Brake pad f/r bias
 

Hey guys,

Question I'm asking myself: given the stock brake force balance, does it make sense to go with lower performance brake pads in the rear? I'm looking at running something like DTC60 in the front and HP+ or DTC 30 (if I can find them) in the rear (at the track).

Up till now I've run HP+ front and back and I like the resulting even brake distribution (i.e. the rear is doing the right among of work for me). So, with higher performance pads, would you recommend going with different pads, or just DTC60 all around?

The rear choices you listed would typically be considered too extreme of a difference. DTC-30 will come in much sooner than DTC-60 and will wear fast at those higher asphalt track temps. HT-10 would be considered more usual with DTC-60 on the front. Some might even use DTC-60 on the rear too depending on the situation, or HT14/HT10 or DTC-70/DTC-60 combinations.

There are some old threads here on the same subject ...

ive been using the DTC-60 front HT-10 rear for a couple years now and cant wait for the rears to wear out so I can go back to DTC-60's front and rear. I get tail wiggle under extreme braking that I dont like and didnt get so much with the same compound on both ends.

I run DTC-60 front and rear and have liked the result.

I ran HT-10 in the rear for a while with DTC-60 in the front...and really didn't notice much if any difference when I went to the 60's front and rear

This is exactly what I noticed when I ran HP+ front and HPS rear and was trying to avoid. Will go with 60s all around. Thanks!

I'm running the same compound F&R too (different brand) I prefer it over a bias

There is a possibility that it's not your brakes and that it's you. In those conditions the slightest movement of the steering wheel while you are bracing yourself can cause that. Try having the lightest grip/touch on the wheel while braking and don't use your arms to brace yourself and see if it goes away.

When I have that problem, I open my hand and palm the wheel and the car tracks straight.

I've always run the same compound front and rear. I find the car has a decent bias stock, so why over think it?

I love my RX8. I have to change the brake pads soon and wanted to upgrade so I can use them for a solo/autocross event. What would you recommend? I have not made any changes to the car yet. Thank you for your help.

There is no single answer, depends on skill level, tires, how much you like dust, etc. research.

I assume you have ABS still hooked up. If you do THAT is your brake bias. No need to try and out think it. Also note that brakes work in different temp ranges better. That is the only reason to change pads. Mazda already figured this out (just like most engineers) and made the rear brakes smaller. If your really using the brakes then you should get pretty good temps front to rear.

So in short you really should have the same pads front to rear, if your using a less aggressive pad on the rear your over working the fronts and not maximizing your opportunity.

I have spoken directly with hawk and the dtc-60 is the way to go. If your racing and getting the temps needed to make them work. They also Lasted the entire 12hr at NJ turning 1:34-1:36 lap times on street tires.

Stephen

PS: I get my pads through Andrew racing. Good guy, a racer, and located down the street from hawk in Ohio. Tell him I sent you. (No he doesn't sponsor me, but he always gets what I need fast!)

Oh and andrew racing helped create that chart above, they can give you a recommendation on what pad to use.

Hawk HPS is what I'd try if I was in your shoes. Mild upgrade over stock, bit better heat capacity enough to be "ok" on track (at least for me), but not so overkill as to suck on the street or suck ice cold at the start of an autox run.

YMMV though.

Very interesting, sblethen... No issues trail braking, etc? I have been using Cobalt Friction but might use some contingency buddy bucks and switch to DTC60s all around.

No issues at all. Without the abs and Hoosiers you need to be careful not to lock up a tie. With abs hammer on them! (We use the abs with the street tires) only real issue not discussed its the rotors take a beating. After 1 session you will start to see heat cracks.

Stephen

Got it. I run aftermarket discs so that should help. For NASA, discs is a free mod (calipers are not).

Thanks!

So I couldn't find rear DTC60s in time for last weeekend, so went with DTC60 front, HT10 rear. LOVE love love the combination, the modulation response is fantastic, and speaking as a heavy trail braker, it was appreciated :P

Will try 60's in the rear when the 10's wear out, probably in a month or so.

Thanks for the feedback guys.

You go through a set of rear brake pads in one month? I must not be braking enough.

:lol:

My 2 local tracks are hard on brakes: Saint-Eustache and Mont-Tremblant. Maybe I lied, the rears should last more than a month, but based on the 2 days I've done so far, I don't think they'll make it to September.

Running with DSC not fully disengaged would result in faster rear pad wear, but I'd hope you wouldn't be running with it not fully turned off using those pads

You will be surprised how long they will last. They are orders of magnitude better that HP+ or other street/track compromise pads. I got 6 days or about 20 hours out of the 60's last set

Alright, how about I report back on this thread when the fronts and rears run out.
One thing I forgot to mention: my club requires more than 50% pad at the start of any event, so 'finished' to me comes much earlier. It's kind of annoying, but we do catch people trying to go on without a safe margin of material on the pads. Had one guy with some fancy Mercedes talking smack until we realized his OE brake pads had 1 mm left. He wasn't happy.

That's a stupid rule for the most part...but if you have even 1/3 left they will likely pass cause it's difficult to tell how much they started with :)

It's a rule that is for people that don't do there own maintenance.....like the Mercedes guy ;)

What can happen when you don't check your pad thickness.

I use HT-10 front and rear on the RX-8 and the Miata. I've tried DTC-60's as well but I feel like they don't have as much modulation near the limit and seem to lock up more easily than the HT-10's.

Ran Cobalt Friction this weekend - XR1 front, XR4 rear. There is a 175-200F delta in front vs rear disc temperature, probably higher if I wasn't using factory rear disc.

XR1s are aggressive; probably fine with BFG R1's or similar. I'd try XR2/XR3 but I'll be trying DTC60's all around next event.

I run the same compound front and rear and it seems to work well with stock brakes and sticky street tires. Wear is fairly even as well. Has been DTC-60, but now giving some Raybestos pads a try.

I’ll just add that Porterfield Racing can usually machine them for you as long as there’s a large enough pad in that compound available for them to work with. They’ve made me plenty that way for the rear factory calipers. Just a general FYI for anyone who comes across this post.



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so what is the track pad front/rear combo people use these days, or do you prefer same compound all around?

thinking about trying one of these hawk DTC-60/30 or porterfield R-4 or Cobalts XR2/4.

would bi nice not to have to swap pads out for occasional street use (few weekends a year, so not a big deal as long as they are safe on the street)

Carbotech XP10 front, XP8 rear. Excellent modulation and very gentle on rotors.

Ive run DTC60 all around for a few seasons now. No complaints. And when I'm lazy I keep them on for the street, and they behave better than many other lighter duty pads. Dusty, but not noisy or sloppy when cold.

Yep I second the dtc-60’s all around! Best track pads I ever used! Loved them! Can street them a little but not a lot

DTC 60 it is then.

good video as a point of reference on what kind of surface rotor temperature you would see at big power track (VIR) with long straights and hard braking zones. temps get easily into 800-900C that is 1472-1650 F by the end of the braking zones:


Stock AP1 Honda S2000 with JRZ dampers, 245 NT-01 tires, and Cobalt XR1/XR2 pads. No aero. No power steering.

Front: 0" toe, -2.2 degrees camber, 625 lb/in spring rate (WR = 320 lb/in)
Rear: 1/8" toe-in, -3.4 degrees camber, 550 lb/in spring rate (WR = 250 lb/in)

I've continued to run the same compound front and rear. The fronts do get hotter than the rears unless you add ducting, but the balance feels pretty good to me. The abs in the s2 works better than the s1 on track, but even on the s1 I've done the same.

Here's a quick summary of the pads I've tried:

1. DTC-60 work well, are pretty much the lowest price high temp pad (at least last time I looked) but wear fairly quickly. Also, the paint made a mess for me. (My brakes run hot).
2. Raybestos ST-43. Last ~2x DTC-60. So cheaper over the life of the pad. Work well from cold (even well enough on the street). Do ramp up a bit as the get temp in them on the track so you need to modulate accordingly (fine once you get used to them, and not necessarily worse than DTC-60, but I did need to adjust myself). I like these, only downside is having had to file the backing plate a bit to fit them on occasion.
3. CL brakes 6E. My current favorite pad. Feel nice and firm and very little ramp so makes consistent braking easy. Last way longer than DTC-60, but not quite as long as ST-43. Recently went up in price and so ordered my last set from Europe.
4. Porterfield R4-E. Not run this on the RX-8, but have been happy with them on a ford focus lemons car. Last at least twice as long as stoptech performance (street) pads and feel better. That car keeps the brakes cooler than my RX-8. I expect these will last somewhere between DTC-60 and ST-43. Also ramp up with temp on track.
5. Carbotech XP10. Have not tried them on the RX-8, but did run them on a stock civic (which runs the front brakes super hot). Didn't hold up to the heat well at all, went through them quicker than DTC-60 on the same car, and I was not too impressed.

interesting, so maybe I should actually get ST-43s then?

F/R set of DTC-60 is $162/$145 so $307 for set on amazon :-)

F/R set of ST-43 is $219/$169 so $388 vs 2 sets of DTC-60s at $614, that is significant cost difference!

ST-43 would be my pick. I also find them easier on the rotors across a range of tracks (The hawks seem to be hard on rotors when not quite fully up to temp)

P.S. don't be tempted by slotted or drilled rotors for the track... blanks are the way to go.

I ran DTC-60 square and DTC-60 F and DTC-30 R for a couple years. I would drive ~2 hours to/from the track and do 2 hours of track time on them roughly once per month. I found them to wear out quickly, and they were hard on rotors. I also thought they had too much bite and poor modulation. Since switching to Carbotech, I get twice the life out of my front pads, double that in the rear, and I went from replacing rotors at least yearly to something like every 3 to 4 years. This experience started with my Miata, and my RX-8 is tracking (pun intended) the same way. I would guess blu3dragon was using too little compound for his car, or his braking habits are much different than mine.

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Interesting, I suspect I was simply out of a viable temp range for the carbotechs, or really any pad, on the civic. It went through DTC-60 in two days, and XP-10 in about 1.5. I also had slotted rotors at the time which likely didn't help.

On the RX-8, my rotors don't last more than a year (10-15 track days), before I dump them due to heat cracks. There is some wear, but that doesn't tend to be the limiting factor.

Different tracks can make quite a difference to brake temps. At Sonoma, I don't really keep enough heat in DTC-60, and they eat the rotors. At Thunderhill and Buttonwillow they seem to work well. At Laguna Seca they seem to get too hot and the pad wears more quickly.

Yeah, I think you probably needed the XP20 compound. When run in their proper heat range, they do not fade and last a long time. They have just the right amount of bite and offer excellent control.

My Miata is on year 3 of its cheap Centric blanks. I change its front pads twice per year, and its rear pads once per year. That is a true momentum car, though, and I brake as little as possible when driving it. It sees at least 12 track days per year.

My RX-8 is on year 2 of its cheap Raybestos blanks. I change its pads with the same frequency as the Miata's. As a heavier and faster and poorer handling car, my approach to braking is more standard. It sees around 8 track days per year.

So I was able to grab set of Hawk Blue and Carbotech XP-10 front pads on the forum for cheap.

If I do remember correctly carbotech is more finicky than hawk if there was other brake compound on the rotor previously.

I have set of new rotors so I should run carbotech first followed by the hawks, right?

or I can run hawks blue on my current rotors with EBC blue compound on them, then swap rotors and put carbotech pads on?

^ Yes. Carbotech pads really like virgin rotors and do not mix well with other brands of pads. I run XP10 front and XP8 rear on the track and a set of 1521 on the street on the same rotors. That setup works well, because Carbotech pads are very gentle on rotors. Using an aggressive track pad, such as a Hawk DTC60, with a street pad, such as a Hawk HPS, does not work as well, because the mating surfaces between the worn rotors and the street pads never match up.

i used dtc60 front dtc30 rear when i first got the car, it was too much brake for the car. a few of my friend who are seasoned racers said the same. i then moved to dtc50 endurance pads in the front. they felt great, much easier to modulate but under threshold braking, i can feel the rear abs comes on and the rear step out a little, so i moved to HPS for the rear. the dtc50 is also thicker, i cant even fit new pads in the caliper with the backing shims, i leave the shims out. about 20 track days later and the front pads are still over half left.

my car is 2900 lbs with driver and fuel running on 245/40/17 hoosier R7. and i also have front 2.5" brake duct.

HPS on the rear is likely doing nothing except overheating, lol

The rear is completely controlled by the ABS software, which would otherwise be working to overcome/defeat any pad bias. I still would recommend using the same compound at both ends. If the rear is stepping out under braking it’s likely due to something else imo; alignment, shock settings, etc.

Ht-14 front
Blues rear

the abs does control rear bias but only at max braking when the rear locks up. but when you're only applying 50% braking, it the pad bias comes into play. even with hps pad in the rear, i can still feel the rear abs comes on before the front at threshold braking. when i ran dtc60 front and rear, the rear abs came on much sooner.

I supposed that was too obscure of a response. The EBD (electronic brake force distribution) software portion of the ABS system determines the rear brake bias under all braking conditions, not just during extreme brake pedal use. It’s an electronic proportioning system that alters rear brake bias through the ABS brake line force output rather than through a static bias valve/orifice device.

By your own words, you’re treating the symptom rather than the actual illness in deference to the prior comment. Nobody else is running such an extreme pad bias. Many RX8s run the same pad or slight bias in the rear and don’t note what you still do with a full on DTC60 race pad in the front and a HPS street pad in the rear. There’s another issue going on that you aren’t recognizing. It just makes itself more known/is exacerbated under braking.

i lied. i thought i was running HPS but i check my purchased order and they were HP+. i started out with dtc60 front and dtc30 rear. then switch to HP+ rear. then switch to dtc50 front. so currently i'm running dtc50 front and hp+ rear.

so if the EBD is adjusting rear bias on the fly based on current car condition, that is good to know. i still have the dtc30 rear and i'll put them back on and see, now that my car is a little more developed then before when i last tried them.

Here is updated Hawk compound temp vs friction chart.

https://www.hawkperformance.com/compounds/motorsports


https://cimg1.ibsrv.net/gimg/www.rx8...7dd4306dc4.jpg