19.5 or 20" rims?

[dzzz]

Which wheel size would you choose for an F550? I'm not familiar with 20 inch wheels. I assume this is more of a commercial truck size. I'm looking for a 37 inch tire. That tire size seems common here.
Highway driving to bad road driving. (I think for a 15-20K pound vehicle "off road" is somewhat optimistic)
I need at 6700 ish weight rating at 60 mph

 

[boblynch]

I'm going through the same thing now. Most of what I've found is compiled in this build thread. http://www.expeditionportal.com/forum/showthread.php?t=23173

The short version is decide if you need to ability to air down beyond the limits of commercial 19.5 tires and are willing to pay for the lift/suspension changes required to run singles. If yes, consider 20x11 rims and MPT81s. If no, there are a number of options. If you stick with stock DRW rims 245s are the biggest that will fit without spacers (which I'd avoid). If you opt for singles on 19.5s then look at 285s. Pick your tire and work back to the rim required.

Post more info about what you're working on.

Bob

 

[haven]

19.5 is an odd size if you're traveling outside North America. I think this size is in use in Australia, but you won't find it much elsewhere. The most common sizes worldwide are 16 inches (light and medium trucks) and 22.5 inches (heavy trucks). 20 inch tires are available, too, but they are harder to find.

In North America, 19.5 is much easier to find than 20 inch truck tires. There are a growing number of low profile tires available for 20 inch rims, but they are a mall-cruising fashion statement rather than for overland use.

Chip Haven

 

[Tennmogger]

20" wheels have the advantage of being able to use mil surplus tires from Michelin, Continental, Dunlop, etc, plus new 20" tires. It's a common size for larger offroad vehicles including many military trucks, and all Unimogs (with a few rare exceptions). A 15k to 20k pound offroad vehicle (or 24k for a U-2450 Unimog) is not optimistic at all. Might make the trail a little wider though, but not as wide as a Hummer needs!

Tennmogger

Which wheel size would you choose for an F550? I'm not familiar with 20 inch wheels. I assume this is more of a commercial truck size. I'm looking for a 37 inch tire. That tire size seems common here.
Highway driving to bad road driving. (I think for a 15-20K pound vehicle "off road" is somewhat optimistic)
I need at 6700 ish weight rating at 60 mph

 

[Carlyle]

The Goodyear G-124's are awesome tires on the 19.5 inch wheels. They will work on a 550. After a season of winter driving I can say they are the best tires I've had to date. I don't know much about the 20 inch rims except to say the military has dibs on pretty much all new stock of decent tires at this time in the US.

 

[dzzz]

I'm going through the same thing now. Most of what I've found is compiled in this build thread. http://www.expeditionportal.com/forum/showthread.php?t=23173

Bob, Most of what I know comes from your research

What do you estimate 5 20x11 will cost? I'm been somewhat concerned about the MPT81's on the highway. The MPT80 look interesting, although I've never seen a review.

I assume military type tires have good tread life. How far can they de deflated for sand?

I do plan to do a lift, air suspension and SRW. Otherwise I'll just pay twice - first for a less expensive alternative. Then in a year for the full SRW treatment.

 

[boblynch]

The Goodyear G-124's are awesome tires on the 19.5 inch wheels. They will work on a 550. After a season of winter driving I can say they are the best tires I've had to date. I don't know much about the 20 inch rims except to say the military has dibs on pretty much all new stock of decent tires at this time in the US.

Carl's right the G124 is a great tire. Unfortunately they stopped making it, so if your interested in 19.5s you'll need to look for someone that overstocked 124s or consider another tire such as the Michelin XDE2+, Yokohama TY303, or Bridgestone M729F. The military has pretty much consumed all the Michelin 20s, but the Continental MPTs are available at about the same cost as 19.5 285s.

 

[charlieaarons]

Bob, Most of what I know comes from your research

What do you estimate 5 20x11 will cost? I'm been somewhat concerned about the MPT81's on the highway. The MPT80 look interesting, although I've never seen a review.

I assume military type tires have good tread life. How far can they de deflated for sand?

I do plan to do a lift, air suspension and SRW. Otherwise I'll just pay twice - first for a less expensive alternative. Then in a year for the full SRW treatment.

As I've said before, the only good reason to do a SRW conversion is offroad use.
That said, 20" tires are superior to 19.5s in that the 19.5" rim has poorer bead retention at low pressures. Unimog in their published inflation tables in the owner's manual of newer Unimogs (UHN and UGN) recommends 75% of highway pressure for general offroad up to 50kph, 45% in sand/mud/snow up to 20kph, 33% emergency up to 10kph, for 335/80R20 MPT81s; which is an appropriate size for an F550 on 20" singles. MPTs have a load rating of 147K: 6780 lb @ 68mph. Michelin 335/80R20 XZLs are 141K: 5680 lb @ 68mph.
285 and 305/70R19.5 have a footprint of only ~70 sq in, but are only 35-36" tall, whereas 335/80R20 MPT81s have a footprint of ~100 sq in, but are 40.7" tall. For comparison, 225/70R19.5s are 46 sq in.
One primary problem is determining whether you can use the same wheel "flipped" for front and rear. I'm not sure, but I am suspicious that Earthroamer is using some sort of spacer, based on their pictures. Personally I'd rather use two different wheels rather than use a spacer.

Charlie

 

[dzzz]

It seems a 22.5 rim would be the opposite. A better road tire but not as good offroad.
I would rather have a Sprinter camper conversion if I was going to stay on paved surfaces.
Ford now has a GVWR of 19,500. One document I read said the frame is heavier. If the earthroamer is coming in at 15-16,000 pounds, it has a fair amount of headroom left.

 

[jesusgatos]

20" wheels have the advantage of being able to use mil surplus tires...

Underline that! You can get mil surplus tires at incredible prices. Check out 100dollarman.com and militarytires.com.

 

[dzzz]

I'm leaning towards 20x11 and the Mtp81s. I was going to make significant suspension changes anyway. I'm also leaning towards ordering a F450 instead of a F550. I should be under 10K pounds on the rear axle. That allows me to purchase less expensive wheels.
41 inches seems a bit silly on a pickup, but it raises the rear diff. nicely.

 

[dzzz]

If I purchase 20x11 wheels and I want a shorter tire than the MPT81 , what are my choices?

 

[haven]

"It seems a 22.5 rim would be ...a better road tire but not as good offroad."

There are lots of 22.5 tires made for traction off-road. The problems are
(1) the tires are very tall (42 to 44 inches tall are common diameters)
(2) they are designed for vehicles that carry heavier loads than the typical overland vehicle, so the sidewalls are stiffer
(3) the tires with the aggressive tread are usually for the drive axle, not the steering axle

 

[charlieaarons]

I'm leaning towards 20x11 and the Mtp81s. I was going to make significant suspension changes anyway. I'm also leaning towards ordering a F450 instead of a F550. I should be under 10K pounds on the rear axle. That allows me to purchase less expensive wheels.
41 inches seems a bit silly on a pickup, but it raises the rear diff. nicely.

I would think about a 550; I will guarantee you keeping the weight of an expedition camper under control will be a challenge, and you will be kicking yourself if you buy a 450 instead of a 550.

Charlie

 

[Sleeping Dog]

I would think about a 550; I will guarantee you keeping the weight of an expedition camper under control will be a challenge, and you will be kicking yourself if you buy a 450 instead of a 550.

Charlie

IIRC when Earthroamer first entered the market they offered the LV with the choice of the F450 or 550, the 450 option quickly disappeared. To Charlie's point.

Jim