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Wheels have different offsets side to side

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I had new tires put on my GT350 Widebody yesterday. At one point the guy mounting and balancing the tires comes into the waiting room to let me know that my offsets are different on the L and R rear wheels. Huh? I go back in and sure enough, there's roughly a quarter inch difference between the two. My first reaction was that Shelby American had milled off a quarter inch to make the axle/wheel combo fit inside the widened quarters. But, no, the part number from the supplier is stamped in the same spot on both inside faces. After a little discussion, I tell him there's nothing we're going to do about it right there so just put them back on.

Next he comes in and says the fronts are the same way. Sigh... We call the president of SA and confirm that they didn't and don't mess with wheels like that.

My theory is since the car was very low production at 36 units, and the widebody was only I think 3 of them that year, and mine might be the only black ones, that the 4 wheels were made to order and they (Weld?) screwed up the machining. I think they probably set up the mill to machine the offsets differently for the F and the R, but accidentally milled the LF and LR to one depth, then the RF and RR to another, instead of LR and RR sequentially, then LF and RF.

The car drives fine, and has for ~23k miles now. I'm thinking several years from now when I get tires again, I'll take them down to my buddy's machine shop and mill the two with more meat to match the others.

Weird.
 
1,246
1,243
In the V6L
I had new tires put on my GT350 Widebody yesterday. At one point the guy mounting and balancing the tires comes into the waiting room to let me know that my offsets are different on the L and R rear wheels. Huh? I go back in and sure enough, there's roughly a quarter inch difference between the two. My first reaction was that Shelby American had milled off a quarter inch to make the axle/wheel combo fit inside the widened quarters. But, no, the part number from the supplier is stamped in the same spot on both inside faces. After a little discussion, I tell him there's nothing we're going to do about it right there so just put them back on.

Next he comes in and says the fronts are the same way. Sigh... We call the president of SA and confirm that they didn't and don't mess with wheels like that.

My theory is since the car was very low production at 36 units, and the widebody was only I think 3 of them that year, and mine might be the only black ones, that the 4 wheels were made to order and they (Weld?) screwed up the machining. I think they probably set up the mill to machine the offsets differently for the F and the R, but accidentally milled the LF and LR to one depth, then the RF and RR to another, instead of LR and RR sequentially, then LF and RF.

The car drives fine, and has for ~23k miles now. I'm thinking several years from now when I get tires again, I'll take them down to my buddy's machine shop and mill the two with more meat to match the others.

Weird.
If you want to equalize them, then run a spacer. Milling the wheel center weakens the wheel and that's not a good thing.
 
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I can't believe they'd do that without notification.

I really don't think anyone did this on purpose. Seems like a machining mistake to me.

If you want to equalize them, then run a spacer. Milling the wheel center weakens the wheel and that's not a good thing.

I'll try to figure out if the thicker ones have more than intended "meat" on the bones, or if the thinner ones were milled too much. I'm hoping it's the former, as it'll help with my tire/quarter panel clearance.
 
1,246
1,243
In the V6L
To give you an idea of how deep the mounting section should be, if you measure outward from the inside of the rim, the straight part of a mounting hole in a factory aluminum rim is 10mm. That's from the inner mount face to the start of the 60 degree cone-shaped recess that the lug nut sits in.

Your rims could be thicker than that - it's up to the wheel manufacturer - but I'd be concerned if they were thinner.
 

Grant 302

basic and well known psychic
If you want to equalize them, then run a spacer. Milling the wheel center weakens the wheel and that's not a good thing.

That's not true for all. But is a real concern if it is machined thinner than 'allowed' for a given casting. Some wheels are cast for ability to machine custom offsets.

----

Andy- please post what you find...or some pics if you can.
 

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