I was checking tire pressure today and noticed that the max pressure was 50 psi! Made me wonder about the optimum pressures for wear and mileage with these tires on the Prius. As often as not, the car manufacturer's recommended pressure has as much or more to do with ride than anything else and frequently results in an "under inflated" tires for a softer ride. I already felt the 35/33 pressures to seem a bit low for "low rolling resistance" tires. I'm going to see what Bridgestone has to say.<br><br><br>WaltR

FWIW, I've been keeping an extra 5 PSI in the tires on my Prius (40/38 instead of 35/33) on the theory that it may improve mileage by reducing rolling resistance. <br><br>Since the PSI which I am using is less than the tire's rated maximum, and I don't typically carry a large amount of weight in the car, I think this is safe, and _might_ possibly be beneficial.<br><br>I haven't really noticed any difference concerning mileage or handling, and it's too early to tell if the higher PSI is causing undesirable tread wear (such as in the inner area of the tread.)<br><br>I'd be very interested in hearing other's opinions/findings on this topic. Thanks!<br><br>- Peter

uarzmass said on 11/30/01 3:51 pm:<br><br>&gt;&gt; What are the front and back pressures supposed to be? I heard 38-40 and 40-42... but which one do you guys recommand? Thanks for your input! &lt;&lt;<br><br>See "Tires" under section 9 "Specifications" in your owner's manual (taken from p. 233 of an early US manual):<br>"<br>standard front: P175/65R14 84S, 240 kPa / 2.4 kgf/cm^2 / 35 psi<br>standard rear: P175/65R14 84S, 230 kPa / 2.3 kgf/cm^2 / 33 psi<br>spare: T125/70D16 96M, 420 kPa / 4.2 kgf/cm^2 / 60 psi<br>"<br><br>Personally, I keep my tires around 40psi all around, although I attempt to keep the +2 psi bias on the front when possible. 45psi tends to give too harsh of a ride for me, though.<br><br>basically, anything over what's listed in the manual (but less than the 50psi max for the tires) will help with the longevity of our short-lived tires, but the 42F/40R and the 40F/38R seem to be the favored settings of owners. Try each, and see what you like.

Here's what I'm trying, 42/40 in the Fall and Winter, 40/38 in the Spring and Summer. I live in northern Illinois and with big temperature drops, I expect the tires to lose a couple of pounds, although I haven't seen it yet in the first 14 days of ownership/1000 miles, with 25+ degrees drop in temperature.<br><br>In the Spring when the weather warms up I expect the pressure to potentially go up, so I'll use the 40/38 and monitor every couple of weeks. My full size spare will be kept at 40.<br><br>I'm using tire minders set at 40 all around. When I see one change in the future or I get a tire rotation, I'll check all 5.<br><br>JT

Thank you guys for the inputs!!<br>I just checked mine tire pressure and it's showing 37.5 in the front.. I guess I will pump in 2 more and see what happens... I want to see if there is any MPG improvement.. not that I am complaining about mine (46MPG for this tank), but just want to see if it gets better :)<br><br>Thanks again!

When is it best to measure tire pressure? When they are cold-just starting or after they have been driven? We haven't measured them yet and I didn't want to over or under fill them. THanks!

I sent this out last spring... should still apply.<br><br>Tire pressure will fluctuate approximately 1 psi for every 10 degree Fahrenheit change. <br>This 'change of season' period is one good time to recheck pressure. <br><br>Another 'change' would be if your car was inside for service or parked in a heated garage and then driven out into frigid temps -- You would want the tire psi to be artificially high (in the heated surroundings) to compensate for the outside temperatures the car would be driven in. <br>i.e. Zero degrees outside and 70 degrees in a heated garage. You would want 7 psi more in your tires (as checked in the heated garage) because as the air temp in tires reaches zero there would be 7psi less in tire! This scenario is now disappearing but will return in the fall and winter in the northern climes!<br><br>The best time to recheck pressure is before driving and at the air temperature you will be driving in so that the air temp in the tires (b4 driving) is the same as the outside air temp!<br>Tony in Wisconsin