Best Wheel+Tire configuration for Class 7 Commercial Truck?

[tmckenna13]

So I bought a Class 7 Truck for my "Expedition Vehicle" build. Originally I was planning on doing 22.5x12.25 super singles with 386/655 tires on each corner of the truck. My question is would I be better off with a slightly narrower tire on the front axle and keeping duals in the rear? I would assume no because as far as I know the super singles would provide a bigger contact patch at each corner. I don't want to run 20" military tires so please don't suggest any of those (yes I'm aware the beads are more conducive to low air pressures).

 

[mog]

I run 385/65R-22.5 (Hercules Ironman I-402) on 22.5x12.25 Alcoa aluminum rims on all 4 corners of my truck (C4500 Kodiak) and am very happy with that set-up. The track is not perfect but with the Kodiak using 8x275 rims, the choices are extremely limited. As you have the 'normal' 10-lug wheels, there is a better selection of super single rims (and a zillion times cheaper). So it comes down to the pluses and minuses of super singles vs. duals, which there are plenty of threads addressing.

 

[charlieaarons]

If you think you want singles, don’t want 20s despite ability to do lower pressure and run beadlocks, and especially if you are going to travel to all sorts of places:
The answer is quite obviously 385/65R22.5s. Available everywhere, great load capacity, multiplicity of tread designs.

 

[shortbus4x4]

If you want a commercial tire with all different tread flavors and can be found anywhere go with 11R22.5s.

 

[charlieaarons]

I think 385s were designed to have the same OD as 11R22.5; 425s similar for 12R22.5; and 445s same as 13R22.5s.
So that a truck with a heavy front axle load like a cement mixer might run 425s in front and tandem/dual 12R22.5 in the rear. And have to carry only 1 spare. And/or work ok with AWD.

 

[tmckenna13]

I run 385/65R-22.5 (Hercules Ironman I-402) on 22.5x12.25 Alcoa aluminum rims on all 4 corners of my truck (C4500 Kodiak) and am very happy with that set-up. The track is not perfect but with the Kodiak using 8x275 rims, the choices are extremely limited. As you have the 'normal' 10-lug wheels, there is a better selection of super single rims (and a zillion times cheaper). So it comes down to the pluses and minuses of super singles vs. duals, which there are plenty of threads addressing.

I currently have the understanding that super singles on all corners provide better traction and "floatation" for mud and sand applications. Obviously this makes sense on the front because the super singles will be far wider than the original. Now the rear is where most of my questions arise. The dual wheel assembly will be wider as a whole than a single 385 wide tire, but I'm under the impression that because of the gap between the tires, and also weight distribution (biasing one of the tires) that the dual wheel configuration will yield a smaller contact patch and worse traction?

 

[mog]

I currently have the understanding that super singles on all corners provide better traction and "floatation" for mud and sand applications. Obviously this makes sense on the front because the but I'm under the impression that because of the gap between the tires, and also weight distribution (biasing one of the tires) that the dual wheel configuration will yield a smaller contact patch and worse traction?

Actual tape-measure measurements (+/- .25")
385/65R-22.5 (W-L) 12" x 18" = 216 sq. in {with vehicle weight}
245/70R19.5 (W-L) 7.5" x 10" (x2) = 150 sq. in {without vehicle weight}
The super single had the vehicle weight on it, but I don't get a lot of 'squish' as I run 80psi and the four tires are rated for 39,680 lb total, with my truck/camper at 15,240 lbs,
I would guess that a larger circumference would also give more contact area (disclaimer-hopefully wiser minds will confirm or disprove that)

Recommend 'floatation' combination ?

 

[tmckenna13]

Actual tape-measure measurements (+/- .25")
385/65R-22.5 (W-L) 12" x 18" = 216 sq. in {with vehicle weight}
245/70R19.5 (W-L) 7.5" x 10" (x2) = 150 sq. in {without vehicle weight}
The super single had the vehicle weight on it, but I don't get a lot of 'squish' as I run 80psi and the four tires are rated for 39,680 lb total, with my truck/camper at 15,240 lbs,
I would guess that a larger circumference would also give more contact area (disclaimer-hopefully wiser minds will confirm or disprove that)

Recommend 'floatation' combination?
View attachment 757216

Yeh I had some surprising traction issues driving a DRW RAM 3500 on wet grass (without 4wd engaged) recently and more or less "accidentally" confirmed the DRW traction thing. I just know there are some people that swear by DRW configurations for highway safety purposes and such.

 

[heimbig]

not following your measurements. if one patch measurement is on a loaded vehicle and the other is has no load, then your measurements have no value. perhaps I'm missing something.

 

[charlieaarons]

According to a database I found years ago “Michelin truck tire characteristics “ 4/13/04:
385/65R22.5 has an average footprint of 95 sq in. The 245/70R19.5 about 56 sq in.
Both at full load/inflation.
Generally if a tire is at X % load and X% inflation, the footprint stays the same.
Lots of knowledgeable experienced vehicle-dependent travel people (like Tom Sheppard and Chris Scott) think a 10% increase in diameter is better than a 10% increase in width. IF the gearing is done properly of course.

 

[tmckenna13]

According to a database I found years ago “Michelin truck tire characteristics “ 4/13/04:
385/65R22.5 has an average footprint of 95 sq in. The 245/70R19.5 about 56 sq in.
Both at full load/inflation.
Generally if a tire is at X % load and X% inflation, the footprint stays the same.
Lots of knowledgeable experienced vehicle-dependent travel people (like Tom Sheppard and Chris Scott) think a 10% increase in diameter is better than a 10% increase in width. IF the gearing is done properly of course.

Would there be any "cons" to do maybe a 385/65r22.5 in the front and than "super" wide duals in the rear. Thinking maybe dual 315/80r22.5. This would give a bigger contact patch than the 385.65r22.5s and also give the "piece of mind" in the event of a blowout.

 

[Peter_n_Margaret]

It is not so much the footprint at highway pressures that is important as the contact area when the tyres are deflated for sand or mud that becomes important.
In that circumstance, the duals are very limited because they kiss together with just a little deflation and that is not good for them.
So give me super singles every time and maximise side wall height by choosing maximum overall tyre diameter and smallest rim diameter.
Cheers,
Peter
OKA196 motorhome

 

[charlieaarons]

It is not so much the footprint at highway pressures that is important as the contact area when the tyres are deflated for sand or mud that becomes important.
In that circumstance, the duals are very limited because they kiss together with just a little deflation and that is not good for them.
So give me super singles every time and maximise side wall height by choosing maximum overall tyre diameter and smallest rim diameter.
Cheers,
Peter
OKA196 motorhome

Agree 100.00%