18 or 20" wheel. Better for weight carrying and towing.

You might talk to a couple of tire stores about cost. When I switched trucks going from a 16.5" to a 17" tire there was a larger price increase than I was expecting - then times four or six tires. Up here most people have sets of winter and summer tires.

Bill

I would consider a couple of things. First, look at the specifications of the rims and see what they are rated for. Secondly, consider your intended use. If you off road you need side wall height and flexibility when going over rough sections. If you camp on beaches you need to look at air down capabilities.

IMO, these reduced height rims and tires are made for the highway. If used off road you run the risk of damage to the rims when encountering get obstruction.

Finally, I'd look at the tire ratings. Bottomline, depends on use.

I would also look at tire variety, availability, and pricing for future tire purchases that fit your needs. I chose 18" over 20" back in 2012 due to studded winter tire availability and cost.

I would check the load and tow capacities on the vehicles for each option.

I have 20s on my Duramax and the spare is 18 witch are the same height, The 18s have a higher pay load and a better range of tire tread. The 18 inch spare has the higher load range. i wished my truck had 18 inch tire and rims. I believe the 20s are designed to track and ride better then the 18s.try a google search on 20s I found them to be miserable for 265/60/20.

I have 20s on my truck, as it came that way from the factory.

I'd definitely go 18s, and go for more tire, less wheel. Better tire life, and 18s are definitely cheaper.

Can't help to notice some misconception.
Lower profile tries - in this case 20" does deliver better cornering, but LOWER ride comfort.
With pickup tires you can also play with load ratings for comfort, but for some time we had 2 identical cars where 1 was on factory 16" wheels, the other on 18" wheels with super-duper tires.
On few occasions I drove them both on the same day and the fishtailing on 16" was more obvious on the first turn, but even more expensive 18" did lower ride quality on our bumpy roads.
Can't have it all.

I ordered mine on 18s because the 20s just seem like a teenagers big fancy tires.

Just did a quick check on tirerack.com and they only have 2 tires for the Ram truck in 20" size with the cheaper Firestone TransForce (Ram factory tire) and a Michielin M/S. When looking the other day for future tires for my truck, they had a bunch of 18" available including everything from street to a true mud tire. The same Firestone TransForce (also factory) was $28 cheaper too.

Payload between the tires was the same 3640.

All good posts, thanks for the info.
Looks like the 18" is the best overall.