The BRM Nascar rims just came in today's mail.
They are NOT identical in dimensions as the original Scalextric Nascar plastic rims. Specifically the centre rib width is larger, the same as Slot It 15's at a fraction over 5mm.

Not a bad thing. Looks like a Ninco F1 front tire will fit and there's no doubt Paul Gage will have a variety of tires that work.
The inserts are nice and cover over the aluminum rim edge so I don't have to paint them black. They measure .425" in diameter.

I hope some retailer in N.A. will carry them.
On to getting the chassis rolling.
Dan