Is it better for my tires to be slightly over inflated or under inflated?
 

Hi,

I have 2 tire pressure gagues (both pretty cheap). One is a slime analog gague ~$3 and the other is an electronic one that came bundled with one of those 12V air compressors.

The electronic gauge consistently reads about 1psi higher than the analog one.

I know the simple answer is that it doesn't really matter, but I'm curious. If the ideal pressure is 33psi, would it be better to be at 32psi or 34psi?

Those readings are on "cold" or hot" temp.?

That depends whether you prefer wearing out the edges of your tread (low) or the middle (high).

Personally, I'd err on the high side for gas mileage but meh. Unless you measure wear with a tread gauge and keep records it would take a year of driving to notice the difference

+- 1psi won't make a difference with the Primacy Tires. Don't sweat it, just get as close to the door sticker PSi as you can.

The recommended pressure on the door sticker is only so the manufacturer can get their desired score for comfort rating on the vehicle. On the standard tyres it makes sense to follow this sticker as a guide but as soon as you change to different tyres I would only follow the tyre manufacturer recommendations

You want them to be just like everything else in life and that is 'just right'

As others have said, +/- 1psi isn't going to make any difference on the street but if I had to choose, I'd rather be slightly over. If under, you can get pre-mature shoulder wear which makes you sad to throw away tires with 4/32nds tread remaining in the middle because you've torn the shoulders off. Ask me how I know:

http://i1299.photobucket.com/albums/...psohukhfmd.jpg

Lynxis: that might be also from pushing on track with suboptimal too less negative camber. I stripped outside thread of tire exactly this way even with stock pressures. It's not as bad now with moderate camber dialed in now (car primarly is dailydriven, not tracked).

These would be cold readings.

Thanks! Pretty much exactly what I was wondering.

Yep, I completely agree. I tend to be curious about these sorts of things and the more you know, the better! What Ultramaroon said about wear makes complete sense though.

Happy motoring! :cheers:

Oh, it's definitely from that but also running too low tire pressures which caused the tires to roll over heavily. You'll never see this type of wear on the street, it's just an extreme example of the reason why I'd rather be over than under.

I understand what you are saying but when tires are made they aren't made specifically for each vehicle. Tires only come with a max pressure, the recommended pressure is determined by the car manufacturer. The tire company has no idea what car they will be on. The car manufacturer however has engineers determine the pressure for the car. My understanding is the car manufacturer sets the pressure based a combination of comfort, handling and MPG's. They typically try to strike a balance of all three. I like to add 2 -3 more PSI-G to what the door says getting better feel and maybe some MPG's.

Overpressure decreases comfort and increases center tread wear.
Underpressure increases comfort, increases outer tread wear, and increases flexing to increase the chance of a pre-mature tire failure.
It usually takes a lot of variation to cause bad things to happen, but erring on the high side is the rule in aviation tires.