I am trying to see if I will get any gains from steping from a 20 x 8.5 to a 18x10 combo. My 20s are getting old, and may retire them. I really hate the fact they are so narrow. And Its time for a new design. I could do a 20x10. but Im limited on options to choose from as well.

will a 18x10 be a light package than a 20x8.5?
or will it be worst for performance?

Im mostly looking for performance, and the width, in my new combo. plus Im going to be going a bit lower too.

 

Weight will be negligible unless you have heavy chrome 20s and go to an ultra light forged 18. Adding 2" in width and dropping 2" in height will work out to be similar in weight. Plus your tire will be similar is weight between the two.

Post a pic of the truck. I am curious why you want wider? 18x8.5 or 9 will save a tiny bit of weight but I doubt much more then 15 lbs. a tire. That is 60 lbs. of rotational weight that could help you 1/4 time by about .2. So if you save 15 lbs. or get lucky and get closer to 20 you could help performance but a small amount.

 

The tires are going to play a huge roll here... and its nearly impossible to answer this question as a blanket. Each set of wheels is completely different. In general I would guess an 18x10 is better than a 20x8.5 but its hard to say.

 

What "performance" are you looking for? Better traction, lighter weight, mpg...? If you are looking for traction it is more about tire choices. For example, a NT05R 305/45/18 and a 315/35/20 are both going to weigh ~33lbs but for equivalent wheels, 18x10 will be lighter by a few pounds over a 20x11. That puts the 18" combo a few lbs lighter with more sidewall and a little extra diameter over the heavier, shorter yet slightly wider 20" setup.
If you are just looking for a lighter setup for a standard size radial, like has already been mentioned, it depends on what 20x8.5 and what 18x10 you are trying to compare.

 

well I picked up some 275 / 45 - 20s. and ewww it was just awful. I replaced them the next morning with my AT tires I used when the truck was lifted. Now the truck is lowered 2/4 and Im not runing the wheel spacers I did before. So it tucks the 305 /50 - 20s I just put on it with this setup. IMO it looks good. They are way wider and more of what I wanted. It s mostly for traction. As the turbo is in the works as we speak. Ill try to post some pics. But just right now, these tires I can hear a way deeper tone in the exhaust which makes me beleive its going to spool the turbo good.