I have the original owner's manual that came with my uncle's 1970 Mk1 V6, which is interesting. It lists the original tyres as 165/13 crossply. Naturally I'm not going to go with a crosspy, but the Rostyle wheels on the car currently have 185/75R13 on them - so what is the correct tyre size for the Capri?

The brochures of the day state that the wheels used were 5 inches wide x 13 inch rims and the GT/V6 model had 175 x 13 radial tyres fitted.

Here's a couple of pages from the 1970 12 page brochure and from the GT/V6 specific 2 page brochure.

Thanks for the information. What is the preferred diameter/size with modern tyres and what gives reasonable handling? 75 series are not that common any more.

205x60x13 if you want to go wider.  Getting harder to find but Maxxis still do them.

OK thanks for the information. The section size of the original tyres was not given, so I'll look that up to get the diameter. 75 section would be comfortable, but a bit baggy for handling. I have a spare set of 14" hotwires in the garage, 6" wide I think, but they'll need straightening. Will the 205/60/14 fit in the wheel arches OK?

It all depends on the offset.  The front guards and strut are very tight for 6in rims.  Rear not a problem.  I used to run 225's on the rear but cant get them any more in 13 in.

14" wheels I have are +20/22 offset from a Cortina, which might be OK.

To settle the original query - when I picked up my 1 owner 1972 V6 a few years ago the spare in the boot appeared to be the original tyre, still on the Rostyle rim.  Dunlop SP41 - 175 SR 13.  I still have the tyre with legal tread if anyone is chasing that concourse finish. 

that looks very familiar. What were the aspect ratio of these tyres - I've never run crossply.