911 sc/carrera upgrade to boxster?

[gchappel]

Does anyone have any experience or thoughts on the brake upgrade package Bruce Anderson seems to like in this months 2/02 Excellence techh notes?
It uses the boxster calipers, which have been discussed here in the past, but on all 4 wheels, not just the front. I have an 85 carrera that sees a fair amount of track time, and sometimes still gets a little bit of a soft pedal after 30-45 min-yes it has cooling ducts, etc. I realize the boxster setup uses the same front rotor and actually a slightly narrower rear rotor. These brakes really work well on the boxster though, would this really be an upgrade?? BTW the kit from TRE automotive that Anderson talks about is about $2100 without rotors and $2700 with- using new boxster calipers.
TRE's webpage is www.tremotorsports.com
Again, not associated with them, don't date their daughter, etc.
Thanks, Happy Holidays
Gary

[boyo]

The Boxster is a different car, due to the weight distribution. I would think there are more appropriate kits for the 911. For example, why not use the 996 calipers?

FWIW, I've got a '97 Boxster. It's for sale if you want to buy it and part it out...

-Boyo

[pbs911]

I only scanned Bruce's aticle last night, but I don't think he stated the is an upgrade in performance, only that the Boxster brakes MAY provide some increase in breaking. He does note the rotors are only a little larger and this is where you dissapate heat. He further states the Boxster brakes are good for those who want to change out their old system and retain the vintage look of 15" Fuchs. I don't think the change would be cost erffective. You would probably have to go with the brake set ups as Clark and Jack have posted in recent threads. That said, if I was looking at a rebuild of my calipers and the purchase of new rotors, I may go with the Boxster set up since you have to get new parts anyways.

[Bill Verburg]

The boxster front calipers will be heavily front biased when used with 83 and earlier M rear calipers. They will be only slightly front biased when used with the 84-89 Carrera 3.2 rear M calipers.

This is not really an effective brake upgrade because you can gain the same increase in thermal handling(at 25% of the cost) due to the larger Carrera rotors by using the stock Carrera A front calipers with the bigger Carrera rotors. I would however use the 83 and earlier rear Ms with a spacer to accomodate the Carrera rear rotors.

The factory used a 33 bar proportioning valve when they used the Carrea A with the Carrera M. This valve is not necessary or desireable when the Carrera A is used with the SC rear M.

[911pcars]

Hey Bill,
Are these M caliper spacers available or do they have to be fabricated? I haven't seen them sold separately.

Thanks,
Sherwood

[89911]

$2700? You are getting close to $3200, the price for a Brembo package for all four corners. You are only going to get appreciatable improvement with increasing your rotor size to dissapate heat. $2700 while keeping the same size rotors is not worth it IMHO.

[Randy W]

Gary, if you have not already done so, I would try going to a more aggressive pad like a Pagid Orange on you Carrera brakes. You may go through rotors a little more often, but you should not have anymore fade. I assume you are already regularly bleeding a high quality fluid (Motul, etc.) now. I have heard about the extra pistons on the Boxster brakes being better, but they are not necessary. If you need more then you are in RS/993 brake territory anyway.

Another non-ABS option is S calipers in front with Pagid RS14 Black and 84-89 Carrera calipers on the rear with Pagid Orange, no power assist and no proportioning valve. Great feel, Good balance (as long as you are smooth), and it is much harder to lock the fronts.

Randy Wells

[Bill Verburg]

Sherwood, I have never looked fror the spacer so have never seen them and am 2000 mi from my parts books. We have always swapped parts between the old and new calipers to get the desired spacing and pistons in one caliper.

Of the 3 available front calipers; SC A, Carrera A, and aluminum S, the only one capable of taking advantage of the slightly larger Carrera rotor is the Carrera A. All 3 do have the same size pistons. The Carrera A is just the SC A with a spacer between the halves to accomodate a wider rotor.

The Carrera rotors provide a small improvement in thermal endurance over the older SC rotors but are a large step down from what is available in the 930 and larger rotors.

Randy, the S front and Carrera rear is quite heavily rear biased(this is why the factory used the 33 bar p/v on the rear circuit for that f/r piston combo). This is good for street driving where the concern is even wear all around but without yhe p/v looses the ability to take advantage of increased stopping power at the front under hard braking due to the increased normal forces on the front tires. Everyone has their own preference but you will get better stopping ability with more front bias(under heavy braking). You should shoot for a ratio of ~1.6:1 as the factory did in all non ABS cars(including the race cars)

[Randy W]

Bill, actually after a lot of trial and error, the S front/Carrera rear combo (with more aggressive Pagid pads up front) is what I use on my '72 911T autocross/track car. With front ducting and Motul, I do not have any fade and do not feel the need for anything more on the track, and the fronts will still lock before the rears. In my opinion, the P/V valve does nothing to actually improve the stopping power of the front. I know the factory did it for safety reasons, but it just causes the fronts to lock too soon. Getting rid of the proportioning valve and putting a more aggressive pad up front is the first thing I would do if I were autocrossing a Carrera. You DO have to be very smooth on the track or the rear will wiggle and want to step out under braking, but you will be able to make the car rotate more easily with trail braking in autocross events.

This is a very personal preference (less unsprung weight up front) and is not for the faint-hearted, but it works.

Randy Wells

[MMARSH]

Randy,

Interesting combo, obviously your car is a hell of an autocross car and works well. Have you tried this setup regularly on higher speed road courses where your braking from 130mph down to say 70-80 repeatedly. I have heard warpage of the aluminum S calipers is a common problem and I'm also curious about the difference in brake bias at these speeds.

I also think Pagid oranges are a great pad.

Its always interesting to me to see these posts about upgrading the brakes. I have stock Carrera brakes on my early car. This weekend at Laguna Seca I had five 20 minute sessions on Saturday and five of the same on Sunday. I had no brake problems at all(zero fade) and the car stopped just as well at the end of the day on Sunday as it it did on the first session on Saturday. I even had someone approach me in the pits and comment on how late I was breaking. Another thing that was interesting is that Jack and Tyson completely wore their brake pads down to metal while I still had quite a bit of pad left. I think alot of that is due to experience.

I think a stock brake system in good working order with good fluid, good pads and good ventilation works very well. I do think that the newer brake systems have a better feel though.

[Randy W]

Hi Mike, at SIR we brake from 130 to 70 mph in turn 2. I have been using S calipers there for about 20 events (each 3-4 sessions of 30 minutes each) over the past five years and have not had any problems with warpage of the calipers. As long as you are smooth, the brake bias with my combo is fine for repeated high speed braking. If you were to jam on the brakes at this speed, you would want to be going in a straight line I can tell you! This combo is more demanding on the track, but allows you to pitch the car in ways that others do not. There are lots of stories about S calipers flexing and warping, but I have not experienced this and think they are great for a light car. They dissipate heat rapidly and are very light.

If you wanted to make this driving a 911 stuff easy, you would just buy a 996, right?

Randy Wells

[gchappel]

Thanks for the interesting discussion.
I thought the boxster upgrade was going to be of little real value on the track, but thought I would get others opinions as well.
I do run pagid orange pads all around, ducting, AP600 fluid, etc. I will admit that a lot of brake "fade" in the 3.2's is related to the driver. This time last year-my second year of driving a couple of DE's a month- I would have brake fade by the 20min mark. This year- and nothing has changed except my driving exlperience -I get no fade at all. Maybe a little softer pedal by the end of the last run, but even that is questionable. I also get about 10-15 track days-about 90 to 120 min of track time a day- out of a set of pagid pads now, and no rotor problems either. I was looking to do the 930 brake upgrade this time last year-want to stay with 16" Fuchs- but my mechanic talked me into waiting- now I don't need it.
Thanks again, and have a great season.
Gary

[Bill Verburg]

Randy, as I stated, there is a lot of personal preference in the way brakes are set up. You have compensated for the rear hydraulic bias mechanically by using the more aggressive pads in the front.

The caliper/rotor/pad combo needed for a given car is highly dependant on speed potential, weight, track configuration and driving style. Calipers/rotors that are perfectly suited for a lighter/slower car may be totaly inadequate for a heavier/faster car. Calipers/rotors that are great for autocross may be inappropriate for Watkins Glen Enduros.

[Randy W]

Glad to be of help, Gary.

[MMARSH]

Randy, thats interesting. I have a set of aluminum calipers and will have to give that a try and see if that works any better for my setup. Thanks for the info.

Yeah getting a 996 around the track fast wouldnt be nearly the challenge or has rewarding. When you start making the true 911's dance alittle around the track it's alot of fun.