Not a Chevy issue but thought I would try to tap the expertise here.

My son got a great deal on some 18 inch rims for his 05 GT however, the offset, bolt, pattern, and bore are all different.

We are trying for the lowest cost/effort solution that is still safe.

The stock rims are 17x8 with a +50mm offset and a 5 x 4.5" (114.3mm) pattern.
The new rims are 18x9 with a +35mm offset and a a 5 x 4.75" (120mm) pattern.

If he goes with the thinnest adapters (15mm) we could find, his offset will now be only +20mm and this will push the rim face out almost 1.75" which we are concerned is too much all around- though we did find out the fender lips are rolled (he bought the car used) and he has about that much in gap between fender lip and tire side.

We looked into redrilling the axle flanges, the front hub flanges and the discs- it seems like a lot of work and if the rim pattern can be changed maybe thats better.

 

I don't want to come off as a ****head but sell them and get a set that fits. I don't see how it's a great deal if they are completely wrong? Custom axle shafts and hubs are the proper way to do this , but at a huge expense and it still doesn't fix the offset issue.

Does the 15mm spacer have studs? Seems thin.

 

Possible the wheels could be be drilled depending on the face of the wheel. (so you have the 5 original holes and 5 new holes like cheap wheels that come with two bolt patterns) If you could run 2 inch spacers you can get pattern adapters but I don't think you can on 15mm (.59 inch) spacers. I don't see it as worth it, take the free wheels to your local tire shop that always has used wheels for sell and see if they will trade. Any solution will lead to a weaker situation, on the front you might be able to find hubs and rotors that have the right pattern that will bolt to your spindle and you can re drill the axles on the rear or buy new axles with the right pattern... unfortunately your free wheels are going to cost $1000 to mount

 

Thanks for talking sense! I'll advise him to sell those and get the right ones.

 

You can run 15mm adapters, I am, but unless the wheels have dimples cast between the lug holes the adapter lug nuts won't fit. The lug nuts that hold the adapter on stick out above the 15mm thickness by 1-3mm. Best to buy better fitting wheels or at least an 18mm adapter.