15s to 18/20s

[Warlock13]

I just wanted to post because I spent a ton of time looking for information about swapping to 18/20s and I wasn't finding tons of information, so I Hope this helps someone.

I had the 235 75/R15s on my truck which by my old (wrong) excel spread sheet calculated out to 30".  I now realize they are 29", but I will get to that.
With the 5/7 drop the fronts would rub at almost full lock and bigger bumps.

I wanted to go to 18/20s because I saw Harrison Customs Trucks, and I really like the rake of them.

So I ordered Riddler 650 18x8 w 4.5 Backspacing, and 20x10 with 5" Backspacing.
My problem was the tires.  I was having issues finding tires in the same model that I could get the sizes I wanted.
I ended up on Priority Tires website and founds some Atturo AZ850 that I could get both.
I wanted 245 50/R18 for the front to get me at 28" diameter, and 285 45/R20s for the back.  That got me the 30" diameter (wrong) that I wanted, but still had a bigger sidewall than the 50 Aspect Ratio in the front.  I was worried a slightly smaller Aspect Ratio in the back with the rake would look dumb.

So as I was mounting them tonight, just got the tires mounted today, I noticed that the backs were indeed taller, but they fill the wheel wells just about the same.
They do make 285 40/R20s, but I don't think it looks bad, it is still a huge improvement over the Stock GMC Rims.

It also got rid of the rub at full lock, and I haven't noticed any rubbing over bumps, but I haven't hit many bigger bumps yet.

[VileZambonie]

it is still a huge improvement over the Stock GMC Rims.

  I'll be that guy that thinks the other wheels looked better but appreciate you sharing detailed fitment results of the new wheels.

[Warlock13]

All good Man!
Up close the stock rims looked really bad.

[78 Chevyrado]

it is still a huge improvement over the Stock GMC Rims.

  I'll be that guy that thinks the other wheels looked better but appreciate you sharing detailed fitment results of the new wheels.

Guys still get mad at me sometimes that my 3/4 ton doesn;t have rally wheels on it...   

[ehjorten]

I don't prefer low aspect ratio tires on our trucks, but the problem with 15's is that it is getting pretty hard to find performance tires in the sizes we need. My personal opinion is that 17's would have been better, but to each their own. If you love it, it is your truck, and that is what matters. The deduced air volume in the tire will contribute to a rougher ride, but going wider helps to offset the lower aspect ratio some.