Over inflating a tire causes it to micro bounce. Beat up the suspension and lose contact with the road. You could probably go over by one or two PSI but when you start doing that crazy nonsense 45 psi junk that people think is right. You wind up with the car that is all over the road and for what? Suspension is taking a beating where the tires should be doing that for you
We keep our Prime XSE in Mexico ... not the best roads but not that different than Tucson either. Dropped pressures to 30 front and 29 rear just to try and smooth things up a bit, rather take the hit on the MPG's than replace bushings (our last three Prius all wore through the suspension bushings before anything else gave out) so will walk that fine line between too low of pressure and damaged 19" wheels vs too high of a pressure with damaged bushings. Would love to find some tires with larger side walls ... maybe swap out for 17" wheels and larger sidewalls - we will see.
Not sure if you just mean for the Prius or in general but in general over inflating does make a big difference in efficiency. It reduces rolling resistance. BUT, BUT it can be at the cost of grip or cornering control.
Mine starts complaining about low pressure at anything under 34. They end up around 37 because my pump's gauge is kinda garbage.
I raise the tire pressure above my nominal setting by 10% and then reset the TPMS. Then I lower the PSI back to my nominal settings. This makes the TPMS alarm sooner than it's typical 20% PSI loss. JeffD
Curious if there are any updates or changes in thoughts regarding tire pressure now that these cars have been in the road for a couple of years. I don’t want to wear out suspension components early by putting PSI at 40 but I’m just as concerned about tire wear as I am about pinch flats. Maybe I should aim for something in between? Upon delivery tires had multiple PSI range of 37-39.
I suspect not; Daisy’s poised on the event horizon, of the black hole of 5th gen acquisition, eternally.
Yes! You noticed. Ha! I will definitely make a new thread. I received it last night. Things went smoothly. Trying to let go of the fact that someone put several scratches on the plastic along inside of door after I test drove it. There were additional 13 miles on it after I test drove it. This dealership is really strict about not letting people drive sold cars. I’m not worried about the miles just wish I could have berm tge inevt it except wishing I had th chance to put the fire scratches. Ha! Big reveal coming soon!
I’m back asking about tire pressure. My 19” tires were delivered with 40 psi. On cooler days the psi dropped to 37-38. After my last visit to the dealership they put the tires to 40 again. Today it’s in the 80’s and during my 20 min drive the psi reached 44. This is obviously too high especially when temps are going to increase. Priorities: Avoid pinch flats/damaged wheels Avoid premature suspension wear Why does the manual say add 3 psi when driving speeds above 100 mph? At this point I have no way of adjusting pressure when tires are cold and I have no idea how much the pressure will increase on high 90 degree days. I can’t imagine putting rear tires down to the recommended 33 psi. Does anyone who has 19” tires have experience with these fluctuations and have recommendations? Thanks
IMHO; don't worry about it - the temperature fluctuations are baked into the 'measure tire pressures when cold'. You need to be concerned about the Max. tire pressure when cold, stamped on the side of the tire. So if the tire is at or near max pressure when cold; you can only imagine what the pressure would be on a hot day, on hot black-top pavement, and getting hotter on the highway.
33 psi is fine and will increase to about 37 on the longest drives. With low profile tires the pressure makes a big difference in ride quality with the recommended being the best ride. A smoother ride also reduces future squeaks and rattles. As far as checking when cold, almost any tire gauge can let out air. The trick is adding air if you let out too much or if a tire is low (typically after the first freeze assuming no nails). For that purpose I carry a lithium powered air-compressor similar to the link below. It's an easy to use tool that can be as important as a jump starter. Lithium Air-Compressor Link here For an easy to read and accurate gauge Link here An optional Air Line Quick Connect Makes any compressor easy to use since you don't hold the air chuck on or screw the air hose on Link here
Old rule of thumb was for every 10 degrees change in temperature(F), the tire pressure changed 1 psi. The pressure of a tire filled at 70F will go up about 2 psi at 90F. As long as the tire pressure when cold is below the max, you shouldn't worry about the increase from being driven. The higher pressure at high speeds is to increase the sidewall stiffness. This provides better performance in turns. It also counters the heat build up from driving at those speeds. The friction between road tire isn't the only source of heat to the tires. The other is in the side wall flex that takes place at the contact patch spot of the tire. Bend a paperclip back and forth and it heats up at the bend spot. The same thing is happening in the tire rubber. That heat generation why an underinflated tire is more likely the blow out than an overinflated one. More flex equals more heat. We have TPMS now because people let their tires get too low. Stiff sidewalls also improve rolling resistance, and might help avoid pinch flats.
That would be a good screen to look at with your morning coffee. That'll give you a better idea of how far off you are from OEM recommendations. Bear in mind that if you take them down to OEM recommended pressures, you may trip the TPMS system, if it was calibrated to those higher pressures and you may have to pump more air into them come fall and winter months. Good Luck.
What does the decal in driver’s door jamb say, 33/32 psi f/r? I would at least give that a try. The TPMS is likely set with those pressures, at the factory, then tire pressures raised for shipping.
