Boxster brake upgrade for a Carrera?

Has anyone ever tried the Boxster brake kits that some vendors are advertising as an upgrade to the stock front calipers for the 75-89 911's? Check out this site - it looks like a great deal, and half the price of the Brembo kits for the front. I wonder if Pelican can get these? And are they safe....
http://www.smartcart.com/Paragon/cgi/display.cgi?item_num=BOXBBK74-89

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Bill Atkins
william.atkins@oracle.com
1985 Carrera Coupe

I'm delivering second-hand information, so take it as such. But I consdiered these, and was told that some track groups will not allow cars with the Boxster caliper upgrades. The problem is that a brake upgrade's main function isn't to provide more "gripping" power for the brakes. It's to allow the braking system to dissipate heat more effectively. This is the chief virtue of bigger brakes. The problem with the Boxster caliper upgrade -- and the reason it's so inexpensive -- is that it doesn't increase the rotor size. The larger calipers themselves don't dissipate heat as efficiently as larger calipers and larger rotors together. You can inadvertantly increase your chance of boiling your brake fluid.

At least, that's my layman's understanding of it. Vendor claims aside, I think it merits more investigation before you take the plunge.

Brakes are a very expensive upgrade, and most of the time they're completely uneccesary. Properly maintained stock Porsche brakes may not look as sexy as big reds, but they are tremendously efficient and very lightweight. Street use doesn't even test their limits. Extended track use is the only real justification for this upgrade.

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Jack Olsen
1973 911 T (3.6) sunroof coupe
jackolsen@mediaone.net

Make sure your brakes are in good working order, throw in some high performance pads. And go. The brakes on 911's are fantastic. I've done much to my car, but I can't improve much on the brakes.

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8 9 9 1 1, The last of the line.

on the other hand...

If you are looking for a styling update those boxster brakes are *****in. Not cheap but much less than Brembos.

The comments about performance above are spot on. In fact, if you aren't overheating your brakes the stock setup is BETTER than the big'uns. This is because the smaller stock rotors are lighter, reducing unsprung and rotating weight, therefore handling, accelerating and braking better.

My car is a compromise - performance is very important to me but I also want it to look good.

The boxter caliper is a good compromise delivering "the look" while retaining the lighter stock rotors.

I've struggled with this particular tradeoff myself and so far have kept the stock setup. I'm using the cash for more meaningful performance upgrades. But each to his own priorities.

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Chuck - '86 Cab, '77 Targa, '85 toyota 4wd rain mobile http://www.cheaterswayside.com/911/

Jack you're correct. Calipers don't make the car stop faster alone. Tires do.
There are 2 reasons for a brake upgrade. One is for better heat control. If the brake parts cannot shed heat effectively then you can boil the fluid or melt the pads. Bigger alloy parts tend to shed heat faster and more effectively.
The other reason is better gripping force, more stopping torque from the calipers/rotor. 911's have plenty of this in stock form. The only time you need to upgrade the rotor diameter or piston area is when you need more stopping torque, and this is only when you have grippier/bigger tire contact patch. So when a race car runs big slicks or stickier rubber it now needs more stopping torque to counteract the higher forces that the tires are capable of giving.
If the stock calipers allow you to lock up your wheels with your current tires, a brake upgrade for more clamping force may not be a good use of your money heat issues aside.

"The problem with the Boxster caliper upgrade -- and the reason it's so inexpensive -- is that it doesn't increase the rotor size. The larger calipers themselves don't dissipate heat as efficiently as larger calipers and larger rotors together."

IMO, $800 smakers is not inexpensive .. but I guess it is compared to $2-3000 brakes. If I'm not mistaken, these larger Boxster calipers are paired with the thicker 24mm Carrera rotors (at least compared with the earlier vented rotors). So on any pre-83 Porsche, this combination does indeed provide a larger caliper as well as a larger rotor for improved heat dissipation. There are other caliper/rotor combinations one can use as an alternative to Turbo brakes.

Sherwood Lee
http:members.rennlist.org/911pcars

I had SC brakes on my 73 911, and -- in spite of larger wheels and a larger engine -- I never had a problem with brake fade on the track. I'm currently upgrading them to Turbo brakes, and I have to admit to having mixed feelings about it. The final impetus was what Orbmedia mentions, I got a new set of wheels for stickier track-only tires. I figured the additional grip, plus plans for more time spent on the track, plus the additional power (and weight) of the 3.6 liter engine all combined to justify the switch. I got a pretty good deal on the calipers and the machine work and installation, but the thing that surprised me was how heavy the whole setup was. Bigger brakes may look cool, but they do also add a lot of the worst kind of weight -- unspring, and inertial.

I'm sure I'll be happy I did this in the long run, but I wished I had checked my 0-60 times with the lighter brakes, so that I'd see just what I'm giving up in exchange for the insurance agains brake fade.

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Jack Olsen
1973 911 T (3.6) sunroof coupe
jackolsen@mediaone.net

Everyone - thanks for the replies. I think I will just do the following for now:
* Change to some race pads - I heard Hawk Pads are pretty good
* make a custom cooling kit via ducting through the fog light holes (sounds kind of nifty - I will investigate), and
* consider drilled rotors.

Thanks Again

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Bill Atkins
william.atkins@oracle.com
1985 Carrera Coupe

I have the Boxter upgrades and have had no problems getting onto any track. The rotors were much bigger than stock and also Cryro (sp?) or frozen with cross drilled holes. I have boiled the stock ones twice and lost all brakes in the middle of a run group-- this was NOT fun! Just recently I have had some serious fade in these as well, so I'll be moving up to the Big Reds soon. But overall I think it is a great improvement over the stock stuff.

I run back to back sessions with 40 minutes of continous threshold braking at regional track events. I also am running 225 and 255 G-Force R1A and my 89 coupe is not light. With proper pads, I have never had any fade. I do have a front brake cool kit and SS lines. I can lock up all four at any time, at any speed. I like the bias they designed in the stock system and would not want to change it. I would think going to Brembos in a similar car would be one the would be on the verge of lock up all the time. Also changing a part, such as the fronts, would also change the balance of the braking. A friend recently changed his 930 to Brembos and it wasn't until he installed a adjustable brake bias, that he could balance out the front to back braking. This was after a few sets of flat spotted tires!

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8 9 9 1 1, The last of the line.