Basically, can you put any tire ending in R17 onto any 17" wheel or is there a width factor too? It seems strange to think a 255 and 195 mm wide tire would go on the same rim, but they are made of flexible rubber?!

 

There is a limit. If you look up a particular tire size (255/40R18), it will list a range of wheel widths that are recommended (8.5" - 10").

You could not put a 255mm wide tire on a 6" wide wheel. In fact, most times a 255mm tire is not mounted even to an 8" wide wheel, even though that is how the XJR was setup from the factory.

-Caleb

 

so wheels have a width defined as part of the size? like 16x8?

 

Yes, wheels have a defined width. Just as a reference, here are all the various wheels installed on x308s and x350s over the years:

http://www.wheelcollision.com/jg4.htm

I forget what the guidelines are for maximum tire width on a given rim width. But as 1999XJR wrote, Jaguar was pushing it by putting a 255mm tire on the 18x8 Asteroids.

 

Thanks, that is a fascinating link

America has the stupidest measurement-standards, err, non-standards. Wheel-width is measured in inches, tire-width in mm, who thought that was a good idea?!

 

It's true that the different measurements are a bit confusing... inches for wheel, millimeters for tire width, percentage for sidewall, coding for speed and load rating, some ambiguous number for treadwear, and now they're putting on coding for roll resistance (mandatory in EU starting from 2013 I think).

The french car manufacturers (atleast Citroën) tried to make things a bit simpler, and used metric wheel sizes for a while in the 70's and 80's... it didn't quite catch on, and tires for those wheels are ridiculously expensive nowadays

 

The french car manufacturers (atleast Citroën) tried to make things a bit simpler, and used metric wheel sizes for a while in the 70's and 80's... it didn't quite catch on, and tires for those wheels are ridiculously expensive nowadays [/quote]

Michelin TRX - Wikipedia, the free encyclopedia

That's TRX wheels. BMW also afflicted their cars with them, at least the E28 5-series and E23 7-series that I've seen. The wheel diameter is deliberately made different (and in metric measurement) from a regular wheel, to make it impossible to put a regular tyre on.

I've heard that there's some TRX sizes that can have their flanges machined down to regular inch size and shape. I think it's 415mm to 16-inch that's supposed to work.

--
Roy