Brake upgrade for early cars with steel trailing arms

Shaun @ Tru6 · 08-09-2011, 04:32 AM

I know going 930 calipers requires machining rear Al trailing arms, but what about steel?

I'll be making my 73 safer and more capable for the track soon and brakes are high on the list. It now has SC calipers up front and early M's in the rear. Car has a 3.2 and goes pretty well on the street.

What are my options?

Should I just go with Carrera calipers/rotors? How difficult is it to put in a Carrera pressure regulator into an early system? Where would it go?

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by Shaun 84 Targa

I know going 930 calipers requires machining rear Al trailing arms, but what about steel?

I'll be making my 73 safer and more capable for the track soon and brakes are high on the list. It now has SC calipers up front and early M's in the rear. Car has a 3.2 and goes pretty well on the street.

What are my options?

Should I just go with Carrera calipers/rotors? How difficult is it to put in a Carrera pressure regulator into an early system? Where would it go?

The trailing arms are not modified to install 930 brakes, the caliper is modified to fit the existing 3" mounts.

the heat issue which is what needs to be addressed is at the front, not the back.

A lot of folks use what you already have successfully
it helps if the car is as light as possible
has as much air directed to the rotors as is possible
fresh high quality fluid like SRF is used
track pads >50% thickness are used(PFC97 is very popular)

Some folks go an additional step by using 3.2 Carrera front rotors and calipers, these are 2mm wider and have somewhat better thermal capacity(from slightly increased mass and better breathing ability) than stock '69-83 20mm rotors.

Leave the rears alone, the thermal issues rarely if ever arise in back and the bigger 3.2 Carrera rear calipers throw bias off too much.

Shaun @ Tru6 · 08-09-2011, 04:53 AM

Thank you Bill. So I just leave as is and put on some front fresh air ducts, use proper fluid and pads? That would be great actually. It does stop very well on the street with Ferodo pads F+R. I'm just budgeting out the car now and wanted to start with brakes.

The car is pretty light too.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by Shaun 84 Targa

Thank you Bill. So I just leave as is and put on some front fresh air ducts, use proper fluid and pads? That would be great actually. It does stop very well on the street with Ferodo pads F+R. I'm just budgeting out the car now and wanted to start with brakes.

The car is pretty light too.

I'd use A arm diverters as seen on 964 & 993 and big ducts, the small diameter ducts I usually see are almost useless

Shaun @ Tru6 · 08-09-2011, 05:07 AM

Would you recommend both of these?

Diverters:

Porsche 911 Exterior Trim - Page 4

Ducts:
Porsche 911 & Carrera Brake Pads & Rotors - Page 4

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by Shaun 84 Targa

Would you recommend both of these?

Diverters:

Porsche 911 Exterior Trim - Page 4

Ducts:
Porsche 911 & Carrera Brake Pads & Rotors - Page 4

I would do both, the more cooling air the better, the 993 diverters put air on the inner face of the rotor, the scoops put air into the middle and it transits through the rotor and exits at the edge, they complement each other

the only issue w/ the under arm scoops is that they have a tendency to get torn off if you have an off.

Shaun @ Tru6 · 08-09-2011, 09:26 AM

Thank you Bill, I'll add them to the list.

Chilling in VT · 08-09-2011, 03:38 PM

I agree 100% with Bill. I am using the Carrera fronts on my 73 with the 993 diverters. The only other thing I would add is the Smart Racing blockoff plates for the back of the hubs. These light cars stop amazingly well.
Joe

Shaun @ Tru6 · 08-12-2011, 05:24 AM

Thanks for the confirmation Joe. Any pics of your diverters installed? Your car?

moneymanager · 08-12-2011, 06:39 AM

Amen to all of this. Forget the rears, they are fine as is. The wider "A" caliper and rotor that went with the later Carrera is a very worthwhile change. I no longer remachine the rotors every 5/6 events to restore the surfaces, and the pads last 5 times as long as they used to. All of this the result of using a heat dissipating 24mm rotor instead of the earlier 20mm product. IMHO, the superior heat handling ability of the bigger Carrera rotor setup more than compensates for the extra unsprung weight of the A (compared to the S) caliper.

Chilling in VT · 03:54 PM

Hi Shaun,
Sorry for the tardiness, I was out of town (at Lime Rock). I spoke with a friend there who just did the changeover to 930 brakes on his Carrera. He loves them, but it was a $5k proposition all done with rotors. machine work, calipers and spacers. They look spectacular but still $5k. If you are running in the very upper run groups, you will probably need them.

Here are a couple of pictures of the diverters and the car.

GaryR · GaryR's Garage

Quote:

Originally Posted by Shaun 84 Targa

I know going 930 calipers requires machining rear Al trailing arms, but what about steel?

I'll be making my 73 safer and more capable for the track soon and brakes are high on the list. It now has SC calipers up front and early M's in the rear. Car has a 3.2 and goes pretty well on the street.

What are my options?

Should I just go with Carrera calipers/rotors? How difficult is it to put in a Carrera pressure regulator into an early system? Where would it go?

Save your money - Toss in a set of PF97's, Flush with SRF or Motul 660 (or 600), and go. I don't run brake cooling, bet I push substantially harder than you will in my (2740# with me in it) race car (stock SC calipers and rotors), and have no braking issues..

Shaun @ Tru6 · 08-18-2011, 04:45 PM

Quote:

Originally Posted by GaryR

Save your money - Toss in a set of PF97's, Flush with SRF or Motul 660 (or 600), and go. I don't run brake cooling, bet I push substantially harder than you will in my (2740# with me in it) race car (stock SC calipers and rotors), and have no braking issues..

Thanks Gary, that's the plan. Roll bar going in first.

Shaun @ Tru6 · 08-18-2011, 04:49 PM

Thanks Joe, love your car! Are those 7x16s or 15s all around? Tires?

Brave man taking rare fender arch trim to the track.

I'm staying with stock brakes for now, but thanks for the info. I won't need better brakes for quite some time is the general consensus.

Quote:

Originally Posted by Chilling in VT

Hi Shaun,
Sorry for the tardiness, I was out of town (at Lime Rock). I spoke with a friend there who just did the changeover to 930 brakes on his Carrera. He loves them, but it was a $5k proposition all done with rotors. machine work, calipers and spacers. They look spectacular but still $5k. If you are running in the very upper run groups, you will probably need them.

Here are a couple of pictures of the diverters and the car.

Chilling in VT · 08-19-2011, 01:44 PM

7x15's all around with 205/50 15 Toyo RA!'s. I could probable fit a 225/45 15 in the rear but am happy with the 205's. I really had no problems with stock M brakes but figured when I made the move to new Bilstein struts with 3.5" mounts I would upgrade to the Carerra rotors and calipers. They are probably overkill but seem to work well. I also concur with Gary about the PF97's, great bite and they last forever.
Good luck.
Joe

Shaun @ Tru6 · 08-22-2011, 10:55 AM

Thanks Joe, hope to see you on the track next summer, I'm joining North Country PCA.

jpnovak · 08-22-2011, 12:11 PM

Shaun,

With SC brakes up front, good fluid and cooling ducts you should not need any more brake at the track. If you are overheating them look more into the driver than the equipment.

if you find that pad and/or rotor life is an issue then the 24mm Carrera Setup is a nice improvement. I am sometimes amazed at how long a set of brakes will last with cooling ducts.

FYI, I run the cooling ducts and block-off plates. I do not have the 993 diverters.