I'm trying to wrap up my winter projects before the upcoming track season and one of these projects is installing proper brake ducts. I previously had brake ducting similar to https://www.rx8club.com/do-yourself-...ack-use-83801/ but with the addition of the Mazdaspeed front bumper i realized these were likely no longer receiving the airflow they used to due to the new bumper blocking the inlet.

I'm planning on re-positioning the inlet and running high-temp brake duct hose back to a mount on the hub directing air directly into the rotor. I believe i will have enough room to run 3" hose but i can't seem to find any examples where people have done this. I'm running 18x9.5 +45 RPF1 with a 5mm spacer and 275 Hoosiers so space gets tight at full lock. I'd like to avoid any rubbing, which i think is possible, but just haven't been able to find any examples to confirm.

Anyway, I'm just looking for other's experiences and/or pictures with proper spindle mount brake ducts before i dive into my project. Thanks.

 

laying off the brakes will be faster, cheaper, lighter, and less complex

 

But that's no fun! Plus some race tracks are VERY taxing on brakes even if you try to take it easy.

Jantzen: Are you have having issues with brake fade? If so make sure you have fresh top quality brake fluid and good racing specific brake pads. I've pushed the brakes on my RX-8 very very hard and not had any problems even without ducts. However, I have heard from some reliable sources that keeping the temps down with some ducting will help the brake pads last longer.

I think a good spot to run the duct inlet hoses to would be next to the oil coolers. If you have fog lights there remove them and replace them with ducts. Way cooler

Doesn't the Mazdaspeed front clip have monster openings? You should have plenty of options.

 

Yeah, im not sure if braking less is an option.

As for fade. Not really. BUT, when i'm going clockwise on my home track i've had fade going into turn 6. Going CW is a bit faster in this section and the straights are in decreasing top speed rather than increasing top speed when you're going CCW. Obviously there are a lot of variables at play here but i've only had fade in this turn going CW.

Having said that i am very surprised i get fade at all. Contrary to Team's assumptions I try to stay off the brake pedal and im using Motul 600, Wilwood 14" BBK (13" rear with OEM caliper) with Cobalt Friction XR2/XR3 pads and stainless steel lines. SO the fact that i'm getting any sort of fade and the fact that i have zero (functional) ventilation to the brakes makes me think i'm running them on the hot side of their functional temperature range and could benefit from some cooling -- even if it is just for a couple CW track days a year and maybe a little better pad/rotor life.

edit: yes, i'm going to use the section in the MS oil cooler ducts

 

I made some adapters for the spindle side of the ducting...but never got around to installing the ducting or the bumper ducts...going to do that soon. The spindle side is quite easy to fabricate out of aluminum...you can just bolt it to the mounting bolts

 

Yes, strange your getting fade. Maybe try a different brake pad?

 

That was the plan.

What size ducting were you planning on using?

I just ordered Raybestos ST-45 for the fronts but its hard to say if it was the pad that faded. It may have just been the fluid. I changed it at the end of the day and it was probably getting old. I typically only change my fluid 2-3 per season which is roughly every 3 track days. I did see some interesting caliper cooling on a grand-am car this past weekend. Not sure if that would be worth investigating or if the standard rotor ventilation would reduce enough of the heat transferring to the caliper

 

Was planning on 3"...

 

Generally the caliper cooling is only really needed when the class or rules limit brake/wheel size a lot. Your huge brakes should have no need for fancy caliper cooling.

 

I thought about trying to make some brake ducts but I've never had brake fade issues, even while running in the 100+ degree heat here in AZ.

17x9" RPF1's with either NT01's or Hoosier R6 in 275/40R17. Stock brakes with Hawk HT-10 pads, cheapest blank rotors I can find from O'Reilly's, Agency Power braided stainless lines and ATE Super Blue fluid.

 

My point was, what tracks for someone in Norman, OK are so taxing on for the RX8 brakes that this is required?

As usual I must assume that someone's assumptions of my assumptions are fubar


.

 

Hallett Motor Racing Circuit. I'm sure there are more taxing circuits as far as brakes go but its a pretty short course with only one good long stretch (turn 10 through 2). Turn one you can still take at 75-80 mph but you should be well into fourth gear on the straight so you still need to slow the car to get around it. Turn 2 is ~115 down to 30 and there is a lot of 100-115 to 50-60. I can't really remember speeds, i dont pay attention to that very often so those numbers may be way off. Although it's safe to say at least half the turns involve braking from over 100 mph.

Like i said, its not torture on brakes but its no pure momentum track like Roebling Road or Harris Hill Road. I'm not so much doing this for fade issues -- as i mentioned they're minimal. I'm a believer that proper cooling will increase my pad life and from what i've read that seems to be the case on many cars on many tracks. A good friend of mine works on a grand-am team and has suggested i fit brake ducts even though I'm not exceeding the thermal limits of the pad. And, to steal a quote from Eric Meyer "Get the MSpeed brake ducts as made by SpeedSource. You'll double or triple your brake pad life. "

I'd like to believe I'm not just doing this for kicks. Whether it be the two times a year we run CW and i avoid brake fade or few the extra track days i get in between buying $300+ track pads i'd like to think i would reap some sort of benefit from fitting brake ducts.

I'm also trying to figure out an easy way i can partially or fully block them if necessary.

 

For Raybestos I would have chosen ST-47 in the front and ST-45 in the rear

Over the years I've just developed a minimalist mentality, if it absolutely is needed then do so, but why add the weight and complexity if you can get by without it? Plenty of people have a monkey see, monkey do attitude in racing. Just because a bunch of people use a specific mousetrap doesn't mean you cant come up with a better one or that there isn't any way around using one at all


.

 

Yeah, i thought about it. I still have a lot of meat left on the cobalt XR3 rears so i was going to try the ST-45's paired up with the XR3. I couldn't find a ton of reliable comparison data but it seemed like a more balanced combo. Plus Raybestos suggested the ST-45's so i just went with it. I guess we'll see how it goes.

I'm all for being minimalist and I know where you're coming from with the monkey see/do mentality. I guess im just less concerned with ultimate performance or being a featherweight and more concerned with having a bulletproof super-durable track car.

Who knows, maybe i'll report back down the road and let everyone know this is a completely worthless addition. But for the time being i'd like to think it is going to be beneficial.

 

Here's a kit, or one can get only certain pieces from it:

Mazda - RX-8 - Rx8 Brakes - Sneed4Speed

 

I've seen that kit before. It wont work with the MS bumper but i didn't know they sold the brackets separately. $75 is pretty steep for $5 worth of material and two welds though. I think i'll try fabbing something up myself.

It's good to know they use 3" ducting though. From their pics it looks like they have plenty of clearance.

 

as a corollary to that, its hard enough to get a car dialed in, adding complexity just makes that harder.

or if you like, the biggest problem in racing (and other places) is actually figuring out what problem you actually have.

always, once we've figured out what was wrong/needed to be done with the car the fix has always been super simple.

 

The 3" hose is normally used for ducting on small aircraft. Many places supplying parts for mechanics or homebuilders carry it and various fittings. Example: Ducting from Aircraft Spruce

 

the ST-45 has a broader torque range, but the ST-41 and ST-47 are more suitable for sustained high temp use which is really what you are attempting to address with this thread

unless I was having an issue with heat affecting the hub bearings etc. then I wouldn't consider this mod and when I did decide to do it I might be more inclined to move air through the top fender surface instead

but if you're dead set on it Speedsource had a kit, not sure if it was sold through Motorsports or just racer direct

 

... well is you is or is you ain't?

https://www.rx8club.com/rx-8-racing-...pounds-212094/

 

How do you like the HT-10s? I use DTC 60. Also, tell me about the OReilly rotors. Work as well and cheaper than Mazdas Racer Support prices? I'm going through rotors like crazy from heat cycling, not wear.

Jantzen. IMHO If you are doing track days, or even TT, you do not need brake ducts. If you are going to W2W race, you will be braking under different scenarios. I run my ducts through the fog light frames. Simple.

 

Good info on the pads, maybe i'll give them a try on the next set.

... of course i care about weight. But everything is a compromise. There is no free lunch. Sometimes you have to give something up to gain something else. I'd be willing to give up 5 lbs if it means my pads would last longer, components wouldn't wear out as fast or i avoid an occasional brake fade. That's why im trying to figure out if this 5 lbs is worth it or not.

Unless you're talking endurance racing im not sure what the difference is. I'm still on the track just as long (at least for the w2w races at Hallett), try for my best time and rarely get stuck in traffic (with the exception of a few the A group at Hallett post pretty similar lap times). Are NASA races longer than 20-30 mins?

 

There are a lot of variables at play here. Your choice of pads is important. I haven't seen a huge variable discussed: Driving style. Some people are simply harder on the brakes. If that's the case, you will need to adjust to that.

Regarding the difference from HPDE and TT to W2W. The differences are immense. Braking zones are dictated by traffic and track position. You write you are rarely stuck in traffic. In W2W I am rarely out of traffic. Because you are driving "offline" a large part of the time, and fighting for position, you use your brakes differently. The flip side to that is that more experienced drivers are likely to be lighter on the brakes.

Most SCCA and NASA sprint races are 30-45 minutes. Most local "enduros" are around 3 hours. So yes, they can be twice as long as you quote.

Ultimately, the answer is simple. If you feel brake ducts would help, put them on.

 

I've never personally checked but I was told Mazdaspeed carries the Speedsource kit.

If your driving the car as hard as you should be and standing on the brakes at the last possible second then brake cooling can't hurt. As many above have said.

 

^^ words of wisdom.

You made a front brake pad decision based on having old rear pad life left, rather than looking to buy a complete optimized set. But now you want to spend time & money installing brake ducts that maybe you don't need?

Unless you believe making less than optimum choices is the answer then you may want to re-evaluate the decision making process that's leading you down this path