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I use either ATE 200 or Motul RBF600 and am happy with both. Boiling fluid is not a problem for me. Cooking pads that should not be cooking is my problem.
I can see how removing the rear shields might open up some airflow to those rotors, but the fronts seem to be designed to direct air into the vanes. Are you sure removing the fronts helps? What is your evidence of this?
In any case, adding 4 or 5 extra miles of cool-down at highway speeds seems to be the ticket for me. I have 2 more track days this month and will confirm my results.
I've always read that removing the shields helps, since there will be airflow around the inner face of the rotor and the shield is no longer reflecting heat back towards the rotor face.
Mount a wheel and judge for yourself if those scoops will actually see any airflow. Especially with my 17x9, 48mm offset track wheels, they'll see very little, if any real airflow, as the inner barrel is closer to the rotor and the inner edge of the wheel sits further in than stock, both things working to block flow.
Use what you want and what works for you, but I looked at price and boiling point and the Wilwood has the highest rated boiling point for a price that`s near the bottom of the list of racing fluids. Seems like an easy decision to me. If you don`t need that much, their 570 fluid is probably the cheapest you can get with a better boiling point than many.
According to this brake fluid summery chart, Wilwood EXP costs about the same as Motul RBF 600. ATE Typ 200 costs less than half that. I buy ATE for $15 per liter. It also costs less than Wilwood 570 and has higher boiling points.
In any case, 9 or 10 degrees improvement in either of the boiling points is not worth much money in my experience. Around 400 wet and 500 dry seems to be enough for my car, so I see no advantage to spending more than I do for ATE. I typically manage 3 to 4 track days before bleeding the brakes, and even then, I don't necessarily need to. I just do it to be on the safe side.
Determining whether to gauge a fluid by wet or dry boiling point should be based on your driving and maintenance habits. I use wet boiling point as my benchmark, but that may not be appropriate for everyone. Use whatever makes you happy. Anything in the top half of that chart when sorted descending by wet or dry boiling point should be fine.
Last edited by Steve Dallas; May 10, 2015 at 10:03 AM.
I finally managed to do some measurements on a couple of track days. I got a load of temperature measurements, albeit that other factors on the day prevented me from getting consistent cool down experience.
I measured the temperature of the brake discs and callipers immediately on getting back to the pits with EBC slotted discs and EBC Yellowstuff track/fast road pads. The majority of runs were made with road tyres and the final few were on track tyres.
Using the differences in temperature between the front and rear discs and callipers I was able to deduce that the underside ducts substantially reduced the front brake temperatures and removed the hot brake smell that I got in the pits without cooling. I only did one run with a take-off in the bumper, insufficient to give confidence in the results, which in any case were higher than I'd expected.
Given these results, I'm happy to run the cooling on track with a take-off at the underside.
Ian can you show us some data charts comparing the two approaches with baseline(no brake ducts) and impact of street vs track tires on the brake temps..etc....
what kind of temperatures were you seeing front and back?
Are the yellowstuff pads up to the job?
Also can you describe what kind of the track you used to get the data. Is it a track that is hard on brakes?
Nice, I might have to try this. Really clean install which was my main concern for a street car.
(as above) Any chance you can share some numbers for the front and rear brake temps with and without the ducts connected?
I have not done any measurements, but based on rotor and dust boot condition I am under the impression I am getting similar temps front and rear and both are getting quite toasty.
Last edited by blu3dragon; Jun 2, 2015 at 06:45 PM.
Update on this. Keith at FM posted on another forum that he thought they might fit. I emailed Goodwin Racing, who sells the same part and has several RX-8s in the stable, and the reply was they do not fit.
The fitment problem probably has to do with the mismatch in rotor diameters. That isn't anything a few minutes with a pair of aviation shears and a file or a BFH can't solve, so there may be hope still.
I happen to have enough parts left over from my Miata brake duct kit to copy Ian's work here, although I think I will look into routing the inlets to the mouth and zip tie them to the undertray. I just need to find the time...
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Last edited by Steve Dallas; Feb 22, 2017 at 07:07 PM.
BTW, my Miata is ducted basically the same way I am approaching my RX-8. Brake pad temps after one cool-down lap dropped from ~750F before ducting to ~280F after ducting. Directing air to the back of the rotor works well enough, that directing it precisely to the center is unnecessary, except in very high performance applications. Plenty of air makes it into the vanes.
My Miata:
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Last edited by Steve Dallas; Apr 28, 2017 at 07:16 PM.
