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So, looks good to me. Plus looking at the DOT code on the bottom of your picture, I think I can make out the last of the 4 numbers: 21, thus. fairly new tyres.
In case you did not come across that one: Every tyre (except maybe those from Tin Lizzie (Ford Model T)) has a DOT number: 4 digits: The first 2 are the week of the year and the last 2 are the year, in which the tyre had been produced...
PS: I strongly assume that 7-5 means: Your 17 inch rims are 7.5 inch wide. And that is normal for S-Type. My 2005 S-Type also has 17 inch rims with 235mm wide tyres on.
PS2: I just spotted a difference!
Your S-Type '01 tyres are just like my '04 tyres: 235 / 50 R17.
That 50 is the aspect ratio: tyre section height/width.
50 means 50% = 50/100 = 1/2 = 0.5 and that is height / width = height / 235
So the height on your S-Type tyres is 0.5 x 235 = 117.5mm, this includes the rubber stuck in the rim.
This was only to explain, what the 50 means,
And the tyres from the XF seem to be different there. I can't quite read it.
It is not a 50. It it a 35 or a 55 maybe?
so, if 35: 235 x 0.35 = 82.25mm
if it is 55: 235 x 0.55 = 129.25mm
And this means: If it is just 35, your car is 17.6mm closer to the road surface and not as fast as the speedo indicates, comparing the circumfences of the tyres mathematically, you can also calculate exactly the percentage your speedometer would not be wrong.
...and if it is 55, the car is 5.9mm higher off the road surface, and there is a possibility that the bigger tyres could touch the inside of the wheel-arches - and you are driving faster than your speedo indicates.
So, the rims seem to be right, but the tyres are not...
Last edited by Peter_of_Australia; Nov 15, 2022 at 06:10 AM.
Peter has summed it up well. The XF usually has slightly bigger tyres than the S-Type so the aspect ratio probably is 55.
The other change will almost certainly be the offset. Nominally, S-Types need 58-60 mm. Later Jags like the XF use 49 mm. I personally really don't like the the change to the steering that such a significant change to the offset causes. Been there often enough and gone back at significant expense to know and not repeat The scrub radius, which is an important steering parameter, changes usually for the worst even though many will say that they don't notice it! But the wheels will sit wider increasing the track and the way the car looks - more Hot Wheels like - which appears to be popular
Very good point about the offset!
Many rims will bolt onto your car but watch those offsets!
Lot's of potential for rubbing as Jaguar has moved them around over the years as neilr says above.
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4 rims with relatively good tyres will cost me $800. I do not mind keeping them as spare for the next Jag that I get (another S-type). So, aside from looking at the numbers, do I mount them and check what the effect is?
Yes, the offset was in the back of my mind, but did not make it all the way to my fingers and the keyboard...
I do not know what the offset difference between XF & S is, but if it is just the 1mm between 49 and 50, I can't see that you would feel the difference in driving, but if it has been designed really on the dot, it could mean that even this 1mm leads to a touch-condition on the wheel arches, esp. if the tyres are 55 instead of 50 (aspect ratio).
I made a positive experience with going off the much traveled path regarding offset...:
Decades ago I replaced on my van the old iron-rims with really nice Aluminum rims. A design imitating the old spokes. There was a massive offset difference - the wheels were moved many Centimeters outwards. It gave the van a massive improvement reg. stability on the road and in the curves. In Australia it is not legal to have the wheels poking out from the side of the car. In the rear it was just OK, in the front I had to widen the wheel arches and I adjusted the van to max. height (there is an adjustment bolt) so that that rubbing of (or "off" ... ) rubber (when driving thru potholes) came to an end.
I just went outside to measure the diameter of my S-Type wheels: 650mm (that is easier than adding up inch and mm and then substracting the overlap).
So if the XF tyres have 55 instead of 50, they have a diameter of 661.75 (see above: 129.25-117.5 added to the 650mm).
circumference of S-Type tyre: Pi x d = 204.2cm
circumference of XF tyre: Pi x d = 207.9cm
This means that when you mount aspect ration 55 tyres to the S-Type (and nothing rubs), your real speed is 1.8% (so nearly 2%) more than indicated.
(On my van that would be much more, as the tyres are heaps bigger.)
Last edited by Peter_of_Australia; Nov 15, 2022 at 05:12 PM.
Yes, the offset was in the back of my mind, but did not make it all the way to my fingers and the keyboard...
I do not know what the offset difference between XF & S is, but if it is just the 1mm between 49 and 50, I can't see that you would feel the difference in driving, but if it has been designed really on the dot, it could mean that even this 1mm leads to a touch-condition on the wheel arches, esp. if the tyres are 55 instead of 50 (aspect ratio).
I made a positive experience with going off the much traveled path regarding offset...:
Decades ago I replaced on my van the old iron-rims with really nice Aluminum rims. A design imitating the old spokes. There was a massive offset difference - the wheels were moved many Centimeters outwards. It gave the van a massive improvement reg. stability on the road and in the curves. In Australia it is not legal to have the wheels poking out from the side of the car. In the rear it was just OK, in the front I had to widen the wheel arches and I adjusted the van to max. height (there is an adjustment bolt) so that that rubbing of (or "off" ... ) rubber (when driving thru potholes) came to an end.
I just went outside to measure the diameter of my S-Type wheels: 650mm (that is easier than adding up inch and mm and then substracting the overlap).
So if the XF tyres have 55 instead of 50, they have a diameter of 661.75 (see above: 129.25-117.5 added to the 650mm).
circumference of S-Type tyre: Pi x d = 204.2cm
circumference of XF tyre: Pi x d = 207.9cm
This means that when you mount aspect ration 55 tyres to the S-Type (and nothing rubs), your real speed is 1.8% (so nearly 2%) more than indicated.
(On my van that would be much more, as the tyres are heaps bigger.)
Thanks, Peter. I just have to visit the seller and have a look/see. I cannot find the size from the photo.
Sorry, I had a typo on the S-Type offset. It should have said 58-60 mm. These wheel tyre combinations have been fitted to S-Types and they physically fit and apparently don't rub.
However, for me the offset difference is too big. For German rules, the tyre size would make them "illegal". So, they wouldn't be for me.
@ neilr: So if you would fit XF tyres to an S-Type, would the wheels sit further inside of the wheel-arch or would they poke out more?
Yes, I know about the madness of German road-safety regulations - I am from Germany originally. My van would be totally illegal in Germany: Wheels poke out way too much, the wheel-diameter is way too big and they are probably too wide as well, plus I have that massive bull bar - bull bars are illegal in Germany. And as far as I know, that Leaper-hood-ornament as well.
@ Roberto: I am fairly sure now that the size of those tyres is 235 / 55 R17, thus a tad larger in diameter then the OE ones. And that offset might be of concern....
If you decrease the offset (ET value), a wheel sticks out further, so a normal XF wheel should stick out a further 10 mm or so over a normal S-Type wheel (ignoring the wider rear wheels on a staggered setup).
The stock 17" tyre for an S-Type is a 235/50-17, so the XF tyre will be that little bit bigger in diameter.
If you decrease the offset (ET value), a wheel sticks out further, so a normal XF wheel should stick out a further 10 mm or so over a normal S-Type wheel (ignoring the wider rear wheels on a staggered setup).
The stock 17" tyre for an S-Type is a 235/50-17, so the XF tyre will be that little bit bigger in diameter.
Forgive my ignorance and this question; as I understand it, 235 is the width and 50 is the profile (thickness), and 17 is the rim. So, if these tyres are 55 and standard S-type 17' is 50, why will the tyres stick out when they are both 235? Again, I know very little about tyres, unless they need more air. Thanks Neil and Peter
The lower the offset, the less inwards the wheel sits. We have about 10 mm less offset on the XF wheels compared to the S-Type wheels so it will sit 10 mm less deep in the wheel well. The tyre just takes its position from the wheel.
The lower the offset, the less inwards the wheel sits. We have about 10 mm less offset on the XF wheels compared to the S-Type wheels so it will sit 10 mm less deep in the wheel well. The tyre just takes its position from the wheel.
What neilr meant is: The tyre is there, where the rim puts it!
Offset has got nothing to do with the tyres.
Offset has to do with the rims. If you imagine a plate going thru the rim (actually, you don't really have to imagine: It is there...) and this is the plate thru which the bolts go to fix the wheels to the car - that plate can be further inwards or further outwards. As I wrote above reg. my van-rims: That "plate" is way further inwards on my alu rims, compared to OE, thus the rim, and thus the whole wheel sticks way out of the side of the car. So this would be the case with XF rims on an S-Type. I my opinion, that is a good thing (if you are lucky), because in my opinion that gives the car more stability. BUT, that is only good, as long as you do not have any touch-condition with the tyres, and if - with those XF wheels on the S-Type - the wheels do not stick out THAT much of the car, that you can't pass rego - at least not without adding wider wheel-arches.
What neilr meant is: The tyre is there, where the rim puts it!
Offset has got nothing to do with the tyres.
Offset has to do with the rims. If you imagine a plate going thru the rim (actually, you don't really have to imagine: It is there...) and this is the plate thru which the bolts go to fix the wheels to the car - that plate can be further inwards or further outwards. As I wrote above reg. my van-rims: That "plate" is way further inwards on my alu rims, compared to OE, thus the rim, and thus the whole wheel sticks way out of the side of the car. So this would be the case with XF rims on an S-Type. I my opinion, that is a good thing (if you are lucky), because in my opinion that gives the car more stability. BUT, that is only good, as long as you do not have any touch-condition with the tyres, and if - with those XF wheels on the S-Type - the wheels do not stick out THAT much of the car, that you can't pass rego - at least not without adding wider wheel-arches.
thank you, Peter, for breaking it down to something that I can comprehend. This will help stabilise the car when going through a roundabout. It the tyres do not touch. Cheers
A wider track increases stability but changing the front track by changing the offset alone (or using spacers), i.e., not designing a system, with a wider track changes how the front suspension reacts and usually brings with it a load of negatives - more tramlining, bump steer, resistance to change direction, strange behaviour under emergency braking, particularly if the surface friction is different from side to side. Manufacturers spend a lot of effort making the car drive the way it does and even what appears to be a minor change can have unexpected side effects, may be improving one characteristic but spoiling others and even making it less safe under some conditions. Check out the effects of changing the scrub radius and you will see what is happening. If a wider track was simply better by fitting a lower offset wheel to a system not designed for it, they would have done it from the factory.
The scrub radius, which is an important steering parameter, changes usually for the worst even though many will say that they don't notice it! But the wheels will sit wider increasing the track and the way the car looks - more Hot Wheels like - which appears to be popular 
