Mix and match brake upgrade question

[dd74]

I recently purchased the entire front suspension of an SC for my '74. I was really after only the struts to supplant the bent strut I currently have. But trying to find a 3-inch-spacing strut was difficult, so I decided to go with a 3.5-inch-spacing strut to fit on larger SC brakes - I've heard this is a worthy upgrade.

So I have everything - from the aluminum crossmember to the steering rack, "A" calipers, rotors, tie rods, OEM 19mm torsion bars, struts that have been reinforced, Bilstein HD inserts, steering rack, A-arms, etc. I don't know yet if I'll be using all the parts, nonetheless there's a good chance there will be much hardware left over from this swap.

I plan on getting new brake pads and OEM rotors - I can't see the true value in slotted or drilled rotors for a street/occasional track car.

Beyond that, my question is what, if anything, can I use off my current brake system with the SC brakes? Or would I even want to mix and match parts from my old brakes with the SC brakes?

Thanks in advance.

[KTL]

Just my opinion, but i'd take the SC brakes themselves and trade them/turn them around to fund Carrera brakes. Shouldn't cost a whole lot if anything. Used Carrera calipers are somewhat plentiful I think. Then you can use the thicker 24mm rotors all around instead of the SC's thinner 20mm rotors.

Not sure how the characteristics of your car will change using the SC/Carrera stuff with your non-vaccuum boosted master cylinder and if you may need to add a proportioning valve?

If you choose to install it, be sure to relube that "new" used steering rack you got. Worthwhile and easy to do:

Rack Rebuild Topic

[Bill Verburg]

I agree w/ Kevin that the Carrera front upgrade is worthwhile, though it is likely to be unnecesary unless you have significantly increased your cars speed potential.

As far as the SC front end, bolt it on, use the oem m/c and rear brakes. There are no compatibility issues there.

If you do go for the Carrera mod, only do the front. Again no other changes are necessary.

[palle7688]

As Bill.
If you never use your brakes hard it's waste of extra weight with the thicker Carrera rotors. The wider rotors can absorb/dissipate more heat.
Except for width the Carrera and SC calipers are the same.
Rear are diff. SC has smaller 38 mm pistons vs. 42 in Carrera.
SC front brakes are a worthwhile upgrade.

[KTL]

dd74 has a 3.0 in his 74, so I figured the Carrera brakes would be a good step up from the SC calipers and rotors.

Certainly can't hurt to have some extra thermal reserve? Especially if he does any future work to further increase the speed of his 911.

Bill,

Any texts you'd recommend for general brake sizing/configuration on vehicles? I'd like to have a little better grasp of the principles that determine the brake bias of a complete brake system.

Thanks!

[Bill Verburg]

Kevin,
I've seen a couple of decent books but can't remember the titles or authors. Most of it is just physics and experience.
Primary Variables that influence bias are[list=1][*]hydraulics[*]rotor diameter[*]weight transfer[*]coefficient of friction m[/list=1]

the hydraulic bias is just Physics 101.

Rotor diameter and m have a direct linear relationship on bias

weight transfer is directly proportional to vehicle mass, g, height of C_g and wheel base

There are other peripheral varibles such as caliper stiffness, line stiffness, mount stiffness, suspension mounting stiffness, pad material/substrate stiffness, resonance characteristics of the system, thermal related variations in the above

[Randy Webb]

Try starting at stoptech.com

[KTL]

Thanks for the info. Bill and Randy.