Welcome to Priuschat, Tow Truck. :welcome: There have been many studies and the data has been posted here on Priuschat. After you present your data, we'll present ours.
It was so long ago (1993)...but I want to say doorjamb psi was 32r/30f and I inflated about 8-10 psi higher. Guessing there. They were definitely radials - Michelins. I felt sick to my stomach because I hadn't had them on all that long. The center treadwear was definitely obvious; very flat and smooth compared to new. It's why I don't radical-inflate today..but perhaps technology has changed in 18 years. I loved that car; it was so fun.
Makes me wonder if your psi gauge was accurate. See photos at cleanmpg of xcel's Accord tires at 120000 miles on their way to 150000. They have never been south of 50 psi.
The OEM Toyo tires on my Prius have always been inflated at 45 to 48 lbs. I presently have 39K miles on them and all four have about 4/32 tread left. They are actually worn just a bit more near the edges than the center, from cornering forces I would guess. I have been inflating tires to higher than the car manufacturers recommendation for years and have never seen the center wear faster. Good radial ply tires are flat and stiff across the tread area and do not bulge out the way bias ply tires would when you raised the pressure. Here is an interesting article I ran across, it is a few years old and written with police cars in mind but I think most of it applies to us as well. Driving Under Pressure: Editorial & Features at Officer.com
Tire Rack also has some good information on tire inflation but they don't really address overinflation too much. They do state that handling, cornering etc. is improved with overinflation which is why autocross racers overinflate their tires. When I would autocross we would overinflate the tires then mark the sidewall with window chalk. We would then run a lap and check the tire marks to see how much sidewall roll we were experiencing. Obviously this is for extreme racing situations and only somewhat applicable to street use but the fact is, overinflation does increase performance and reduces rolling resistance. What I would like to see is a test on braking with under, over and properly inflated tires because that is of the most concern to the average commuter. Does anyone have any good links on this info? Here are links to information on tire inflation: Main Tech Center: TireRack.com - About - Tech Center Air Pressure -Correct, Underinflated and Overinflated Air Pressure vs. Wet Performance Air Pressure vs. Dry Performance
I've been playing around with different psi and went as high as 60. 50 should be the absolute max. The vibration in particular gets very noticeable at 60 psi and I could clearly notice issues with slowly down bc he tires were so inflated. I've found that 48(front) 44(rear) is the best medium. Even at 50 the ride quality is poor and the vibration is pretty bad.
Took delivery 2 weeks ago and was able to check the tire pressure the dealer put in. 32 front and 30 back. Why would they do such a stupid thing? I was wondering why it drove like an old Caddy! OK, I went up to 37/36 yesterday and may try 42/40 today. Definately a harsher ride. Odd thing is that I got great mileage with under infalted tires. Could be the new first tank was a fluke!
