Hey Folks,

I have read on here (and on super duty forums) about "airing up or airing down" tires for different applications or because of purchasing new tires. I understand the offroad/rockclimbing reasons, but I am more wondering the street reasons. I read other posts about folks buying LT tires for a 1/2 ton truck and "airing them down", or someone who is towing who "airs them up" to higher psi. Is there a science to this? Is it all trial and error? What are the thresholds? I tow often (3500lb boat, about 15K miles a year), and was curious if I should be doing the same. Thanks so much for all the input.

Respectfully,
Craig

 

The max PSI listed on the sidewall of the tire is how much air the tire needs to handle its specified weight limit. This much air dosent always have to be in the tire, as when you are not hauling/towing it will make the ride harsh. This is why people will air down (usually to manufacturers suggestion on door sticker) when they will just be driving around and air back up to tow, the tire needs the extra air to handle the weight. If not it will be like trying to drive on low tires, generating more heat and opening yourself up for possible tread separation issues.

 

Be aware that the pressure in the tire affects the profile of the tire. An under-inflated tire will wear the outer edges of the tire because the center of the tread is not carrying the weight of the load. The opposite is that when over-inflated the tire will wear the center of the tread as the outer edges are lifted due to the bulging of the tire.
One way of checking for a good pressure point is to find a smooth area of hard surface (concrete or asphalt) and make a puddle to drive through. Look at the tread pattern coming out of the puddle and see if there is an even footprint across the path. If it is heavy on the outside and lighter in the middle the tire is under-inflated. Heavy in the middle and light at the edges you have too much pressure.
Check the inflation info on the door post of the drivers door for the correct inflation for your vehicle.
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From my '07 Taurus

 

My tires are load range E and call for 80psi. If I put them that high the rear of the truck jumps around and it gives you a really hard ride. I keep them at 50 for everyday driving. When I tow my camper I have to air them up to at least 65psi so the truck doesn't feel "mushy" and handles correctly. If your tires are are lower load range and only call for 44psi you really don't have to worry.

 

Great info guys! I appreciate it. Bigtony: it sounds like you adjust based on your feel, correct? Shorebird: that puddle test seems like it would work great. I run whats on the door panel for everyday driving, and I will try the water test and some different psi's when I have the boat hooked up. Thanks again all.

-Craig

 

I do adjust by feel. When you get up in the 60's and 70's the back of the truck becomes very stiff and wants to jump out if you hit a bump going around a corner. At 75 mph that becomes a little dangerous.