I hope I am posting this in the right area. My question is about raising tire pressures to the max limit stamped on the tire. I see in most "hypermiling" articles that this is recommended to increase mileage, does not cause excess wear of the tires and that the harsher ride is soon gotten used to. Here's my question: if this is such a "free lunch", why don't the auto makers do this? They are struggling and competing for every 10th of a mile per gallon. Why would they ignore such low lying fruit on this amazingly tough issue? Maybe this is not REALLY safe, after all????
Like stated above, it's mostly because of a reduction in ride quality. Most people don't want to feel every pebble on the road. Set the pressure too high and handling/traction can suffer on non-smooth surfaces.
The higher pressure will also cause the rattles & squeaks to increase. Soft tires wear faster so the owner will be buying tires (maybe from the dealer) sooner. What evidence have you found indicating that higher pressures are unsafe? Firestone & Ford had problems because the recommended low pressure caused the tires to heat up & blow out especially during evasive maneuvers. It's your money & they are your tires. Do whatever you want but don't complain that your tires need replacing after some low amount of miles because you ran them at Toyota's recommended pressure. The Goodyear Integrities on my 2006 showed signs of underinflation even at max sidewall.
JimN: I did not claim higher pressures were unsafe. I wondered if safety was the reason very desperate-for-MPGs car makers would ignore this "free lunch". And it's not clear if you are saying that higher or normal pressures will wear tires faster. And later it sounds like you are saying that Toyota's recommended pressure is a recipe for low tire life. But above you sound negative on high pressures due to a rough ride. Seriously, would you please clarify your points? Thank you!
They were both perfectly clear to me. You need to decide which characteristics are important to you and go for them.
You hear everything about tires and pressure. My opinion is you need to experiment. Some tires wear faster and some people like a certain ride quality that will change depending on the pressure. Miles per gallon can also go up or down and handling will change. I have not found big differences in the above. Ran mine at 40 front 38 rear for 20 thousand miles. I'm now at 38 front 36 rear works best for me. Play around and report where you feel best and have fun the Prius will allow you to learn everyday.
'Best' tire pressure is a compromise between competing factors. Historically, typical Americans have been much more concerned about ride comfort than fuel economy. You may well place different values on each of these various factors than do typical drivers. In that case, your 'best' tire pressure may be different. In previous discussions, some PC members with more tire industry experience have noted that the consequences of below-placard tire pressures are very well documented, in part because common poor vehicle maintenance produces a very high prevalence of low pressure. In contrast, while opinions about above-placard pressures are often strong, actual documented study is scarce. At the end of the day, you will have to make your own choice. Many Gen II Prii owners here reported short tread life and wear patterns consistent with underinflation on the original tires run at placard pressure. Increased pressure appear to improve both tread life and wear patterns. I don't remember enough Gen III owners running placard pressure for long enough to reveal whether or not Gen III has the same problems.
Right off the bat, no way is Toyota going to ship a car with 42 psi stamped on the tire sidewall if 42 psi is unsafe. If that were so, they'd definitely make the tire maker change the imprint. But the higher pressure might create a harsher ride, and it may not provide perfectly optimal handling in some formulaic way, but it will fall way within the margins of safe or they wouldn't ship it that way.
