Hey guys,

What's up? I have the 2012 G37 Sedan...I checked my tire pressure yesterday mid day after the car was sitting for hours. The tire pressure read out was 30 PSI in each tire, and I think about 28 PSI in one.

I had quite a few questions regarding this...

1. The car rides smooth, but I saw on the door jam the tires should be at 35 PSI, should I put more air in the tires? How important is it?

2. I checked the tire PSI in the hot Florida sun, does that have any affect on the reading?

Where do you guys usually fill up your tires? Do you own your own air pumps? I've gone to gas stations in the past, but was wondering if those were bad for the tires? My only reasoning on that is they may be dirty with debris, or pump in bad air? Are gas station are pumps fine? I didn't want to cause any problems with the valve stem.

Thanks,

Brad

 

Yeh, put 35psi like it says. Air is air unless you go nitrogen. It is more stable than regular air. Ambient temp does affect tire pressure. Make sure to use a quality tire gauge.

 

Fill it up to 35 psi and you good to go. Get the air at the most convenient place you can. Hard to find free air theses days

 

Discount Tire does it for free. Try them!

Also 34-35psi is desirable. Do it.

 

This^ I'll even go up to 40 psi if I'm going on a long trip. If you fill it to just 30 psi the psi may drop to 28ish and the TPMS light may come on.

 

The placard for my Journey says inflate to 33psi for each tire. I guess the 35 everyone seems to recommend is for sport models only. My dealer, when they check them while I’m in for service, also ignores the 33 requirement and inflates them to 35.

At any rate, I check mine when the tires are cold, not having been driven for at least 8 hours. And I do have my own pump, and a good tire gauge for accurate readings. Otherwise if you go to a gas station you’ll find yourself checking pressures when the tires are somewhat warm if not hot, giving you an “inflated” reading.

 

Always do it cold first thing in the morning if you can and hopefully with no sun hitting any of the tires which might cause one tire or so to read high. Use any source of air but if you can get nitrogen purge and refill that's even better. Two things occur with nitrogen. 1. It's a dry air as compared to normal air we breathe which has moisture in it. A lot of the tire pressure increase as we drive comes from this moisture expanding more rapidly than the air similar to steam. Remember the temperature of a tire can reach over 200 degrees on a really hot day. 2. Nitrogen is a larger molecule than normal air and thus has less of a tendency to leak through a tire over time. This makes the tire pressure more stable over a longer period between checks and refills. That's one reason Costco has gone to nitrogen for all their new tire installs. Also again since nitrogen is a very dry gas, it doesn't rise in pressure as much when heated as normal air does so your tire pressure won't change as much while you're driving especially on a long hot road trip. And ask yourself why do professional and even amateur race teams use nitrogen for their race tires. Same as #1 and #2 above. Finally as recommended, get a good quality tire gauge and carry it with you in the car and use it to set your tire pressures. At least this way you'll be consistent from refill to refill. Good luck.

Al

 

To add to these folks great posts:

• Follow the recommended tire pressures, if you're still on OEM tires.
• On aftermarket XL-rated tires, you can go lower on pressure and achieve the same load rating. For example, Infiniti recommends 33psi on my sport sedan, on OEM tires, but i can get by with 30psi on my Conti DW's.
• When possible, only add air when the tires are cold.
• With regular air, pressures can increase by 4-5 psi driving regularly on a mild summer day. This is a reason you shouldn't put air at max sidewall pressure when cold, otherwise, once the air heats up you'll risk a blow.

 

I check first thing in the morning(or afternoon if not driven) when cold after sitting in garage overnight. I fill to 2-4 PSI over the door jamb with my 12v compressor. Not that it really matters, but I try to do it on days with less humidity.

 

The recommended tire pressures on the door jamb are cold PSI. As mentioned above, you should check your tire pressures in the morning, or after the car has not been driven for a while.

As the tires heat up during driving, PSI will increase. When it gets colder out, PSI will decrease. I've read that for every 10 degree drop in ambient temp, you'll lose 1 PSI.

As far as using a pump at a gas station - it should be fine. Just make sure you have your own, quality pressure gauge. I check my tire pressures every Sunday morning when I get my newspaper.

 

I'm surprised that nobody has mentioned that keeping after tire pressure will improve gas mileage. (Gas Mileage Tips - Keeping Your Vehicle in Shape) Furthermore, tires will wear more evenly if a fairly constant tire pressure is maintained.

I'm a bit of a slacker, but I check mine once every two weeks, which is probably not as often as I should. In my inventory, I have one of these guys to check: Accutire MS 4000 Tire Pressure Gauge and a small air compressor with a tire adapter at home to fill up when I need to.

Some other things to keep in mind are not to over or under-fill your tires significantly, and even the the altitude you're at when filling your tires. See the following for more info on Over/Under-filling (#11): http://www.safercar.gov/Vehicle+Shop...mation+FAQ/#q3 (specifically #11)

Hope that helps.

 

I've been told the opposite, to run the tires a pound or two under the recommended pressure if you drive a lot on the highway, and a pound or two over if mostly city.

The tires elongate slightly in the center of the tread at highway speeds, meaning more wear is in the center of the tire, meaning the center will wear out faster. Likewise, in the city you're moving slower, so there is little elongation - so you run them a little higher (35) to compensate.

You do get better gas mileage with higher pressure (less resistance with a smaller footprint) but it's not worth the additional safety risk of less traction.

I just leave mine at 33 as it says in the driver's door jamb, and use a digital gauge that's accurate to .5 lbs, in .5 lb increments.

 

...and get an air compressor - I bought a blue tank model on wheels at Wal-Mart for about $130 and it's well worth it. At one point I had three cars, two bicycles, and a dolly to maintain.

 

Must be a Texas 'thing' - I've got 3 cars, 3 bikes, and a wheelbarrow to maintain

But with Nitrogen in the G's - the compressor has been used far less...

 

The nitrogen thing may help with a nascar, or other special vehicle... but it's a waste of money in a passenger car. One of the car magazines, or it may have been consumer reports, did a test and after a year, the tire with air only lost 1.5 psi more than the nitrogen tire. Check your air pressure at least once a month and you'll be fine.

Even tire rack agrees... "Rather than pay extra for nitrogen, most drivers would be better off buying an accurate tire pressure gauge and checking and adjusting their tire pressures regularly."