here are the front and back of the bare hubs

and mounted with M caliper and vented SC rotor

Hey Herb,

I don't have any photos and I've made the car into 5 lug. I did up the brake cooling and removed all the backing plates. I was (and still am) running Raybestos pads. They take more heat than anything.

I'm running Wilwood Superlites all the way around now. I can give you the part numbers if you want. I can also do up the trailing arms for 3.5" spacing calipers or send you the mounting brackets.

After talking with the Wilwood guys at PRI, they have more options than I realized. They make radial to lug mount adapters and have some really cool radial mount calipers. Also, I believe that they are making a new caliper with an ebrake setup in it!

Once again John thanks for taking the time to describe your logic, I really appreciate that.

Just for fun I looked at your F/R caliper pressure ratios as you've progressed through the brake changes. You've probably already done this but for the sake of conversation here it is:
Setup 1: SC A caliper 48mm piston / 914-4 42mm piston.......1.31 F/R hyd press. ratio
Setup 2: 930 4 x 38 mm piston / 914-4 42mm piston............1.64 F/R hyd press. ratio
Setup 3: 930 4 x 38 mm piston / M (rear) 38mm piston..........2.00 F/R hyd press. ratio
As a reference point the stock 914-4 setup:
.................914-4 42 mm piston / 914-4 33 mm piston...........1.62 F/R hyd press. ratio.

As the ratio for F/R gets larger you have greater levels of hydraulic pressure in the front relative to the rear. Less regulation at the rear is possible then (everything else being equal)...

I get what you are going for now.

BTW, The valve looks like it progresses from y=.3x at max regulation to y=.5x at min regulation. As you decrease the regulation level the resolution at the knob, all other things being equal, will be reduced.

Best regards,
Kevin

Well that is what my conclusion is from 18+ years of track work with the same car.

One day we just may get it right. It's always fun to run away from the high dollar cars in this 30+ year old VW.

That picture looks like the bridge on the 2nd half of the back straight at Heartland Park...

miss that place.
its been 10 years since I raced there.
I think our vintage club may visit in June or July this year!
brant

That car is gorgeous John.

You got that right.

Thanks Eric, It's dad's car he bought new in 1974. For the last 19 years it has been mostly on the track. Still haven't finshed the second track car yet. Still looking for rear hubs.....

Thanks Matt,
Here's a pic of the duct I made. I used to have this on my website but took it down as there didn't appear to be sufficient demand to produce them. It fits under a stock Fuchs alloy wheel.
Click to view attachment

Chris,

I remember seeing that duct before. I always wondered how much air you were able to move through there. There appears to be a lot of restriction in there, and I was currious as to how much air actually flows through there.

-Josh2

Josh,

I can't speak for Chris, but they probably pass a lot of air. That is the way a lot of pro teams cool brakes. If you look at pictures of 935s and other cars of that era, that is how they were all cooled.

Yes, and I think that would be THE way to do it with vented rotors as the air gets forced through the interior of the rotor (where there is open space) to pull away the heat. My question is about using that with a solid rotor. I'm looking at where the air can go once it gets to the end of that duct. Not many outlets, and they're quite constricted.

Just thinkin' around this. Brake cooling is the single best thing to do for stock 914 brakes. And anything is better than nothing. Just currious if this method is as efficient as plumbing a duct with a larger opening that directs air onto the face of the rotor as opposed to the edge.

-Josh2

I chose this method because it puts the cool air right where the heat is generated. There is sufficient openings around the pads for a decent amount of air flow. As far as effectiveness, I no longer cooked my brakes at NHIS during 20 lap regionals in ITB once I installed these. Doing laps at NHIS is the best test for brake fade in the northeast. There are no long straights to cool the brakes, and several hard braking zones.
I have looked at doing the same thing on other calipers and haven't been able to come up with a decent arrangement.
Click to view attachment

You need to blow equal amounts of air on both faces to avoid rotor warpage.
I have made ducts for the rear that were kind of like a soda can with a slot cut out for the rotor. They're easier to make but harder to make effective IMO.