ITS Brake Ducting - Rear

BeerBudgetRacing

BeerBudgetRacing

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I'm new to IT and building a car that was originally built for Lemons..... So, we have some repairs and replacements to make.... :o

I know I can use the existing holes in the front Air Dam for front brake cooling - my concern is the rear....
GCR 6b says:
Air ducts may be fitted to the brakes, provided that they extend
in a forward direction only, and that no changes are made in
the body/structure for their use.

My initial plan was to add some NACA ducts in the rocker panel to bring air to the rear brakes. My interpretation of the above is that I can't.
Am I correct? It's no-go on rocker panel ducts?

If that is a no go... :blink:
Can I mount scoops on the lower suspension to scoop under-car air - as long as it doesn't hang lower than the exhaust and wheel?

I'm trying to absorb all the rules & regs but I'm certain I will miss or misinterpret something....

Thanks !
 
Rocker panel NACA ducts are a no-no. There was talk of some people putting them in the rear corner windows too, but then you'd have to cut a 3" hole in the body somewhere to get that air to the wheel wells.

For ITS, I'm not real sure that cooling of the rear brakes is necessary. Yes it will make things last a little longer, but I don't think it's necessary to reliably finish a race..
 
If you end up over heating your rear brakes in IT, something else is seriously wrong. Focus your energy on the front brakes. I'm "assuming" it's a rear wheel drive? All the front wheel drive cars I've raced I've put the cheapest pads in the back because they really dont do much. Rear wheel (i.e. Miata, RX7, BMW) are a little better balanced but still............ over heating shouldnt be a concern......
 
ugh.. sorry dude. you're fooked. Actually the drums aren't that bad on those things, all things considered.
Put a 10psi residual pressure valve on the line going to the rear brakes and it'll save you a LOT of hassles.

You didn't buy Troy's old Z, did you? No way that thing would ever be legal for IT.....
 
I run Porterfield R4 shoes on my ITS 240Z. Never had a problem with them overheating. I tried the Carbotech shoes for a while, but they swell when they get hot. Your biggest problem will be the front brakes. You need to get 2 ducts to each side, one on the rotor, one on the caliper/pads, and the highest temp brake fluid you can afford.
 
What Dave said. We have run both R-4s and Carbotechs in the back. Never had the issue with the Carbotech's swelling in the rear, and they used to give us a much more pronounced bite, but I think Carbotech may have changed the shoe. Doesn't seem the same. When you get the rears working right you should be blueing the drum friction surface. Definitely get two ducts up front and stay on top of your calipers. Ours had needed rebuilding about every 3 weekends. We run SRF fluid and bleed after every couple sessions on track. Brakes are by far the biggest maintenance issue on a Z.
 
Not trying to brag, but I've probably got more time and effort in brake development and in making a fast ITS car with solid discus up front, rear drums actually work. Here's what I've learned over the years after a lot of trying various things. First, note that my front discs (Triumph TR8, 2011 SARRC champion) are slightly smaller than a Z cars, and the pads the same, slightly smaller. Rear drums are about the same size as are the shoes, but your drums are ally while mine are heavy metal. So, onto my experience:

1. You MUST get the rears to work for the fronts to have a chance of surviving at CMP, Road Atlanta or VIR. To do that, you simply must you race shoes and right now, in my view, there is only one option: Porterfield's new race compound (LS something I think). R4 does not work. You need LS and it's magic. Good friction coefficient, and it lasts. I'm on season two of my FIRST set of shoes and the shoes still look good, and the rears work.

R4 can't handle the heat. Carbotech has discontinued their race shoe material while trying to solve the swelling issue, which was terrible. Shoes would swell on the first use so bad that the car would not roll. Would create enough drag to cause a measurable 10 hp loss on the dyno. I love the Carbotech guys but that material sucks.

Porterfield went all out to help the burgeoning vintage scene and this new compound they have is awesome. Handles heat, no swell.

2. You must duct the rears. I think the main reason is to keep the wheel cylinder alive. I've seen it happen to Z cars and to my car, the cylinder gets crusty hot and just disintegrates. Hell, I've seen fires on Z cars from this happening. You can't cut holes in the body to get air to the drums, so I just drill the backing plates for "exit" and then add a three inch duct to the backing plate and run a hose under the body of the car. It's not ideal but it gets some air to them and I've not had a wheel cylinder failure since I did this.

3. Pad choice for the fronts is crucial. After trying everythign under the sun, I've settled on Raybestos ST-43s. Wear hard. Don't kill rotors. Can handle heat and keep stopping. Expensive though, $275 a pop. But last much longer than the Blues and HT-10s I was using before. I've never had much luck with Carbotech on the front although I love the guys. Have a pair of Ferodo FS3000s thta I've not tried but will report when I do. Still, hard to see it being any better than the ST-43s (do NOT get the 41s...they generate too much heat).

4. Get a good duct to the rotor. Make it as straight (the duct) as possible, and have the intake as close to the centerline of the car as possible. Caliper ducts can't hurt but in my experience they don't help much either. Coating the back of the pads iwth heat treatment will make the caliper seals last longer (I generally go a half season now without changing calipers).

5. Use SRF. $70 a bottle that you use once in a season is still better than a $20 bottle that you have use 4 of due to boiling and bleeding fluids.
 
Jeff,

Really appreciate the information - very helpful....

Q: The new Porterfield race compound - is that R4-S ? They said no such thing as LS....
They said "RD-4 is better for race vehicles that do not generate a lot of heat. R-4 is better for high heat race vehicles and the R4-S is for street use."

They quoted me $249 for RC114 ST-43's....

My first impression: Porterfield is extremely responsive to their customers.....
 
It was originally called LS or LD something. I went back and looked, it is RD-4. It's specifically recommended for IT cars -- we don't generate as much heat as big old vintage cars with drums, etc.

Try it. Great compound.

Porterfield are great people.
 
I'm considering replacing my rear aluminum drums with the all steel. Some people have said the alum will warp, etc.
Since the aftermarket primarily supplies steel the are considered the replacement.
 
Excerpt from "Racing the 260Z" that I wrote when I sold the car. Maybe it'll help:

· Drum Brakes-These need to be adjusted every 30-45 mins of race time but are easily taken care of. Jack up the wheel and spin it. The brake should lightly drag on the wheel. If not the brake pedal probably won’t feel good and the rear braking will be weak. To fix it adjust the shoes out to increase drag by turning the star adjuster with a flat blade screwdriver. Look at the brake drum and you’ll see a 1” diameter hole. Rotate the wheel to approximately 6 oclock and you’ll be able to see the star wheel adjuster. Use the screwdriver as a level to turn the wheel and increase the brake drag. You’ll probably need to remove the wheel and drum once to learn how it all works before you can do it without removing the wheel and using the access hole.
 
Send me your email and I'll send that along with the old Seth Thomas setup notes I have. A lot of it will apply to you.
 
Motorsport Auto is looking into getting the rear drum made in aluminum again. I don't know when (if?) they'll be available again. I got lucky and picked up a new pair at the Carlisle Import & Kit show a couple weekends ago.

Chuck
 
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