Tire Pressure When Towing

[Tireman9]

I suggest that everyone go, look at your tires and actually read what the words say. Most tires have a warning or Safety warning in a sentence about mounting and inflation in general. That is where you will see something about 40 psi or 44 psi being the maximum to use.. This is not the same as the standard statement on load and the inflation needed to support that load.


The reason for the 40 or 44 "max" is that some people insist on inflating tires till they "look right" and in some cases this can be 50% to 100% above the normal inflation for SatndardLoad tires.


LT tires have Load Range C or D or E
Passenger tires are either "standard load or "Extra Load".


Standard load would be similar to Load Range B or 35 psi just as LR-C is 50, LR-D is 65 and LR-E is 80 for most tires.

[wrvond]

Originally Posted by Papahoosh

Should the tires pressure be different in my TV when I am towing vs. not towing?

Check your owner's manual.
Here's what mine has to say on the subject:


The Ford recommended tire inflation
pressures can be found on the Tire Label,
which is located on the B-pillar or the edge
of the driver's door. This information can
also be found on the Safety Compliance
Certification Label (affixed to either the
door hinge pillar, door-latch post, or the
door edge that meets the door latch post;
next to the driver’s seating position).

Ford strongly recommends maintaining
these tire pressures at all times. (emphasis mine) Failure to follow the tire pressure recommendations can cause uneven treadwear patterns, reduced fuel economy, and adversely affect the way your vehicle handles.
Note: Check and set the tire pressure at the
ambient temperature in which you are
intending to drive your vehicle and when the
tires are cold.
Note: Check your tire pressures at least
once per month.
Set the pressure for your spare tire to the
highest value given for your vehicle and tire
size combination (if equipped).


Lots of opinions and information in this thread. My take on it is I have a lot riding on my tires and I'm going to follow what the manufacturer of my vehicle tells me is best. I've got 60,000 miles on my current set of tires (OEM Michelin's) fully half of which is towing campers. Went in for service just yesterday and the report says I am at 50% tread life.



It don't get no better than that.

[Lins]

Originally Posted by Tireman9

Simple answer is YES. Since proper load capacity is a function of having the proper inflation and since towing will increase the load on the TV rear tires by a few hundred to more than !,000# depending on the trailer you will most likely need to adjust your pressure unless you are running the "towing inflation" all the time.

Finally, some common sense. Using scale weights and load charts for my stock tires, it's surprising what PSI is actually required compared to what Ram is forced to say what I need.

[Lins]

Originally Posted by andymil

I never thought about it but this makes sense. With the bed empty and one or two people in the cab, there has to be more weight on the front axle. Why would you need more pressure in the rear tires unless you’re loaded?

I’ve been running 60 and 65 like the door sticker says when not towing and bumping the rear tires up to 80 when towing. I may have to rethink that.

Andy, our Ram specifies 65 front, 80 rear. With the factory 20" E rated tires, which are huge and wide compared to donut tires that typically came on older HD trucks, do NOT require that PSI according to the load chart for the tires. Scale weights on our recent summer camping trip with trailer hooked up are 5192 lbs front axle, 4554 lbs rear axle (note: 250 lbs below the 10k GVWR). According to the load chart provided by Ram for a 2016 model (no longer available for newer models) that puts me at 50-55 PSI front, 40-45 PSI rear. I had the TPMS reprogrammed on our truck last summer, and those are the PSI's we ran for our trip this summer.

[Hersbird]

If you have switched from P series tires to LT series tires for sure don't go by the door sticker even when not loaded. LT tires at 40 psi or less hold less weight than the same size P metric tire at 40 psi. LT tires need that extra pressure they are designed for.

I personally go max cold even when not towing on all my cars and van. I have backed off my Ram a bit off the 80 psi because it goes off road more and 80 isn't good off road. When towing I put it back up to at least 70 psi. On everything I have ever owned I get more life and better MPG with max cold on the sidewall. Ride may suffer but everything besides the Ram rides like a dream anyway. Never have had center wear issues at max psi and that's cold. They will go well above max when hot and that's OK too, never adjust them down when hot.

I know that is going against the grain but everything is a compromise. I'll take a rougher ride for a little more MPG. Anybody will tell you under inflation is definitely really bad. I'd also rather be further away from the danger zone then right on the edge. Those TPMS don't constantly update. I can pull my summer tires off, and put the snows on which don't have sensors. The car will go weeks without the light coming on because it still is getting reading for the tires just sitting at the edge of the garage every morning before driving off to work. To me that shows it's really not checking itself very often.

[Boomerweps]

Always go by the vehicle manufacturer's recommendation?
In 92 time frame, Ford recommended about 20 PSI (or so, foggy memory) for Explorer tires. In the manual it stated to increase the PSI by a certain amount for each 10mph over the legal speed limit. Why would that be stated clearly? National speed limit was 55mph. Ford thought they could make the Explorer ride softer that way. Many deaths and injuries later, and after throwing Firestone under the bus, Ford bumped the Explorer's tire PSI back to a more reasonable range (28 IIRC). Firestone accepted the blame to keep Ford's business and Ford paid to replace those model tires (as good as any I had owned).

[spock123]

In between trips I lower the air pressure in my rear tires for a softer ride. I usually run 60psi in the front tires and 80psi in the rear when towing with my 3500 Silverado. At home I run 60psi all around, if I leave 80 in rear it makes for a rough ride

[Lock1]

I did not read all of the posts, so if I'm repeating something, I apologize.


My method is as follows:

1. Weigh your vehicle and trailer with all of your gear, all of your passengers, and a full tank of gas at a certified scale (used for semi trucks mostly). The scale will give you the weight on each axle.
2. Then look up the ratings of the tires (TV and trailer). For instance my ratings for my Michelin Lt275/70/R18/E are 3640lbs @ 80psi. Then divide the max load by the max psi (3640lbs / 80psi = 45.5lbs/psi). Then divide the weight of each axle by 2 (if you have 2 tires and not 4 on a dually). My drive axle is 5080lbs, (5080lbs / 2 = 2540lbs). Then divide 2540lbs by the 45.5 lbs/psi (2540lbs / 45.5lbs/psi = 55.82psi). 55.82 is the minimum psi in each rear tire. I add about 10lbs to each tire for a safety factor.

So I inflate my drive (rear axle) to 65lbs (just to be safe), and I'm ready to tow.


Good luck and enjoy!

[itat]

I scaled my F250 both loaded (with the TT attached) and unloaded as my daily driver. The truck has LT tires. I checked the load and inflation chart for the tires and set the psi for a bit higher than needed for the load they are carrying in each scenario.

[Villagerjjm]

Cold PSI on my tow vehicle tires is 35psi. When I drive, that may raise up to 40psi. Tire guys say that is normal. When I tow my trailer with my weight distributing hitch, cold pressure on my tow vehicle is 35psi. After I tow for a while, the psi on all 4 tires is 40psi. The tire guys say that is normal. Tires grip because of friction. Friction causes heat. Excessive friction creates excessive heat. Excessive heat causes tire deterioration and premature failure. You may not notice it with pressure sensors. When you stop for breaks, do a safety check that includes tire temperature.

[Airdale]

The correct tire inflation pressures for your tow vehicle’s Original Equipment (OE) tires was set by the vehicle manufacturer. They displayed those pressures on the vehicle certification label, tire load placard and in the vehicle owner manual. If they determined a need to adjust those pressures for unusual circumstances/conditions they provide the adjusted pressures in the vehicle owner manual.

Optional conditions are open for discussion. Those optional inflation pressures start at what was recommended and end at the pressures needed for the tire to carry its maximum load.

There are rules and regulations that the vehicle manufacturer must follow when building any vehicle under the guidelines outlined in the Federal Motor Vehicle Safety Standards (FMVSS). For Automotive vehicles there is a mandatory load capacity reserve. They do it two ways. One is by providing load capacity reserves with the GAWR settings. Another is by tire inflations that provide load capacity reserves above the vehicle’s certified GAWRs. Look at the recommended cold inflation pressures on any of your vehicles certification label. Are they going to provide more load capacity than the axle rating?

Now we go back to the optional conditions I described above. Why would anyone use that option to set their tire inflation pressures to the load carried? There is no room for error. You’re relying on your inflation equipment to be perfectly calibrated. And, to insure your pressures are correct you’ll have to insure your weight is correct every time you are +/- a passenger. A ballpark figure is a 1# loss of inflation pressure equals a 1.6% loss of load capacity in that tire.

Load capacity reserves for our personal vehicles have worked well for a long time. Don’t let some wishy-washy statement from the commercial side of the house interfere with the way your tow vehicle’s tires are supposed to be inflated.

[phfkef]

A tire is an engineered component.

The correct answer is to use a load inflation table. Definitely increase pressure with increased load, the table will tell you how much.

[Dkhinz]

Thanks Airdale.

Best and most comprehensive article I have seen on tire inflation. I have seen the same results with my rig. I have a Yukon XL with 10 pl. tires, max inflation 80 psi. My 26' trailer has tires inflated to 45 psi. My Yukon runs fine around town on 50 psi. but towing my RV is no good, too squishy and uncomfortable. When I inflate to 80 psi. everything is as it should be. I keep my RV at 45 psi. all the time.

[LegacyFB38]

Originally Posted by phfkef

...The correct answer is to use a load inflation table. Definitely increase pressure with increased load, the table will tell you how much.

2X...no, actually 1000X!


There is some good information in this thread. And some not so good. And some just plain wrong.

[mwdilday]

Or do like the tire manufacturers and vehicle manufacturers say and look in your vehicle manual for inflation instructions. They give you detailed inflation instructions and I have NEVER seen anything about weighing or any inflate to the max pressure on the sidewall or any crazy mathematical calculations. Also, never seen a manual say "put on a bigger tire and inflate it to the max and you'll be good to go". Just look at your vehicle owners manual for info and use your tire pressure and loading info sticker. Don't overload, obey tire speed limits, use the correct tire specified, inflate to proper PSI before every trip, buy quality name brand tires, inspect tires often and get a TPMS. There is no magic here.

[Lins]

Originally Posted by LegacyFB38

2X...no, actually 1000X!


There is some good information in this thread. And some not so good. And some just plain wrong.

Agreed.

There's a big difference in traction, ride and how the tire wears running 40-45 PSI per the load inflation table vs RAM's 'mandatory' 80 PSI.

[mwdilday]

Originally Posted by Lins

Agreed.

There's a big difference in traction, ride and how the tire wears running 40-45 PSI per the load inflation table vs RAM's 'mandatory' 80 PSI.

I can go along somewhat with lower PSI on a truck that is a daily driver to some extent. But a RV has a static load and playing with the numbers is just wrong. All RVS are close enough to the gross weight even when empty that just go with the sticker.

[Lins]

Originally Posted by mwdilday

I can go along somewhat with lower PSI on a truck that is a daily driver to some extent. But a RV has a static load and playing with the numbers is just wrong. All RVS are close enough to the gross weight even when empty that just go with the sticker.

I was talking about the TV, we run 50 in our C load tires on the TT. When they get replaced next time we'll go with Goodyear Endurance and run a little more PSI.

[LegacyFB38]

Originally Posted by mwdilday

...and get a TPMS. ...

1000X

[BandJCarm]

Originally Posted by LegacyFB38

2X...no, actually 1000X!


There is some good information in this thread. And some not so good. And some just plain wrong.

Every thread is full of same. Many legitimate questions are answered with "This is what I own/have/do", not what the OP SHOULD own/have/do.

Experience is good, if it is directly related. But I'm sitting here now waiting on a Fuel ECM wiring harness to show up for my Duramax LML engine, so I can finally get on my way!!! I posted that, but it has surprised me I don't get these answers:
-You shoulda got a Ford
-My RAM doesn't have that problem
-Try adding a fuel additive
-Not sure why you want to camp there

LOL

P.S.
I'm also having unusual tire wear, but have not said a lot about it. MorRyde suggests (in a multiple email conversation about it, with pictures) that it's due to overinflation. We discussed actual CAT scale ticket numbers, etc etc etc. But I'd also bet that one would get 1,000 responses of what I should do, mostly from folks with vastly different setups.

That's also a concern I have about this site. I read about a problem, and think I might can help, then see that the issue is from a Motorhome. So I bow out. I really wish this site were split in two, MH's and Trailers.