CashGap

So, the door jamb of my '19 300h says 35psi.

Vehicle was delivered with all four at 45psi.

I assume that:

Overinflated: Less rolling resistance, slightly higher MPG, less compliant ride, less tire life due to uneven wear.

Inflated at spec: More rolling resistance, slightly lower MPG, more compliant ride, even tire wear.

Any thoughts/recommendations?

jfz219

jimv1983

Maybe meet in the middle and go with 40?

95bat

Use the recommended 35 psi. Tire pressure will go up as the air warms. If your tires are 45 psi in the morning, they're too high. They should be 35 psi first thing in the morning and if they get higher as the day goes on it's fine.

Tires that are over/underinflated do wear out faster, affect ride quality, but also put you at a much higher risk of hydroplaning during the winter.

Sulu

Hydroplaning is more likely to occur with under-inflated tires than over-inflated tires. With lower tire inflation, there is a larger surface area that the car must push through and push the water out of the way. With higher inflation, there is less tire surface area to push the water out of the way.

This is the reason tire specialists recommend narrower tires for winter (snow) driving: Less surface area means less risk of floating on top of the wet stuff.

95bat

The tread pattern is not as effective when the tire is under inflated, still causing an increased hydroplaning risk.

Tire Rack has an excellent article on it here. After I read that article I became much more vigilant about proper tire pressure, especially in the cars of my loved ones!

chromedome

I keep mine at 35 psi cold. It's important to check pressures when cold, first thing in the morning before the car has moved and the tires have warmed up. And don't forget the spare if you have one.

Freds430

Also keep mine at 35psi. Regarding the cold for every 10 degrees drop in temperature the tire will lose 1 pound. Think about just two months ago in my area it was 90 and today it is 50. That is a four pound difference. Just yesterday pumped up each tire four pounds back to the 35psi cold.

Steve300h

Thank you for starting this thread, I added checking the tire pressure to my checklist for picking up the car and sure enough they were inflated to 51psi

mikemu30

That should make for a nice firm ride😣

AnthonyMJ

can you please share the article. There are dozens of threads about tire pressire. Thank you for narrowing it down for us.

95bat

The link is the blue "here" word :P You literally click "here" for it

Here is a full link: https://www.tirerack.com/tires/tiret...e.jsp?techid=3

CJS57

I like mine at 33 psi. Slightly better ride is why. I don't care if they wear out sooner. I think the 35 psi factory rating is a compromise for an unloaded vs a fully loaded car. My car is always unload except for the driver. The tires warm up to 35 psi during highway driving anyway.