Tire Pressure

Lower your pressure to about 33-34 PSI. This is equivalent to about 31-32 cold tire pressure (if your car has not been driven for about 8 hours).

The recommended pressure is too low, and the pressure put in by tire places, car dealers, etc is too high.

29 is to low, 40 too high. I check mine on the weekends, in the morning before the sun hits the tires, and maintain a 32 psi all the way around. It's a good idea to check the spare every once in a while, too [now that one I will overinflate a bit since I know it loses a little over time].

Just check the tires cold (before driving more than a mile or so) and set to 32 psi. 29 psi (or whatever the manual says, but the manual tends to favor ride over handling) is OK, but all tires tend to loose air over time, so it is better to start on the high side. 40 psi is too high, in fact, a lot of tires have a maximum safe pressure (when cold) of 35 psi. Newer cars have a pressure sensor in the tire valve and a warning light will come on if the tire pressure is too high or too low.

Merritt

all tires tend to loose air over time, so it is better to start on the high side =3D=3D=3D=3D=3D=3D=3D True, but better still to check and adjust regularly.

S... Series Tire Gauges - $10 straight chuck,plus an inexpensive little air pump that plugs into the cigarettelighter socket plus a few minutes Saturday mornings is one of the best performance and safety enhancements available, and once you've made the small initial outlay - it's free.

Thanks for the web site and recommendation. I have been hesitant to buy a gage as I wonder about the accuracy of the usual ones you see on sale.

Merritt

I've been using a regular dial gauge for years now. [Daniel's link isn't working right now, but it looks like he linked to a really good straight dial gauge.]

Be sure you have a good gauge 5 lb off is common. Go with the lb rating on the drivers door

I am always amused when people think car manufacturer's tire pressure recommendations are too low. Anytime they list one set of pressures for all conditions, the listed pressures are a compromise, but I doubt that ride quality is the number one factor when the pressures are determined. I believe safety is number one, followed by fuel economy, then ride quality, then performance, and finally tire life. The weight given to performance, ride quality, and economy may vary depending on the marketing segment (family car, performance car, cargo vehicle), but I think I have the relative order of the factors about right.

There are industry standard load / inflation pressure table for all tire sizes. The vehicle manufacturer's recommended pressures are well above the minimum pressures required to support the loads carried at normal speeds. It used to be that alternate tire inflation pressures recommendations were given for heavier loads and/or higher speeds. These days usually only one number is given. This number is usually specified based on the highest rated load and normal maximum highways speeds (I'd guess that they expect maximum sustained speeds to around 75 mph). Therefore the recommended pressures are probably significantly higher than actually necessary for light loads and lower speed driving. Adding another 3 or 4 psi is overkill from a safety, mileage, or performance standpoint and just makes the ride worse for little or no improvement in the other areas. On the other hand, lots of people like the feel of stiffer tires. And with modern radials, you probably aren't hurting anything. And if you are not careful about maintaining tire pressures, starting out higher than necessary is not a bad thing.

Still, for most people under most conditions, who are using the OE size tires, the vehicle manufacturer's ratings are the best compromise and are conservative from a safety standpoint. Once you change tire sizes, you are often on your own when it comes to determining the best pressures (unless the size you change to is an alternate originally offered on the car).

Regards,

Ed White