# Tire Psi When Towing



## bka4tcu

I have been towing trailers of many varieties for many years. The Outback has caused me more concern than anything else I have towed. I usually run my tires at 75psi on the rear and 65psi on the front when towing the trailer. Doing so with the OB I notice I was getting a weird wear pattern n the rear tires. So I rotated the tires, went back to the tire recommendation on inflation and put 70psi in the rear and 62 in the front. After a couple trips, I noticed I am getting the same excessive wear on the center tread of the tire. I do not think I am overinflated, but maybe I am. That is the only reason I can see for the tread wear I have. So, I now have a set of tires with excess wear in the center of the tread. The tires have 38,000 miles on them and are the ones that came with the truck, all but about 10,000 of those miles have been with a trailer. I am going to buy new tires and will probably go with a Michelin tire of some kind.

Does anyone have a suggestion or a formula for calculating the right tire psi when towing? I would like to avoid a repeat of the problem I currently have if possible. I am also thinking it could be that the stock tires are just not holding up to the wear and tear of pulling the trailer.

Thanks for any advice you may have to offer.


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## Herbicidal

My first thought was WOW!!! That tire pressure is really high! I know my truck may not be as heavy as yours, mine on a scale came in @ a tick below 6,000 lbs with only me and a full tank of gas. I run my truck tires (load range E) @ 40 psi (when towing) and the Outbacks at 50 psi. Everything works great! I realize we don't have the same tires either so not exactly apples to apples. An old trick to check if tires are over-inflated or under-inflated is to take a piece of childrens sidewalk chalk (these are quite large) and taking the long edge, rub it on as much of the tire as you can get, then on flat/smooth ground and in a straight line, drive forward for several tire revolutions. Stop and check to see where the chalk has rubbed off and where it remains. Adjust tire pressure accordingly to get the chalk removed evenly across the entire tire face. Yeah, I know, rather low tech but each vehicle has different tires, is loaded differently etc. My .02.


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## Lad79der

Herbicidal said:


> My first thought was WOW!!! That tire pressure is really high! I know my truck may not be as heavy as yours, mine on a scale came in @ a tick below 6,000 lbs with only me and a full tank of gas. I run my truck tires (load range E) @ 40 psi (when towing) and the Outbacks at 50 psi. Everything works great! I realize we don't have the same tires either so not exactly apples to apples. An old trick to check if tires are over-inflated or under-inflated is to take a piece of childrens sidewalk chalk (these are quite large) and taking the long edge, rub it on as much of the tire as you can get, then on flat/smooth ground and in a straight line, drive forward for several tire revolutions. Stop and check to see where the chalk has rubbed off and where it remains. Adjust tire pressure accordingly to get the chalk removed evenly across the entire tire face. Yeah, I know, rather low tech but each vehicle has different tires, is loaded differently etc. My .02.


I run 65psi on all 4 corners empty... I run 65 up front, 80 rear when towing... 07 Ram 2500 Cummins 4x4 Quad Cab. Says it on the door.


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## WYOCAMPER

I think it depends on your tire. P-rated tires will be different than LT rated. And even LT rated may be different between Lod D or Load E. I am assuming you have LT on your Chevy 2500? Do you know the brand, size and if they are D or E rated off hand?


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## Joonbee

I am 65 front and 55 rear when empty, 75 front and 80 rear when towing. Need to weigh new trailer and truck combo, but so far I am getting decent wear and control.


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## duggy

bka4tcu said:


> I have been towing trailers of many varieties for many years. The Outback has caused me more concern than anything else I have towed. I usually run my tires at 75psi on the rear and 65psi on the front when towing the trailer. Doing so with the OB I notice I was getting a weird wear pattern n the rear tires. So I rotated the tires, went back to the tire recommendation on inflation and put 70psi in the rear and 62 in the front. After a couple trips, I noticed I am getting the same excessive wear on the center tread of the tire. I do not think I am overinflated, but maybe I am. That is the only reason I can see for the tread wear I have. So, I now have a set of tires with excess wear in the center of the tread. The tires have 38,000 miles on them and are the ones that came with the truck, all but about 10,000 of those miles have been with a trailer. I am going to buy new tires and will probably go with a Michelin tire of some kind.
> 
> Does anyone have a suggestion or a formula for calculating the right tire psi when towing? I would like to avoid a repeat of the problem I currently have if possible. I am also thinking it could be that the stock tires are just not holding up to the wear and tear of pulling the trailer.
> 
> Thanks for any advice you may have to offer.


Are you running load range "E" tires? If not, you shouldn't be running those kinds of pressures. What are the manufacturers recommended pressures? What tire pressures do you run when you're not towing? Do you have a weight distributing hitch? If so, and you have say 800 lbs tongue weight, you're probably adding about 500 lbs to the rear axle, and 300 lbs to the front axle. That's not much different than having a couple large men in the back seat, and one more in the front seat.
I don't run my tires any different when I tow, than all the rest of the time. I carry tools in my truck when I'm working, and remove them when I'm camping. I think the weight pretty much balances out. Mine are load range "E", and the recommended pressures are 80 psi in the rear, and 50 psi in the front. I now run 70 psi in the rear, because the ride was too bone jarring with 80 psi.


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## wolverine

My 2007 1500HD has load range E tires and the truck calls for 80 psi rear and 50 psi front. The tire wear is likely from the limited slip rear end. My 1500HD and my 2003 1500 work truck both wear the rear tires faster than the front. My work truck has load range D tires and it rarely pulls anything. My uncle's 2005 Dodge with a Cummins wore the rear tires faster than the front and he had Michelin tires.


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## KTMRacer

I'm pulling a 295RE with my CC duramax. I run 65 front and rear when towing, tongue weight is 1400lbs and a Reese dual cam trunnion WD setup. I suspect yours is similar in tongue weight. I have about 4400lbs on each TV axle. So far no unusual wear patterns, and we tow the trailer about 10K miles/year. When I tow my cargo trailer or empty I drop the rear by about 10lbs. If you got 38K out of OEM tires, you beat me by a long shot. Mine came with Bridgestones, and I wasn't impressed, to put it politely!! Mine were gone in about 25K miles. Then I went with Toyo's lasted about 45K miles. Now have Michelins, look like they will go 50K or more. Just remember the Eaton autolocker rear on the silverado can really eat up rear tires if you aren't carefull on sharp turns from a stop. It's easy to engage the locker and end up skidding a tire.


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## huntr70

Probably more the factor of junk stock tires than the inflation you have in them.


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## W5CI

Just look at the Recommended Pressure on the tire sidewall, that is what you are supposed to run, Loaded or Empty


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## CamperAndy

danny285 said:


> Just look at the Recommended Pressure on the tire sidewall, that is what you are supposed to run, Loaded or Empty


That is not true for pick-ups due to the significant load differences between unloaded and loaded. The truck manufacture normally posts the tire pressure recommendation inside the drivers side door that is based on its carrying capacity.

The side wall shows the air pressure when at full rated tire loaded weight. If you run that high all the time you will get accelerated center tread wear.


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## Stance

danny285 said:


> Just look at the Recommended Pressure on the tire sidewall, that is what you are supposed to run, Loaded or Empty


Like Andy mentioned, the sidewall is not the OEM's recommended tire pressure. It's the max allowable pressure from the tire manufacturer. You cannot exceed it.

The OEM recommended tire pressure is on the door jamb or elsewhere on the truck. I strongly suggest sticking to it because you don't really know what the minimum pressure is or what the side effects are. If you go below it, you risk tread separation. Secondly, and more importantly, tire pressures are set up by OEMs to achieve _safe handling_, proper wear, stopping distance, fuel economy, etc. If you mess with it, you may affect how the vehicle handles in emergency situations.

If you want to change it, you can look up what the tire pressure should be for a certain load and tire size in the Tire & Rim Association charts (http://www.us-tra.org/index.html). What these charts show are the industry standard minimum tire pressure needed to carry X load on Y tire size. You would have to stay above that minimum.



Herbicidal said:


> ...I realize we don't have the same tires either so not exactly apples to apples. An old trick to check if tires are over-inflated or under-inflated is to take a piece of childrens sidewalk chalk (these are quite large) and taking the long edge, rub it on as much of the tire as you can get, then on flat/smooth ground and in a straight line, drive forward for several tire revolutions. Stop and check to see where the chalk has rubbed off and where it remains. Adjust tire pressure accordingly to get the chalk removed evenly across the entire tire face. Yeah, I know, rather low tech but each vehicle has different tires, is loaded differently etc. My .02.


That's pretty much a static test. It doesn't take tire dynamics (speed, cornering, etc.) into account. If you want to try something at home, a better means is to drive around and then measure the tread surface temperature across the tread. You are looking to set the temperature evenly across the tread. You would need something like an infrared temperature gauge.

I work for Ford as a chassis engineer. So, I know a little about tires. However, my knowledge isn't very deep.

Edit:
I should point out that my comments and opinions are completely of my own and are not necessarily shared and/or endorsed by Ford.


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## bka4tcu

I have run at the OEM pressure and on either ride, higher and lower. I am guessing it may be a combination of things, but probably the tires themselves. I'll be getting a new set before our first spring trip.

Thanks for the input. I love this forum!


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