By Ron Fraser
First published in Rootes Review, 2007
Here are some basic facts about tires that we should all keep in mind, not only for fuel efficiency but for safety as well.
Correct tire pressure obviously has an effect not only on tire wear but also fuel economy. The proper tire pressure for the Tiger running bias ply tires is 26 psi front, 32 psi rear. Today’s radial tires have a maximum load rating on the sidewalls, and the correct pressure for these tires is 35 psi. I prefer to inflate radials to 32 psi front and rear; most manufacturers also recommend this pressure.
There are also tires with a maximum load rating at 44 psi, but there are no published recommended pressures for them. OK, let’s throw a little math at this and get a proportional pressure.
32/35 = X/44 X = 44(32/35) = 40.2 psi
I have this type of tire on my 91 Ford Escort and if I put 40 psi in the tires I can feel every little pebble and grain of sand through the steering and suspension. For my car, 38 psi is more comfortable; a less harsh ride. You can always experiment with the tire pressure, but I recommend at least 38 psi for these higher rated tires.
Higher tire pressure = less rolling resistance = more MPG
There are limits to this theory. Very high pressures create adverse wear patterns, as well as reduced braking efficiency. It only makes sense that the smaller the footprint on the road the less effective the brakes will be. One certainly does not want to exceed the manufacturer’s recommended maximum pressure.
Breaking in your tires:
Did you know there is a break in period for tires? This is new to me. I’m well aware of heat cycling tires to toughen them, but not a break in period. It is recommended that you drive new tires easy for the first 500 miles to get the release agents they use during manufacturing worn off the tread. Tires can feel greasy while driving during this period.
There is a date code molded into every tire and you should know how to read the code. Note that most tire shops will not guarantee tires longer than 5 years. Additionally as tires age the rubber tends to crack; sidewall surface cracks are generally OK but deeper cracks in the sidewall or the tread can be dangerous. For more information on how to determine tire age see Tech Tip L15 – Determining Tire Age
Speed vs. tire pressure:
Did you know that the faster you drive the more tire air pressure you need? Your tires will heat up with distance driven, so be careful to have the correct cold air pressure in your tires.
Look under: Products / Tires / Tire Tech
Tire Rack has a lot of excellent information on tires and wheels. You can navigate their site from the starting point listed above.