The ultimate brake upgrade page.

[911pcars]

Originally Posted by Flojo

Hello, what 28mm Discs to get?
I can only source the 24s for a plug and play mount to the SC hub (Sebro 275197 or Zimmermann 45662Z).

And what hard line do I get to adapt the 964 caliper?
re-bend the SC line? get the 964 line and re-bend?

Thanks

My archived notes (thread by Bill Verburg, 2002) say the front rotors from a 1986 944 Turbo can be used (298 x 28mm), same as used on the brake kit sold by VCI;

944 turbo brake upgrade

In another thread (2009),
Kevin L (KTL) adds that the 944 Turbo rotor must be spaced outward on the spindle approx. 5mm (~0.20”) to center the rotor within the caliper…….

…. and that a C2 front rotor (same size, different offset) will work with the rotor slipped over the front hub (hub OD machined to fit), a setup created by Steve Timmons (Instant-G).

https://forums.pelicanparts.com/porsche-911-technical-forum/493457-c2-front-caliper-sc-carrera.html

Sherwood

[Bill Verburg]

Originally Posted by 911pcars

My archived notes (thread by Bill Verburg, 2002) say the front rotors from a 1986 944 Turbo can be used (298 x 28mm), same as used on the brake kit sold by VCI;

944 turbo brake upgrade

In another thread (2009),
Kevin L (KTL) adds that the 944 Turbo rotor must be spaced outward on the spindle approx. 5mm (~0.20”) to center the rotor within the caliper…….

…. and that a C2 front rotor (same size, different offset) will work with the rotor slipped over the front hub (hub OD machined to fit), a setup created by Steve Timmons (Instant-G).

https://forums.pelicanparts.com/porsche-911-technical-forum/493457-c2-front-caliper-sc-carrera.html

Sherwood

I have never said that 944 rotors can be used on a 911

[911pcars]

Originally Posted by Bill Verburg

I have never said that 944 rotors can be used on a 911

Bill, I stand corrected.

944 Turbo rotors are 299x28mm, used by VCI in their upgrade kit (front) and used by others.

You suggested the larger 930, 309x28mm rotor (rear) to avoid pad overhang. That right?

S

[Bill Verburg]

Originally Posted by 911pcars

Bill, I stand corrected.

944 Turbo rotors are 299x28mm, used by VCI in their upgrade kit (front) and used by others.

You suggested the larger 930, 309x28mm rotor (rear) to avoid pad overhang. That right?

S

When I used 964 calipers on my car I used 930 f/r rotors, 304x32 front and 309x28 rear, It was so long ago I forget the reasoning, but I seem to recall that they were the best fit that was available for a 911 w/ 964 calipers, Today I would probably use the same rotors w/ 993 calipers. Currently on my hot rod I have 993RS calipers and rotors, Same as on my track car

[911tracker85]

my 78 SC/930 conversion still had the original SC brakes and suspension.

got a set of 930 calipers, just got the rears back from being modified to fit.

[spuggy]

Originally Posted by 911pcars

…. and that a C2 front rotor (same size, different offset) will work with the rotor slipped over the front hub (hub OD machined to fit), a setup created by Steve Timmons (Instant-G).

https://forums.pelicanparts.com/porsche-911-technical-forum/493457-c2-front-caliper-sc-carrera.html

Sherwood

The hubs Instant-G supplies for the 993/993TT/996/996TT kits - which use the appropriate factory rotors for each caliper BTW - do not use 911 hubs AFAIK. It's been years, but seem to recall him saying there was not enough there to safely machine them down when I bought my 996 conversion.

Someone else said they were machined-down 951 hubs, but i dunno...

If you go with an Instant-G kit, for best results budget in a dual-master pedal box/Fabspeed conversion as well. Otherwise the front bias inherent in all of those setups leaves a lot of potential on the table.

But the rotors/pads don't wear, and brake bleeding becomes a 2-3 year maintenance item because brake fluid is hygroscopic...

[911tracker85]

Otherwise the front bias inherent in all of those setups leaves a lot of potential on the table.

when I did the boxster caliper upgrade to my 85, I replaced the factory rear bias valve with a tilton adjustable. completely opened up the rear bias and the rears never locked up prematurely.

now when I tried this on my 86 951 build I did not open the rear bias much before they were locking up.

I plan to install an adjustable bias valve on the rear line. expect that will give me enough adjustablilty to max the braking.

[Bill Verburg]

Originally Posted by 911tracker85

when I did the boxster caliper upgrade to my 85, I replaced the factory rear bias valve with a tilton adjustable. completely opened up the rear bias and the rears never locked up prematurely.

now when I tried this on my 86 951 build I did not open the rear bias much before they were locking up.

I plan to install an adjustable bias valve on the rear line. expect that will give me enough adjustablilty to max the braking.

Boxster/Boxster on 3.2C rotors has a native brake torque bias of 1.669
Boxster/WideM on 3.2C rotors has better bias @ 1.554

911 goal for bias is ~1.5('72- '83 is 1.491) or even a little less if the car is setup for it, Both of mine have 1.426

A p/v can only move bias forward, having too much front isn't dangerous it just leaves brakeing potential on the table. W/ either of the above Boxster changes(I refuse to call them upgrades) you wouldn't want any p/v

[911tracker85]

A p/v can only move bias forward, having too much front isn't dangerous it just leaves brakeing potential on the table. W/ either of the above Boxster changes(I refuse to call them upgrades) you wouldn't want any p/v

dont understand....

there is no bias valve on the front brake line, but there is on the rear.

so if you remove the bias valve from the rear line and replace with adjustable, you can increase the amount of brake pressure to the rears. dont see how that affects the front pressure? that is how I see the system and how it worked for me. and when trying this on my 951, the rear calipers are big enough they start locking up as I opened the bias valve on that line.

[Bill Verburg]

Originally Posted by 911tracker85

dont understand....

there is no bias valve on the front brake line, but there is on the rear.

so if you remove the bias valve from the rear line and replace with adjustable, you can increase the amount of brake pressure to the rears. dont see how that affects the front pressure? that is how I see the system and how it worked for me. and when trying this on my 951, the rear calipers are big enough they start locking up as I opened the bias valve on that line.

there is no bias valve on the front brake line, but there is on the rear.

correct, a 3.2 C has a 33bar p/v on the rear circuit

so if you remove the bias valve from the rear line and replace with adjustable, you can increase the amount of brake pressure to the rears

no, a p/v can only reduce line pressure on the circuit, an adjustable one just allows you to vary the amount of reduction. It is true that an adjustable might increase the line pressure above what the stock 33bar one would allow, But it will never allow more than an open line. bias is derived from integrating the effect of the brake torque in front w/ the brake torque in back.
target bias fora 911 is ~1.5
a stock 3.2 is 1.220 below the 33bar knee and 2.260 above it, below the knee is too much rear which is fine as long as the rear tires have enough grip and above the knee is too much front, this is the safer regime and also fine until the front tires grip is surpassed. An adjustable p/v justs changes where the knee is

[porschke911]

I'm in the process of installing 993 calipers on my 73 911. I notice a few installs use square aluminum stock as a front adapter. What size stock do I need and is it standard 5051 aluminum?

[Jeff Alton]

Originally Posted by porschke911

I'm in the process of installing 993 calipers on my 73 911. I notice a few installs use square aluminum stock as a front adapter. What size stock do I need and is it standard 5051 aluminum?

Measure and machine as appropriate. 6061 T6 would be a good choice.

[Flojo]

Bill, please, what connecting hose do you use between the caliper and the hardline?
Thanks,
Flo

Originally Posted by Bill Verburg

993RS/993tt

[Bill Verburg]

Originally Posted by Flojo

Bill, please, what connecting hose do you use between the caliper and the hardline?
Thanks,
Flo

The pic is of my C3 w/ 993RS brakes

here's the line



With the 964 on 930 that I used to use

[Flojo]

thank you, that's the one.
I was looking for such a line... jus ordered a set of custom made ones.

Originally Posted by Bill Verburg

T
here's the line

[porschke911]

Another question as I progress with my 993 brake install. Does one modify the brake rotor backing plate or get rid of it?

[Flojo]

Originally Posted by porschke911

Another question as I progress with my 993 brake install. Does one modify the brake rotor backing plate or get rid of it?

racers would leave them off, better air-to-disc access and some weight saving.

you can do this though:

[porschke911]

Thanks. That is kind of what I was thinking since alot of the pictures of upgraded brakes don't show the plate.

[Flojo]

Anybody modified SC front hubs to carry 930 discs?
What to do? I recall from somewhere that the diameter must be reduced? Is that all? What are the specs?

Thanks!

[911tracker85]

Anybody modified SC front hubs to carry 930 discs?

I am on the same quest.