Selecting brake pads for rain and low-grip tracks
 

So, yesterday I drove on a wet, cold track for the first time in a few years.
On the back straight, I had a few cases where the tires would lock up with a reasonable amount of warning, but without warning the car would continue to slide even after releasing the brake pedal entirely. Very scary.

I initially chalked this up to cold tires having no grip at all on the rubbery section of the track, but then I wondered if maybe my brakes weren't releasing properly.

Then I remembered the brake release characteristics are part of selecting pads.
I am running racing pads (Project Mu 777) which claim excellent release characteristics, but I wonder if maybe that's compared to other race pads, and only when the pads are in their optimal heat range (they probably weren't yesterday).

Should you generally change to less aggressive pads when driving in poor conditions?

Or might my poor old calipers just need a rebuild?

come to think of it, part of the problem may have been I wasn't running enough tire pressure, causing hydroplaning...

what tires(?) might be the dominating factor …
.

Honestly, I hate racing in the rain.
Its nerve wracking to me and Im doing lowspeed stuff. But I still see my friends totalling their cars occassionally.

Plus, you arent ever going to set a new course record in the rain.

All the factors contribute to what you experienced.

You have to remember the rubber laid down in the "racing line" is slimy in the cold and wet. Often ots better to drive "off line" on the bare granular surface.

Over inflated (rounded tread surface) can help water evacuation and rain race tire are of course king, but all seasons are decent if its really cold.

Disconnecting sway bars can make the weight transfer slower as can pads with more linear friction progression as you mentioned.

Sounds like you were finding you had to be more smooth with inputs to avoid front washing out at turn in or rear coming out with trail braking.

Yup... Takes so much concentration.

cold as fuck (but nearly new) Nankang AR-1s lol

I was so slow that I realized I was better off using left-foot braking to keep heat in the tires and brakes... normally I would be too busy with the clutch to use LFB.

Also, yeah, the problem is that the track surface isn't that old, so you can't tell the wet line by just looking at the track...

When I was driving an MR-2 with nice Advan Neovas, I was pretty fast in the rain.

I race Miatas and have not seen anyone switching pad compounds dry vs wet but I suppose some people might. I run G-LOC pads nowadays. Specifically the R12 front and R10 rear. GLOC and Carbotech are probably the most popular brakes due to release characteristics and overall modulation. Used to run Hawk DTCs and the GLOC/Carbotechs are indeed better from that perspective.

GLOC temperature range of 173°F to 1860°F (78°C to 1015°C)
Mu seems to run 300～800℃. Also, it seems to have high initial bite. Combine those two factors, I'm going to speculate that the MU's probably increase probability of lockup in slippery, cold conditions.
https://cimg8.ibsrv.net/gimg/www.rx7...77e768cd95.gif


https://www.project-mu.co.jp/en/products/pad_777.html
https://www.g-locbrakes.com/products/brake-compounds/


Once the tires are locked up and/or a slide starts, you are at the mercy of the wet, slippery surface. It takes a lot longer to regain control. Tire compound (soft sticky) and siping design play a big role in wet grip as you probably know. Not sure how good those AR1s are in the wet... The Neovas are known to be pretty good in the wet.

Is that because you want more front bias?

Its rated as 300 c and above, but they seem to work reasonably well when cold.

no. Most of the Miata class uses the lesser compound on the rears to make trail brake easier. Not just Miatas actually.
Straight line braking felt like it was more effective with the same, more aggressive pads on the rear but did make it more difficult to trail brake.

Neovas have *excellent* wet grip, but they're sooooo expensive.

I think maybe I'll go down a notch in the rear first (since my rears are nearly gone anyway) before changing the fronts to someone less aggressive, while adding a master cylinder brace to compensate for the increased pedal pressure (my MC moves like crazy)....

I don't think G-LOC (or any of the other western brands) are readily available, though.

Sounds like a plan.
Surprised about the MC movement. I'll have to take a look at mine. Not that it matters anymore since it's just a street car at this point.

FD?

I had ~1/16" deflection at the firewall if I pedaled the brake hard with the booster leaked down (car off).

I put a stopper in, but with the booster working I doubt it moves.
I need to concentrate on being gentler ininitial application. When I jumped back into my non abs FC 2014 after a couple seasons in the FD I had developed bad habit of hammering onto the brakes too hard on initial pedal.

I was watching the brakes be bled and I was like "damn, it moves that much!"
It wasn't like the firewall was bulging out by an inch, I just remember it seeming like enough to be felt in the pedal during maximal braking.

It's an excuse to buy some anodized engine bay bling, anyway...

I wouldn't worry about pads, people have gotten away with a street compound when cold or wet enough though....hopefully the ABS is serviceable. If the car is low and stiff (especially on R comps and not on proper rains), it can be near undriveable even with bars disconnected

What ABS? lol

(if I went and bought some new sensors, I could probably restore it, but at the moment, it's dead.)