For the purpose of adding to the technical database, I thought it would be useful to provide an update on my project of converting from 4 lug wheels to 5 wide wheels at the rear.
As background, my car is a 57 Vintage Speedster made in 2000 with a short swing rear axle and 4 lug Mangel 15x5-1/2 wheels all around. Vintage Speedster uses +69 backing plates (with the brake adjusting holes) on all of its IRS builds as well as its swing axle buids, as reproductions of these backing plates are readily available. Vintage fit the rears with the type 315 brake shoes (40mm wide) and 69+ wheel cylinders as these are compatible with the 69+ backing plates. To get the 4 lug rear brake drum to fit on a short swing axle Vintage cuts the hub down to enable the castle nut to properly fit with the necessary cotter pin hole access. This is how many of their short swing axle cars are made.
It is relatively simple, if this is your set up, to convert from the 4 lug set up to run 5 wide wheels at the rear, e.g., Mangel 15x5-1/2. I was lucky enough to find a set locally, which were basically NOS.
What you will need to do is buy 67 drums that are German or Italian made. These drums are available from So Cal Imports, and can be identified in the part number by the "IT" at the end. These drums are technially made to be compatible with the smaller width type 270 shoes (30mm wide) that are consistant with the shoes run in 1967. However, these drums are actually cut having a friction surface of about 43mm (wider than their Brazilian made counterparts). While you would think that this would permit running them with the 315 type shoes, it's close but upon tightening the castle nut the drum will bind on the outside edge of the shoes. So out of the box they will not work.
But, here is the trick. Have a maching shop, i.e., one set up to resurface drums, simply cut the drum friction surface an extra 5mm or so (all the way to the inside wall of the drum). Once this is done the drums will fit over the 315 shoes, and permit tighting of the castle nut with proper access to the cotter pin hole and you are set.
Also, changing from the 4 lug rear drum to the 67 wide 5 drum moves the wheel mounting surface about 1/2 further inwardly towards the backing plate, giving you another 1/2 in of rear fender clearance, which is precious for those seeking to run tires wider than the 165Rx15s.
For the fronts, I am planning on running AC Industries' wide 5 disc brake conversion kit.
So there it is for anyone in the future looking to make this rather common conversion at least for a Vintage Speedster with a short swing axle rear setup.
Thanks, Grant
