Isuzu npr 4wd

[SkiFreak]

Thanks i'll be underweight . The rating on the rear is 3950 lbs a tire. So 7900 lbs on the rear.

That is on flat ground, but it does not take into account how much weight would be over a single tyre if your going up an off camber 4WD track and one rear wheel went into a deep rutt.

Tyre ratings are based on running them at the specified tyre pressures. When you go offroad you will likely be lowering the tyre pressures, which lowers the load rating of the tyre.
When running with lower pressures you will also get additional heat in the tyre, and the heavier the load, the greater the heat will be. Overheated tyres are a common cause for tyre failure.

I agree with @Ferjablito... 1800kg will be very tight.
Personally, I would not feel comfortable working right at the upper limit of a tyre's capacity, which is what you will be doing.

 

[gator70]

That is on flat ground, but it does not take into account how much weight would be over a single tyre if your going up an off camber 4WD track and one rear wheel went into a deep rutt.

Tyre ratings are based on running them at the specified tyre pressures. When you go offroad you will likely be lowering the tyre pressures, which lowers the load rating of the tyre.
When running with lower pressures you will also get additional heat in the tyre, and the heavier the load, the greater the heat will be. Overheated tyres are a common cause for tyre failure.

I agree with @Ferjablito... 1800kg will be very tight.
Personally, I would not feel comfortable working right at the upper limit of a tyre's capacity, which is what you will be doing.

Not concerned thanks

However, when I air down, I will keep the speeds low. At my age, i'm fine if the trip takes longer.

Since the articulation is still of concern to me, more so because of the cab over bed. I'm going to avoid those deeper ruts.

Ground clearance is a big part of off-road camping. Not rock-climbing.

Just will not go down those trails.

Not trying to compete with a unimog.

 

[gator70]

Higher rated tires, especially Goodyear's have a much higher risk.

@drivetheglobe will tell you

 

[rruff]

Since the articulation is still of concern to me, more so because of the cab over bed. I'm going to avoid those deeper ruts.

Get it teetering on diagonal tires, and see how it looks. I doubt it will touch. I have 2" clearance when flat and level and wish it was less. And mine is on poly isolators which have some flex.

 

[gator70]

Get it teetering on diagonal tires, and see how it looks. I doubt it will touch. I have 2" clearance when flat and level and wish it was less. And mine is on poly isolators which have some flex.

I designed in 4 inch clearance to the cab roof.

Then the spring brackets, have higher compression closer to the cab. The same in frame center. And in the back medium compression with an extra travel of 2 inches (plus 3 inches). Where as the others have only 3 inches.

This should mean the habitat follows the front axle somewhat more with a 3 inch movement side to side, and the main twist is over the rear axle.

(There are 12 springs of 5,5 length in total)

This is over a 14 foot on frame length.

This is always, an engineering assumption requiring testing to know for sure.

 

[Ferjablito]

Thanks i'll be underweight . The rating on the rear is 3970 lbs a tire. So 7940 lbs on the rear. By manufacturers spec.

Currently I'm at 1800 kgs with the habitat "dry" - this is according to manufacturer

A tire marked "128Q" has a load index of 128, meaning it can support a maximum load of 3,970 pounds per tire, and a speed rating of "Q," indicating it's safe for speeds up to 99 mph.

The truck empty is 5900lbs

Due to crew cab the truck is 55% front, 45% rear weight distribution.

The habitat due to the cab over bed is 55% rear, 45% front weight distribution, and that changes with water tanks full.

Can I guess I have an extra 1800lbs of payload over the rear axle?

I'm going to build a storage compartment between the rear bucket seats and store heavy stuff there as practical.

Check the load on the front axle as well. I don't know exactly how it will be in the Isuzu. In the Fuso, the front axle cannot be overloaded by more than 1000 kg. They are vehicles designed for loading on the rear axle.

 

[SkiFreak]

the front axle cannot be overloaded by more than 1000 kg

Neither axle should be overloaded at all.

 

[gator70]

With each tire capacity at 3970 lbs, and each axle capacity at 7940lbs

chat GPT lays out the actuals

To properly plan the truck's weight distribution with all liquids, let's calculate the following:

1. Base Truck Weight Distribution (Dry)
   • Truck weight: 5,900 lbs
   • Front axle: 5,900×0.55=3,2455,900 \times 0.55 = 3,2455,900×0.55=3,245 lbs
   • Rear axle: 5,900×0.45=2,6555,900 \times 0.45 = 2,6555,900×0.45=2,655 lbs
2. Habitat (Payload) Weight Distribution (Dry)
   • Habitat weight: 1,800 kg = 3,968 lbs
   • Front axle: 3,968×0.45=1,7863,968 \times 0.45 = 1,7863,968×0.45=1,786 lbs
   • Rear axle: 3,968×0.55=2,1823,968 \times 0.55 = 2,1823,968×0.55=2,182 lbs
3. Fuel and Water Weights (Over Rear Axle)
   • Gasoline:
     • 40 gallons × 6.3 lbs/gal = 252 lbs
   • Fresh Water:
     • 150 liters × 2.2 lbs/liter = 330 lbs
   • Total liquid weight: 582 lbs, all over the rear axle

Total Weight on Each Axle (Fully Loaded)​

Front Axle Load​

• Truck front dry: 3,245 lbs
• Habitat front: 1,786 lbs
• Total front axle load: 5,031 lbs

Rear Axle Load​

• Truck rear dry: 2,655 lbs
• Habitat rear: 2,182 lbs
• Fuel & water: 582 lbs
• Total rear axle load: 5,419 lbs

Final Truck Weight (Fully Loaded)​

• Front axle: 5,031 lbs
• Rear axle: 5,419 lbs
• Total: 10,450 lbs

Note: As you see i'm in good shape - but thanks to everyone for the comments

 

[gator70]

Some Mercedes, MAN, LMTV trucks are much higher capacity. Over 20,000 lbs

Right sizing your rig is complicated. The American pickups are too light duty, and some rigs mentioned above may be too heavy duty

Both the FUSO and Isuzu are more in the middle

Habitats over 16 ft, are more of an issue.

I can't break my back changing a military tire

 

[rruff]

Where did you get the .55 and .45 numbers from? Pretty sure your front axle will have >55% of the weight when bare, and more than 55% of your added load will be on the rear axle.

 

[gator70]

I'm a newbie at changing a tire

What jack equipment should I keep onboard?

 

[gator70]

Drinking water system under the sink planned

 

[Eizenjin91]

I'm a newbie at changing a tire

What jack equipment should I keep onboard?

I assume you will have an air compressor for airing up/down tires? If so use an air/hydraulic jack. You can get a cheap one at walmart even. Way faster and easier than hand pumping a bottle jack. You just hold an inflator lever. We run 50” tires on beadlocks which weigh a hell of a lot more than these. I run a 1/2 M18 Milwaukee electric impact for the lugs. Zips them right off and on with no effort. Can easily do a tire change single handedly. Just make sure you keep the tire upright and you’ll be fine at any tire weight.

 

[SkiFreak]

chat GPT lays out the actuals

Maybe you should use ChatGPT for all of your future questions, given that you seem to have so much faith in its accuracy.
Personally, I would prefer responses from real people with real life experiences, but you do you...

 

[gator70]

Does anyone know where I can source departure angle storage boxes??