SC rear brakes on 68

[stubble88]

I have a full set of freshly rebuilt SC calipers. So I would to get the rears to work on my stock 68 trailing arms. Bolt mount holes are not the same. Is there an adaptor? What vented rotors would I use? SC rear rotors will not work. Too deep. Way different. If this is impossible then what’s the next best thing? S calipers? Thanks.

[bkreigsr]

Please explain 'Too deep'.
I did this conversion to my 76 912 and the SC vented rotors worked fine.
But, probably a world of difference in the 68's geometry?
Bill K

[carwash]

SWB arms have a caliper mounting bolt pattern that matches no other. I am putting 996tt calipers on my SWB 68 and it has been quite a nightmare making adapter brackets. I will look for my thread on it and post a link here...

[carwash]

Short Wheel Base arms with 996TT brakes

[stubble88]

Originally Posted by carwash

Short Wheel Base arms with 996TT brakes

Why would you go that big?

[carwash]

Originally Posted by stubble88

Why would you go that big?

There was supposed to be a link in that reply. I will have to look it up again.

Why? Why not? It’s sentimental. I had them from a previous car that was totaled. Nobody else has done it that I’m aware of, that was reason enough.

[carwash]

Short Wheel Base arms with 996TT brakes

[1QuickS]

You can put SC rotors on the rear if you get longer studs and make a spacer to go between flange and disc. Deep 6's (5 1/2's or 7's if you re-work the body to accept them) are needed when you use the SC disc. The outside diameter of the disc may also need to be reduced by a small amount to accept SWB 911S calipers. SWB 911S calipers are fine when used with SWB 911S calipers in front but if you use larger calipers (aluminum 911S, 911SC or others) in the front then your brake balance will be upset (too much front brake) and you will then want a brake pedal assembly with balance bar, possibly with two different diameter master cylinders.

I know this from personal experience.

[stubble88]

Originally Posted by 1QuickS

You can put SC rotors on the rear if you get longer studs and make a spacer to go between flange and disc. Deep 6's (5 1/2's or 7's if you re-work the body to accept them) are needed when you use the SC disc. The outside diameter of the disc may also need to be reduced by a small amount to accept SWB 911S calipers. SWB 911S calipers are fine when used with SWB 911S calipers in front but if you use larger calipers (aluminum 911S, 911SC or others) in the front then your brake balance will be upset (too much front brake) and you will then want a brake pedal assembly with balance bar, possibly with two different diameter master cylinders.

I know this from personal experience.

I was wondering about the spacer. What size?
All I need is a damn adaptor for the rear and I’ll have sc brakes all around.

[carwash]

no one makes an adapter.... thats your biggest problem.

[1QuickS]

I don't recall spacer dimensions, I measured all components & machined them at the time I set them up. The idea is to adjust thickness of spacer so disc is centered on the caliper.

I looked at removal of brake mounting tabs and welding/machining new tabs but stayed with 911S calipers. Plenty of braking power & bolt-on convenience. Unless you are using race rubber I doubt you can utilize larger brakes in the rear, especially with a good brake pad compound. I made a dual master cylinder brake pedal box & needed to use two different diameter master cylinders and the balance bar to reduce front braking force to balance it out with the rears. I had alloy 911S front calipers with SWB 911S rear calipers and 205/50 fronts and 225/50 rears. Point being SWB 911S rear calipers have plenty of braking capacity, especially with typical tire sizes/compounds you might use on a SWB chassis.

Changing calipers is more involved than just bolting them on, front-to-rear brake proportioning and pedal effort are affected and need careful review.