Hello, my most excellent Jag brethren!
I'm planning to wheel swap and it's my first one, so I want to make sure I get this right. Note: I'm at stock ride height for now. My goals are:

1. better looking wheels
2. a more filled-out wheel well
3. a bit more room for bigger brakes in the future

Source: 18" Vela wheels (front, rear) ---> Target: 19" Niche Vosso M203 (front, rear)
I have no need to modify track width today, so sticking to the standard 8.5 in, 9.5 in widths for OEM 18" and 19" wheels made sense to me.

Offset
A rough measurement from the bodywork to the outermost portion of my wheels came to ~0.75in (~19mm) gap front and rear. In order to meet (2), I'll use the new wheels + spacers/adapters to close the gap.Tires
Michelin PS4S 245/40ZR19 (front) and 275/35ZR19(rear). This corresponds to the "+1" change in rim size, resulting in a net wheel diameter change within 0.1 in according to this calculator.

Bonus question: Based on the fronts filling 14mm of the estimated 19mm gap, is 5mm perceptible in a car's stance? It sounds small to me, but I could always get a wheel with more + offset and use an adapter to fill it out further.

 

Just curious as to why you wouldn’t go up to the 20 inch wheel with the well documented offsets that many have used successfully?

 

That's fair! I could copy FR500GT's offset selections since his setup is pretty great and I'm looking at the same wheel mfr.

I'm not opposed, it just seemed unnecessary to step up to 20s. This is my daily and I don't have immediate plans to track it, so the extra contact is probably lost on my use case. I'll look into it a bit more.

 

Perhaps you already know this? But 20 is the wheel diameter and does not affect the contact area of the tire(s). Only the height (then you get in to aspect ratio / sidewall height). Also, you have wheel dimensions and tire dimensions, and together you get the overall size.

That is.... you could have a 19 X 10.5 wheel with a 295/60 tire and the overall height/diameter would be ~33". Or you could have a 20 X 10.5 wheel with a 295/30 tire and the overall height/diameter would be ~27". Both would have the same (295 mm) contact/cross section.

Again...Maybe you already know this. Just making sure.

DC

 

Yeah, I'm familiar with that. In the Niche Vosso lineup, I didn't see any 20x9.5, which would match stock rear width - and no 19x10.5 for that matter. They seem to manufacture a fairly limited range of widths for a given diameter. There are 20x9s and 20x10s but the offsets are less than ideal, so I think madmax's suggestion may be the simplest approach.

I can probably solve a road noise problem with proper tire selection anyhow. I appreciate that you made me check the basics tho