never cared for the inset look of Asteroid wheels at the rear. So I finally checked clearances for 15mm H&R bolt-on adapters. (That's as skinny as they get). I simply stacked spacers on the wheel studs to simulate the spacers and then (barely) reinstalled the wheel....not much thread left on the studs Tire clearance with suspension compression looks to be an issue for the typical top, rear location. Looks like the tread would clear, but the sidewall bulge would make contact with the fender lip if it traveled straight up more than two inches.

That said there are two mitigating items. First the wheel should lean slightly inward as it moves upward. Second, the hub contacts the bump stop at about one inch of spring compression, and then there's about an inch of "give" in the bump stop itself. So that's about 2 inches before the stop bottoms out...which is about where the side wall would come into contact (if it traveled straight up). Long story short, I'm going to buy a pair of adapters and might trim the inside of the lip just a bit.

Here are some side to side photos (without and with the spacers). by https://www.flickr.com/photos/145246079@N06/, on Flickr
by https://www.flickr.com/photos/145246079@N06/, on Flickr
by https://www.flickr.com/photos/145246079@N06/, on Flickr
by https://www.flickr.com/photos/145246079@N06/, on Flickr

 

I have a friend in Utah, running asteroids with 10mm spacers and 265 tires. He says is perfect without issues.
we counted remaining thread on the studs, within safety.
​​​​

 

Thanks, Eric. That seems a better solution. After I made the original post I looked more closely at H&R's bolt-on adapter info. They have a note that says if the wheel doesn't have "stud pockets", then the existing studs must be shortened so that they're flush with the face of the adapter. So I removed the wheel again to take a closer look. The Asteroid has five elevated pads for each stud, and there is a depression/slot between each of them. That depression is deep enough to accept the excess length of the original wheel stud, but not quite wide enough. So I would have to drill or grind a wider spot in each slot (I'm not going to the trouble of changing out the original studs for shorter versions).

Do you know the section size for the tires on your friend's car, and the specifics of the spacers (source and whether they have a centering lip). I think a 10 mm spacer would exceed the height of the centering lip on the Jaguar hub. I like the look, and new tires are not that far in the future. Thanks again.

 

I checked for you:
- front spacer 6mm
- rear spacer 10mm
- Tires 245/45 R18
From my experience, I think running 10mm all around should work too, but that needs some measuring from the fender back on front and rear.

 

Thanks, that's helpful. I couldn't quite put my finger on what makes the side view of your car and your friends' car look just a little bit more "together" than mine. And while it's very subtle, I think it's that both of your cars are on 26.7" diameter tires, and mine is currently on 26.0" (255/40) diameter. The larger tires fill the wheel wells just a tad bit better. More balanced to my eye.

Anyway, I calculated where the outer tire bead surface of the 9" rear wheel on your car is located relative to the hub, where it's located on my stock Asteroids, and where it would be with a 10 MM spacer. The distance from the hub to outboard bead surface on your car is 79.3mm (3.12"), a stock Asteroid is 70.2mm (2.76"), and obviously a 10mm spacer takes an Asteroid out to 80.2mm (3.16"). So a 10mm spacer it is. U.S.Wheel Adapters say a 10 mm spacer leaves adequate stick out on the hub centering ring. I need to double check that. Thank you again.

 

Front and rear view. He just mentioned the front with 6mm is on the limit!

 

Exactly that!

I calculated till I turned pink, then found out that the tolerances in tires are way more diverse than just a tire calculation.
But yeah, if the rim is the same, you should be fine on the fender, about a finger between there on the rear.

And here are the 10mm spacers he bought, the 6mm were from his shop.

 

And a last one, here is mine with a similar view point (275/40R18 on a 9J ET35).
Looks mine is a slightly bit further inside than Eduardo's, but again, that's tire sizing / tolerances, not the rim.

https://www.wheel-size.com/calc/?whe...cl=50mm&sr=0mm

 

Interesting that the photos of the rear tires on Eduardo's car (245s??) appear to be just as wide as your 275s when viewed from the rear. I would have expected a more obvious difference. Early in the thread you mentioned that Eduardo was using 265's (26.3 diameter) on Asteroids...might that be the case? (Yes, I'm obsessed with the possibilities for squeezing in maximum rubber). Thanks.

 

I have found that one day my 275's can look massively impressive, then the next day they look as small as just the standard tires ... specially on pictures, but also in real life.
Looks can be deceptive I presume ...

On the tire size, I see I typed it wrong initially, he followed my advice for the slightly higher tire to fill the wheel wells better, 245/45, same as I have on the 8J front's.
I am no expert, but 265 on a 8J rim seems to be too wide in all aspects.

Then, as mentioned earlier, you can exactly calculate where your rim will be, but the final tire sizes are varying big time.
I took over rims with 255/45R17 tires on 8J rim for my XJS.
Theoretically they should hardy fit in there, but they do easily.
After being mighty surprised, I measured, they are the exact same width as the 235/50 8J the car came with.
Talk about manufacturing differences between brands ...

 

I appreciate the amplifying information and will now stop bothering you. Best regards. (Your car is a knockout).

 

Well, I'm back. I finally got around to pulling off one of the Asteroids to examine and measure the depth of the concentric hub flange, and the corresponding bore in the wheel. Turns out that the flat portion of the hub flanges is 10.16 mm....and the recess in the wheel is chamfered for about the first 2-3 mm. That means the bore in the wheel cannot overlap the hub flange with a 10 mm spacer. Looks like max thickness for a spacer that will still permit the wheel to overlap a couple mm of concentric hub is 7-8 mm. Almost not worth it. Won't do much for the recessed tire look at the rear. Guess I could go back to the 15 mm bolt-on adapters but would have to roll the rear fender lip. By the way US Wheel Adapters will machine any slip-on spacer thickness you like for about $60/pair. (Billet, not cast)

So, I'm looking at replacement wheels. I like the Corvette five spoke designs from the late 90's with offsets in the 56-57 mm range. That would allow for tailoring a set of custom bolt on adapters to the exact thickness needed for the ideal tire/fender clearance. The two wheel options options I'd consider in the 5 spoke category are a 18x9.5 front and rear design (second photo), or a style with 17x8.5 front with 18x9.5 rear (first photo)....or the front 17's all around. Not sure how a larger diameter rear wheel would look on an XJR. As an old school guy, I like a little more rubber sidewall showing, so maybe the 17's. FWIW.

 

Well, shows again that one has to be careful advising others on friend's experiences ... glad you checked and know what you are doing.
Below 2 pics of X308's I know have Corvette 5 spoke rims.