flipping pads, bleeding, replacing rotors, replacing pads, etc., etc. Last summer I got AP racing calipers and rotors - instantly most of the brake maintenance tasks went away. With SRF they pretty much all go away. I don't know what to do with all the extra time I have between sessions now LOL.

 

[13726548]

The vibration and shimmy you felt is probably due to inconsistent pad deposits on the rotors. As you know by now, the stock pads are designed to last a long time and be quiet on the street, they are not capable of handling the elevated temperatures seen on a race track. In effect what happend was you started to melt the pads and the pad material got smeared all over the rotors. This caused the material to build up more in some spots than others and the result can be bad vibration.

Do you still have the problem now...on the street? Sometimes it will clear itself up - the rotors cool down and the pads just scrape off the high spots. Other times you have to take more drastic action like sanding the rotors, street driving with very abrasive pads or worst case getting them turned at a machine shop.

Personally I don't care for the Super Blue fluid. I use to run it but found that it stains everything, like plastic master cylinder reservoirs and the clear tubing I use to bleed the brakes with. Now I use Motul. Although it would be overkill for the OPs use, next year I think I'll switch to Castrol SRF. Its insanely expensive but (and its a big BUT for me) you never need to bleed. All season long without bleeding. I use to mess with brakes constantly, every day at least and sometimes in between sessions - flipping pads, bleeding, replacing rotors, replacing pads, etc., etc. Last summer I got AP racing calipers and rotors - instantly most of the brake maintenance tasks went away. With SRF they pretty much all go away. I don't know what to do with all the extra time I have between sessions now LOL.

Thanks for the detailed explanation. It all makes sense now.
The shimmy only occurred at that particular braking zone when I was going from 100+ to 50 in a matter of about 300 feet. I know that's not considered severe by road racing standards, but apparently it was too much for my completely stock brakes. On the drive home everything acted as if I never raced it. Even the clutch maintained its original pedal feel and friction point.

As for the fluid, what is considered a "good" dry boiling point? I was thinking something in the low to mid 500s will suit my needs, but if the rotors and pads are seeing 700+ degrees, wouldn't that boil the fluid? I'm assuming the fluid temps don't get as high as the pads and rotors?

 

[Philostang]

Low to mid-500s is good, but there are better for similar prices as most competitors (see Motul RBF600). There's a lot of insulation going on between rotor temps and the fluid, and you can offset that a bit with titanium shims and/or maintaining thicker pads at all times. For example, Carbotechs usually have a wider temp range than their Hawk counterparts, but that goodness doesn't last long. After half the pad is gone the Carbos get real heat sensitive and much more fade prone. Hawks seem happy to take abuse until they're ridiculously thin. For each, they're allowing more heat transfer into the caliper pistons (and then to fluid) as they get thinner, but I don't have any real comparative data to say which allows more. I've never boiled my fluid with Carbos even when running them pretty low (they're fading like mad by then anyway, so perhaps this prevents me from using them in a manner that would lead to the fluid boiling). Anyway, I also run Motul, which has a very high dry boiling point.

The thing to read between the lines in Argo's comment is the difference in a fluids ability to maintain its integrity through all the abuse we dish out on them. Motul needs to be bled regularly to maintain its maximum efficiency, but even if you don't they don't drop off nearly as bad as some fluids. The thing to watch is the WET boiling point - this is what the fluid can do when it's been abused and hasn't been flushed or bled at frequent intervals. Check out the following:

Brake Fluid Comparison Chart (Wet Boiling Point & Dry Boiling Point)

Brand.................... Wet / Dry
Castrol SRF ............518°F / 590°F
Wilwood EXP 600+... 417°F / 626°F
Motul RBF600.......... 420°F / 593°F
AP-600.................. 410°F / 572°F
Brembo LCF 600...... 399°F / 601°F
ATE-Super Blue....... 392°F / 536°F
Valvoline................ 333°F / 513°F
Castrol LMA............ 311°F / 446°F
-------------------------------------------------------------------
Ford HD................. 290°F / 550°F
Wilwood 570........... 284°F / 570°F
PFC-Z rated........... 284°F / 550°F
AP-550................. 284°F / 550°F

So notice the goodness Argo really buys. 518°F wet is just stupid high (it's sneaking up on ATE-Super Blue when dry!). That stuff is the Super Man of brake fluid, you just can't seem to hurt it.

But now look at which fluids "drop off" the most. Wilwood 570 is my favorite, since I used to use it. I was sucked into the lower cost and advertised DRY boiling point. The problem is, they drop off a cliff once wet (approaching the minimum DOT standards), and they get wet quick (or at least they start to act that way once they've been cooked a bit). So you're bleeding very frequently and finding yourself paying in both time and dollars as a result. When I used it I was happy for two or three sessions, then wondering what the heck happened to my brakes for the rest of the day/weekend. Answer to what happened: my fluid was now about as good as the cheapest crap you can get off a shelf at some random truck stop.

FWIW, Motul RBF600 has a wet boiling point higher than the dry point of many top tier non-racing fluids you'll find at your local Autozone. That's what you're buying as you move up the food chain - a tougher and tougher fluid.

Best,
-j