How difficult would it be to make a plate like this? (For early 5-lug rotors)

I don't care for the scoops shown, so $400 bucks for the set seems a bit steep for two plates, scoops, hoses and a few zip-ties ...

If you took a dust cover and just welded on a piece of 2" or 3" exhaust tubing I think thats all it would really take...

The 911 dust shields are not solid as they go on the outside of the rotor and have a cutout for the brake caliper mounts.

The shields pictured above sit flush inside the rotor to effectively close off the gap so the air is forced through the vents on the rotors.

But still, it's basically just a flat piece of metal with a hose adapter welded to it.
You can buy them individually for about $125 bucks, but $250 is still a lot of $$$ for just that ...

Get some of these!

How does it clear the caliper if its sits on the rotor? It goes through the vents on the inside? If it has to sit 1/16" from the rotor then thats going to be a PITA to make it fit and radius that edge.

I still think my idea is better than nothing

No need to. It sits inside the inner recces on the rotor.


Like the one on the right in the picture below. Ignore the one on the left as it is a larger turbo rotor and the plate is obviously too small for it.

But looking at the one on the right you can see how it seals nicely between the rotor and the plate. This forces all the air through the inside of the rotor for maximum cooling ...

This is not quite correct, where the rotor mounts to the hub there are 5 openings that let your air out thru the hub. You can get a flat pieces of sheet metal cut round to put in there to block the air, probably another $125.

I don't do well working with sheet metal but from some of the work I have seen in threads here it seems like it should be easy to do.
I have a set of them in my stash of parts so I won't have to try my luck at fabricating them but I sure would be tempted to try.

Jim

Yes, but those are only $35 a pop so i'm not complaining about that.


It's the backing plate with the hose adapter that seems a wee bit overpriced ...



The deflector to prevent the air from going out the other side:

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The fins on the disks work as an air pump, pumping air from inside to the outside.
The only problem you need to deal with is getting fresh air to that point to be used for cooling.
You don't need that exact adapter. Anything that duct fresh air there will work like:
1. no dust cover, or
2. Hole in dust cover with hose to some cooler and high flow air.

just my 2c.

No dust covers does not work for me ...

After about 15 minutes of hard track use, my brakes rapidly start to fade. I need some way to force air into the brake rotors and the system above seems to be the right solution.

I'm just not thrilled about the $400 price tag.

I think Mark could build those easy. You might be able to find a SS kitchen storage can you could cut down for the disc and weld a 3" SS tube to it. Wall mart, a container store or the $0.99 store may have something the right diameter.

It's the lip around the edge of the sheet metal disc that costs the most. In order to do that, it has to be a die stamped part. The die is what costs the $$$ coupled with the relatively low volume of parts made.

One way to solve the problem and keep the disc stiff would be to fabricate it out of heavier gauge metal, but then you'd have interference.

What's the outside diameter of that disc? Maybe something like a shallow cake pan could be used? Trim the edge if the pan is too deep? A restaurant supply house may have just what you need.

EDIT: Mike beat me to it.

If you had the air guide for the rotors what would you do instead of the scoops shown?

I have run hoses to the front spoiler but I don't think that would work on your car.

Jim

You don't need the plate. The disk sucks air from inside and pumps it out from the outer edge. It's a centrifugal air pump.
You just need to provide it close to the central area. The disk will suck it from there.
You can have that big pipe just hanging out there near the disk center.

I'm getting rid of the 916 front bumper.

So yes, i'll have brake duct openings in the front bumper and hoses from there to the brakes ...

Mike Mitchell (mahler9th on the Pelican board) made his own out of carbon fiber. If you can lay up fiberglass you could make your own pretty easily, it sounds like. He's posted about it several times on the Bird's racing BBS.

--DD

Got it.

Looks like you could make that pretty darn easy... If you had the rotors off the car You could probably make a rough fit in 10 minutes and then spend another hour making it perfect...

I made mine. I had to make larger ones when I went with 930 front rotors.....


I may have a pic......


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Andy you say you're having fade issues, what are you running for calipers and rotors these days?

I've got a set of 996 front calipers and a set of 964 rears for my 3.6 build comming up. I hope that's going to be enough for me.

Thanks!

Yes, if you're making them for production.
If you're just making two it should be straightforward to just hammerform them. Make a big hardwood disk, clamp the metal sheet (ideally aluminum, although my production ones are light sheet steel) to the form, and then gradually, with a rawhide mallet, bend the edge of the disk down over the hardwood disk form. Trim the edges and ta da.

Ron Fournier's Metal Worker's Handbook has lots of fabrication tips like this.

I just use two 993 plastic curved deflectors that were designed for this job. I've cable-tied them to the lower control arm and they scoop air into the center of the rotors. Rich Bontempi (and others) have used them for a long time on their 914 race cars.

~$15 each last time I looked

Andy what pads are you running? You should be putting a street/race pad on if you have fade issues...

Depends if it's pad fade, or boiling fluid, or some other issue. Fluid choice and regular flushing/bleeding is also essential track applications, as you guys know.

Those duct plates are more difficult to make than it appears.
Fitment of the inlet tube around the strut is critical, as there is only one spot/angle where it will fit when installed. Also it needs to have a special shape where it attaches to the disk because part of the inlet tube sits outside the od of the disk.

I made my own, but they would be more expensive to reproduce, not cheaper.
I made the disks fit more tightly to reduce the amount of air bypassing the rotor vents.
I designed the inlet shape to maximize air flow into the rotor.
Rather than attach the inner cover to the wheel hub, I attached it along with the outer cover to the backing plate mounting holes, and used standoffs to give them the appropriate gap to match the rotor.

I also added a bracket and attached the outer cover to the strut with a hose clamp to make sure it doesn't vibrate/rub.
When the steering wheel is turned the hose attached to the backing plate pulls on the assembly, causing it to flex.
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My current brakes are from a '84 Carrera front and rear with vented and drilled rotors. I'm running porterfield pads (not the full racing type).

I don't have any pics of the fronts installed ...

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The current setup works great until they get really hot. Part of the problem is that with the 3.6L motor, my driving style has changed. No more momentum driving ...

I can keep the go fast, brake hard, go fast again for about 15 minutes before the brakes start to fade.


I think my current rotors are plenty big and i'm hoping the Boxster calipers i just bought will help some, but i know i need to get some direct air flow to those brakes.

That's almost exactly how I did mine. I have no rawhide mallet. Instead I use a cheap HF rubber one. If you take your time (more than I did), they can come out nicer.......

The trick is to learn to drive it where you DONT use your brakes so much. Turn in faster......

Don't be scared.

Who said i was scared?

It's simple physics. Like i said, the days of momentum driving are over for me ...