RX8 already seems to need new front brakes, help me decide the best option

When I picked up my RX8 earlier in the, one of the first things I did was replace the well-past-the-wear limit rotors and pads. Picked up some mid-price Centric rotors and Hawk Street/Race pads (yes, that's the actual name, to avoid the confusion we had the last time I mentioned the pads).

One of the front rotors seems to have been marginal for runout when I fitted it (my dial gauge got lost in the move from the UK and I still haven't got around to replacing it). A couple of track days at Laguna Seca, sorry, MRLS and two time trial events at Thunderhill West later and the runout has got so bad that it's rattling the pads when driving down the street and shake the car when I'm hard on the brakes as if the ABS is engaging (which it isn't).

So, at the very minimum I need to replace that particular rotor and probably also run less aggressive pads on the street, although I'm not massively fond of having to swap pads before an event. Mind you, that only takes 10-15 minutes so it's not exactly an ordeal.

The way I see it, I have the following options:

1. Order a replacement rotor and a set of less aggressive pads for street driving. And get a dial gauge to make sure the runout is within spec.
2. Get some improved rotors (slotted or drilled) in the stock size, run the same kind of dual pad strategy as in (1). MRLS is hard on brakes at least with this particular lose nut behind the wheel, but I don't feel that I'm getting close to the brake system's limit so far. RX8s have pretty decent brakes stock...
3. Stop whining, man up and get a big brake kit for the front. There are a couple to choose from, most fit under the 18" wheels I'm running and my current thinking is that the larger rotors dissipate heat better and I probably don't have to run quite as aggressive a set of pads on them. That said, there are a couple of other things I'd like to address with the car first before spending $1600 on a big brake kit, but I can it if makes sense

WWGRMD? Other than mill myself a set of front rotors out of a piece of scrap steel found at the roadside, obviously.

I tracked my RX8 and didn't have the problems you mention. I ran the top of he line NAPA rotors (I think Canadian made at the time) and Carbotech (XP12 on front, XP10 on rear) pads, even on the street. Noisy, dusty, but they stopped great. I didn't have any issues with rotor wear or runout. I think you may have gotten a bad rotor.

I have never actually seen a rotor with enough warp or runout to cause brake vibration.

It is always pad material deposition or a metallurgical issue with the rotor (like a hard rusty spot on the braking surface.

Were the pads run up to the top of their temp range and then allowed to completely cool before hammering on them?

Hawks are pretty sensitive to break in procedures.

Rotors can "twang" with heat cycles. Iron can shift over time as a result of casting stresses, and being hot on the OD and cold in the center doesn't help things any.

They're cheap enough anymore that most people just replace them, but if you can find someone who knows what they're doing with a brake lathe (as opposed to someone who just chucks it in and cuts metal without verifying the rotor is chucked squarely) you can machine them flat, and generally speaking the rotor will twang no more.

On-car lathes do a far better job than off-car but they are more expensive and time-consuming to set up.

Another thing you could try is a set of really, really aggressive pads up front, that only start to bite when super-hot. When driving on the street, the cold pads will eat the rotors rather than wear them, so it's like a self-propelled on car lathe. Bad for your paint though

As far as a BBK they are not any better then the OEM system.

Most I could think is the Hawks are a bit too much for the rotor causing overheating and warping or like others have said a bad rotor.

Good luck in your decision.

I'm surprised you experienced issues. Here are some experienced I've had:

On my RX-8 I found I could get >8 hours on Hawk HPS and I believe something like double that on HP+ on Centric 120 rotors. This was on a local track that is hard on brakes, using max performance tires. IMO the RX-8 has excellent stock brakes.

On my Miata chumpcar (extreme performance tires) I've run Napa rotors with DTC-30 pads. DTC-30 is almost identical to street/race, note Hawk's friction/heat chart uses the same line for both pads. I've found I get maybe ~16 hours on a track that's reasonably heavy on brakes, but a little less so than the one above. On a light braking track I used <50% over 19 hours.

Based on my experience, I probably would have selected the same components you used...

Thanks for everybody's feedback. My current working theory is that the issue is likely to be a problem with the rotor itself. I do remember someone on here mentioning that they weren't too happy with the quality of Centric rotors after I ordered them, but I've used them before and they were fine. This is the first time I've used them with pads that aggressive though.

I don't really know of any shop out here that's competent at turning rotors and TBH at the price point these come in I might just get a replacement as soon as I can find the order confirmation.

The wear on the pads themselves is pretty good, no complaints about that. I'm just not particularly fond of how they behave in normal street driving.

One point no one has mentioned: it is not the best idea to replabe only one rotor. Whichever rotor is thicker, the pads will begin to engage slightly before the thinner rotor bevause they don't have to move as far. That can make for some, ahh, undesireable squirreliness in certain braking situations.

In reply to WildScotsRacing:

I was afraid someone would point that out...

I really should attack the rotor with a micrometer first, but I should probably point out they only have about 4k miles on them, but four days were on the track. I wouldn't even consider replacing anything but the pair if they had some proper miles on them.

OTOH a set of good rotors is only about $250 anyway. Less if I go for the cheaper stuff.

BoxheadTim wrote: I don't really know of any shop out here that's competent at turning rotors and TBH at the price point these come in I might just get a replacement as soon as I can find the order confirmation. The wear on the pads themselves is pretty good, no complaints about that. I'm just not particularly fond of how they behave in normal street driving.

I've never considered the competence of the shop I've selected to turn rotors. It strikes me as a situation where the shop either can or can't do it. ;)

I find DTC-30s a bit grabby on the track, but I through the street/race pads were suppose to be a bit better. Two teammates have no issues with the DTC-30s. I prefer the feel of the HP+, but I don't know if they'd be up to the task you're giving them. HP+ can be less refined than OEM on the street, but I like them there.

I got 60k miles on the OEM rotors on my Rx-8, two sets of HPSes in that time.

I just switched to Centrics & EBC Redstuff in the past 3k, with two track nights on it thus far. So far they're still perfectly smooth, though.

I've had issues with Centric rotors on two completely different vehicles. My last set was on my daily driver Mazda 3. The car would violently shake at highway speeds and under braking. When I went to replace the brakes, one was so bad that you could see that it was warped!

That's not an illusion. The rotor is wavy because it WAS. And that's just from daily driving.

Never had an issue with the Centric 120 Series rotors. Every one of them has been smooth as butter for their whole service life, even on previous cars that have been tracked. OTOH, I always precisely follow Centric/Stoptech's procedure for heat cycling the rotors before getting them really hot.

WildScotsRacing wrote: One point no one has mentioned: it is not the best idea to replabe only one rotor. Whichever rotor is thicker, the pads will begin to engage slightly before the thinner rotor bevause they don't have to move as far. That can make for some, ahh, undesireable squirreliness in certain braking situations.

HUH?

That isn't how calipers work at all.

SilverFleet wrote: I've had issues with Centric rotors on two completely different vehicles. My last set was on my daily driver Mazda 3. The car would violently shake at highway speeds and under braking. When I went to replace the brakes, one was so bad that you could see that it was warped! That's not an illusion. The rotor is wavy because it WAS. And that's just from daily driving.

Wow. That's nuts!

Well, one of the things I teach at school is there there is a big difference between the cast surfaces and machined surfaces of a rotor, and any time you are referencing from an unmachined surface you are probably creating a bad assumption.

I've never considered the competence of the shop I've selected to turn rotors. It strikes me as a situation where the shop either can or can't do it. ;)

It's not always easy. Although it's easy to tell when you wasted your time chucking up a rotor only to find out it's garbage because of hot spots that weren't immediately noticeable and cant be cut evenly with the rest of the rotor surface. So if a rotor is truly 'warped' from heat and not just suffering thickness variations, it probably cannot be trued on a lathe anyway.

Snrub wrote: I've never considered the competence of the shop I've selected to turn rotors. It strikes me as a situation where the shop either can or can't do it. ;)

Given my experience with some shops in this area that managed to screw up just about any simple task you give them, I've become very cynical. Most of the Napzones don't turn rotors anymore either and I don't know if my trusted shop actually does or not.

Snrub wrote: I find DTC-30s a bit grabby on the track, but I through the street/race pads were suppose to be a bit better. Two teammates have no issues with the DTC-30s. I prefer the feel of the HP+, but I don't know if they'd be up to the task you're giving them. HP+ can be less refined than OEM on the street, but I like them there.

I've used HP+ pads on several of my Miatas and do like them, but I'm a little concerned about using them with a heavier car. I actually like how the street/race pads feel on the track, they're just a little too grabby for street use for my liking.

In reply to BoxheadTim:

Was there any visible pad deposit stuck on the rotor? If so, I'm with wvumtnbkr in the "overheated the pads" club. Several cycles of cold hard stops can help grind that crud off, but you'll have the same problem again next track day.

It's always hard to get a decent rotor temp reading if you're alone at the track, maybe try a temp strip stuck on the rotor barrel next time out?

https://www.amazon.com/ALC-THS0080X285-Alcon-Caliper-Indicator-Strip/dp/B005GWRVN6

WonkoTheSane wrote:

SilverFleet wrote: I've had issues with Centric rotors on two completely different vehicles. My last set was on my daily driver Mazda 3. The car would violently shake at highway speeds and under braking. When I went to replace the brakes, one was so bad that you could see that it was warped! That's not an illusion. The rotor is wavy because it WAS. And that's just from daily driving.

Wow. That's nuts!

Yeah, tell me about it!

The rest of the rotors looked like that. They had those "lines" in them, and when running a finger across, you could feel missing material from the rotor surface.

Keep in mind that I followed the break-in procedure to the letter, and these only had 30k of regular, non-track driving.

Those rotors are heavily glazed like I haven't seen since the days of organic pads and 9-10" rotors on the front of minivans and SUVs.

That is generally caused by the pads running way outside their temp range and transferring a lot of material to the rotor. Which, as you point out, can then flake off. That will cause HEAVY pulsation. I've seen it happen so bad that it would activate the ABS in the rain. Which is super duper extra fun when you can't use the brakes on the highway to any degree without the slow cycling GM ABS IV activating.

What pads were used again?

Dashpot wrote: Was there any visible pad deposit stuck on the rotor? If so, I'm with wvumtnbkr in the "overheated the pads" club. Several cycles of cold hard stops can help grind that crud off, but you'll have the same problem again next track day. It's always hard to get a decent rotor temp reading if you're alone at the track, maybe try a temp strip stuck on the rotor barrel next time out? https://www.amazon.com/ALC-THS0080X285-Alcon-Caliper-Indicator-Strip/dp/B005GWRVN6

No visible crud on the outside, but I believe the problem spot is on the inside of the rotor. Haven't had time to pull off the rotor yet. Investigation is planned for the weekend...

Be interesting to see if I did overheat the pads as I'm normally not that hard on brakes. Way too slow for that.

Well, investigation was planned for last weekend but I finally got around to it.

The rotor has almost 0.007" runout according to my new super precise cheapass bought-on-Amazon dial indicator, which is over three times the allowed runout according to the workshop manual. That's not good, but the minor good news is that I didn't find any obvious spots with deposits on them.

That said, I suspect that's not the real problem. The rotor was a bit darker than I expected it to be (indicating more deposits from the pads than expected) and I noticed that both front brakes are dragging. The passenger side - which is the one with the above problem - drags somewhat worse than the driver's side, but both drag noticeably. As in, if you try to spin them by hand, you get between 1/4-1/3 turn max before they stop again.

I did clearance the pad backing plates when I installed them so the pads do move freely. At the moment it looks like the caliper pistons don't retract quite as far as they should and the dragging brakes create additional heat. Shouldn't have surprised me, I already had to replace one of the rear calipers because it had been messed up in the past. The pads show that they've got pretty hot, but at least they're not glazed - benefit of running racing pads.

So I guess the choices have now widened to:

• Buy parts store reman calipers for the front (about $100 apiece with uncertain delivery times), replace the rotor(s), hope for the best
• Get a set of front calipers from Mazda. That's going to work out at around $800-$900 for the calipers and the rotor(s) if I stay with the Centric rotors.
• Sod it, go with the big brake kit. I still don't think I need that, so that's probably the least sensible option and also to the most expensive one. That said, if I take a step up from the Centrics, the combination of better rotors + front calipers from Mazda is getting within 200-300 bucks of the cheaper multipiston big brake setups.

Either way it looks like I'll have to run one more event like this, but it shouldn't be too bad - already ran three with the rotor like this.

Get a caliper rebuild kit. Less than $20 from Mazda IIRC. Front calipets on that car are straight forward to rebuild/reseal. I had issues melting the piston dust boot on track causing dragging. So I removed it and just rebuilt annually.

Didn't realise that Mazda sold those, I need to look into that.

BoxheadTim wrote: Either way it looks like I'll have to run one more event like this, but it shouldn't be too bad - already ran three with the rotor like this.

Have you got brake ducts on it yet?