SUNBEAM REAR BRAKE and CYLINDER CHOICES
There has been much discussion about the Sunbeam needing a better braking system. I for one believe the stock front disc system is adequate even though the replacement parts are becoming more difficult to obtain.
The rears being drum type have often made me wish Rootes would have gone with the disc also. In attempting to improve the rear brakes for my Alpines, I began searching for a suitable system. I discovered a friend had used the 1992 Saturn SC disc caliper on the rear of his Alpine. Later, when he changed out the rear axle carrier for a FORD he also changed the front calipers and rotors to 11 inch. I was fortunate to get his discarded Saturn Calipers because they were now a mis-match/non-compatible with the new fronts.
My Draftsman/Engineer friend was instrumental in design and laser cutting a set of Brackets, Spacers and an E-Brake levers that mates to the Alpine & Tiger. Of course, there were plenty of trial and errors too! Below is some information dealing with the brakes, master cylinders, wheel type and sizes. Hope you can glean the tidbits you need to make the right choices.
The critical factor regarding the master cylinder size is the required brake pedal effort being compatible to brake cylinders, changing from drum to disk brakes should not make much, if any, difference. Rear disk brakes will be more reliable, less fussy to adjust, easier to maintain, easier to get parts, etc., and will stop the car equality or better than properly operating drum brakes. If the cylinder diameter is the same, there is no difference in hydraulic pressure produced by a single output master cylinder or tandem master cylinder. As far as which style of master to use, I'd use the dual (tandem) type for safety. If you will not be using the power boost, I'd start with 11/16" combo with the Saturn caliper which should give the braking feel similar to that of Series I & II cars. If you go with 3/4" it should work just fine but be a bit more on the hard side, performing almost identically to the 11/16" but provide more reserve fluid.
Rootes figured out suitable master cylinder sizes a long time ago. Series Alpines with a brake booster had 0.875" (7/8") master cylinders. Series Alpines without a brake booster had 0.700" (Series I / II) or 0.750" (Series 3 / IV / V) master cylinders. An Alpine with a 3/4" master cylinder, no brake booster and a stock brake pedal is OK, but it may require a fair amount of leg strength to make a hard stop. An 11/16" tandem master cylinder should be a good combination for the Saturn caliper. In theory, the Saturn rear disk setup may provide a little too much rear brake bias, so depending on your installation a proportioning valve may be needed.
Currently, as of this writing, I am satisfied with my Stock Wire 13” arrangement for my SIV Alpine. I must say the Stock Steel 13” wheels are unavailable at present. They are proving too much difficulty for a proper fit. Components will be available for some 14” and 15” wheels for the Sunbeam Alpine & Tiger. I have found the PanaSport 14 & 15 x6 & 7 inch wheels fit nicely. My Ron’s Mags on Blue Boy which are 15x7’s need ¼” spacers between the wheel and hub for clearance between the wheel and caliper.
I also have fitted a Center Line 14x6 wheel without any clearance problems. I have fitted a Pinto 13x5.5 wheel that has the FORD logo and part number E D6ZA 1007-BB-X utilizing a ¼ to ½ inch spacer between the wheel and hub.
Utilizing a Tiger rear carrier for a mock-up I have some good results to report.
My goal is for Sunbeam owners to have an optional rear disc caliper for their Alpine and Tiger vehicles whether fitted with stock 13” wire OR stock steel wheels OR 14” and 15” wheels.
Open to suggestions......