Filling up tires right now. What should E rated tires be at when towing?? All 4 or just back ones?

 

Without looking at the door sticker, I would say 80psi. Especially if towing heavy. What does the door sticker say?

 

On tire it says 80 max psi. On door sticker it says 55psi. I think they are same size as stock. 265's.

Were stock E rated?

Either way I thought you weren't supposed to fill to max because the heat expands. We filled up at 55 for now.

 

I daily drive at 55psi, minimum for towing for me is 65, and that's when I'm towing around 6700lbs. Anything over 7000 I max the pressure according to tire sidewall.

Yes, heat expands and increases pressure - however this is taken into consideration when the tire max pressures are set by the manufacturer.

 

Tire pressure opinions vary a lot around here. I personally prefer 65-70 rear and 60-65 up front towing my camper. I just don't like the feel at 80 PSI.

My suggestion is to try some different pressures and see what YOU like. Even at pressures as low as the door sticker, the tire load capacity is higher than the weight of the truck at max GVW.

 

I would go with at least 65/70 on the rears and 60/65 for the fronts with your setup and then adjust from there based on the seat of the pants feel while towing. Sometimes too high of a pressure or too low of a pressure will feel "wiggly" or "squishy" with a load, try moving the pressure up and down 5 PSI. At a time to get a feel for how they handle the load.
When I had 80 PSI rated Load Range E tires I ran them at 80 PSI when towing and I now run my 65 PSI Rated Load Range E tires at 65 PSI all the time. But most of my miles are towing miles with the heavy TT and a very high rear axle weight. I do use a TST 507RV TPMS system to monitor pressure and temperature of all the tires on the EX and TT. It's pretty cool to see how the tires heat up a few miles into a trip and see that the sunny side tires run at higher temps and pressures that the shaded side.

 

Same here. This works best for ME.

This...you need to find what works best for your rig, tires, trailer weight and length, ect.

x2.

Stewart

 

Wow ! I have to say I am sorta stunned by these answers.

What technical basis are you guys using to justify circumventing the engineering ford put into calculating the tire pressure label on the cerfifactation sticker on the door ?

Even the tire manufacture themselves say to go by the vehicle manufactures certification label.

What is it that you think you are gaining by ignoring the engineers at ford ?

 

Not trying to be a &$#% about this but I find this sort of answer irresponsible.

Not to pick on country mouse here but I will use her to make my point. In the context of this post people are suggesting to a person they know very little about but who clearly does not have a high level of automotive aptitude ( by evidence of the fact she didn't know to take off the removable dash fuse panel to look under the dash ) to basically guess at a setting that is critical to safety.

Country mouse has neither the technical background nor the practical experience to be experimenting with tire pressure settings that are outside the vehicle manufactures parameters.

 

Those stickers are a general good pressure the manufacturer has set to please consumers based on ride and handling and mostly to not get sued. Of course a tire manufacturer is going to tell you to abide by the sticker, they don't want sued either. Road manners and physics are what lead me to take my tires up closer to the tire rating when towing. However take my free opinion for what it is worth....I also don't use Ford branded windshield washer fluid and have aftermarket shocks, so I am kind of a rebel.

 

Technically, if another type/size of tire is installed the door jamb spec isn't much good anyway. Nobody is recommending ignoring the engineers that I can see.

That door jamb spec isn't for max load capacity anyway, but Fords idea for most comfortable ride. It's advisable to note what tires are actually installed, what their characteristics are, inflation recommendations and what the manual says about towing inflation.

 

The "Certification label " on your door jamb is mandated by the .gov and the information it contains is a result of the OEM's engineering and testing so the vehicle complies with the federal motor vehicle safety standards.

The label pretty clearly states the GVWR, the load range tire needed and the tire pressure at GVWR.

The max tire pressure listed on the actual tire is just that, the max pressure for that tire. not the pressure for your vehicle with that tire. The tire mfg has no way of knowing what vehicle you will but the tire on.

 

Not even close.

The info listed is the pressure need to operate at GVWR and is based on engineering, and testing as well as decades of data complied from highway crash data.

 

And, the door jamb label mfg has no way of knowing what tires may be installed on the vehicle. So what's your point?

It's no secret that the automobile manufacturers tend to spec tire pressures on the low side of the spectrum - in order to increase perceived ride quality. That's fine, as far as it goes.

Most problems with tires though, the vast majority in fact, are due to under-inflation. It increases the rolling sidewall flex, and thus temperatures go way up, and leads to catastrophic blowouts. It's easy to slip over the line into silliness on this, but, it's under-inflation that is going to cause handling anomalies. If any errors are to be made especially while towing heavy loads, I would wager any engineer would recommend something closer to the max sidewall inflation than closer to minimum sidewall pressure, (again selected for a comfortable ride).

What does the Ford Operator's Manual say about Tire Pressure and Towing?

edit: The operator's manual does not state anything about increasing the tire pressure while towing. Trust me, I looked. So, you're right.

It's also stated (not in the manual) that the recommended pressure on the door jamb is also equal to (at least) the maximum gross vehicle weight rating - so there is no advantage to inflating above this figure in terms of load rating capability.

It sure seems that everybody who tows frequently, says that's all BS, at least in terms of _handling_ and it seems to be common practice for those who tow frequently to leave their tires at, or close to, the maximum pressure on the sidewall. Hm.

 

lets do some math.

I run a 37x12.5x17 D rated tire on my 2001 4x4 7.3 Ex

The 7.3 4x4 Ex has a GVWR of 9200 lbs with a GCWR of 10,000
the GAWR for the front is 4700
the GAWR for the rear is 5250

Load range D tire in 37x12.5x17 is rated for 3525 @ 50 psi

3525 x 2 = 7050
3525 x 4 = 14,100


7050 exceeds my rear GAWR by 2000 pounds
14100 exceeds my GCWR x 4000 pounds or about 30%
FWIW>>> the actual recommended pressure for a 37x12.5x17 D rated tire on a 10,000# GVWR vehicle is 35 psi


Now lets take the tire size on my Certificate sticker of 265/75/16

a 265/75/16 load range E tire has a max weight of 3415 @80 PSI

3415 x 4 = 13,660 or 2,660 pounds over GCWR

Obviously you don't need 80 pounds with this tire so what do you need ?

well according to the engineers who figure this stuff out and test it before putting it on the Certification you need 50 in the front and 55 in the rear running a 265/75/16 E