Grit dog wrote:
terrybk wrote:
I see the order of importance as (descending):
1. Tire ratings as measured against the axle weights. Most of the camper weight is on the rear tires.
2. Physical axle rating (the actual axle, not the RAWR). Most of the camper weight is on the rear bearings.
3. Rear axle weight rating (RAWR) - Most of the camper weight is here.
4. Front axle weight rating (FAWR)
5. Gross vehicle weight rating (GVWR)
The gross (GVWR) is primarily a function of the tires, axle and frame/suspension. A dually and SRW of the same series (3500/350) almost always have the same frame. The rating goes up because of the tires. For a long time manufacturers capped the GVWR of SRW trucks at 9900lbs for registration and tax reasons. Throw two more tires on there and you get 11k+ rating. This is not a comparison of 2500/250 to 3500/350. That is a totally different topic.
I'm not suggestion or endorsing exceeding any rating but this is the list I considered when sizing my camper to my truck.
As far as "stability" of a dually, I've never been sure what that means. Most lean is in the springs/suspension not the number of tire. No doubt more tires increase number 5 above (GVWR) but they have little effect on sway and leaning or "stability." At least I have never experienced a difference. A big sway bar, air bags and good springs go a long way to limit leaning. If you need an extra tire out there to keep the camper and truck from falling over, you have bigger issues.
Certainly, if you are pushing the truck hard in a turn, more tires tend to give more friction on a dry surface and help keep the truck back end from swinging out. Try an over-sized trailer on an SRW in tight downhills if you want a high pucker factor. You can feel the rear want to get pushed sideways.
The labels on the camper and truck are a rough starting point but you have to weight everything - period. Everything else is a guess. The campers always weight more than their labels and the truck weight can vary too. It's hard to decide if a camper is "too much" before you buy it, but you can with some research get close enough to move forward or rule out a rig. Ask on the forums if anyone has actually weight there rig together and separately. You can learn a lot.
Scales - they are your best friend.
Essentially what he said. But I'll add rim load rating right up there with tires. Both of which are nowhere near their failure point at their rated loads. Regardless of what anyone says, tires and OE rims have a large factor of safety. It's a simple function of the liability of mfgs in the event of a failure (and years of "experience" doing stuff with trucks that should have had bigger trucks do it...lol). Not recommending grossly overloading, but in the context of this scenario, putting 8klbs (4500lb camper and 3500lb truck axle weight) on 3600lb rated rims and tires is 400lbs "over" or just over 10%. Again, not advocating it publicly for others, take it for what it's worth. lol
Good point on rims. I'll insert that for anyone that sees it in the future. My 2005 3500 has steel wheels because the 2500 aluminum weren't rated high enough.
I was thinking about bouncing and the pressures the tires experience when 4000lbs comes down on a bounce. Agreed. The tires can handle a lot more.
