I have acquired a set of 17" Jaguar wheels which I wish to use on my X300. In order to keep the tire diameters roughly the same I will have to use 225/55R17 tires as opposed to the standard X300 225/60R16. Will the shorter and maybe stiffer side wall of the 17’s give a much rougher ride than the taller standard 16" tires?
If I stick with a 60% sidewall, 225/60R17, the tire diameter increases by 1". Other than throwing the speedometer off, is there any other reason to NOT use this size tire? Perhaps interference while steering?
Hi Syd, you might find that the larger tyre circumference brings the speedo closer to a true reading in my experience. Both the wifes Mazda Atenza/6 and our XJR were reading between 8 (mazda) and 6-7 klm (XJR) below the readout on the navigation device, a tomtom in our case.
I went up a width with the same diameter and this brought them closer to actual.
A check with the tyre dealer will tell you how many rev/mile(klm) each tyre will give.
I am running 255/40/18s on my 1999 XJR which is basically the same architecture as your car.
Hi Robin,
Thanks for the information. I’m not sure I understand what you did. By going to a wider tire wouldn’t the diameter increase and for a given speed reduce the wheel revolutions and the speedometer reading, which was the opposite of what you were trying to achieve, I think! I look forward to being corrected.
Would you comment on my question regarding the ride quality between 55 and 60 side wall height.
By the way I have no idea about the accuracy of my speedo. I just assumed the standard tire size, 225/60R16 gave correct readings.
Hi Syd, no the increase in tyre rolling diameter doesn’t change the signal the speedo is getting as the signal is sent from the toothed wheel on the drive shaft I believe. So the engine Rpm stays the same but the velocity has increased. Afraid I cannot comment on the difference in ride quality between the two wall heights I would think it would be marginal though.
As I mentioned both our cars were indicating higher speeds than actual against GPS. I believe it may be a law where the carmakers have to ‘over read’ the speedos or may be just an unwrittten one within the car manufacturers cartel to ensure against law suits regarding speeding tickets?
Don’t know if it’s different for the X300 but, for the X308, Jaguar recommend 235/50 for 17" wheels.
Thanks Robin and Gary for your input. I have decided to lean towards comfort and go with 225/55R17.
Best regards
Syd.