1958 plus 4 car on here we have the tr4 engine and are about to buy tyres crossply or radial apparently the radials don't allow clearance for exhaust etc crossply have more clearance recommended by Longstone tyres are 500/525 x 16 Avon Tourist tyres that car came with were 550 x 16 Avon tourist so were looking at a diameter difference of .5 inch x 2 = 1 inch less diameter car would be .5 inch lower? What did these cars originally have fitted at factory?
Rob,
Where is the clearance issue? at the frame front top lug, the inner part of the front wing , or on the exhaust system? Each of these issues can be resolved with some planning and a few hand tools, but it won't be a case of "plug and play". I used to drive a +4 flat rad on 550 x 16 Michelin (but they are long since gone I think) . I believe Tony Quinn is the only other +4 driver to use cross plies, and I may be wrong but I think he uses 550s. 525 will be fine , but your contact patches are now smaller so the car will be more "lively" with a lot more rear end breakaway (which you may prefer, it depends upon your driving style) and it will be more sensitive to tyre pressure changes so check them more often.
In the end I ditched the cross plies for some 165 x 16 radials, and the car felt much better (even though they were the ill-reputed Michelin X) .
