Are the advantages of floating rotors worth it?

Noel · 10-25-2008, 07:35 AM

I am in the process of researching how I want to upgrade the brakes on my 1980 SC. The car is used on the track 90% of the time. Since starting to track with that car 8 seasons ago, I have always had brake heat issues. They went away when I went to Carrera Rotors/calipers up front with track pads, AJ-USA Cooling and Castrol SRF. However, with my return to using R Compound tires, the heat issues are back.

In researching my options, I have decided to go the 993/965 caliper or 993 Big Red route, but that has left me wondering about whether to go with Floating rotors or not. Do floating rotors really operate cooler? Does less heat get transfered into the bearings? How significant is the temp difference? Will heat really be an issue with those larger brakes anyway?

BTW, I already know about the knocking noises on the street and I can live with that.

Thanks, in advance.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by Noel

I am in the process of researching how I want to upgrade the brakes on my 1980 SC. The car is used on the track 90% of the time. Since starting to track with that car 8 seasons ago, I have always had brake heat issues. They went away when I went to Carrera Rotors/calipers up front with track pads, AJ-USA Cooling and Castrol SRF. However, with my return to using R Compound tires, the heat issues are back.

In researching my options, I have decided to go the 993/965 caliper or 993 Big Red route, but that has left me wondering about whether to go with Floating rotors or not. Do floating rotors really operate cooler? Does less heat get transfered into the bearings? How significant is the temp difference? Will heat really be an issue with those larger brakes anyway?

BTW, I already know about the knocking noises on the street and I can live with that.

Thanks, in advance.

For track use the floating 930s are definitely better, they do run a tad cooler because of the aluminum hats( a tad lighter too for the same reason) but the big advantage is the ability to better accomodate thermal cracking issues.

For street use they aren't so good because of noise issues , but the latest Mclaren type bobbins even mostly cure that.

Big Reds will be overkill for you car if Carreras mostly solved the issues previously.

Grady Clay · 08:13 AM

Noel,

The floating rotors will probably increase the brake ‘feel’ and the effective braking at the limit moving the lock-up point out. In turn they will probably run hotter because of the better braking. That is all good.

The issue is to get rid of the heat.

You need to get more air through the wheel/rotor/caliper area. That is probably going to require a combination of techniques. First, read the rules for your class and find the limits of what you can and can’t do.

The basics are: Scoops that funnel under-car air through the wheel. There is a 993 plastic scoup that is inexpensive and can be modified to bolt on the diagonal brace on your A-arms. There are also aftermarket scoops but too many go under the A-arm but are prone to being scraped off when you drop a wheel.

Ram air from openings in the front bumper and valance.

Air ducted through the inner fender.

Fan forced air from the trunk area and forward. I use a 911/914 fresh air blower because it has two outlets for a single fan. If the fan faile, it effects both sides equally.

Wheel fans. BBS and others make a bolt-on fan assembly that goes in the center of the wheel on the outside. Every 935 used them.

Water spray. Most of the SCCA ‘Big Iron’ GT1 Corvettes and others use windshield washer-like spray inside the brake rotor. See my thread on “Rubbermaid Solution”.

Don’t forget the rear brakes. Too often you see the classic endurance race picture with the rear brakes glowing bright yellow and the fronts relatively cool dull red. You can use a fresh air fan in the trunk and reverse the cool air flow in the heater tubes back to the rear brakes (assuming you don’t need heat/defog).

Best,
Grady

Noel · 10-25-2008, 10:51 AM

Quote:

Originally Posted by Bill Verburg

Big Reds will be overkill for you car if Carreras mostly solved the issues previously.

Many thanks Bill.

So would you recommend the 993/965 setup for my car? Both are about the same $$$ from VCI. For the same $ Steve Timmins can get me a full 996 (Non-turbo) setup, but those rotors are thinner at 28mm in the front.

Would you recommend that I keep cooling to the new brakes too? I would keep the AJ USA set up and just get larger backing plates to fit the larger rotor.

Thanks again,

Noel

Noel · 10-25-2008, 10:53 AM

Thanks Grady, I appreciate the advice and agree that cooling is the # proirity, however, I have been using cooling to the eye of the rotor for several years and it worked well. The issue is that Carrera brakes are too small for track driving with R Compound tires.

BTW, I have tried the 964 cooling scoops too, but they didn't work for me and I went with the AJ-USA under the a-arm set up, as this dumps air right at the eye of the rotor.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by Noel

Many thanks Bill.

So would you recommend the 993/965 setup for my car? Both are about the same $$$ from VCI. For the same $ Steve Timmins can get me a full 996 (Non-turbo) setup, but those rotors are thinner at 28mm in the front.

Would you recommend that I keep cooling to the new brakes too? I would keep the AJ USA set up and just get larger backing plates to fit the larger rotor.

Thanks again,

Noel

the difference between the 3 setups you have maentioned is in the rotors

993/965 will used 304x32 & 309x28(these are 930 3.3 rotors)

993tt/RS aka Big Red use 322x32 & 322x28

996tt will use 330x34 & 330x28

another option is 930/917 which use the same rotors as the 993/965 but can fit in smaller wheels(15s) The 993/965 can fit in 16 but you need 944 front wheels or use spacers

if the Carrera brakes were goo before then likely they can be good again w/ better cooling

Retro · 10-25-2008, 04:49 PM

So the weight savings alone, would not be worth the upgrade?

Noel · 10-25-2008, 05:30 PM

Quote:

Originally Posted by Bill Verburg

if the Carrera brakes were goo before then likely they can be good again w/ better cooling

Thanks Again Bill.

Since I already have the AJ-USA under the a-arm scoops that dump cooling air into the eye of the rotor (Also have the hub block off plates), how much more air could I get by moving the pickup point to the front of the car (Valance vs. under the a/arms). I am not sure of the volume difference between the two locations.