Originally Posted By: tig1
I won't infate my tires to that kind of pressure because of the ride quality loss and the likely loss of tire wear.
To make this a bit quantitative, I'll mention that the best research I have seen on the effect of tire pressure upon fuel economy was conducted by Goodyear. They found that each PSI below the placard pressure cost about 0.3% in fuel economy. IIRC, the effect is something like 0.4%/psi for highway, and 0.2%/psi for city. One presumes that going above the placard pressure results in diminishing returns. If your car calls for 32/32, you might increase that to 35/35 to pick up a percent or so. Center wear would be very unlikely at only 10% above the placard pressure.
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As for running 65 MPH, that's danderous when most of the traffic is doing 75-80.
People typically drive 75-80 mph in the right lane in Illinois? I've never been there. That just surprises me. I drive a great deal in New Mexico and Colorado where the Interstate speed limit is 75. People generally drive 70-75 in the right lane. (That lane being the only one you need to care about. The crazo's driving 80+ never leave the left lane except to pass on the right, and there is little you can do about them.)
I have extensive experience (over 100,000 miles) with driving 65 under those conditions, and it's fairly comfortable. Many 18 wheelers are driving 65 mph these days to save on fuel costs.
Here are some Consumer Reports testing results. The difference a few mph makes is substantial, largely due to the fact that wind resistance force increases as the square of velocity, and work to overcome wind resistance increases as the cube of velocity. You asked for 3%. 10 mph might easily get you 10% - 15%.
I won't infate my tires to that kind of pressure because of the ride quality loss and the likely loss of tire wear.
To make this a bit quantitative, I'll mention that the best research I have seen on the effect of tire pressure upon fuel economy was conducted by Goodyear. They found that each PSI below the placard pressure cost about 0.3% in fuel economy. IIRC, the effect is something like 0.4%/psi for highway, and 0.2%/psi for city. One presumes that going above the placard pressure results in diminishing returns. If your car calls for 32/32, you might increase that to 35/35 to pick up a percent or so. Center wear would be very unlikely at only 10% above the placard pressure.
Quote:
As for running 65 MPH, that's danderous when most of the traffic is doing 75-80.
People typically drive 75-80 mph in the right lane in Illinois? I've never been there. That just surprises me. I drive a great deal in New Mexico and Colorado where the Interstate speed limit is 75. People generally drive 70-75 in the right lane. (That lane being the only one you need to care about. The crazo's driving 80+ never leave the left lane except to pass on the right, and there is little you can do about them.)
I have extensive experience (over 100,000 miles) with driving 65 under those conditions, and it's fairly comfortable. Many 18 wheelers are driving 65 mph these days to save on fuel costs.
Here are some Consumer Reports testing results. The difference a few mph makes is substantial, largely due to the fact that wind resistance force increases as the square of velocity, and work to overcome wind resistance increases as the cube of velocity. You asked for 3%. 10 mph might easily get you 10% - 15%.
