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Rear wire wheel

Hi David: Here is an idea that I have been kicking around for several months. I’m just throwing the idea out for thought not as a fait accompli.

I want to mount a wire wheel on the rear suspension arm of my Supersports. I also would like to see if I could convert the drum brake to disk brake, and, I would like to use as many and as much of existing components as possible.

The rear suspension arm and 2CV rear wheel are already mounted. In order to replace the existing rear 2CV steel wheel with a wire wheel I will have to use a PMC adapter which will position the rear wheel to the left of center by about 1”. One possible solution is to modify the rear suspension arm by cutting out 30mm or so and re welding the axel and drum brake housing back on to the suspension arm. This will have to be done while to suspension arm is still mounted on the axle because the arm can’t be taken off as there is not enough room between the mounted arm and the side of the body and the body cannot be lifted off the chassisto remove the arm.

I started by buying a rear left suspension arm, stripping off the drum brake components, cleaning off the dirt, rust, brake dust and other gunk in a bead blaster. I then put on a thin coat of rust preventative black paint and mounted the arm in a vice so I could more easily work with it.

The next component I sourced was a 2CV rear brake hub. I had the hub in my spares, luckily.The wire wheel I am using is the 48-spoke MGA type. The tire I have mounted is a Firestone 145 R15 with tube. The wire wheel adapter is to be mated to the 2CV wheel hub. The 2CV wheel hub has a large undrilled flange with the three wheel studs pressed in to holes at the very outside of the flange. If the studs are removed you have a large flat surface on which you can mount the wire wheel adapter. The adapter must remain removable from the wheel hub flange because you must be able to mount the hub and bearing to the suspension arm axle in the conventional 2CV manner with the large, high-torque holding nut.

I found that the MGA/B wire wheel adapter does not have a large enough mounting flange to be able to be able to drill matching mounting holes in the 2CV wheel hub flange. The MGC adapter, however, has a much larger flange with holes that fit to the 2CV hub. I purchased a set of used MGC adapters on ebay. After they were delivered I noted that the MGC adapter is very heavy and, for my purposes, could be relieved of much of its weight through machining.

I took the left side MGC adapter and the 2CV wheel hub to a machine shop and had the adapter lightened by boring out the inside and flattening the back side. Then the 2CV hub was drilled with six ½" holes to match the holes in the adapter. I also lightened up the hub by having the mounting flange cut down to the diameter of the adapter

I mounted the wire wheel on the finished assembly and was pleased that the center of the wheel is the same distance from the side of the suspension arm as the existing steel wheel which is centered in the rear of the chassis, about 10½". So, the wire wheel is centered without using the PMC adapter and cutting the suspension arm.

However, I have not yet made provision for a rear brake. Would the very effective 2CV front disk brakes be adequate to stop the car without a rear brake? That might be the case and I could quit at this point and mount the components I have fabricated so far without having to remove the suspension arm. I would only have to first remove all the original drum brake parts and cap off the rear brake line. It would be tempting to do without a rear brake but would it be safe? I decided I better be on the safe side, so the next phase of the conversion will be to try to develop a rear disk brake.


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