Hello all!

Sorry, I promised a while back to post some pics of my new wheels. Things got ugly for me a while back, so I haven't been on here in a bit, but things are straightening out again, so I'm back.

Wheels are OEM C6 Corvette Grand Sport wheels. The GS comes with 18x9.5 wheels on the front, and 19x12s on the back. Obviously the rears don't fit. I think they'd look amazing under there, but they WILL NOT fit without flares and some mini-tubs, as the 9.5s are pushing it. So I'm running a pair of fronts from 2 different sets on either side, which is why they're different colors

The X308 is on the old Chevy 5x4.75/5x120.65 pattern surprisingly enough. So the Vette pattern is already perfect. The only mounting hiccup is that the wheels have a (very large) 72mm center bore, but the Jag has a massive 73.2mm hub. So I had the center bores expanded to 74mm by a machine shop.

They charged me $25 a wheel, 95% of which was time to get it fixtured up, as it's a big, oddly shaped piece of aluminum.

The stock Asteroids are 18x8.5 with a +33 offset. This gives them a front spacing of ~2.95 inches and a backspacing of about 5.55 inches. The C6 GS (and Z06 coincidentally) front wheels are 18x9.5 +42, so a front spacing of about 3.1 inches and a back spacing of about 6.4 inches. So very slightly further towards the wheel well lip on the front side, and almost an inch to the inside.

This presented a significant problem on both ends. On the front, the inside edge of the wheels was contacting the A-arm at full dynamic lock. On the rear, the inner edge was maybe 1mm from the pinch weld of the frame in the rear wheel well and was in full interference with the rear bump-stops.

There was still plenty of space to the outside though and I was looking for a more aggressive stance anyway, so spacers it was. I originally wanted to run some 3/8" spacers, which I tried, and ran into another problem. The Jag wheels use shank or "cannon" nuts, which go through a bore in the wheel and actually almost mate with the rotor surface. This means that the lug bolts are VERY short, barely over an inch.

This means the with standard conical nuts that the Vette wheels use, with the 3/8" spacers I was only getting about 4 full turns of thread engagement, which is completely unsafe. The X308 uses 1/2-20 lugs and lug nuts (Ford standard lug thread), so minimum safe engagement is 6-7 full turns. So I tried some 3 mm (~1/8") spacers, available at about any wheel shop.

This solved the rubbing issue in the front, and with the removal of half the thickness of the bump-stops in the rear (I cut them in half with a band saw), in the rear as well. It also yielded just shy of 8 full turns of engagement, pretty solid and enough that I don't worry about them. I plan in the future to investigate some longer lug studs so I can run some thicker spacers (1/4"?) and get the stance perfect.

On the tire front I'm running 275/40/18s on the back and 265/40/18s on the front. As an added bonus, even though the Vette wheels are much larger, they're slightly lighter than the Asteroids, as the Asteroids are 25-26 lbs and the GS wheels weigh in at 23 lbs. And 2-3 lbs a corner of rotational, unsprung weight is nothing to sneeze at

Hope this helps anyone else looking to get some different wheels on their XJ!

 

Nice wheels. I'd not consider 6 or 7 threads a safe engagement. I believe the rule of thumb to be the bolt diameter, or 10 turns for a 1/2"-20 bolt.

 

Are you sure tha Jag has 73,2? I thought 74,0...

 

Still wondering 'bout a vibrations with that bimmer rims? ROFL.

 

Those look great!! Thank you for all the info, it definitely opens up the realm of wheels for our cars with a little ingenuity.

Chris

 

Have to be honest, I hated the idea before I even looked at them, but changed ny mind.....they actually look quite nice.

I couldn't live with the colour diference either side though

 

General rule of thumb for thread engagement is 1.5 times the bolt diameter.
so in the case of a 1/2" 20tpi - 15 turns would be the acceptable standard.
Cheers
DC

 

@ross1

Everywhere I've read says that 1/4 diameter (~5 threads) is considered dangerously marginal, and approximately equal to the diameter is considered very comfortably safe. So I figure that at 8 full turns I'm probably OK. I've been running them hard for several months with no issues yet. Many people on other forums have run this level of engagement for years with no issue. Until I start making some more power, I think it's plenty.

@ Rostman

I had the bores expanded to 74mm pretty exactingly, and they fit comfortably (no strong contact with the hub surface), so they're definitely under 74mm.

@MoscowLeaper

You can use 120mm wheels (BMW and modern Chevy pattern) and get them to balance out (you just have to be VERY slow and careful when tightening the lugs down), and a lot of people on the Chevy boards have done just that with great success. But that .65 mm difference does mean there is some sideloading on the lugs, and they could fail catastrophically. I thought about BMW wheels for a long time, as I could have gotten a set of (real) BBS LMs for quite a steal that would have fit very nicely. But I decided the risk was too high and went with the cheap Vette wheels, even though I'm not completely sold on the looks.

@JimC64

Yeah, I wanted them to all be the bright silver that's on the passenger side, but I found a killer deal (~$100 a wheel, absolutely brand new) for the pair that's the darker Competition Gray, so I couldn't pass it up. I'm going to put my stock Asteroids with winter tires on soon here, and I think while I have them off I'll get the wheels all powdercoated the same color.

 

Those wheels look amazing!

Nice work!

Powdercoating is a great idea.

Which color are you going with, the lighter, the darker, or something else?

Stewart

 

Yes, looks like you are correct. I found this threadon the topic;
Thread Engagement