I have 18" wheels on my 2002 4.0L S-Type
They are the 25 spoke type, no idea what style they are called.
255/45/18 on the rear,
245/45/18 on the front.
If you put the 255 on the front it just starts to catch when on full lock only.

Apart from that, hunky dory

 

Remember to let your insurer know you've fitted non-standard sizes. (Many won't care - but you must tell them in order to stay insured.)

Also, if it did not originally come with those rims then tell them about those as well.

 

Just for reference, you have different nominal tyre diameters to original and also different nominal diameters front to back. Especially the second case could confuse the ABS/DSC which will have been calibrated for the standard diameter and the same diameters back to front.

The original size is 245/40-18.

 

Speedo will be wrong I think. But they over-read anyway...

 

NOT wrong there !!

i saw the other day whilst doing a instrument cluster re-flash
on my 03
that one of the parameters you manually set was rim size .
i think 4 options , largest one being 18'' .