Monday, August 04, 2008

Tire Gauges Are Funny - To Republicans

If you've paid attention you know that I drag race. I have several tire gauges, one for each vehicle, but in respect to drag racing - I have expensive gauges. My tow vehicle and trailer and front tires on the hot rod use a 100 pound per square inch gauge, the hot rod's rear tire gauge tops out at thirty psi in one tenth increments. This stuff is important.

It is very important when towing a trailer with a three thousand pound expensive car on it to have stable tires, and considering that all those tires on the road add up to a lot of rolling friction there is a lot of gasoline at stake with a powerful engine pulling that show. I have to cross mountain ranges to go anywhere, it counts. The trailer likes 35 psi, depending on which vehicle is doing the towing, the pressure should be 80 psi or 45 psi. Low tires mean poor mileage and worse, hot tires which lead to blow outs and erratic steering.

Then there is drag racing, a motor sport involving small fractions of a second. I run the front tires on the hot rod over inflated in search of reducing rolling resistance - there is no danger involved, the tires will not travel a mile at a time and the difference is startling. The rear tires being drag slicks are very pressure sensitive with track temperatures having a large impact. Depending on the tire compound and maker I'm using on these 8.5 inch by 26 inch tires the pressure may be 8.5 psi or 12 psi. These tires must grip the launch pad sufficiently to move this car from 0 to 45 mph in sixty feet in 1.7 seconds. Tenths of a pound pressure make a large difference.

Pretty obviously gas mileage is not an issue, 4 miles per gallon isn't transportation mileage but that is also as bad as it gets for that car. To give an idea of the effect of softer tires rolling resistance, when the front tires were at standard street pressure the car finished the quarter mile at 99 miles per hour, with the tires over inflated it finished at 104 miles per hour. If the maximum performance of a high performance vehicle in extreme conditions is affected 5% in a short distance consider the results on a street vehicle, and your wallet. A candidate with a millionaire wife might scoff...

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