Auto Q & A
Auto Q & A
By: Dr. Wheels
Topics:
Posted by editor Tue Oct 3, 2006 17:00:23 PDT
Viewed 673 times
1 response 0 comments Dear Q & A: Not long ago a truck mechanic told me the tires on my 3⁄4 ton pickup should be inflated to 80 pounds, for the load I carry. That got me thinking about my big 2002 Lexus SC-300 sedan. The sidewalls on my car’s tires say “205/60R16, 1356 lbs., 44 PSI.” Virtually all of our driving is with just driver and one passenger, on the highway, at around the speed limit. Is a full 44 PSI the safest? When I bought this set of tires, the recommended pressure was 30 PSI. – J.H.
Dear JH: That “44” embossed on your Toyota’s tire sidewalls is maximum pressure, beyond which it can be dangerous to inflate. If you run at 44 psi, you’ll have a harsh ride, increase your tires’ vulnerability to road damage, and rapidly wear out the tire tread down the middle of the tread face. As this column has observed in the past, “recommended” pressure is usually a compromise between comfy ride and tire longevity, in your case, as you said, about 30 psi. However, at your car’s vehicle weight of 3,650 pounds, plus two adult occupants (3,650 plus 300 = 3,950), plus whatever else you normally carry, your ideal over-the-road pressure is more like 32 to 34 psi (checked when tires are cold, of course). PS: Does your owner’s handbook really call for size 205 rather than 215 tires? Some sources raise this question.
Dear Q & A: Somewhere long ago I heard that the Soviet Union used Harley-Davidson motorcycles during World War II. Any truth to this fable? – Arn
Dear Arn: Sure. According to Harley-Davidson: The Legend, by Grant Leonard, during that war, “Harley-Davidson sent 88,000 of their ‘sons’ into battle. Two-thirds of these were used in the Soviet push into Berlin.” In an odd twist of fate, America’s H-D helped the Russians beat US troops to Berlin in 1945. These Harleys were the 45-cubic-inch (750 cc) version, with unsprung rear wheels. (Incidentally, H-D’s lazy design team didn’t come up with any rear suspension until their 1958 Duo-Glide model, way later than the competition.) Thousands of US military surplus “forty-fives” flooded the market in the immediate postwar era, which didn’t help H-D get back into civilian production.
Dear Q & A: How are we doing in the effort to invent and manufacture hydrogen-powered cars to free us from our dependence on foreign oil and clean the damn air? – A Bfld. Breather
Dear Breather: “Damn air” shows some emotion about the issue. Good. A quick review of what’s happening indicates that one of the biggest hang-ups in any future changeover from gasoline to hydrogen power for motor vehicles is in hydrogen storage. This element must be confined at both pressures and temperatures that are practicable for routine, safe, and convenient handling in a broad variety of settings, as gasoline is handled today. There have been breakthroughs, such as in UCLA research led by Professor Omar Yaghi, whose invention, “metal-organic frameworks” (MOFs), also called “crystal sponges,” provides a storage medium that may meet the need. The remaining problem is bringing hydrogen storage temperatures up from an unwieldy minus 196 degrees Centigrade to something that can be dealt with in the real world. It still looks as if we’ll probably have to get along with cars that run on petroleum products for a good while yet. But since hydrogen fuel’s “pollutant” of the environment is just plain water, it definitely remains a damn worthwhile goal.
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