I just widened my rear stock wheels. The machine shop inserted one wheel in to the other so i have to deliver him two wheels . I use the fronts to do this that i have from another set of wheels. They inserted about 2" in each other so you will only see one welding line in the inside and other in the outside. He told me that doing it that way and it is twice stronger than stock wheel and 4times stronger than adding and aluminum center with 2 weldings in both sides-BTW "wheels now are 18" x 10.5" in the rears - I have H&R springs and i wonder if I install the H&R 25mm in my car i can use 305-35-18- the measurement from ground to bottom is 26-1/2" rear and 24-1/2" front - did you think i will have any problem if i go 305-35-18 in the rears???? or should use a 30mm tall tire or change springs to Teins H for 350z???

10.5" = 266.5mm + 3/4" of rim lips wide x 2 = 38.5mm more = 266.5 + 38.5 = 305 so 310mm wheel fit and look perfect.

 

Sorry, dont know the answer to your question, but I was wondering how much did widening the stock wheels cost?

 

widening the stock will cost about 200 bucks to 250 each (the 18"x8" for 18" x 10.5")

 

So you need to buy an extra wheel to widen each of the stock wheels?

 

im pretty sure they just cut them in half and weld in a wide band to makie it wider... so no need for extra rim.

Someone posted pics of it

 

I see both rims cut and all the process so it is really stronger that way
you really dont need 2 exact same wheels - but it's the best way

If you find another rim of the same material and same wide ( the stock wheels are about 19-1/2" total diameter ) he can do it. And yes your rigth another guy do it with the aluminum 2-1/2" belt but that way is not the strongest, is good but not the strongest way. The guy who do that told me that he was doing it for years, and for motorcycle choppers too, and he always do it that way in order to warranty his job. He told me that if i want he can do the belt but also tell me that's not the best way. Any way, both ways are good and no breaking reports at all.

BTW im and ENG. So i see his point perfectly. Both ways are good but one is the best.