Brembo mono block upgrade overheating, Fact or fiction??

[72SMFI]

I want to know were people are obtaining ther info on Boxster Brakes...Do Boxster have bad brakes or is it just when you put them on a lite car they have problems.. I want facts on this subject. I dont want to hear any thing that is hear say..

------------------

[89911]

What exactly do you want to know?

[72SMFI]

I want to know were people are getting there info of Boxster brake upgrade I have read of overpowering and overheating the rotors and boiling fluid. I want to know if this is true or somthing from Art Bell.From my understanding you tae the same rotors and calipers of a Boxtster and bolt on using an adapter..

[72SMFI]

PS my name is Wayne I own a 72 S Thanks

[Jack Olsen]

As I understood it (and here's the hearsay you wanted to avoid), the Boxster upgrade does not involve putting on Boxster rotors.

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

[89911]

Your "hearsay" rule is going to rule out about 90% of follow up post . I will try to use as little "Hearsay" as possible. The Boxter upgrade uses the same rotors at the stock 84-89 911, but usually come with cross-drilled rotors. These are a late innovation and I have heard little of the problems related to them. My .02$,"hearsay alert!!!" I think they promote front brake bias, since they are a more aggressive system then standard. Could be the reason for the brake boiling you mentioned.

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

[This message has been edited by 89911 (edited 06-05-2001).]

[Roland Kunz]

Hello

Every brake system will overheat. Just depends on how it is used.

The boxster uses bigger discs and the monoblock calipers will not bend and transits the heat better.

But if they driver allways has the left foot on the brake he will also overheat that system.

If you use the caliper on a small disc the heatsink brake disc will get comparable hoter to the boxster set up.

Boxster brakes or not only the calipers also the other parts are designed for best teamwork.

Generally a brakesystem is made to convert movment into heat and the system has to stay in a temperature zone to work optimal. To hot will fade to cold will cost friction.

Grüsse

[Bill Verburg]

As Roland pointed out any brake system can be overheated, the trick is to understand the weakness of what you have and address that issue.
I assume that you have a '72S which means that you currently have oem Al. S, 2 piston calipers(48mm pistons) in the front with 282x20 mm rotors, in the back you have iron M calipers(2 piston x38mm ) with 290x20 mm rotors. These are fine and were used up through the '83 SC(actully the front caliper material was changed to iron in '76). In '84 the front rotor was increased to 282x24 mm(4 mm wider) with the same iron calipers(with a spacer in the center) the rear was changed to 2x42 mm pistons on a 290x22 mm( 2 mm wider) rotor. These can be improved by providing better air flow titanium insulators and bettre more agressive pads.
Those who track their cars often boil fluid and/or glaze pads. If this is your situation then you may be a candidate for bigger brakes. As Roland pointed out the pad and rotor is designed to change Kinetic Energy into Heat Energy, this heat has to go some place, it can go into the air if better air flow is devised, or it can go into the pads thence into the fluid, or it can be absorbed and radiated at leisure by the rotor.
Generally the size of the pad is engineered to the size of the rotor, bigger rotor, bigger pad. Better brakes then are better absorbers and transferers of heat energy. The 930 brakes with their bigger rotors, 304x32 mm f and 299x28mm r rotors and commensurately larger pads are better at thermal transfer because of their bigger thermal mass and increased pad area which decreases the energy density at each square mm of pad area.
The problem with the boxster upgrade is not the caliper(which is one of the better available) but with the smallish 84-89 rotors used in combination with the boxster caliper.
The Boxster rotor is the same thickness as the Carrera rotor but has a larger diameter and thus provides more thermal mass than the Carrera rotor. In short it you use the Carrera rotor you might as well save your money and use the Carrera calipers as you are not gaining any thermmal mass.
To get truely upgraded brakes you must use larger rotors ie 930 304x32(they do get bigger 322mm is the next step up) and 299x28 with calipers that match, ie 944/964/993 Brembos.

[72SMFI]

Thanks to all who responded..One more question though. If one were to use 84 89 calipers with drilled rotors and pagid orange pads, on the rear. Matched with Boxster Brembos calipers and stock 84 89 rotors,with less aggresive pad, and brake cooling kit up front . Would that not give a good braking system. That would be light and not prowne to flexing. PS That is the system I am stuck with now.. I did not read all about this Boxster brake problem till after I bought them.. For what its worth I do have some cracking on my rotors and a little miffed by that. I bought them from my Pcar race shop. I am thinking of returning them..Wayne PS on web tv there is no spell chek.All misspelled words are my own..

[Roland Kunz]

Hello

The trouble is that the early S calipers are mostly worn out or stick so they donīt work like new. Those calipers where even used on the early 930. And Porsche gave approval for 330 HP/ 1500 kg in conjunction with a brake booster.

Good S calipers are rare and buy some new big reds.

With the early cars you canīt run to big pistons with the 19 mmm Master as it will have not enough cc to work to full pressure so you have to upgrade in 22 mm and you will need power assitance or a very heavy foot. But mostly if you have to step hard in the brakes you loose the modulation and canīt tip toe on the race track.

So the first quest is what is the background for the story. How will the car be used, what tires, rear axle trailing arm, shocks and torsion bars,.......

Many things to consider. Just puting on big Calipers will not work like the people think.

Biger ainīt better just be smarter.

Grüsse

[Bill Verburg]

Go to this site!

http://members.rennlist.com/sjanes/brakes.htm

[72SMFI]

Thanks Bill great site!!!