TV tire pressure?

[Flapper]

Just replaced the worn out stock Goodrich Rugged Trail "E" tires with Michelin Defender LTX. Of course the tire place did not fill to the right pressure....Ford says 55/60.

Which go me thinking...for trailers, conventional wisdom is to inflate to max. pressure. What about tow vehicles? Is there an authoritative guide to adjusting inflation based on load?

For those that care, my specs are: 2012 F-150, SCrew, 4x4, Eco, Max Tow, HD Payload - door sticker is 2166 payload. Never gave it a thought with the old tires, pulling a fifth that got me right to max. payload, and they lasted 65,000. Now with a TT, payload will be around 1,600. Tire max is 80 lbs. Should I vary from the door sticker inflation?

[jadatis]

P255/65R17 I found with google in Loadindex 108 and when putting XL behind it in 114.
So my suspicion was right , that you have P-tires with AT pressure of 35 psi if Standard load LI 108 /1000kg/2205 lbs , and AT 41 psi if XL/reinforced/Extraload LI 114/1180kg/2600 lbs.
so look on sidewall wich one it is,P says Americansystem, Eurometric tires have 1 psi higher AT-pressure, and mostly 1 Li step higher , but are in fact the same tire so can carry same weight at same pressure.

So the 51 psi you thougt was the pressure you needed to determine the loadcapacity, is in fact the maximum cold pressure the tiremaker allows.

So check the tires to see what they are exactly , and try to determine the weights on the seperate tires , second best axles.
Also give speed you use and wont go over for even a minute for the situation ( so when towing lower speed), And the speedcode of tire ( Q,R,S,T,H,V,W,Y) , then I can give a range in pressure advice with lowest no damage to tires , and highest pressure, still acceptable commfort and gripp.

[steve-n-vicki]

Just to add some more information, the tires are p255-65r17, the tire manufacturer has discontinued this tire and has been superseded by a new improved tire, so no putting the OEM tire back on

[jadatis]

steve-n-vicki wrote:
figure this one out
OEM tires ,2205 max load at 35 psi max pressure, door sticker 35 psi,
replacement tires 2337 max load at 51 psi max pressure , if i run these at 35psi per the door sticker the load chart says 1604 pounds of weight, for me to get back at 2205 load i have to run 48 psi in the tires,
so do i run the truck manufactuers tire pressure of 35 psi or the tire manufctures pressure of 48

the 51 psi of your new tires is a bit strange.
That is mostly given as maximum allowed cold pressure on a Standard load or XL/reinforced/Extraload P-tire ( or european system equivalent.
This makes me suspect the At-pressure ( pressure for wich maximum load is calculated up to reference-speed of tire) is lower.
This is for SL P-tires AT 35 psi and for XL AT 41 psi.
This then is the highest pressure you find in the pressure/loadcapacity list you read from.

This also makes me suspect your OEM tirepressure advice to be yust given for maximum load of tires, so the carmaker can never be hold responcible if you use lower.

So can you give me the exact sises of both new and OEM tires , so I can google for what kind of tires they are and so what AT-pressure belongs to that.

[Grit_dog]

Grit dog wrote:

steve-n-vicki wrote:
figure this one out
OEM tires ,2205 max load at 35 psi max pressure, door sticker 35 psi,
replacement tires 2337 max load at 51 psi max pressure , if i run these at 35psi per the door sticker the load chart says 1604 pounds of weight, for me to get back at 2205 load i have to run 48 psi in the tires,
so do i run the truck manufactuers tire pressure of 35 psi or the tire manufctures pressure of 48

Lower profile tire?
What do I win?

The real question is what capacity do you "need" front and rear for a given condition?
Empty driving, must be a smaller,older truck. Even stripper F150s come with 44psi skinny 235/245 wide tires for years now.
1600lb per tire = enough load capacity for any empty rear axle weight on a half ton pickup. Gettin close on big crew cabs with "standard" beds though. I got about that 37 psi cold in my crew cab half ton with a 500lb tool box and it rides like a dream. OE 255 70 17s.
1600lb per tire is a bit light for a newer V8 pickup front tire especially if there's more than 2 doors in the equation.

[Grit_dog]

steve-n-vicki wrote:
figure this one out
OEM tires ,2205 max load at 35 psi max pressure, door sticker 35 psi,
replacement tires 2337 max load at 51 psi max pressure , if i run these at 35psi per the door sticker the load chart says 1604 pounds of weight, for me to get back at 2205 load i have to run 48 psi in the tires,
so do i run the truck manufactuers tire pressure of 35 psi or the tire manufctures pressure of 48

Lower profile tire?
What do I win?

[TJMarc]

steve-n-vicki wrote:
figure this one out
OEM tires ,2205 max load at 35 psi max pressure, door sticker 35 psi,
replacement tires 2337 max load at 51 psi max pressure , if i run these at 35psi per the door sticker the load chart says 1604 pounds of weight, for me to get back at 2205 load i have to run 48 psi in the tires,
so do i run the truck manufactuers tire pressure of 35 psi or the tire manufctures pressure of 48

The pressures are only valid for the application listed on the label. Once you change the tire size, the pressures are no longer valid. Due to the number of variables involved and the lawsuits...the vehicle mfg position is likely that you should not be changing the tire size from what was provided at the point of sale, so one needs to utilize our best judgment.
The tire mfg and/or the TRA provide minimum pressures are based upon a number of assumptions/limits...its up to the consumer to determin if they fit within those assumptions/limits and that it's an appropriate number.

[steve-n-vicki]

figure this one out
OEM tires ,2205 max load at 35 psi max pressure, door sticker 35 psi,
replacement tires 2337 max load at 51 psi max pressure , if i run these at 35psi per the door sticker the load chart says 1604 pounds of weight, for me to get back at 2205 load i have to run 48 psi in the tires,
so do i run the truck manufactuers tire pressure of 35 psi or the tire manufctures pressure of 48

[TJMarc]

If you are looking for actual published data...other than the door jam. I guess closest to definitive would be corner weighting your truck and using the manufacturers load tables for your tires. Then maybe next up would be axle weights and the mfg load tables. I suppose following that would be either of those methods and using the Tire and Rim Association (TRA) tables. I usually do the axle weight vs. the mfg load tables.

[jadatis]

It would in fact be a good way to measure the deflection of the tire.
That is what pressure for a sertain load on tire is all done for, to give the tire a deflection that wont give to much heatproduction for the speed you drive.

In the bycicle world 15% of free flecible part of sidewall is concencus.
Also for cars I read this 15% a few times.

This can be measured simply with a ruler , mesure for instance from middle of wheel to ground, or from rimm edge to ground .
Once you know howmuch deflection is save , you can always measure that.

But because weight R and L are mostly not the same on the axle, you would need different psi in them to give the same deflection.

[Grit_dog]

My apologies. Not many "authorities" on here, mostly opinions, many of which need to be taken with a grain of salt.
I couldn't find a load inflation table for your particular tire, but any tire chart of the same size and load index will work.
For a rule of thumb, you got E load tires presumably......since you didn't post the size or tire rating, probably like a 265/275-65/70-17/18.
Empty pickup, 35 psi rear is sufficient, so like maybe 1500lbs per tire actual load, but the tires are good for 2000? Lbs at that pressure. Full load on tires = 3100-3400lbs per tire at 80psi.
If you're at about 2500lbs per tire with your tongue weight and a cooler full of beverages in the truck bed, plus some firewood, etc, doing the math will put you in the 60psi range

That's about as authoritative of a response as I can muster with the info given and not looking at a load chart.
After well over a million Windshield miles in pickup trucks, towing and hauling whatever you can think of, for E load tires, standard LT pickup tires, I run 35-45psi empty depending on the weight of the truck. 55-60psi towing or hauling reasonable items, stuff that puts a ton of less extra weight on the drive tires and full 80 psi when hauling a 2 ton camper or a loaded truck with a substantial tongue weight. Never really calculated it but if the tire isn't bulging it has enough air and when loaded it's better to be over the min psi for the weight than under.

Hope this was helpful.

[Flapper]

Grit dog wrote:
4th tire pressure thread in a week!
Read folks, read......

Actually, I do, daily. The threads didn't show up in the last few days when clicking on "Active" to review what's going on that day.....

AND.. the other threads all have mostly user opinion. Note that I asked about "authoritative" sources - implying Michelin, Ford, or other. Going all the way to 80lbs may be the best in some opinions, but that is the max., not necessarily the best for traction, handling, stopping, ride, wear, etc. Your advice should be applied to your own responses, also.

[jadatis]

If the maximum load ( or loadindex) and Loadrange ( old LR E) are the same, you can use the same pressures.

so give of both tires that maximmum load or loadindex, Loadrange or AT-pressure.
and if you can find for both tires, the speedcode wich stands for maximum speed and mostly also the speed for wich the maximum load is calculated.

[Grit_dog]

4th tire pressure thread in a week!
Read folks, read......

[donn0128]

Go with the tire plackard and you should be good. If you had a HD truck and LT tires, I would suggest 80.