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Rear wire wheel - a follow up

This is a follow up to my previous post concerning my attempt to convert the rear wheel of my Supersports to a wire wheel with a disk brake. I have just finished the conversion, having taken almost four months to complete. What have I gained? Well, I did accomplish the conversion. Other than making the car look better have I gained better performance? Probably not. Did I spend a lot of money? Yes! In addition to the costs of getting some of the parts machined I bought a plasma cutter to cut out the caliper mounting bracket from a steel plate and a MIG welder to modify the swing arm so the rear wheel would be centered when mounted. The next conversion will not be so expensive.

I already had the wire wheels on hand because I had them mounted on the front prior to converting those wheels to PMC 19" wire wheels. I bead blasted the wheels to remove the silver paint and repainted them with spray can paint as close to the same red color as the front PMC wheels.

In this first picture I have laid out the final components of the conversion parts. Left to right is the wire wheel mounting hub originally from an MGC. The hub has been machined to remove some unneeded metal and the outside diameter has been reduced to fit inside the next component, the Wilwood disk brake "hat" (part # 170-8493). Fastened to the "hat" is a Wilwood steel brake rotor (part # 160-0201). The third component is a 2CV rear wheel brake drum suitably trimmed, machined and drilled for five wheel studs on which the disk rotor, hat and wire wheel adapter hub will be mounted. The studs are Dorman 1/2-20 (part # 610-173.1) pressed into the 2CV drum. Fourth is the disk brake caliper bracket which I had to design to bolt to the swing arm and to hold the Wilwood single-puck disk brake caliper (part # 120-2498). Finally, is the 2CV left rear swing arm which had to be shortened by about 3/4" so the final wheel assembly would be centered in rear of the car. All of the studs, pins, rivets were remove to accommodate mounting the disk brake components.

The swing arm with all the pins and other protuberances removed

The caliper mounting bracket

The view showing the mounted disk brake components. The Wilwood caliper mounted on the custom bracket; the brake rotor; the flexible brake line; the newly painted wire wheel.

I eliminated the rear coiled brake line inside the rear axle buy making a brake line adapter which allows connection of an AN-3 stainless steel sheathed flexible brake line between the Wilwood caliper and the 2CV master cylinder. This is an adapter which could be used by any builder wanting to eliminate the original rear coiled brake line. The Wilwood caliper calls for DOT 4 brake fluid and, of course, the brake system of the 2CV uses LHM fluid. I know one shouldn't use DOT fluid id an LHM brake system. But, I've not seen any prohibition on using LHM fluid in a DOT component. So, I immersed some DOT seals in LHM fluid for several weeks without seeing any deterioration. I am using LHM fluid in the rear Wilwood brakes to see if it will work. If not, there will have to be some further problem solving. We'll see.

Left side view and right side view of the newly mounted wire wheel.

I will be conducting operational tests for a few weeks. My immediate concerns are: Will the LHM brake fluid be suitable in the Wilwood caliper? Did I properly align the axle on the rear swing arm? Will my welding on the rear swing arm hold? First test drive went OK.

Bob GilPatrick

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