Tire Pressure

I'm tempted to lower the pressures by 5 pounds because I'm getting sick of the rough ride,

 

Look at the driver’s door jam for the proper cold pressures. After the tire is driven pressures will rise 2 or 3 psi and return to spec after the tire cools to ambient.

 

Tire pressures are always taken cold. Dealers often are lax in properly adjusting pressure. I always use a quality tire gauge and measure pressures after the dealer has messed with them, but only after getting home and allowing tire temps to stabilize. No reason not to use recommended pressures year round, 55 front, 33 rear.

 

35 / 33 for 19” wheels

 

Yep, fingers messed up the front pressure. Obviously should have been 35 front, 33 year......

 

^ Just editorial. If you're at a dealership for service, and get in promptly, what are they supposed to do? Best they can do is leave tire pressure check to the last, and maybe set it a pound high.

Having your own pressure gauges and a method to air up the tires, you're able to check cold temp pressure, say first thing in the morning. I manage with a pencil style gauge (one of a collection), and a floor-standing bicycle pump.

 

In a place like where I live, the temperature can drop by more than a few degrees when a winter storm moves in. This causes a lot of low tire pressure alarms that weren't there the day before.

When a storm moves in, I'm concentrating on digging my car out and defrosting the windshield, navigating potholes, the clumps of ice falling off other vehicles, where they've plowed the roads, where there's ice, and so many other things. The last thing I need is a dash warning that a tire is low when it doesn't have a leak, because then I've gotta find a place to pull over and do a walk around to not find a flat tire, just 4 imperceptibly low ones.

Many tire shops in areas like mine (and apparently dealers like yours) compensate by giving the tires a couple more PSI in the winter, just to avoid the issue. I wouldn't go more than about 2 PSI above the normal value though.

 

It's speculated here, and likely true, that it takes about a 25% (aka 1/4) drop in tire pressure, from the pressure set on the TPMS system, to trigger the light. For example, if your tires are at 36 psi (4x9) cold, and the system's set to that value, it'd theoretically require a drop to 27 (3x9) psi to trigger an alert.

 

How regularly does the average car owner check their tire pressure? Set it back during the dog days of summer to 36psi, and forget it until the light comes on in winter, may not be the norm, but it likely enough for shops to get hassled by the ignorant. Many likely still go be how low the tire looks, and 27psi can still look full in many tires.

 

On my 2021 Prius Prime Limited with the nice Dunlop Enasave 01 A/S tires, I put 43 psi front/42 psi rear cold.

It is OK to use a high tire pressure as long as you avoid road hazard and don't drive across bumps fast.

It makes sense to use a higher pressure at winter because the pressure could drop a lot if it approaches freezing, as the humid air in the tire acts less and less like an ideal gas. Some places fill with nitrogen for that reason.