Apollo wheels - questions regarding rim width / tyre size

[XJ_Driver]

When I purchased my '97 XJR a couple of months ago it came fitted with a set of 19" Apollo alloys originally from an XK coupe. I think these look good and really suit the car, but the rear wheels / tyres are conspicously wider than the fronts (9J rims fitted with 255/40 19 tyres, as against 8J rims fitted with 245/40 19) which looks odd.

I imagine there must have been a reason for this with regards to XK fitment, but I can't see any reason for the difference being necessary on an XJ. I plan to change all four tyres soon - due to their age, rather than tread depth - and intend to fit 255/40 19 tyres to the fronts as well as to the rears. Before I do so I just wanted to check on the Forum that there is no reason why I shouldn't do this?

And to follow that train of thought one stage further, is there any reason why 9J Apollo rims should not be used on the front too? I did try swapping my wheels front to back yesterday, and over an extended test drive encountered no problems with front tyres fouling etc. and the wheels / tyres did not protrude outside the wheel arch. The steering was a little heavier, but otherwise surprisingly little difference to the drive overall. If anything I was more conscious, when cornering, that the (narrower) rear tyres were perhaps slightly less firmly 'planted' than usual but otherwise very little change.

Has anyone here had experience of using 9J rims on all four wheels of an XJ saloon? Or otherwise any reason why I should not fit 255/40 19 tyres to my existing 8J rims at the front? As ever, all advice appreciated. Thank you.

[J44EAG]

Rear tyres MUST always be wider than the front. That makes it legal.

Typically the wider tyres are fitted at the rear to afford extra grip.....especially for cars with superchargers.

Others will be able to help with general wheel rim details.

Mike K

[Orkney]

Now I'm confused,
I have a supercharged Daimler SV8 and all four wheels are the same width and tyre section as standard. Solar wheels with Pirelli P Zeros. XK's, I know had different wheel widths, but not supercharged 308's, or did I miss something? Did the law change and am I driving illegally now?

Rear tyres MUST always be wider than the front. That makes it legal.

Typically the wider tyres are fitted at the rear to afford extra grip.....especially for cars with superchargers.

Others will be able to help with general wheel rim details.

Mike K

[ptjs1]

I think what Mike meant was that rear wheels must not be narrower than front wheels, as opposed to must always be wider than front wheels.

Paul

[J44EAG]

Yip. thats what I meant.

Mike

[PTR200Jag]

I think what Mike meant was that rear wheels must not be narrower than front wheels, as opposed to must always be wider than front wheels.

Paul

Yip. thats what I meant.

Mike

Just to add to the debate I spoke to "my" MoT man re the wheel widths whilst there was a lull in proceedings in checking my GT6 exhaust emissions (is there any visible smoke? , no? ok, passed ! love the old cars!! )

Apparently there is NO regulation that requires the car to have wider wheels at the rear or vice versa ...however, there is the one re different size wheels per axle... so, if you turn up with a space saver attached to one side it WILL fail ! And you can't get away with putting TWO space savers on the same axle either! 'cos the speed rating / load ratings are not adequate