Posted 2010-07-01 8:22 AM (#121790 - in reply to #121697) Subject: RE: tire pressure and overdrive
Regular
Posts: 92 Location: Harrisburg, PA
Originally written by gard on 2010-06-29 10:50 AM
The truck's recommended tire pressure is based on more accurate information than a sidewall maximum. But it's definitely not the rule, and on many vehicles it's asking for trouble.
????? What kind of trouble? More tires are damaged and experience blowouts from under inflation than over inflation. The Explorer/Firestone debacle is but one example. The manufactures are interested in a compromise between ride quality and utility, and their recommendations reflect those interests.
The Explorer/Firestone thing is important because it underscores the importance of correct tire pressure. Firestone blowouts were not just about a weaker tire, but in each case it was high speed driving in high ambient temps with heavy vehicle loads, and UNDERINFLATED TIRES. It's pretty safe to say that most all of the issues would not have happened if the driver had checked their tire pressure.
Originally written by gard on 2010-06-29 10:50 AM
The higher the tire pressure, the less rolling resistance will be experienced and a lower opperating temperature will result. Heat will kill tires by delaminating the sidewalls and causing blow outs.
Overinflation very quickly diminishes in value w.r.t. rolling resistance. A little more is a little better, but a lot more is not. While the door jamb value might give up 0.5 mpg vs. adding 5 psi pressure, adding 10 or 20psi is worth nothing.
Posted 2010-07-01 9:39 AM (#121794 - in reply to #121517) Subject: RE: tire pressure and overdrive
Expert
Posts: 5870 Location: western PA
Dgeesaman, I agree with your comments.
Mine were based on LT tires, being run at 80 psi. I don't recommend over inflating a tire, and yes, there is little value in less rolling resistance when the tire is being destroyed by over inflation.
The owners of the Explorers were told to run their vehicles' tires at~<30 PSI, which as you have noted, was underinflated and caused sidewall blowouts. These pressures were condoned by Ford for ride quality, against the recommendations of Firestone. The unknowing vehicle owners could have been very prompt in their mainentance. However by following Ford's schedule, they set themselves up for the exact circumstances you've described.
As I've tried to point out, each of us has different rigs and requirements. We all do things that work best for us. I and some others use one pressure. Others use different ones. The tag on the door cannot differentiate among our various needs, and offer the best recommendation for each of us.
Posted 2010-07-02 1:15 PM (#121833 - in reply to #121517) Subject: RE: tire pressure and overdrive
Member
Posts: 11
Location: The Nederlands Europe
If you read everything from the tires like "max load xxxxkg at yyy kPa cold", or in lbs and psi, you can calculate the needed pressure with spreadsheet I made , in wich I use the European( most savest) equation, that I once got hold of. http://cid-a526e0eee092e6dc.office.live.com/browse.aspx/.Public/Car... in this map the spreadsheet . If it is all abacadabra for you , give me the details, besides the tire-specifications above mentioned, the Gross Vehicle weigt ratings of the trailer ( GVWR) and I will do it for you as an example. For the car I also made and translated a spreadsheet,navigate to it from the link above
Here the linkable link , thougt it went automatically.
But b ythe Ford Explorer/firestone affaire the American Tire-manufacturers discovered that they had used the wrong power in the universal equation ( 0,5 ) , and after the affaire they upgraded it to the european power of 0,8 wich comes to higher pressures at reduced loads.
You could read next article about a new way of calculating and the comparison with the diferent used power-equation in America and Europe
tire pressure and overdrive
