Col wrote:

I think you would struggle to get a 255/55 x 20" fitted under the car, I manage to get 275/45 x 21" in

Hi Col,
There actually 7mm narrower Larger diameter than the ones you had

Hi KevH,
bit of ManMaths for you for every kilometer that you drive with that wheel/tyre combo it will want to rotate 3 more times than the rest of them 40 times for the 20" and 43 times for that 19"
Diffs are designed to do this but you dont get many 1Km roundabouts
the wheel speed sensors will pick up the speed difference and try to sort it out, so you may get traction/ABS/stability warnings
only real way to tell is try it
Have a go with the search button and you will find other threads.

I would still have gone with a s/h 245/75/17 on the wheel you already had as an emergency combo or waited to pick up a matching 20" wheel and same size tyre

 Porsche Cayenne 2022
gone Porsche Cayenne 2020
gone Corris Grey HSE Dynamic 2016
gone Ipanema HSE lux 2010
gone Rimini HSE 2005
!!

Hi, couple of tyre comparison sites I looked at definitely had the 255/55 x 20" which the OP says he has fitted to his car, at a larger diam. than the 275/45 x 21" which with a new tyre fitted will fit under the car inflated with a little bit of a small "engineering" mod with a rotary file to a couple of brackets.

Click image to enlarge

Hi Col,
your right they would be 7mm Bigger not smaller
I will think up a good excuse and add it later for now I got them the wrong way around



and will edit the post above. Porsche Cayenne 2022
gone Porsche Cayenne 2020
gone Corris Grey HSE Dynamic 2016
gone Ipanema HSE lux 2010
gone Rimini HSE 2005
!!