I’m looking at a couple of 2019 F-350 one has the 20” tires I’m going to use the truck to tow 15,000 fifth wheel which tires are better for towing both tires are rated E

 

I think you will find 20" have 250 pounds capacity each over 18. To need the extra you will exceed max cargo of truck, if that matter to you.

 

Assuming we’re not talking about LT275/65R18E AS tires...

The 18” wheels and LT275/70R18E AT tires and the 20” wheels and tires provide the same GVWR and rear GAWR.

The E rating just means the tires’ load ratings are based on a maximum 80 psi cold pressure. The 20s have a higher load rating because they’re larger.

With the 20” set, you run out of spring rating before tire load rating.

Technically, the 18” set should tow better because they’re slightly smaller diameter. The larger tires reduce the effective axle ratio.

If you’re interested in the optional OEM camper package, it’s not available with the 20” set.

Finally, I don’t know this for sure, but I suspect the 18” tires cost less to replace than the 20s.

HTH,
Jim / crewzer.

 

Once again! ^^^^^^ Jim hit it on the nose!

 

Also with 20s, add about 700 bucks to the cost because the spare tire will be an 18 and Ford will not replace it so you need to buy your own.

 

Never own 20’s again for me they are rough as hell.

 

18's get the job done and the combination of larger wheels and tires will be heavier. More unsprung weight might give you more wheel hop, especially when unloaded.

 

I will never have 20's again, unless I am running 37 inch tires.

IMHO, there is a significant ride difference in the same brand/tread E range tire between the two sizes, at the same diameter.

More air/rubber on the 18' is a good thing.

 

For me there was no consideration of the 20” wheels. These are my opinions. To replace tires, the cost of 18” is significantly less than 20”. The wheel to tire ratio looks much better with the 18” wheels. With 18” I can still go up to a 35x12.50x18 tire. Back long ago in a much better time, guys put 35” gumbo monster mudders on 15” wheels.

 

My truck will have 20's but the 18's are smoother, maybe more side wall and more flex for a better ride. I had 22's one time and never again. horrible off road feel

 

I have 20's on my F250 CCSB Lariat. I chose the 20's because I liked the looks of the wheels better, tire fills the wheel well more and looks better to me and I wanted the Michelin tires instead of the Goodyear tires. The Michelin A/T tires had slightly better performance reviews in my research. All very subjective reasons.

The ride quality is fine. The side wall of tires on the 20" wheels are a little over .5" shorter than the tires on the 18" wheels. I would not consider that a low profile tire that is typical of a rougher ride.

I don't see a need to replace the standard spare (18" wheel). The standard spare can be used in place of the 20" wheel if needed. Sure, I'm not going to run with the 18" for hundreds of miles but it will get be out of a jam. Given that I haven't needed to use a spare tire for 20 years or more across two vehicles, I consider the risk to be low. I expect the spare to stay tucked away for the life of the truck, except for servicing of the cable lift and air pressure checks.

The tires on the 20" wheels are more expensive to replace. I researched this before buying and its about $50/tire depending on brand and model of tire.

As SDcrewzer wrote, there are other considerations depending on how you plan on using your truck, that may dictate your selection.

 

I would not go 5 miles on a tire that is 1 inch shorter and has less travel compared to the other stock tires. In my “discussion” with Ford they recommend that it only be used in an extreme emergency for a very limited range. Granted, I carry a plug kit and a compressor but if you cut a sidewall or have damage you can’t plug and need a spare, you better have the correct size unless the repair shop is 5 minutes away. The best comment I received from Ford was “While we provide a spare, the spare is not required to fit the vehicle it comes on”...What a joke. Drop over 80k on a truck and they won’t even put the correct tire on it. Yet another example of the modern Ford business model of get the customers money and if there is a problem, ignore them until they go away.

 

Also with the 20's, Ford has you sign a document saying tire chains are not to be used with the 20's.

 

I did not sign any such document

 

I'll find it tomorrow and post it.