Finally! A solution!! What we have here is the ultimate short wheelbase 911 rear caliper solution. This kit is the cleanest, the easiest and by far, the least expensive way to get a real caliper on the back of your beautifully elegant SWB (1965-68) 911.
We field these questions daily...
"What calipers are out there to upgrade the rear of my SWB? I know I can bolt on a later front suspension and get A-Calipers and S-Calipers but, I'm not finding anything substantial for the rear. This 2.25" mounting ear spacing is killing me!!"
We knew there was a demand in the market for a "real" solution. Probably one of the easiest ways to visualize this is to layout what we've had in the past.
If you've built a sports purpose SWB car, chances are you'll want to (as did the factory) upgrade the braking system to accommodate your increase in performance and your potential to get yourself into, and now out of real trouble.
* In the beginning - SWB cars shipped with either a 356 caliper (the first 75 or so), an L-Caliper (which is the father of the later M-Caliper) or an M-Caliper/Spaced M-Caliper up front. These are all essentially "identical". They have 48mm pistons and a FMSI D31 pad. In 1967-68 the SWB S and L models had Wide M-Calipers up front and vented rotors but, the piston and the pads (bias and stopping power) were all the same. In the rear there were, again, the 356 calipers for the first few and the L-Caliper and finally, for our 67-68 S and L models, the "Wide L-Caliper". As with the fronts, these were all basically the same with the exception of the Wide-L. These 356 rears and rear L-Calipers all had 35mm pistons and the small FMSI D30 pads. The real problem is the smaller 2.25" mounting ears.
Now, this part is important so pay attention to what happened in 67... The Wide L rear calipers came along and received two things that their predecessors did not have:
1. 38mm Pistons - This created a 1.6:1 bias ratio that lived on until 1984.
2. M7 fasteners to accommodate the extra force generated with the larger piston.
These two modifications were done to the existing L-Caliper casting so, the dust boot flange was very thin on a Wide L. You "can" make an L-Caliper into a wide L-Caliper but that will involve boring them out to the 38mm size, re-cutting the beveled bore seal journal and boring the fastener journals to 7.2mm and finally, finding the NLA M7 fasteners to go into those journals. That's a lot of work and money and, you'd better have a machinist who knows what they're doing.
What's more important is what they "didn't" do... they didn't have a new casting so, the pad size remained at the very small D30 size.
Price is an issue here as well. When we get an inventory pair to restore and sell, they sell for $1,699.00 out the door. They're very rare these days. Now we're beginning to see why there's a need in the market.
* Will other calipers fit? There are a few ATE calipers that will bolt on to your odd 2.25" spacing (various Alfa and BMW makes) but again, the piston sizes can be either too small, just right or too big (as in 42mm for the 3.0 CSI rear calipers) and, again, you're stuck with the smaller D30 pads. You'll get a little more rear bias (which can be dangerous in the case of the 42mm pistons) but, no benefit of more friction material. No real benefit here.
* What about adapters? - We looked at various adapter styles and, none of them really made us feel safe and comfortable in a track situation. None of them really exist right now regardless.
* Can't I just change the mounting ear spacing on the rear control arm? - Yes, you're welding cast iron/steel. Make sure you know exactly what you are doing regarding welding cast metals. The item needs to be heated to 800º, welded with perfect penetration and then cooled properly. Probably not a great idea for a control arm on a really cool vintage Porsche and, not something I'd want to sink my confidence into at the track.
* Can't I just change the mounting ear spacing on the calipers? - Yes, read above regarding welding cast steel/iron. In fact, this project started out with the thought of designing "adapters" then "welding 2.25" ears on an M-Caliper" then... naaaa, that's all kludgey, let's investigate a radial mount. Perfect.
* I can have LWB arms modified for the SWB application. - As it stands, this would be the best alternative to this kit we're producing. It would give you a more modern bearing and the factory 3" mounts. However, what sounds nice on the surface requires a lot of parts, skill, expertise and money. You'll need:
1. LWB arm cores.
2. A pair of M-Calipers.
3. New bushings and bearings.
4. New LWB hubs.
5. New rotors.
6. Someone who is very skilled and knows "precisely" what they're doing with the suspension geometry.
7. A wheelbarrow full of cash.
That said, again, I like this conversion. It's just damn pricey and there's only a few smart cats out there doing such a thing. I'll guarantee that whatever they're charging, it's not enough.
So now that we know all of the pitfalls associated with getting a larger caliper on the rear of a SWB car, here are the benefits of this kit:
1. Factory Parts (basically...).
2. A true bolt on kit that incorporates all of the bits and bolts needed to get these calipers on your car.*
3. Larger rear pads to match any front caliper upgrades (A-Caliper or S-Caliper).
4. Larger 38mm pistons (like the 911S and 911L SWB models) for improved and factory 1.6:1 bias ratio.
5. A bolt on improvement that will not damage the integrity of your valuable SWB 911 whatsoever.
6. A pair of completely restored calipers. Fresh zinc plating inside and out. New 38mm stainless steel pistons and new ATE seals with proper square cut EPDM o-rings.
7. New caliper hard lines in factory OM steel with Cohline ends for a perfect fit.
8. Factory look through the wheels (you won't see any spacers or adapters or funky caliper locations).
9. You'll have vented rotors on the rear of your SWB 911.
10. SWB 911S and L owners will now have a larger pad in the rear.
11. Should be acceptable under most rules for vintage racing.
*this kit will require 944 rear rotors or the more expensive SWB vented rear rotors (at the time of this writing, around $450.00 each). The SWB vented rear rotors have the proper rotor mounting screw location to line up with you 911 hubs. The 944 rear rotors (@ $86.00) are indexed differently for those mounting screws but will work by setting the handbrake with a few open lug nuts.
Current pricing is $999.95 outright. $899.95 if you send in a pair of rear M-Calipers for this conversion (you will receive a $100.00 core refund once your restorable cores arrive at our facility).
Why is this a deal? A vintage L-Caliper restoration with stainless steel pistons is currently retailing for $579.95 (for stock L-Calipers) so, for an additional $320.00 you get upgraded calipers with all of the machining work, adapters, lines etc. and, you get to keep your original L-Calipers for posterity sake.
*this kit will require 944 rear rotors or the more expensive SWB vented rear rotors (at the time of this writing, around $450.00 each). The SWB vented rear rotors have the proper rotor mounting screw location to line up with you 911 hubs. The 944 rear rotors (@ $86.00) are indexed differently for those mounting screws but will work by setting the handbrake with a few open lug nuts. 944 Rotors must be turned down 2mm to clear.