Adjusting tire pressure for load

[4xMike]

So my tires on my dually are wearing heavily in the center indicating over inflation. I typically run 80 psi loaded (load range e) and 65 empty. Judging by the wear, I should be running significantly less


Beware: math ahead!!!

I haven't weighed mine, but found someone with a nearly idenical setup and got their weight.

Empty is 4500 front, 3000 rear
My camper weighs between 3000 and 3500 wet, and his weight bias was nearly 100% of the camper weight on the rear axle.

My tires are range e and rated at 2850 in dual or 3050 in single at 80 psi

Would it be proper to deflate my tires in a linear fashion to match the weight on them?

Example. 4500 lbs divided by 2 is 2250. The tire is rated at 3050 at 80' or 38 pounds per psi. By this theory the front tires should be correctly inflated a t 60 psi

On the rear they are at 35 lbs per psi ( 2850/80). 6500 lbs across 4 tires is 1625 lbs per tire. Divided by 35 lbs/psi is 46.4 psi.

This would explain my overinflated wear pattern, but it seems crazy to run my tires at 45 psi in the rear while loaded. One one hand it makes sense as I am only running st 1/2 the tire capacity, but at the same time I'm afraid of the loss of tire stability (specifically lateral stability) by running at almost 1/2 of pressure

Any insight? Thoughts? Input?

Thanks,
Mike

[canuck_1]

On My Dodge 4x4 dually I run 70 in the front and 45 in the rear empty, 75 in the front and 55 in the rear loaded.

[jadatis]

stevenal wrote:
http://www.goodyeartrucktires.com/pdf/resources/publications/2010_loadinflation.pdf
The source is the Tire and Rim Association, so it should apply to all manufacturers.

I already stumbled on this article, and it shows at the bottom of page 1 that the pressure most think is the maximum is in fact the minimum required presure for the maximum load.
TRA allows even 10 psi for LT tires above that, and for truck tires even 20 psi above that maxloadpressure as I saw it called also.
so dont be afraid to go over the fi 80 psi if that is the pressure printed on the sidewall ( E-load/10plyrating).
for topic starter this all is not the issue.

Page 2 even gives at lower speed 9% addition above maximum load without highening up the pressure.

[DWeikert]

Perhaps I'm oversimplifying, but it seems to me the goal should be to have at least the required pressure for the load. Setting the pressure to "match" the load isn't necessary. As long as you don't exceed the max cold inflation pressure on the tire, adding more than the load chart indicates would affect tread wear but not do any harm. I prefer low rolling resistance so I keep my rear 75-78 and the front 60-65.

[Butch50]

Take a peek at you driver side door panel and I'll bet that they have tire pressure there. Normally on a dually 80# is way to much on the rears and the manuf probably calls for somewhere around 60 PSI on the rears and this is for a full loaded truck to the max GVWR.

I agree with using a tire inflation chart for the weight carried but you do need to spend the 9 to $10 to get the weight of your rig and not use someone elses and guess what your camper weighs loaded ready to go camping with everybody and all your stuff in it. Then you well have an idea what pressure to run with the pressure charts.

And there is a difference what people run in a SRW and a DRW so taking what people say when they are running a SRW does not work for you. It would be nice if people that are responding would keep their responses to a DRW as that is what the OP has.

This is IMO

[bedrocker]

56 all around unloaded
80 all around loaded
rotate every 5000 miles 🙂

[jimh406]

I agree, use a load inflation chart like stevenal posted. When in doubt, use too much air.

[stevenal]

http://www.goodyeartrucktires.com/pdf/resources/publications/2010_loadinflation.pdf
The source is the Tire and Rim Association, so it should apply to all manufacturers.

[MTRhino]

I have always run 50psi front and back when using as my daily driver and then airing up to 80 when I load the camper. I had to have the TPMS system reset in my current ride to allow 50PSI as it was set at 70PSI and I hate looking at the light in the dash. I just replaced the factory Bridgestones at a little over 45,000 miles and they were wearing very evenly. In fact they could have gone another 10,000, but I run many miles very rough dirt road every month both loaded and unloaded and hate changing flats so replaced them before camping season.

[bjbear]

4xMike wrote:


Would it be proper to deflate my tires in a linear fashion to match the weight on them?

The way I set my tire pressures is to weigh my rig fully loaded, add a little for safety factor and then use the tire pressure charts from the manufacturer.

I have a chart I made up for reference. As you can see, the relationship is not exactly linear, but not that far off. Assuming a linear relationship would not put your calculations off by much and would tend to over estimate the pressure by a small amount. Of course, different manufacturers will have different charts, but I am betting they don't differ by that much.

[bcbigfoot]

I usually run what the truck manufacturer calls for or 5 psi more (if load is under manufacturers gross axle weight rating), this info can typically be found on the drivers side door or pillar. On my dually with a 4000lb camper I typically run 55-60 psi in the fronts and 50 to 55psi in the rears when loaded. The tires on my truck are 235-85-16's and find no stability issues.

[Nemo667]

I use chalk

[jadatis]

Using my spreadsheet i come to 64F and 49 back, and I use my own formula that gives a bit lower pressure then linear math. This is higher then your linear math because I add 10% reserve to the load first.
These pressures wont give damage to the tires, assuming your given weights are right, and thats the tricky point here, but you realise that , I make of your story.
The tires stability is yust how you feel it, a little swaying wont say that the car is dangerously unstable, is my opinion.
Nowadays cars are made that stiff, that we have gotten used to the discomfort, wich a stiffer tire gives, but before 2000 the tiremakers also gave minimum advices.

Here a picture of the spreadsheet but will also give the link to the map where you can download the spreadsheet, search for 4xMike,
Then you can chanche things or add in dark blue the GAWR's and to use reserve % , wich is now set on 10% standard.

Now the link to the map.
The examples map with the spreadsheet 4XmikeRVetc.
See what you can do with it.

[Lowsuv]

srw 2002 duramax with 9200 # gvw
replaced my stock 245 with LT 265/75R16E tires on an 8 inch wide wheel
tires rated 3415 each so 13,660 capacity in the tires .
i run 50 psi year around except when towing when i go to 70 psi.
the charts say 50 psi is good for about 2470 # each
65 psi good for 3000 #
stock 245 were rated 3042 # at 80 psi
i have about 55,000 miles on my 265/75r16E michelin highway tires.
i anticipate another 10,000 miles or so before replacing .
they seem even across the tread

[ChooChooMan74]

Look up the load chart and go from there. I almost never tan my old dually at full pressure.