Porsche 911 Brake Upgrade Question

[jamesjedi]

Bill, thanks for the information. Also, I had to look up "das macht nichts" I am seriously considering selling my Rebel brake parts.

[Mothy]

My current setup on my SC with wide body guards is Turbo Rotors front and rear (flat hats on the front), with 928S4 callipers on front and 964 callipers on the rear and a 23mm Turbo master cylinder. No PV but have power assistance.

I am very happy with that for both street and track. Nice balance under heavy load. And they fit under my 16" rims.

Tim

[Luccia at Pelican Parts]

Yes, we have the Boxster Brake kit HERE for your 911.

[Bill Verburg]

Originally Posted by Mothy

My current setup on my SC with wide body guards is Turbo Rotors front and rear (flat hats on the front), with 928S4 callipers on front and 964 callipers on the rear and a 23mm Turbo master cylinder. No PV but have power assistance.

I am very happy with that for both street and track. Nice balance under heavy load. And they fit under my 16" rims.

Tim

You would be better off w/ 993 rear calipers, get the rears working a little more

[jamesjedi]

Perhaps there could be an equation that would be "generally" applicable for brake upgrades. It would determine if stock brakes are adequate, or if you meed a different setup.

Not sure how it would be done, but it would be doable based on other experience.

[Bill Verburg]

Originally Posted by jamesjedi

Perhaps there could be an equation that would be "generally" applicable for brake upgrades. It would determine if stock brakes are adequate, or if you meed a different setup.

Not sure how it would be done, but it would be doable based on other experience.

It's all in the threads, search

here's a good starting point, but there are many, many more

[jamesjedi]

That is what I have been looking for. I have searched...should have searched "brake fade". Thanks Bill.

[chrismorse]

I am going to try PMB calipers, new stock discs and air to the front rotors, (with block off plates).

I have seen numerous recommendations, (in this forum and other high performance venues), to put the brakes in new condition, with fresh fluid current Pads, then add air - before going to the big brake upgrades.

I am looking to get a very rough understanding of how much help the ducted air is going to help. For the moment, I am planning to use the under arm scoops.

How does this compare to A calipers & good pads with 24 mm rotors???

I have done a lot of autoxing and some tracking and witnessed lots of brake fade, (mine and others) and ridiculously short pad and disc life, as the brakes get pushed into thermal hell. The cost for running in the "red" is bad and the loss of linearity and predictability - un-nerving.

I have put C discs on a stripped, pumped speedster, (long ago, when they were cheap); Vented S brakes on a killer flared 914 hot rod and F-50 fronts, (355x32) and 360 challenge rears,(full floating 330x28) on a 308, with dead straight linearity, almost no wear - perhaps a bit of overkill - but confidence inspiring.

So, I am hopeing to get a sense of how much the air will help, with fresh stock brakes, (74 2.7 cis coupe).

Thanks,
chris

[Mothy]

For track or autocross it's thermal mass and cooling which makes the difference. Standard brakes can lock up the wheels BUT won't handle it so well lap after lap. Once they get too hot and your brake fluid gets too hot, you can expect spongy brakes and fade.

So bigger rotors and/or cooling us what you need - longer to heat up and able to get rid of the heat.

I have found the under A arm scoops have work great for me for track days. Have kept them in place as I have gone up in rotor size and thickness.

Would recommend them. Only issue is they can get damaged if you go off track.

[GT2BH]

My shop says that the fronts fit directly but the rear wont fit because the 930 is wider in the rear. Are there parts I need to replace in order to get the brakes on?

[jamesjedi]

Rears need to be machined. Go to VCI or Rebel Racing web site for more information and pricing.

[winders]

Originally Posted by GT2BH

My shop says that the fronts fit directly but the rear wont fit because the 930 is wider in the rear. Are there parts I need to replace in order to get the brakes on?

If you shop doesn't know what needs to be done and all they tell you is that they won't fit, you might want to find a better shop to fit your brakes. Some machine work needs to be done to the rears.

Both Rebel Racing and Vehicle Craft can help:

brake system components Rebel S Racing Products

930 Brake Upgrade 911 - Carrera - 914 - 914/6

Scott

[JOHN21BLACK]

Just finished mine. Front will fit. Have to add spacer. Rear need to be machined for carrera trailing arms. Had my rears done by rebel racing. Speak to clint. Great guy. You also have to change MC to 23mm.also need to change to 930 front hubs or go floating rotors.

[DonNewton]

(Devil's Advocate) Is your car a dedicated track car? Do you find that your engine has overwhelmed the chassis/suspension after you changed to a much larger engine? If the answer to the aforementioned questions is 'No", then you need to answer the final question: Can you still lock the wheels in a panic stop? If the answer to the last question is yes, then you really don't need a 930 braking system. (/Devil Advocate)
I have to agree that they are cooler than hell (see what I did?), and I too would like to have a set. These are the questions you have to ask to see if the cubic dollar outlay will have a good ROI. The thing is that Porsche designed a world-class braking system early on and only improved on what existed.

What I did with my 914 (track car with a built 2.7) was put Boxster brakes on it. Even with 9" Goodyear slicks, I can easily lock 'em up. Just an option. . .

[Bill Verburg]

Originally Posted by GT2BH

My shop says that the fronts fit directly but the rear wont fit because the 930 is wider in the rear. Are there parts I need to replace in order to get the brakes on?

930 are bolt on in the front, w/ 7 or 8" Fuchs there will be plenty of room, 6" Fuchs will need a spacer.

in back the 930 caliper need to be modified by a machine shop, after that it is a bolt on w/ stock 930 rotors. The backing plate will need to be removed. Again 7, 8 or 9"" Fuchs will have plenty of room, 6" would need spacers.

930 trailing arms are quite different from 911 trailing arms, they are wider but that makes no difference to the brake mounts. The 930 brake mounts are 3.5" in the trailing position on the trailing arms, 911 are 3" in a leading position, hence the calipers will need to be altered.

[Bill Verburg]

Originally Posted by DonNewton

(Devil's Advocate) Is your car a dedicated track car? Do you find that your engine has overwhelmed the chassis/suspension after you changed to a much larger engine? If the answer to the aforementioned questions is 'No", then you need to answer the final question: Can you still lock the wheels in a panic stop? If the answer to the last question is yes, then you really don't need a 930 braking system. (/Devil Advocate)
I have to agree that they are cooler than hell (see what I did?), and I too would like to have a set. These are the questions you have to ask to see if the cubic dollar outlay will have a good ROI. The thing is that Porsche designed a world-class braking system early on and only improved on what existed.

What I did with my 914 (track car with a built 2.7) was put Boxster brakes on it. Even with 9" Goodyear slicks, I can easily lock 'em up. Just an option. . .

You could lock stock A & M too.

The point of brake upgrades is rarely to increase brake torque, they are generally intended to increase the thermal envelope

Boxster brakes on the usual 911 rotors do marginally increase brake torque but they do nothing to enlarge the thermal envelope.

[Canada Kev]

I don't think that being able to lock up the brakes with a good stab at the middle pedal is a very good measurement of braking performance. I could lock up the front drums containing ten year old fluid, probably with a bunch of air in the system on my old '68 dodge pickup with ease.

However, what you say is true: most people don't need the 930 brakes, but they certainly are cool. I want some myself even though my brakes are pretty effing fantastic in stock form.

[911tracker85]

going with 930 brakes on my 930 clone project.

built in a 78 SC, modded 930 motor and all metal, wide body slant nose conversion. but stock SC brakes and suspension and 915.

all of that will change.....

building for DE/street ... in that order.

already got a set of 930 calipers. I am having Steve Weiner, Rennsport systems, doing all such mods for me, including rebuilding the trans (930 4sp), heads, split/rebuild the case/crank, and eventually the suspension.

this will take a lot of time.....

[JOHN21BLACK]

This is how the front came out with solid rotor and 930 hub. This is how the rear looks after being modified for carrera trailing arms.

[thotdoc]

Originally Posted by Bill Verburg

Stock brakes have always been fine on the light, stripped out race cars. It's the porker street cars that weigh ~3k# that have issues

bigger surface area does allow the pads to last longer, I wasn't aware that longevity was an issue. Silly me I always thought that heat management and brake torque were the goals

Like I've said before lots of nonsense flying around, Ergonomic studies have shown that the human leg is far better at modulating force at a fixed position than over a moving range of positions, that's why the highest hardest pedal is the design goal, the trade off is pedal effort, the higher and harder the pedal the less mechanical and hydraulic advantage is accrued by the system, hence the desire for boosted brakes. Unboosted 911 brakes have a hydromechanical boost of ~93:1 as the lower limit for a very healthy leg, of that ~16:1 comes from the hydraulics which means that for 964 brakes an unboosted 23.8mm m/c is as big as you can use for a driver w/ a very healthy set of legs and 19mm while providing more hyd boost has been shown to move insufficient quantity of brake fluid. You could probably get by w/ a 20.6mm m/c but they are all boosted so you might as well make the best decision and use the boosted 23.8mm

Bill-

All I can do is thank you for the endless and in depth education I get when I read your posts.

Gordon