OptionXIII

• 2001 with Sport Brakes. Dual duty, daily driver and track car.
• Stoptech Sport Pads
• Cheap replacement rotors

I ran this car for 2016-2020 on the original rotors and Stoptech Sport pads - street, HPDE track days, sitting outside for a few weeks, whatever. Never had an issue. It was stored outside for the 2020 winter in a rainy area. That rusted the rotors so bad they had to be replaced, and since then I can't keep the pads from rusting to the rotor if it sits outside for a few rainy days. The end result is I get pedal pulsation that doesn't clear up. My current rotors have multiple pad imprints on them in the rear. I'm about to buy a third new set of rotors since 2020. As per conventional Miata track car wisdom, I've always bought whatever rotor was cheap on Rockauto. Never run any other pad but the Sports, but now I am thinking they are the issue.

I've tried to fix the pedal pulsations that come from the rust. I've sanded the rotor surface as per Stoptech recommendation. I've also tried chemically derusted the surface after sanding with naval jelly or phosphoric acid or whatever, just to make absolutely sure there wasn't a pad transfer layer still present. Pad imprints or rust divots remain, they fill up with pad material and rust, and pulsation comes back in a days worth of driving. I've resurfaced a set of rotors and still seen pad marks. At half the price of a new rotor I won't bother with that again.

Now, my questions.

1. Has the Stoptech Sport pad compound changed in recent years, or are there multiple variations of it? I've only ever run these pads. My only complaint about them is this rusting issue, they've performed great otherwise. Buddy of mine had a similar experience - his Civic's Sport pads rusted them to the rotor, his 1.6 Miata ran Sport pads and never had an issue.
2. Any recommendation for pads similar to Stoptech Sports for a dual duty car? I'd rather avoid pad changes for each track event if possible. G-Locs?
3. Are there any rotors with an actual difference in rust resistance on the friction surface? Paint on the hat doesn't help me. I know FNC treatment exists, but that seems to be an OEM level treatment and I don't know of any FNC rotors available aftermarket.

The car is garaged almost always now, but I also moved to a more rainy area and use the garage for working on other stuff too. I've got a spare set of Sport pads I'll use up, and maybe the more regular garaging will help, but I think for my next pad purchase I'd like to change it up.

curly

iTrader: (25)

Stoptech has changed owners multiple times in the last few years. I wouldn’t be surprised if there’s been some changes, I know parts are near impossible to obtain on a number of their products, but I haven’t heard of changes to the sport pads. My shop still recommends them for aggressive street or first time track drivers.

is it possible the rear calipers aren’t working well, and not getting hot enough to truly dry out the pad/rotor before setting the parking brake?

related question, are you using the parking brake any different?

There’s no coating or paint I know of that would survive brake conditions.

OptionXIII

I've been much more cognizant of my parking brake habits since this started. If I am leaving the car for more than a day and it's in a safe level location, I try not to use the parking brake. I don't use the parking brake when the brakes are hot, and since I don't make a habit of washing the car then applying the parking brake it's not a matter of wet rotors at the time the parking brake is set. This seems to be all down to rain splashing on my brakes. Pad marks do exist on the inside rotor, but they're faint witness marks compared to deep imprints on the outside of the rotor. I'm not sure if the relatively better condition of the fronts is due to higher heat, or not having a parking brake.

In general, I'm pretty on top of brake maintenance. I chased a soft pedal I couldn't explain for the past year and a half, but it seems to be finally working well enough again to go to track days. More details here if you're interested, but it's not the complete story.

I regrease the slider pins with every pad change, and bleed the brakes regularly during track season. The rear calipers were replaced with rockauto remans in 2016, the front calipers were rebuilt by me in 2020, and the right rear replaced again in 2022. The parking brake adjuster on that corner would loosen itself since new, I finally got tired of it and changed it. No change in braking behavior from that caliper other than having a parking brake that isn't useless in 600 miles. I do not see any drastically uneven wear in pads.

x_25

I have noticed the pulsing issues with my Stoptech Sports as well, but never really looked into it much since it goes away with a few miles of hard driving. It very much changes by day if I am just toodling around though.

OptionXIII

I replaced the rotors with Dynamic Friction fully coated rotors. Geospec or some kind of coating. It won't protect the friction surface. I'm hoping they will last a lot longer than my previous rotors and the visual appeal will be worth the cost bump. The pads I reused, but I did swap inner and outer pads.

It's so nice having a smooth brake pedal again. I had no brake problems at an HPDE event over the weekend at VIR.

Below are some pics. Reminder that just a few days before, these were completely cleaned and had no rust or anything on the friction surface, and I'd been dailying and garaging the car for months beforehand.