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Old 06-29-2012, 09:18 AM   #1
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Glenn5995's Avatar
Join Date: Feb 2011
Location: Phoenix AZ
Posts: 927
Why the correct tire PSI may not be on the door or the max on the tire

An over inflated tire causes the tire to ride on the center of the tread, an under inflated tire on the outside of the tread as pictured:

An underinflated tire can't maintain its shape and becomes flatter than intended while in contact with the road and could lead to tire failure. The tire’s tread life is reduced. Lower inflation pressure will allow the tire to deflect (bend) more as it rolls. This will build up internal heat, increase rolling resistance and cause a reduction in fuel economy, but more importantly is one of the leading causes of blow outs and tire failures. You will experience a significant loss of steering precision and cornering stability.

An overinflated tire is stiff and unyielding and the size of its footprint in contact with the road is reduced. An over inflated tire can be be damaged more easily when running over potholes or debris in the road. Higher inflated tires cannot isolate road irregularities well, causing them to ride harsher and tend to "bounce" over road irregularities and at times not be in contact with the road surface. Like the under inflated tire, the tire's tread life is reduced. However, higher inflation pressures usually provide an improvement in steering response and cornering stability up to a point.

Both under and over inflated tires have a decreased contact with the road surface, resulting in a decrease in handling and braking performance on wet surfaces.

In a recent case a member changed tire size and load range, so the sticker on the door for tire pressures means nothing now.

The weight of the vehicle will be dependent upon options and if the Tahoe (in this case) is four wheel drive or not and what cargo you will carry. A base Tahoe has a curb weight of around 5600 with around 2900 on the front axle and 2700 on the rear. The SV-291 (camper in this case) has a dry tongue weight of 544 and dry weight of 4807 with a GWR of 7544. Lets assume you don't overload the trailer and have a trailer weight of around 7300 with a tongue weight of around 850. That would give you a weight of 6450 on the trailer tires or about 1612 per tire if the weight was equally divided between the tires (which it never is). I would therefore make sure you have enough pressure for your specific tires on the trailer to support 2000 pounds each.

Your Tahoe will now have its 5600 plus the 850 from the tongue weight of the trailer for 6450. You now have to add the weight of passengers and cargo, so let's say your Tahoe is at about 7300, which is about the GVWR for a Tahoe. You are of course using a weight distributing hitch , so the weight is fairly equal, being slightly heavier in the rear with 3500 on the front axle and 3800 on the rear axle. So the front tires would have 1750 per tire and the rear tires 1900 per tire.

When you weigh (if you do), you will probably find like most, that you are over on just about everything, so I would start with this info as a guide, make your calculations and then add 10 PSI per tire as long as you don't go over the max PSI rating for the tires. Hope this helps with at least finding a starting place, but to get it right you need to go to the scales.

Good luck and Happy Camping!

Glenn & Beth (Dad & Mom)
David & Audra (12 year old twins)
2006 Dodge Power Wagon (Adventure & Tow Vehicle)
2006 Rockwood 8281SS (Home away from Home)
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