Boxster Vs Boxster S brakes

[RichHawk]

I've been researching for a couple hours, and have inferred a bunch of things, but want to make sure.

My Friend has a 2003 Boxster (non S) and the brakes went soft on the track from overheating the fluid. We changed the fluid out with ATE super blue and the next track day, no fade.
BUT that didn't stop him from thinking he could benefit from the S brakes.
I'm unsure.

So Question 1: Are the Front calipers, Non S to S, the same hardware / casting / mounting / width, and just different color? How about the rear S to non S calipers?

2: The S front rotors are cross drilled and 4mm thicker. Can you install S rotor on a Non S Boxster with no other changes?

3: The rear S rotors are not interchangeable with the non S ones. (Parking brake incompatibility, needs S knuckles, and some mystery spacer that the internet doesn't define. ) What are the S to non S rear rotor / caliper benefits?

Thanks,
Richard

[Cajundaddy]

Many Boxster drivers have moved to Box S front brakes/rotors with no issues. They are a direct bolt on. This may be $$ overkill though. Quality rotors and fresh bedded track pads, fresh brake fluid and a set of 997GT3 front brake ducts solve about 90% of Boxster brake overheat issues. The most common reason for boiled brake fluid is simply air or moisture still in the calipers. Re-bleed thoroughly and test again.

[dad911]

I just started racing a non-s boxster, and with ATE the brakes have been fine. I used the 'cheaper' ducts: Brake Cooling Duct Upgrade - Rennlist Discussion Forums

How old was his fluid? Were the pads worn? Thin pads cause more heat in the calipers.

[RichHawk]

Originally Posted by Cajundaddy

Many Boxster drivers have moved to Box S front brakes/rotors with no issues. They are a direct bolt on.

Direct bolt on check. But are the calipers identical except for color?
I have not found anything that outlines the differences in calipers, and actually have found multiple places that suggest that all Boxster front calipers, C2, and C4 calipers are the same:
The piston diameters are all the same

36mm/40mm Front Pistons 28mm/30mm Rear Pistons
C2 - Gloss Black
C4- Silver
Boxster - Dull Black
Boxster S - Red (same caliper size as the C2/4 & non Boxster S)
But that doesn't say anything about max rotor thickness, or mounting.

EDIT: Read below. S rotors are bigger per Dad911
Given the S rotors are the same diameter, but 4mm thicker, I could imagine that the S calipers are wider by that 4mm. But then again, 4mm isn't much, and the pistons in the calipers move this much and more, opening the possibility that rather than use a different caliper, that the non S calipers just squeeze a thinner disk

Who here actually knows? I'm just speculating...
Richard

[RichHawk]

Originally Posted by dad911

I just started racing a non-s boxster, and with ATE the brakes have been fine. I used the 'cheaper' ducts: Brake Cooling Duct Upgrade - Rennlist Discussion Forums

How old was his fluid? Were the pads worn? Thin pads cause more heat in the calipers.

I tend to agree with you, He's probably fine now. The pads are stock compound, and 3/4 thick. The old fluid was of an unknown age, but obviously not up to the task. But having someone say they are actually racing on the non S brakes will make him feel a lot better.

Thanks for the Duct link. that's a cool mod (Pun intended)

Though I still want to know if the calipers are different...

Richard

[dad911]

ALWAYS start the season with fresh fluid. Flush the whole system, then bleed between events.
Per Factory Manual:

Non'S':
F Disc 298mm, Pistons in Calipers 2x40,2x36 mm , pad area 216 cm^2
R Disc 292mm, Pistons in Calipers 2x30,2x28 mm , pad area 196 cm^2

"S":
F Disc 319mm, Pistons in Calipers 2x40,2x36 mm, pad area 254 cm^2
R Disc 299mm, Pistons in Calipers 2x30,2x28 mm, pad area 196 cm^2

[RichHawk]

ok, so one step closer.

Facts:
S rotors are thicker AND larger diameter.
S pads are larger
S calipers bolt in place of non S ones,

speculation:
S calipers are different (other than color) from Non S, to sit higher to accommodate the extra diameter of the S rotors, and to offset correctly for the extra 4mm thickness that the S rotor brings to the table.

Can anyone confirm the above speculation?

[Cajundaddy]

Yes. To change over to Box S front brakes you will need Box S rotors, calipers and pads. All are bigger than Base 986 components.

FYI: I have been running performance driving events including Time Trials for 4 years, boiled some old fluid once, and gummed up a set of rotors once. Both were my fault. Otherwise they have been good for 40+ track days.

All the Boxster Spec race cars in the country run Base 986 front brakes.

[racer]

Boxster S rotors and pads are the same as the regular 996! (therefore, larger and thicker than non-s set up.) Yes, they are a direct bolt-on.

Better pads, fluid and airflow will certainly help the brakes last longer. So will using the brakes less

[Doug&Julie]

FWIW if you run Boxster S / 996 brakes you need a minimum 17" wheel, where the standard Boxster brakes fit under a 16" wheel. Not usually a problem as most Boxster owners have upped their cars to 17" wheels. I think 17" may have been standard base wheel by 2003 anyway. But now you know.

[Bill Verburg]

JMO and based on what I see at the track

Boxster S rotors are 318x28 vs 298x24 for non S and 299x24 vs 299x20 rear

hydraulicly the S and non S are the same but the S pads are a little bigger in front same in the rear. 121 x 86 front S, 114 x 78 front non S, 112 x 74 rear both




Even the S are going to be overworked by a fast driver, all the good shops are using SRF as the fluid of choice for these cars

[Schumi]

Mathematically, there is a 6.7% increase in braking torque generated by the larger diameter 318mm S rotors vs. the 298mm rotor. There is no increase in hydraulic pressure or force on the rotor, as the pistons and masters are the same. The larger rotor thickness allows for better cooling/more mass. And the larger pad area means less brake fading.

[JMatta]

Not technical, but an observation from an 15 year track instructor. Your friend is running stock pads, old fluid and is very hard on the brakes; i.e. braking early and looooong. Track pads and a better fluid will help, but he/she needs to learn proper braking techniques to avoid heating the brakes to the point that they cook.

[RichHawk]

Originally Posted by JMatta

Not technical, but an observation from an 15 year track instructor. Your friend is running stock pads, old fluid and is very hard on the brakes; i.e. braking early and looooong. Track pads and a better fluid will help, but he/she needs to learn proper braking techniques to avoid heating the brakes to the point that they cook.

Hmm... this is a good discussion point. It's one I've tried to reason out in theory, but without the practical experience behind it, the theory truly comes down to nothing but speculation.
All my track experience is in my Spec Miata. and I never had to brake much in it anyway, so I never taxed the brakes temperatures, and therefore don't really understand braking on a track. Now I have my 87 911, and it WILL be going to DE events, and so I WILL have to learn how to brake properly.

Theory says for a 100MPH straight line speed down to 50MPH corner, whether you do all of that braking in the last 50 ft, or stretch it out for 150 ft, the amount of energy the braking system needs to absorb is the same.

Other than making you slower around a circuit, why would long early braking be worse (IE more heat soaking intensive) than short hard braking? Jmatta implies above that short hard braking is proper, and will create less fade issues than longer softer braking.

Does anyone have first hand experience on how they learned braking techniques?

Thanks,

[ronster]

Good post as I just changed my OEM brakes to the Big Red S system on my '99 Boxster, installed the GT3 ducts and tracked it two days later at Infineon. To me the difference in stopping and slowing ability was significant with the Big Reds. I had much less brake "feedback" through the steering wheel (actually none), much better progressive braking ability allowing me to go deeper into turns before braking, more "tap" to slow down ability versus hard brake pressure. All of the increased capabilities of the Big Reds gave me more confidence on the track and allowed me to carry more speed into turns, shorten braking time allowing me to get on the acceleration out of the turns earlier. I do a brake fluid flush before every track event. In my opinion the upgrade was one of the three most significant upgrades I've done on my Boxster and well worth the money spent.

[Grant Lenahan]

If you want S brakes, they are some % larger and therefore better at dissipating heat. But that's not your friend's problem. He/she needs good fluid ( ate super 200 or better); it must be changed at least annually, maybe more, and at some point you will want to move to higher temp pads. All these are in fact mroe important than the incremental difference in S brakes - and WAY cheaper.

If oyu want S brakes you need to buy the entire lot - calipers, rotors, etc and swap it out. And kiss 16" snows goodbye :-)

Grant

[cretinx]

Originally Posted by Doug&Julie

FWIW if you run Boxster S / 996 brakes you need a minimum 17" wheel, where the standard Boxster brakes fit under a 16" wheel. Not usually a problem as most Boxster owners have upped their cars to 17" wheels. I think 17" may have been standard base wheel by 2003 anyway. But now you know.

are you POSITIVE that a 16" wheel won't clear the brakes?

has anyone ever tried and knows for sure?

[Cajundaddy]

Originally Posted by cretinx

are you POSITIVE that a 16" wheel won't clear the brakes?
has anyone ever tried and knows for sure?

Yep, many have tried but none succeeded. 16" Boxster wheels do not fit over Box S brakes. It is possible that some exotic, aftermarket, custom, carbon fiber, super expensive, super trick 16" wheel might fit; just not stock Boxster 16"s.

[ronster]

I believe the early non S model came with 16" wheels with 17" as an upgrade. When the S model was introduced it came with 17" with an 18" optional upgrade. Since the wheels are designed for the car with the proper brake clearance it makes sense that the 16" OEM wheels will not fit over the S calipers.

[EPWilson]

When I put 16" wheels on my 99, I couldn't believe how close the clearance was to the base brakes, so the bigger S calipers would definitely not fit with the OEM 16" wheels.