My rig is getting close to the GVWR—can I get new/better tires to improve weight?

[TheArgobus]

I have a 1995 E350 4 row shorty. Here’s the specs off the plate (in lbs):

GVWR: 9600
GVWR FRONT: 4050 with LT245/75R16E tires at 55 psi (rims 16 x 7.0k)
GVWR FRONT: 6084 with LT245/75R16E tires at 80 psi (rims 16 x 7.0k)

And here’s what I got from the scales:

Front: 3980
Rear: 4080
Gross: 8060

That was with my fat ass in the driver’s seat, a full fuel tank, and an empty water tank (which holds ~40 gallons and is situated between the two axles). My bus is mainly complete: the only two things left to complete are the toilet (composting in a 5 gallon bucket) and a rear bumper Storage rack.

What can I do to prevent my tires from blowing out? Can I replace them with something a little more modern? Should I swap out the stock metal fuel tank for a plastic one? Any other modifications I can do to keep my Skoolie safe and secure? Or reduce the weight? Are the numbers on the plate primarily for the wheels or the axles/bus structure itself?

[FatBoySTL]

Your front tires may not be over capacity. Check them and see what their load rating is (printed on the sidewall). I would bet that they're load range E, good to 6,000lbs or so. If not, swap them, but understand that your GAWR is based on the whole system (and the weakest link in that system). If it's not your tires, it could be suspension, springs, frame... You'll be "safer" with higher capacity tires, but you'll still be overloaded up front.


Otherwise, you're still 1500 pounds under your GVWR. If your build is just about done, then it's really just a matter of watching how much stuff you pack and where you store it. Ideally you should be trying to load just about everything else behind your back axle. Maybe even consider relocating that water tank behind the axle.

[dzl_]

Seems like you are not in bad shape so long as you keep your tires properly inflated and weight is balanced front to rear and side to side. You've got 1540lbs of margin (1200lbs once you fill up that 40gal water tank).


Not sure what tires you have but a quick search for a tire of the same size and load range shows it can handle 3040lbs per tire properly inflated. I believe stepping up to a larger diameter rim or a higher load range, would increase tire weight rating. Brakes and suspension are the other primary considerations.



I believe almost all parts are interchangeable between the E-350 and E-450, so you may want to look at the E-450 if you want to increase the GVWR (not legally). Unfortunately, I believe the E-450 increases its weight rating (to 14k) primarily through the use of duallies in the rear which is probably not practical or desirable for your situation. I believe an E-350 with duallies has a gvwr of ~12k +/-

[TheArgobus]

Thanks for the replies. Here's what I've got:


- I just had the rear suspension done, they took out a few leafs and put new bendier ones in
- I'm going to bring it back for new front springs (unrelated to this weight issue, but just to level it out)
- I'm going to remove the compressor hardware under the hood for the nonexistant dash/school bus air conditioner, that might save a bit of weight and help balance it more to the back
- I want to replace the metal fuel tank with a plastic one--again unrelated to the weight, it's recommended in the 7.3L thread, and I want to plumb a line for my diesel heater
- I'll start asking around for bigger, more robust tires
- The brakes are getting replaced/serviced next week, so we should be good there


I am terrified of the idea of one of my four tires blowing while driving down the highway, so I'm pretty open to whatever I can do to prevent that from happening. Maybe I should've looked into dual wheels a little more!

[DixonM]

I had a single rear wheel box truck with a 12ft box on it with all of my tools it came in just under 11,000 pounds. The first year or two I upgraded the tires to 265-75-16 load range E tires helped out but I then bought 19.5 wheels from ricksons and had 225-70-19.5 on the front and 245-70-19.5 on the rear never had a worry of overloaded tires again for your bus I would just step up to the 265 tire as long as it will fit the wheel well.

[DixonM]

Another consideration is when you install rear storage rack it will load the rear tires and pull some weight off the front tires.

[demoman]

Some good and bad about the 19.5 tires
They will ride rougher than the 16 inch tires
They are so much higher in load rating that you won't have to worry about overloading them in your application.
I had a set of 19.5s on an Isuzu npr the original tires from the factory lasted 100k miles.
My other truck with 16 inch tires lasted 30 k but got a lot more flats and blowouts along the way. But the application involved going to the dump a lot.
19.5 Are expensive but worth it for the miles and reliability.
I have never bought from rickson but that is the only name I see come up when people are talking about the change over.
If you don't plan on putting more than 30k miles in the next 5 years then the extra life of the 19.5s may not outweigh the extra cost of the conversion.

[banman]

Your only danger at the moment is running under - inflated tires. Make sure your tires are properly inflated, in your case, at or close to the full 80psi.

Regarding your springs, instead of "bendier", think in terms like: softer; more compliant; progressive or rising spring / suspension rate.

Springs carry the load. Shocks minimize the oscillation of the load.

[TheArgobus]

What kind of price difference are we looking at for the 19.5's vs 16? If I had a blowout on the road, I'm certain it would cause significant damage to my water/grey tanks, which are hanging underneath between the two axles. If it means less risk of blowouts, I'm biased more towards spending the extra money for peace of mind.

[TheArgobus]

Also I've thought about the type of driving and terrain, and we really stick to paved roads most of the time, but we primarily use Argo for boondocking on gravel logging roads... it seems I will be driving through those much slower now

[TheArgobus]

I just got these installed today. $700 for four brand-new Americus CLT265/75R16 tires. The sidewall says it's Load Range E, with a max load (single) of 3415 pounds at 80 psi. The mechanic who installed them said that I should keep them at 55-60psi (they're all at 58psi), so I wanted to see what their load is, and found this chart (https://www.michelintruck.com/reference-materials/manuals-bulletins-and-warranties/load-and-inflation-tables/#/).


So when I read that I see that at 60 psi for a LT265/75R16 the load limit (all mine are single) is 5580 per tire. Which is significantly more than what the side wall load limit says.

Am I reading this wrong? Is the sidewall limit for each tire, and then the chart above for the whole axle?

If that's the case, then the whole axle limit of 5580 is still significantly more than what it was before (4050 pounds), and gives me a much greater margin of error for weight loading. Am I understanding this correctly?

[FatBoySTL]

The sidewall maximum weight is the maximum Each tire can bear at the maximum listed Air pressure. The chart you linked it tells you what the maximum is if you want to run less than maximum air pressure.

Basically, if each tire is rated for 3000 pounds and you are running dual lies, then those four tires could carry 12,000 pounds. That does not change your GVWR even a A little bit. It just means your tires are not the weakest link on your truck.

[TJones]

Originally Posted by TheArgobus

I just got these installed today. $700 for four brand-new Americus CLT265/75R16 tires. The sidewall says it's Load Range E, with a max load (single) of 3415 pounds at 80 psi. The mechanic who installed them said that I should keep them at 55-60psi (they're all at 58psi), so I wanted to see what their load is, and found this chart (https://www.michelintruck.com/reference-materials/manuals-bulletins-and-warranties/load-and-inflation-tables/#/).


So when I read that I see that at 60 psi for a LT265/75R16 the load limit (all mine are single) is 5580 per tire. Which is significantly more than what the side wall load limit says.

Am I reading this wrong? Is the sidewall limit for each tire, and then the chart above for the whole axle?

If that's the case, then the whole axle limit of 5580 is still significantly more than what it was before (4050 pounds), and gives me a much greater margin of error for weight loading. Am I understanding this correctly?

You do not want to exceed the load limit that is on the sidewall of the tire. Also you don't want to exceed either the front or rear axle rating from your vehicle. If you removed leaf springs I'd put them back. If you are that close to your max gross vehicle weight you run the risk of bending or breaking the remaining springs.

Ted

[demoman]

Originally Posted by TheArgobus

I just got these installed today. $700 for four brand-new Americus CLT265/75R16 tires. The sidewall says it's Load Range E, with a max load (single) of 3415 pounds at 80 psi. The mechanic who installed them said that I should keep them at 55-60psi (they're all at 58psi), so I wanted to see what their load is, and found this chart (https://www.michelintruck.com/reference-materials/manuals-bulletins-and-warranties/load-and-inflation-tables/#/).


So when I read that I see that at 60 psi for a LT265/75R16 the load limit (all mine are single) is 5580 per tire. Which is significantly more than what the side wall load limit says.

Am I reading this wrong? Is the sidewall limit for each tire, and then the chart above for the whole axle?

If that's the case, then the whole axle limit of 5580 is still significantly more than what it was before (4050 pounds), and gives me a much greater margin of error for weight loading. Am I understanding this correctly?

If you scroll to the bottom of the page it shows that the loads are per axle either single or dual. You will see at low inflations the tires have about half the load capacity as the fully filled tires. By filling them to 58 psi you will get a better ride but less excess load capacity. Because you are not coming close to this axle weight it is probably a good tradeoff. For safety and handling the door sticker or owners manual says what inflation pressures to use. But they also probably didnt anticipate the off label use we are doing to these buses.
John

[TheArgobus]

Well it worked out just okay. I moved the inverter charger and battery pack to the most aft compartment behind the rear axle. I installed the toilet, a porcelain counter top for the kitchenette, painted the interior, removed a bunch of unnecessary 2x4 framing, cleaned up and tidied the whole thing, put a vinyl floor in, and declared the interior of the bus to finally be complete.

I put in the baseline supplies that will go with for every trip, including cat litter, first aid kits, kitchen supplies etc, and brought it to the scales. Fortunately the scale on base is always open and for free, AND it has a hose on site.

So with a full fuel tank, full baseline supplies, and NO water, and no driver, the weights came out to be:

Front 3680
Both 7880
Rear 4040

With a full water tank:

Front 3800
Both 8180
Rear 4260

Add my fat ass to the drivers seat, and I have about 100 pounds of slop remaining in the front axle. That is NOT ideal, considering that load doesn’t include any clothing or food, but the passengers sit behind the rear axle so that will help shift the CG back. We haven’t added the bumper rack yet so that too will help out.

In any case, my plan is to fill up with water at the destination so as to minimize the load while driving.