Kizashi Club

Today i increase my front and rear tire pressure front 45# and the rear 42# with this combo i felt the car drove much better than the 38# the recommend pressure , don't know if I'm doing the right thing by increasing the pressure.
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No worries as long as you haven't exceeded the tire's max rating embossed on the tire itself. I haven't run vehicle manufacturer 'recommended' (door jamb label spec) pressures in my tires for decades. The Kiz was increased the first week of ownership 6 years ago. Every tire brand/size/model is different. These new Kumhos I put on do better with a bit less air than what I had been running in the Generals and before that the OE Dunlops.

I got a good air gauge.
I adjust tire pressure then test.
Repeatedly.

I ignore tire wear, and adjust for ride/handling.

I think there are pros and cons to increased tire pressure. The pros tend to be a little better handling and better fuel efficiency. The cons tend to be lower traction (especially emergency, braking, and wet/snow/mud/sand traction), degraded ride comfort, and especially tire wear.
I haven't really played around with the tire pressure and just keep it to the 38 PSI that's recommended. Heck, I'm agonizing in stop-n-go traffic most of the time anyway.

Tests were done to determine the influence of tire pressure on fuel efficiency in personal vehicles. Results showed conventional wisdom was (once again) incorrect, and tire pressure, unless at the extremes, has minuscule affect on MPG.

Certainly has an affect on wear, and wet/snow traction......

Another way to find the correct tire pressure is by doing the chalk test method.

I've read that car manufacturers do a lot of testing to determine the footprint (contact patch) that they desire for their vehicles as well as taking into account handling and ride comfort. That's how they arrive at the what's posted on the door pillar sticker.

Did you ever notice that folks bump up the tire pressure on their stock vehicles before auto-crossing / etc.?


I suspect vehicle manufacturers determine tire pressure for MPG and ride comfort; handling last on any list.

LPSISRL wrote:I've read that car manufacturers do a lot of testing to determine the footprint (contact patch) that they desire for their vehicles as well as taking into account handling and ride comfort. That's how they arrive at the what's posted on the door pillar sticker.

That 'ride-comfort' scenario you mention is exactly what caused everyone to blame the OE tires for coming apart on first gen Ford Explorers. People were overloading the vehicle, which was in reality a Ranger Ext cab truck chassis at that time, w/ Ford's ridiculously low 'door-jamb' tire pressures (passenger car tire pressures). Those tires were meant to be inflated to around 38psi as I recall and not what Ford said on the door jamb 28psi??. People died, Ford ef'd up and Firestone took the hit. Major, unnecessary, expensive and wasteful tire recall of perfectly good tires. Hmmm can you say Samurai and Consumer's Reports?
I distinctly remember looking at those those pressures on our '91's sticker and laughed at the Ford idiots. No way was I hauling my family around with what I knew would be severely under-inflated tires. Inflated them to a few pounds below max pressure on the tire's sidewall and life was just fine. I used it as a truck loading it up and towing. I put another set of the exact same tires on it (at an unbelievable discount of course) when the OE's wore out. Treated them, and the vehicle, for what they were light truck tires on a light truck. Want a car ride, by a car. Don't buy a truck, load it up heavy, neglect to read the tire's pressure information and expect it to not have issues riding around on comfy squishy tires.
More culling of the heard.