Tire Pressures

Depends on the car, really. But so long as the cold pressure is not higher than the max pressure on the sidewall it's not going to cause catastrophic tire failure. Hot pressure is more or less irrelevant. What is important is how the car rides and handles. I've found that on my company car (Chevy Impala) running the tires at the recommended pressure results in a floaty ride and imprecise handling, and also fast wear on the outside edges of the front tires, so in that car I do run the pressure a little higher than spec. But really that just requires some experimentation to determine whether that's the case for your car or not. (I suspect that the Lacrosse is basically the same chassis, yes?)

nate

Bob wrote in news:j6pl1r$7gc$ snipped-for-privacy@dont-email.me:

It's perfectly /safe/. But is it something that will be liked by your government-mandated tire-pressure-monitoring system? That's another story.

If your TPMS eventually complains, take the pressures back down to 30. If the TPMS light stays off, leave the pressures where they are.

I'm suspecting Buick has specified the slightly-lower pressure simply to help improve the ride.

I usually cold set the fronts at 32-33 and rears at 31-32. Auto manufacturers like the mushy soft ride of 26-30. Unfortunately that makes for minimum control and is prone to roll overs, as Ford found out the hard way a few years ago.

#1 Soft tries cause roll overs.

Soft tires can also cause excessive heat buld up which may lead to tire failure. I follow the sidewall max pressure less 10 percent. If it says 44psi I make the cold 40.

Drive through some mud, or put some chalk on the tires and drive around the block making sure to do some tight turns.

Find out what the actual contact area of the tire is.

If the tires are not the same profile as the ones that came with the car, the optimal pressure may not be the same as the recommendation.

If you overinflate the tires, you will have reduced contact area on the edges, and so your tires will wear out faster in the center. This will also affect your handling adversely. But then again, underinflation is just as bad.

Unless you actually look at the footprint you won't know.

--scott

Yes. If you underinflate, you'll somehow wear the tires out faster at the edges. I've certainly done that.

The goal is to have the tires flat on the bottom, so the whole width of the tire is evenly pressing against the road.

AIUI, if you take the area of the tire that touches the road, multiply it by the tire pressure, add that value for all 4 tires together, and the sum will be the weight of the car and its contents.

There is also the fact that high tire pressure increases mileage, but I have no idea how much. I don't know if low pressure really makes a softer ride or not, but smaller wheels with the same diameter tire, thus a wider side wall., will make a softer ride. 16" or 17" wheels with a narrow side wall will make a harder ride.

And as someoen said, it's the cold pressure that all the numbers are given for. It's assumed that the tire will warm up and the pressure will increase. But they don't want people on the hood measuring tire pressure while the car is moving.

____________________________ Well, except for the fact that THEY DIDN'T LISTEN TO YOU, THE CUSTOMER'S INSTRUCTIONS!!! (Read my tire pressure drama at:

Irrelevant to this discussion, but there is out there in WWW Land a site that suggests you inflate your tires to 36-37psi cold IN WINTER if you live north of 45 degrees north, and closer to the door sticker come spring & summer, implying that 36psi in winter = IE 30psi in summer. Whaddever my brain hurts!!

-CC

Reely? How's that work? For which cars is it safe/not safe?

What if you drive on it, say, at a "perfectly safe" 80 mph, and hit a wicked pothole?

Good to know tread wear isn't important...

That doesn't make any sense. Far more likely you brake while cornering, too hard.

You should shut the f*ck up about s*it you know nothing about. -----

- gpsman