SWB brake gurus...

[mjmoran]

I am looking to see if either Carrera M type or earlier rear calipers will fit the front of a SWB 1968 911. My 68 has solid rotors and brake cooling is impossible. The brakes as they stand can barely handle a fast 30 min session on the track (SRP, PIR, SIR) and this past weekend I froze out both inboard pistons in the front as well! This is with using ATE super blue, porterfield R4 pads, Ti pad backs, and no backing plates. The weather is not even hot and there was even a bit of rain...hate to see what could happen in June! Anyway, it looks to me that I could fit a set of Carrera (or earlier) vented front rotors and the same rear M type calipers in the front for a huge benifit in heat sink capabilities. The Carrera with the wider venting preferrable of course and working down from there.

I could then fit the front caliper off my 68 to the rear to work out the break bias issue. Better yet, I could fit a earlier rear M type off a T,E,S and a vented rotor as well. Although I have heard that the rear hats on >69 cars will not fit a SWB car ( I have not tried this though). There is other talk of a 944 rear rotor fitting with a small amount of machine work

Does anyone know if this will work? If not, what will. I am not wanting to change out the front suspention to a later style as some have done as this is a completely original car and I would like to keep as much of the originality as possible.

So bring it on...

[304065]

Saw this on the S registry but I'll post here.

Before you do any of those mods, switch to Pagid Orange and Castrol SRF fluid. Neither are cheap, but I've run an entire club racing season on ONE purchase of each (six races, including two 90 minute enduros) in a 2300 pound 911 on 6's with Hoosiers. I have Aluminum "S" calipers up front and vented rotors, however, but try the fluid and pads first, they are a way cheaper fix, and both are significantly superior to the ATE and Porterfields (I used R4s for AX but like the Oranges better for racing).

[Jerome Ryals]

Michael, I don't know if this helps or not but the 68 911L's had vented rotors, used a small spacer plate to mount the calipers to the hubs, otherwise the same calipers, etc were used. Thought this may help, good luck. Jerome

[mjmoran]

Thanks Jerome and John.

John, the main problem lies in that there is no cooling either rear or front with the solid rotors...using SRF or better pads is a possible fix for a lap or two, but they will overheat as well without cooling -- everything does eventually.

Jerome, yes both the 67S and 68 L/S had vented rotors. I have a 67s (306317S) and have thought of just adding the spacer in the caliper as the factory did...although my thought is they are probably the same or better in later years with the M caliper. Also splitting the caliper is a PITA! From my readings, the M caliper in one form or another was used in 911s from early 901s up to 89 Carreras. Logic says that I should be able to add a late model 89 Carrera rear M type caliper on the front and have loads of cooling for track sessions.

Before I start looking and buying calipers though, I thought I would see who has done this in the past...anyone???

Thanks,

[Grady Clay]

Michael,

Here are some of the big issues and potential solutions.

First, in the rear a ’69 and later rotor won’t fit because of the difference in the parking brake. Yes, it is possible to fit the ’69 and later parking brake assembly with a lot of work and some custom and modified parts. The easiest solution is the ‘67S and ‘68L/S vented brakes. The disadvantage is it still has the 356C size pistons which limit the size of the front brake pistons.

The front SWB struts have a separate caliper mounting plate. This allows you to modify or replace it with a custom caliper mount to accept almost any caliper. The best solution is to replace the entire front suspension with ’72-’73 parts. That includes; cross member, steering rack, tie rods, A-arms, ball joints, struts, hubs, rotors, calipers, and all the associated little parts. The additional benefit is improved handling and less expensive and more available components. I enjoy this setup because I can trail brake into a corner right on the limit of traction and not feel like it wants to lockup a rear and swap ends.

My original ’68 Normal came with S brakes because I ordered it with Konis and sway bars. Porsche included the vented brakes NC. Very soon I converted the front to the later components. It now has the original ‘68S brakes in the rear and ’73S in front.

The other big issue is air flow through the brakes. My little GT-2 914-6 has aluminum S calipers in front and M in the rear. The difference is there is huge air flow. The fronts have two ducts to each wheel. One is 6” from the front valance and the other is 3” also from the front but has fan assist (a regular 911/914 fresh air fan.) The rears have similar fan assisted fresh air from the front via the heater tubes and flex ducting. Additionally all four BBS modular wheels have brake fans. Even with stock street pads and non-trick fluid there never was a brake problem even at altitude and 100F+ with race slicks in heated competetion.


Best,
Grady

[mjmoran]

Thanks Grady...some very useful information. So another ? then is can I use a 68 rear rotor (to retain the parking brake) and a later M style caliper with a larger piston for brake bias?

So, sounds like I can have a new front plate made to adapt to the suspention and put A calipers on the front and possibly Ms on the rear...

I do have a spot for ducting to go to the front for cooling via the fog light openings in the lower valance. These will go to some custom backing plates similar to the AJ USA set up..

[Grady Clay]

Michael,

To use an M caliper in the rear requires different caliper mounting bolt spacing. You can make an adaptor or weld a new ear on the trailing arm. You want to make sure that the pad covers the rotor surface and none hangs off the side. That is a reasonable solution. You want to err on the side of more front brake.

To answer your specific questions; yes, you can use the ’67-’68 vented rear rotor with an M caliper with suitable modifications. Yes, you can adapt S or A calipers in the front.

Unless your class rules preclude it, I still recommend you up-date to the later front suspension. There is a remarkable difference.

Apparently the 993 style brake air deflector is very effective and simple.

Best,
Grady

[mjmoran]

Grady,

Thank you for all the answers to my questions. I have been aware for a long time now that the updated suspention is a great improvement and this may be in my best interest. I was hopeing to, for my own stuborness if anything else, look for another alternative to this though.
Since I am just DEing and regular track daying the car there are no prohibative rules and the update may soon come. In the meantime, I may try some of these other methods. I have a set of Carrera M calipers that may work on the front and some 2,7 calipers for the rear. The bias should be the same...but I will see. I did not realise that the rear spacing was off as well...Gotta love the SWB trials...always a new obsticle to overcome.

cheers,

[Vintage911Racer]

Vented or sloted rotors may be the ticket. I have run the stock brakes on my 67S for 5 years before switching over to "A" Calipers. I never had any brake problems. I do use Pagid orange pads with ATE sloted rotors. Yes, I work them hard and pad life is not the best, but no problems with heat or stoping power.

Maybe you are using the bakes too much. LOL

[Steve Marshall]

I think the big issue on ugrading brake on the early cars is the bolt hole spacing for the calipers. As I recall there are 3" spacings and 3.5" in spacings. These are the holes on the spindle where the caliper mounts.

I recall that some cars early cars with S options had the 3.5" spacing. It doesn't sound like yours does if it has solid rotors. Thus, bigger breaks could require new spindles too. I would confirm this prior to laying out cash for new calipers.

Also, if you are new to track driving,... more to follow my laptop battery is dying....

[Steve Marshall]

If you're new to track driving I'm betting your braking technique could use some improvement. This is cheapest brake mod you can make. Also... SRF/Pagid Orange combination is great for early to mid year 911's. It ain't cheap but very dependable and worth the money.

[mjmoran]

Mark,

Your right. The only addtion that I am looking for is a vented rotor. I run my 67S with all stock brakes no problem on the track. My 68 L is one of those Porsche odd balls with solid rotors, but the rest of S options. I have found an old set of 74 M calipers with old rusty rotors that I will do a test fit in the front. Also, I have heard of 944 rotors fitting the rear witha small bit of machine work on the hats. That will give me much more cooling.

Steve, yes there is all different spacing for the brakes. The early SWB cars have the narrow spacing both front and rear though. In 69 for the B models the "s" struts were designed that allowed 3.5 spaceing. This will allow both S calipers or Carrera M calipers to fit...This is why Grady has mentioned a strut upgrade along with the suspention improvement.
I am not new to tracks though. I am a PCA driving instructor as well as having an SCCA and POC license and have been drigin on tracks in Porsches for over 20 years. Your point is well taken though and a good suggestion to many.
I am surprized that many of you use SRF over the ATE or Motul 600. The cost per liter is quite a difference. I realise that the wet boiling point is more, but with effective cooling and continuous flushing of the fluids the ATE and Motul should be fine (and $12/liter v. $75/liter...ouch!)

Thanks all for this contribution on the tread. I will keep everyone updated on my modificatinos.

Cheers,