Help Please on brake ducts

[bcarter]

After one race weekend, about 200 miles, and one serious test day, another 200 miles, I have cracked another rotor. We have to use stock rotors, and I have the bias pretty strong on the front to prevent rear "hop".

I just don't know how to duct the air into the centre of the rotor. The wheel seems to get in the way. Are there any plans, drawings or ideas. I don't think my rules will allow me to use the IMSA style because it means modifying the backing plate.

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G. Brooke Carter
Wheat Buckley Racing
# 10 Challenge Car
2002 Class Champion
Calgary, Alberta

[ITSRX7]

What gen?

AB

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Andy Bettencourt
06 ITS RX-7
FlatOut Motorsports
New England Region
www.flatout-motorsports.com

[Jim Susko]

Brooke,

Your rear wheel hop is from lowering the rear with stock bushings. That shortens the rear side view swing arm geometry and leads to axle windup and stick-slip behavior. If your rules allow sold spherical bushings in the bottom arms that would improve your situation, and allow you more rear brake bias and less front rotor heat. Or, a Tri-Link and Panhard would eliminate or reduce the problem by lengthening the side view swing arm.

In my experience the IMSA style ducts are the ultimate solution to short (but not infinite) rotor and oil seal life. There must be a method to duct to the center of the fins in the rotor.

What class are you running in and what are the rules? Perhaps I could help you find a solution.

Jim Susko
G-Force Engineering

[Chris Wire]

www.iscracing.net

for you brake ducts.

Also, seek out Mike Cox (maybe in the SEDiv Forum) for a very successful recipe for DIY rotor treatment.

Good luck.

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Chris Wire
Team Wire Racing
ITS Mazda RX7 #35
[email protected]

[bcarter]

Wow...you guys are fast...

OK, ITSRX7 - it's a first gen, '84

Jim, - I have your book and was going to contact you. I am in an "orphan" class here in Canada. No class like it anywhere else. Streetports, and not much else. The Tri-Link isn't legal, but "...suspension bushing kits are allowed within stock dimensions" Does that fit? I haven't lowered the rear, but run a 175 spring, on a stock rear suspension. Front is a bit lower with coil-overs and 350 springs.

At the end of our straight, the longest in Canada, I'm getting about 125 mph, and then a pretty tight left. Without the bias, the rear end "hops" with the weight transfer, and as you can imagine, I like to wait as long as I can to brake.

The car goes good, we do well, but it is just a hassle having to change the rotors, AND the front bearings so often. HEAT. I can do it blindfolded in minutes... but the $$ !

I agree that getting more rear brake would be a benefit. Also, air on the rotors..

Thanks guys

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G. Brooke Carter
Wheat Buckley Racing
# 10 Challenge Car
2002 Class Champion
Calgary, Alberta

[rx7chris]

What pads are you running in the rear? I used to have a problem with the fronts locking up with blacks in the rear(didnt do enough braking), switched to blues on all corners and the problem disappeared, plus i could go in a bit deeper.

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Chris
PowerTrip Racing
http://www.geocities.com/ptripracing/

[bcarter]

The problem is not the front locking up, it is the rear locking up, hence the bias towards the front.

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G. Brooke Carter
Wheat Buckley Racing
# 10 Challenge Car
2002 Class Champion
Calgary, Alberta

[Allen Brown]

Brooke.

Next time when we are both at the track, pop over to look at how I fished my ducting into the center rotor area. To date, I have never had a rotor go bad. Even the ones, that I ran the entire season (approx. 1500 miles or so), nothing more than the beginning of a few 2 to 3mm long surface cracking starting. I think it all comes down to the expensive aluminum 3 inch ducting from Home Depot that I use.

I know, my SE has better and slightly bigger rotors, but I can not help to wonder if my cooling ducts are doing that good of a job.

Ya gotta stop practicing so much...I hear you were being timed in the 1:31s on the last practice session. This is going to make it even more difficult for me to get by you.

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Allen Brown
#36 IT-1
GT-3 in 2004
[email protected]

[Speed Raycer]

So... your rules wont allow you to modify the backing plate at all?

What we did... and it's an amazingly cheap and fairly effective, is just safety wire the brake tube onto the spindle with the outlet blowing directly into the center of the rotor. It sounds hokier than it is. We removed the backing plate completely, then took the good/expensive brake duct and ran it in from the air dam until just in front of the tire. Then we joined it with regular 3" flexable alum. duct from Home depot. This duct is easily pre-crimped and holds its form pretty well. We molded the alum. duct to clear the tire and brake lines then wrapped racers tape around the ends (so that the holes wouldn't pull through) and safety wired the end to two holes drilled into the backing plate mount.

We haven't "had" to replace a wheel bearing since (also running $$$$ bearing grease) and the rotors are lasting forever (knock on wood) with Hawk Blues up front.

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Scott
It's not what you build...
it's how you build it


E-mail me for deals on
Lightweight Replica Blocks!

[This message has been edited by Speed Raycer (edited June 06, 2003).]

[Skid]

Speed Raycer, how did you deal with the sag in the ducting that's needed to accomodate turning the wheel? I.e. ducting has to stretch to reach the outurned wheel but compress to allow the wheel to inturn.

[Speed Raycer]

The duct is supported midmay with alum. strap and the attachment is left a little loose with the safety wire so that it can move around with the wheel. It probably isn't the model of absolute cooling, but it definitely works.

[bcarter]

So, back to my original question. Once you have a duct picking up the air from the front dam, where do you route the hose. I have heard of two versions. I saw pictures of one set-up, where the hose came in high, around the top of the fender opening, while another comes in low, almost beneath the control arm.

My question is, if the duct is behind the wheel, does that not restrict your turning circle considerably, and are you using the "stop" bracket on the control arm to keep the tire from hitting the duct?

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G. Brooke Carter
Wheat Buckley Racing
# 10 Challenge Car
2002 Class Champion
Calgary, Alberta

[Boswoj]

Since my car is now modified beyond IT specs some of this might not be applicable but if teh hose is held to the back of the wheel well there is enough room that it just gets touched by the inside of the tire at full lock. Another racer suggested that since the high temp hose is kind of pricy that he used the cheap galvanized metal ducting to route back through the wheel well and only used the hose to turn the corner and direct air on the hub and caliper. I will try to take some digital pic's of my set-up and you can see if it would work for you.

Boswoj

[bcarter]

Hey Boswoj,

Pics would be cool...

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G. Brooke Carter
Wheat Buckley Racing
# 10 Challenge Car
2002 Class Champion
Calgary, Alberta

[rx7chris]

As fars as duct routing, i made mine run straight from the opening in tha air dam to a point on the inner fender perpendicular to the hub. From there i made a 90deg. turn with enough slack for the the wheel at full lock. Try and route it up and over the front fender support(helsp hold it on in front and less chance of it getting pulled under the car). as far as the actual hole into the center of the rotor you have to notch the backing plate, then get a short piece of exgaust pipe(biggest union discount sells) angle cut it and tack it on. Aside from the hose, the whole system costs maybe $10. and works extremly well.

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Chris
PowerTrip Racing
http://www.geocities.com/ptripracing/

[bcarter]

Well, the ducting is in. I sprung for the MazdaComp duct attachments that fit to the strut. A bit $$$, but PERFECT. A little bit of cutting, but very tidy. I then used the suggested Home Depot plastic rain downspout funnels, which fit over the slots in the factory air-dam. Then 3" from the scoop to the ducts on the strut. Easy.

My biggest concern was the reduction in turning, but I still get a full 360 plus another 180 on the steering wheel, so no problem. I am going to put on a longer stop screw to hit the block on the control arm, just for sure...

Thanks guys for allthe thoughts. I hope I have put in the last new rotors for the season, but we'll see.

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G. Brooke Carter
Wheat Buckley Racing
# 10 Challenge Car
2002 Class Champion
Calgary, Alberta

[ddewhurst]

Brooke, if ya need more than 90* steering either way while racing ya got more to worry about than your brake ducts.

Have Fun
David

ps: ya did the correct thing with your DOLLARS, one of the best places to spend $$$$$$$.

[This message has been edited by ddewhurst (edited June 20, 2003).]

[bcarter]

The 90* works fine for racing, but you sometimes need a bit more when doing agricultural work.

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G. Brooke Carter
Wheat Buckley Racing
# 10 Challenge Car
2002 Class Champion
Calgary, Alberta

[bcarter]

Further to the saga..

We had a good race weekend. It was hot for Calgary, in the high 80's, so track temp was high. After 20 min practice, 20 min qualify, about a 2 hour race, and the next day, same practice / qualify, and three sprint races, 10, 20, and 10 mins, all on the 2 mile road course, the rotors/bearings are in great shape, BUT more to the point, the car brakes way better, I can go deeper into the corners all of the way through the race. Ran really good times, times I usually only get in September when it's quite cool. The rotors are still silver, not that burnt black colour I usually end up with.

If you haven't done it, DO IT.

Neat stuff.

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G. Brooke Carter
Wheat Buckley Racing
# 10 Challenge Car
2002 Class Champion
Calgary, Alberta

[Dick Elliott]

What I have always done is run the hose back from the air dam, and tape it to the front sway bar with good ole silver tape. If you do this the hose will end up pointed at the center of the rotor. On a vented rotor, thats where you want to dirrect the air too. Even if you turn the wheel too far and touch the hose, the tape will keep it from getting hurt. I just leave the hoses on the car after removeing the air dam to load the car. DICK

Originally posted by bcarter:
So, back to my original question. Once you have a duct picking up the air from the front dam, where do you route the hose. I have heard of two versions. I saw pictures of one set-up, where the hose came in high, around the top of the fender opening, while another comes in low, almost beneath the control arm.

My question is, if the duct is behind the wheel, does that not restrict your turning circle considerably, and are you using the "stop" bracket on the control arm to keep the tire from hitting the duct?