BrakesSo the first season I raced my NA6 I used DBA slotted front rotors and stock rear rotors with a proportioning valve (full open). I had race pads in the front, Ferodo DS3000 and semi street pads in the rear.
I was amazed at how well the car pulled up on the tiny rotors. My brake points and control were awesome but only when the brakes were at temp. When the pads were cold I'd get front lockups constantly. The main issue with the little rotors was pad and rotor wear. I chewed through a set of pads and a set of rotors in less than a year. On the track I could see the rotors getting thinner between sessions and at night it was fireworks! You could even see the rotors glowing in the braking zones. I didn't experiment with ducting but I suspect with good cooling and maybe slightly less aggressive pads the stock setup could be made to last longer but still retain the excellent brakes.
For anyone with a NA6, if you can deal with rotor and pad replacement the stock NA6 brakes are excellent in track scenarios.
BUT, I do mostly sprint / time attack events where I'm driving on cold brakes... the stock brakes with race pads were completely useless in this environment. I also didn't want to spend $300 replacing pads and $250 replacing rotors each year. Some internetting later I found my target rotor which was the 11.75" wilwood. This rotor is a two piece with a very cost effective replacement friction surface $35 per ring. The problem with this sized rotor is fitting it inside a 15" rim. More internnetting found the dynopro radial mount caliper which has a slimmer profile than the standard dynalite. So here is my setup:
Fronts:
11.75" Wilwood vented rotor with 4 pot radial mount Dynapro calipers.
Now the issue is Wilwood don't make the correct offset brackets for these calipers to work with the MX5 spindles. There happens to be a kit for the Newer Mini Cooper S that is the exact combination of rotors, calipers and brackets, but you need to make some custom spaces, extend some of the mounting studs and find the correct hub centric rings. This is fairly well documented by Bundy on Miataturbo.net. The process wasn't hard but a little time consuming.
To balance this much brake I had to upsize the rear.
Rear:
11.44" Wilwood solid rotor with stock NA6 caliper. (based on a Honda rotor kit)
This is a really good solution for anyone wanting more rear brake. It uses the stock caliper just offset by a metal bracket that I made myself. This is just a 6mm metal plate that I hacksawed and drilled that offsets the caliper both away from the spindle by 38mm and outwards by 6mm. With the Honda Wilwood hat and rotor this places it dead center in the right spot.
With the stock brakes I could never get enough rear brake. It was probably the street pad in the rear as well as piston sizing / rotor diameter. With this wilwood, I'm having to dial my proportioning valve back a bit to stop the rear squirming under brakes. I think this has moved my braking point a little later, but not by a massive amount. When I first ran the car I was braking at my standard points but washing off too much speed through the corner. It took me a while to adjust.
Here is the bracket:
Why this big on a N/A car?... well really rotor size affects the leverage of the brakes vs the wheel. So the larger the rotor diameter the less the pad has to work. The other benefit is more surface area that the pads are working on so wear level is less and heat is less. I've also never subscribed to the theory that more powerful cars need bigger brakes. Sure they probably work them a bit more, but there are times when I'm stopping from 180 kph down to 60 in 50 meters... Really brake size is more dependent on the tyre your using and mass your stopping and has less to do with power.
The pads I'm using now are simply unreal. Unfortunately they require lots of effort to fit into the calipers. Based on the mixture of events I've gone with some hi-tech silicon based endurance pads. Ferodo DS1.11
Here is the temperature to friction co-efficient graph:
You can see why I'm using this pad... it offers almost constant braking friction independent of temp. So when cold these brakes stop as good as the 4th lap on the track. I had to manually hacksaw and grind the pads to fit both the Wilwood Dynapro as well as the stock NA6 rear calipers. The fronts were easy with only a minor mod but the rears required much more effort...
Overall I'm extremely happy with the end result. Braking is not an issue and I can focus on getting the braking point as late as possible and turn in right. I don't think my braking point has moved at all on the track, maybe a few meters later but I have a lot more confidence on the hillclimb and sprint events. Rotor and pad wear has been massively reduced, so much that I think they will pay for themselves within a few years.
Next stage is to add ducting to the front brakes to keep them cooler.
NA8: N/A 200whp | Haltech | Skunk2 Intake | S90 TB | RCP | 5 speed c/r dogbox | 4.78 diff | AST Shocks
Barbs L: 64.12 | S: 58.62 | Collie: 49.72
