GVWR vs. Axle ratings.

[vinmaker]

Could someone explain something to me?

In looking at the numbers on the new pop up I will be getting, the white sticker on them says that the GVWR for the pop up is 4,573lbs. It lists the front axle at 2,100lbs and the rear axle at 2,100lbs. If I combine the ratings for the front and back axle I get to 4,200lbs. This is under the GVWR.

Why does it seem logical that the axles would need to support the weight of the trailer? How can something rated for 4,200lbs support 4,573lbs?

What am I not understanding?

Thanks,

Vin.

[Joe_GA]

Some of the weight is on the tongue which is supported by your tow vehicle or the stand, when disconnected from the tow vehicle.

[Joe_GA]

BTW, the tongue weight is probably about 15% which is 630 pounds. That leaves 3570 pounds or 1785 per axle.

[TURBS]

As Joe said the difference in weight is tongue weight which is supported by tow vehicle.

I have two 6000# axles "12,000#" with gross at 14,000#'s my pin weight is 2,000 #

Hopefully that helps.

TURBS

How can I annoy OC today?

[vinmaker]

Ah. Ok. I can see that.

Sure as heck does not leave too much extra does it?

Vin.

[vinmaker]

As you know the unit builds can cause a bit of variation from unit to unit.

But in doing some quick math based on the above.

Both axle rating are 4,200lbs total. The spec sheets per mfg brochure say a 373lb tongue. These both add up to 4,573lbs which is the published GVWR.

Vin.

[thebrakeman]

It's ridiculous that they made this popup with everything so close to the limits. I guarantee one of those axles will be overloaded.
4573 - (2*2100) = only 373lbs left for TW.
That's only 8%, which is not acceptable.
And that assumes that you can balance the weight perfectly across the 4 wheels.
I would not load this camper more than about 4000 lbs.
They should have used 2500 lbs axles for some flexibility.

[Kaadk]

Originally Posted by thebrakeman

It's ridiculous that they made this popup with everything so close to the limits. I guarantee one of those axles will be overloaded.
4573 - (2*2100) = only 373lbs left for TW.
That's only 8%, which is not acceptable.
And that assumes that you can balance the weight perfectly across the 4 wheels.
I would not load this camper more than about 4000 lbs.
They should have used 2500 lbs axles for some flexibility.

Yes, but the more you put on the tongue, the less you put to the wheels. So, the better approach is:

4573 * 15% TW = 686 (rounded) TW.
4573 - 686 = 3887 lbs

Distribute that across 2 *2100 lbs = (2*2100) - 3887 = 313 lbs

313 / 2 axles = 156.5 leeway per axle.

Assuming an even weight distribution that puts 15% on the tongue and an even load per axle.

[thebrakeman]

But nobody will ever check individual axle weights on a 2-axle trailer. I used to have a popup for 7 years. There is not much ability to fine-tune as you suggest. You put weight where there is room, and usually right at the door so you don't have to pop the top.

[Kaadk]

Originally Posted by thebrakeman

But nobody will ever check individual axle weights on a 2-axle trailer. I used to have a popup for 7 years. There is not much ability to fine-tune as you suggest. You put weight where there is room, and usually right at the door so you don't have to pop the top.

I agree. I was just referring to how I think FR rationalizes the ratings they use. In actuality, it's quite easy to overload the load ratings of the individual tires just by loading the one side of the trailer more than the other.

In the OP's case, the floor plan he's got on order according to his signature looks like it really only lends itself to adding weight forward of the axles. So whatever weight he adds is going to be distributed to the tongue somewhat and wouldn't be 100% over the axles.

[AquaMan]

When you realize that the GVWR is a calculated figure, it all makes sense. The designers don't start with a number(GVWR) and work backwards, they start with a camper, add axles, figure tongue weight(designed), and then calculate the GVWR. That's why it always seems so close.