Tire Pressure

[MIDNIGHT RIDER]

Grab your kids sidewalk chalk and make a thick line across the tread. Then drive the truck slowly forward about a half a block and see how it wears. You want enough pressure that it wears off evenly. So just add or subtract it till you find it.

My compliments on the ingeniousness of the chalk trick.

I have been around tires and in the business all my life and that is the first time I ever heard that chalk trick.

I am sure going to experiment with it, as soon as it ever quits raining.

 

[jauguston]

The pressure shown on the tire side wall is the MAXIMUM pressure for that tire and almost always is not the correct pressure for your vehicle. Weigh front and rear axles and the chart will tell you what the correct pressure is. Overinflation is almost as bad as underinflation.

Jim

 

[TLBREWER]

My compliments on the ingeniousness of the chalk trick.

I have been around tires and in the business all my life and that is the first time I ever heard that chalk trick.

I am sure going to experiment with it, as soon as it ever quits raining.

I never considered using that on automotive tires. 'Course I drive on a lot of gravel and dirt roads. Used the chalk trick for twenty years on aircraft tires. I believe it was even specified in the tech manuals. Hmmm...

Tom

 

[Mr_Roboto]

Same here, I would guess 7,000 or so empty.

For the sake of comparison, when I come out of the scrap yard (empty) my rig weighs 9400# to 9500# (depending on fuel level). Subtract me @205# takes it to 9200 - 9300#.

While I'm 2wd, I have the whole front push bumper filled with concrete, the bed, hydraulics and lots of hydraulic fluid.

A cheap way to get weighed is to run some scrap metal to the local salvage yard. You'll get the weight to the nearest 20#.

Another note on inflation. In my experience, narrow tires can handle overinflation better than flotation type tires. Something like a 235/85 just gets stiffer if overinflated, where something like a 33x12.50 (which is about the same height) will have the center of the tread bulge out if overinflated. I suppose they all have the tread bulge, but the wider tires have more tread room to change shape.

 

[icanfixall]

Also a point and shoot heat temp gun (laser dot) type thermometer will tell you lots about your tire pressure, front end alignment and heat buildup in a tire. The wife uses it when we stop. I just use my wooden stick fish knocker along with my had for tire temp.

 

[sle2115]

I can't believe no one has recommended the "kick your tires" method!!!

 

[ericboutin]

The Dewey weighs approx 7200 lbs everyday loaded with just my toolbox and all the crap I have in it. I had new tires put on the truck and they filled em to 80 lbs and it scared the crap out of me the first time I made a corner!! I thought for sure I was gonna run off the road. As soon as I got to the house I lowered the pressure. I think I ended up with 60 in the back four and 55 or 60 in the front. These are load rated E tires. I've also found that with the TT hitched up this tire pressure still works good.

 

[tonkadoctor]

I can't believe no one has recommended the "kick your tires" method!!!

I don't kick 'em......I use a 4 lb short handle sledge ....... Years ago when I was driving OTR I used to be able to tell very accuratly by the sound of the thump if I was a couple lbs low in pressure, then again I was checking them 4 - 5 times a day too.

I still do this on my dually once a day on the rears and if one sounds slightly different than the rest I break out the gauge.

Thinking of putting cat eyes on the new dually

 

[Mont91]

Here's my inflation story.

I run a school bus 140 miles a day on dirt and gravel. Currently I am running a B-600 Ford, in the past I have also run 1 ton van chassies. I got new drivers over Christmas break. First thing I did was drop the pressure from 90psi to 50psi. I also run 50psi in the front. With 90psi the bus bounces all over the place and rocks tear them apart. I never run over 45mph and check side wall temp, this tells me when a tire is a few pounds low. But I know when they have lost a meaningful amount of air by the change in squat. Radials are supposed to squat. When I first started running busses the tire man told me the centers were chewing out and leaving unharmed edges because they were underinflated??? I haven't listened to him much since.

My spray rig, 3/4 ton Dodge, runs about 8,500lbs so I keep 70 to 80lbs in the rears and they wear nice and even. About 45 in the front. My personal pickup has 50 in the nose and anywhere from 45 to 80 in the rears depending on the load.

Our county belly dumps run 70 to 80lbs loaded with 20 yards of gravel. Of course they doen't go very fast as we have no paved roads.

Speed and load are very important when determining tire pressuers. Even passenger vehicles tell you to increase pressure when hauling anything other than paasengers or traveling at high speeds for extended periods. Under inflation for the load and speed is what blew those firestones on explorers.

If the centers are wearing out you have more air than is needed to carry the load. If the edges are wearing out you do not have enough air for the load. The chalk or paint idea is a quick way to tell.