dry truck weight

kaydeejay wrote:

Dayle1 wrote:
On a similar line, when people ask about what PSI to use in their trailer tires, the most common answer seems to be to inflate them to the max PSI on the tire sidewall. I can't recall anyone referring to the sticker on the side of the trailer.

Because trailer tires are spec'd by the trailer manufacturer to be able to JUST carry the load on them when the trailer is fully loaded.

That is a generalization. The four stock ST tires on my fiver were rated for 3200 lbs more capacity at max. PSI than the axles they were mounted on. Also, many units have CCCs that are very large and the trailer is unlikely to be loaded to the GVWR. In my case, If I inflated the ST tires to the maximum sidewall PSI, they would be overinflated to the tune of almost 1200 lbs per tire.

The "6100lb" rear axle on my F250 has all the same hardware that makes a 7k axle on an F350 except 2" blocks and overload springs. The blocks don't increase suspension travel; they just jack the truck up in the air. I put air bags on that serve the same purpose as the overloads but ride better when you don't need them. The 20" wheels are the same ones on a 7k axle and the tires are rated for 7500lb combined. You can put an 8lb label on a 12 lb sledge but it's still 12 lb.

Just because someone puts 7k on a 6k axle doesn't mean the wheels are going to fall off.

edit: I made the assumption he would increase pressure to cover the added load but now I see that's what you were worried about. And, I'm not advocating overloading... I will never be near my 6100lb rating but know I have more to spare.

rhagfo wrote:

Why are you so sure that he is over his GRAWR????

Full timing in a Lifestyle LS38RS, dry pin of 2814 lbs, so I’m guessing he is around 7k on the rear axle vs. 6100 lbs GAWR.

4x4ord wrote:


As far as convincing him that he is overloading his truck goes you need to ask yourself "what for?" He has already bought the truck and trailer and if he's overloading his rear suspension by 1000 lbs its not like its a safety issue. Its not going to affect the handling or braking of the truck. Worst case is that if the nose is pointing to the moon he will have a bit of an alignment issue which could cause a little front tire wear. He could add airbags to level it out.

The “what for?” is to maybe prevent a blowout and serious accident. I’m not concerned about the suspension carrying an extra 1000 lbs, but guess I feel different about overloading the tires, especially since the tires are rated for the extra 1000 lbs if inflated to the proper PSI.

To the first question, the only way to truly know the dry weight of his rear axle is to weigh it. By comparison, my 2010 F250 with a V-10, crew cab, short bed tipped the scales at 3140lbs.

To the second, the tire pressure on the door sticker reflects the OEM tires' recommended pressure for the maximum axle loads. So, for example, my door sticker lists the max pressure as being 65psi because, at its 6600lb rear Gross Axle Weight Rating, that's the air pressure Bridgestone recommends running at to support 3300lbs per tire. The tire is rated for something like 5600lbs @ 85psi, but there is no reason to run them at the max pressure on the sidewall if they're never seeing that load.

That being said, I run them inflated to the pressure for the load. So, when it's empty, the recommended pressure is something like 55psi. Loaded for a weekend of camping, trailer in-tow, they run at 65 if my memory serves because, loaded-up, they are seeing 4280lbs, and that's the recommended inflation pressure for the tires under that load.

So, all that being said, adjust the tires for the load they're seeing, plain and simple.

kaydeejay wrote:

Dayle1 wrote:
On a similar line, when people ask about what PSI to use in their trailer tires, the most common answer seems to be to inflate them to the max PSI on the tire sidewall. I can't recall anyone referring to the sticker on the side of the trailer.

Because trailer tires are spec'd by the trailer manufacturer to be able to JUST carry the load on them when the trailer is fully loaded.
At this load they SHOULD be inflated to max sidewall pressure.
The recommended pressure on the sticker (for OEM size tires at least) will probably agree with the tire sidewalls.
Unlike an empty truck, the empty weight of a trailer is still up there and the load on the tires will not be a whole helluvalot less percentage wise. No need to reduce pressure for that.
Plus of course, once the trailer is loaded with all your stuff (except perishables) it will probably not vary that much from one trip to another.
OTOH I DO adjust my truck tires. I run 70psi rear with the fiver on, reduced to 45psi when unloaded. I do not adjust the front tires as the weight on them hardly changes.
These pressures are 5psi higher than the tire pressure tables suggest for the loads I am running.
The empty ride is much improved with the rear pressures reduced.

Same here. I do run the fronts higher on my Dually at 80 because I don't rotate front to back just side to side on the fronts. Seems to wear more even with a bit more pressure. The rears at 45 solo and 60 loaded wear evenly.

On the newer Mobile Suites they are using GY H 17.5's and have a lot of excess capacity. I will be running 110 instead of 120MAX on new MS 39' on order. I run 105 on current 36' MS with the 17'5's I added and with many thousands of miles I have even tread wear.

Agreed MOST RV's should run MAX psi.

Dayle1 wrote:
On a similar line, when people ask about what PSI to use in their trailer tires, the most common answer seems to be to inflate them to the max PSI on the tire sidewall. I can't recall anyone referring to the sticker on the side of the trailer.

Because trailer tires are spec'd by the trailer manufacturer to be able to JUST carry the load on them when the trailer is fully loaded.
At this load they SHOULD be inflated to max sidewall pressure.
The recommended pressure on the sticker (for OEM size tires at least) will probably agree with the tire sidewalls.
Unlike an empty truck, the empty weight of a trailer is still up there and the load on the tires will not be a whole helluvalot less percentage wise. No need to reduce pressure for that.
Plus of course, once the trailer is loaded with all your stuff (except perishables) it will probably not vary that much from one trip to another.
OTOH I DO adjust my truck tires. I run 70psi rear with the fiver on, reduced to 45psi when unloaded. I do not adjust the front tires as the weight on them hardly changes.
These pressures are 5psi higher than the tire pressure tables suggest for the loads I am running.
The empty ride is much improved with the rear pressures reduced.

lbrjet wrote:

handye9 wrote:
On my 08 F250, axle ratings are:

Front 5600
Rear 6100

My door sticker also says 65 PSI. I run them at 75 when loaded up. Max is 80.

Same axle ratings on my 2010. My door sticker says 75 all around.

Is that what you run unloaded?

handye9 wrote:
On my 08 F250, axle ratings are:

Front 5600
Rear 6100

My door sticker also says 65 PSI. I run them at 75 when loaded up. Max is 80.

Same axle ratings on my 2010. My door sticker says 75 all around.

Sport45 wrote:

Dayle1 wrote:
On a similar line, when people ask about what PSI to use in their trailer tires, the most common answer seems to be to inflate them to the max PSI on the tire sidewall. I can't recall anyone referring to the sticker on the side of the trailer.

That's because heat/UV/Road Hazard/ect kills trailer tires long before the tread wears out. Keeping them at max cold inflation pressure lets them run a little cooler. They also roll easier, saving some fraction of a mpg. Again, the tire won't last as long as the tread so it's best to get all you can out of it.

Good points.
I would add tire on our trailers side scrubb around each corner and while backing. This action in very hard on the tires internal belts. Watch a 80 psi rated tire with say 65 psi in it under these circumstances ....... the tire is very distorted. Now air it up to the max sidewall and watch it on the same scenario. The tire has a much less distorted shape and less internal belt stress. Tire damage is cumulative.
Out trucks with tires at the corners where the front set steers and the rears simply follow don't have a side scrub issue like a close spaced axles in the center of the trailer.

Door placard inflation pressure recommendations are a good starting point. Watch the tires wear pattern on the rear and on the front and fine tune for the best pressure and best wear. I air up the rears when towing or carrying loads but drop the pressure down to the 45 psi range when empty. None of my other trailers or the RV add weight to the trucks front axle so I leave it at 65 psi 24/7.

Your trucks tires and loads will be different so fine tune them for their best wear pattern across the tread.

Dayle1 wrote:
Thanks for all the responses. In my personal experience, I've never owned a tow vehicle where the rear GAWR didn't match the tire load capacity. And always figured that optional tires were an appearance upgrade and they would not have a higher load capacity.

On a similar line, when people ask about what PSI to use in their trailer tires, the most common answer seems to be to inflate them to the max PSI on the tire sidewall. I can't recall anyone referring to the sticker on the side of the trailer.

But now I know. Now to explain to my friend that he is overloaded, especially running just 60-65 PSI. The obvious answer is to get to a CAT scale. However we are in a remote area for awhile, don't even have cell phone reception w/o driving 30 miles. But I'll work thru that in the next few days. Again, thanks.

It could be the best thing to do is just show him a tire load/inflation chart so he recognizes that he needs to run his tires to max pressure if he needs the max load rating. As far as convincing him that he is overloading his truck goes you need to ask yourself "what for?" He has already bought the truck and trailer and if he's overloading his rear suspension by 1000 lbs its not like its a safety issue. Its not going to affect the handling or braking of the truck. Worst case is that if the nose is pointing to the moon he will have a bit of an alignment issue which could cause a little front tire wear. He could add airbags to level it out.