tire pressure questions

[sdpapet]

Hello, I have some questions about air pressure questions.

1>What is the recommend air pressure (Sonic Hatch 2013 LT, 1.8L)? I checked the manual book, but I can't find? Is it 35 -38 PSI or 40? Thanks.

2>How to measure the air pressure? I can't tell my tire pressure is good or not? I only have a cheap gauge. When I measure, I got the readings from 20 to 35 PSI form the same tire? Should I ignore the readings if I hear the air is leaking?

Should I buy good digital gauge? Will this help?

Thanks,

 

[perrymk]

Open your driver door, check the door jamb. There should be a sticker with the recommended tire pressure. Mine is 38 psi.

A digital gauge is usually better than the non-digital variety, at least for me. I have a cheap digital gauge that gives consistent results.

I regularly use a Black & Decker Inflator. It allows me to preset the pressure and it shuts itself off when the pressure is reached. It has to be turned off and on between tires to reset. I set mine for 40psi. When I check my pressure using OnStar after a trip or two it usually reports 38-39.

I recently had the plastic end piece break on my B&D Inflator. I emailed B&D, they asked for a receipt. Fortunately I purchased from Amazon.com so was able to easily email the receipt to B&D. The sent me a new inflator. Awesome!

 

[Maddmatts]

Recommended tire pressure will change with tire width. Mine says to use 35psi for 205-width tires.

I almost always end up grabbing a digital gauge over an analogue one. The only fault I have with digital ones is they can't be left in the car in the winter if it gets below freezing. The display will be unreadable until warmed up.

 

[AKghandi]

i have 235/45s. 42psi seems to be the sweetspot

 

[Stew]

The tire pressure on the door jamb sticker is only the CAR MANUFACTURERS recommendation. How does the car manufacturer decide that? The 2013's owner manual says "The recommended pressure is the minimum air pressure needed to support the vehicle's maximum load carrying capacity."

What this means is the MINIMUM pressure you need to run is what's on the sticker inside your door jamb, the MAXIMUM you can safely run is what's on the side of the actual tire itself.

Towards the minimum end of the tire pressure range you'll get a quieter ride, a little lower mpg and a little less cornering ability. As you get to the higher side of the tire pressure range you'll likely have a harder noisier ride, slightly better mpg and a little better cornering due to stiffer sidewalls.

It's up to you to decide what's more important to you, as long as you are within the acceptable range.

 

[Natesriv]

Too low and you'll trip your TPMS warning. I had been running ~32psi and it was going off. Bumped up to 36, problem gone.

 

[Papasonic]

Too low and you'll trip your TPMS warning. I had been running ~32psi and it was going off. Bumped up to 36, problem gone.

That makes sense. I'm sure that the control module that operates the TPMS is calibrated with what tire is originally installed on the vehicle. Some had a recommended pressure of 35psi, others I believe were 38psi. At 32psi cold, you probably would get a low tire warning, unless the ambient temperature was high enough to raise the tire pressure enough to satisfy the TPMS threshold.

I drive a company E-350 van that has different tire pressure front and rear. When the dealer services the vehicle, they rotate the tires and readjust the tire pressure. What the fail to do is relearn the tires to their new position; soon after I start driving after servicing, I get a low tire warning. I check all of the pressures and they are fine. Then I realize that because they failed to relearn the tire positions after rotation; the ones that were calibrated to have a higher pressure now have too low a pressure, setting off the warning. It took me a while to figure out what was happening, but after a relearn process, everything was back to normal.

 

[MORTIS]

"The recommended pressure is the minimum air pressure needed to support the vehicle's maximum load carrying capacity."

The minimum pressure for the maximum carrying capacity may be an important consideration. I run the minimum pressure because I rarely carry anything in the car and I usually ride alone, and I weigh only about 140lbs. I even run the rear tires a couple pounds lower than the front because the rear of the car is much lighter than the front.
I never get any TPMS warning in the vehicle; only a warning about the rears from my monthly Onstar diagnostic report.

I always use a quality analogue gauge, the type with a dial and needle. It's fast and quite accurate and works in any ambient temps.

 

[The Champ]

I almost always end up grabbing a digital gauge over an analogue one. The only fault I have with digital ones is they can't be left in the car in the winter if it gets below freezing. The display will be unreadable until warmed up.

I've never had a problem with my digital gauge and I live in MN where winter temps are frequently below zero.

I keep a Black Jack digital gauge in each car.

 

[g30360]

what is the threshold pressure to trigger light?

On this topic, does anyone know at what pressure the low tire presure light will come on? The manual says it will come on when "one or more tires are significantly under inflated" I just want to make sure my system is working. Onstar reports low pressure as follows.

Left Front:
Low, 220 kPa

Right Front:
Low, 220 kPa

Left Rear:
Low, 220 kPa

Right Rear:
Low, 216 kPa

recommended tire pressure -
Front: 241 kPa,
Rear: 241 kPa

So I wouldn't say significantly under inflated but it would have been nice if the light came on by now. These were taken during the last drive on or before the afternoon of January 3rd. the temperature was around -24 C before wind chill.

 

[gnonne]

Pressures

I have three Sonics. The only time I get the light coming on is when one (or more) tires are significantly lower than the other tires, like a leak or a tech forgot to air up one side of the car...

My cars all say 35 psi and that is where I set the tires, but if temps drop significantly, they could all be at 30 or 31, which has never caused the tire pressure light to come on in any of the cars.

I use a large analog truck gauge that goes up to 150 psi. Its frozen up on me a few times in the garage, but not too much trouble.

 

[K-Bob]

The recommended 38 PSI for the 195/65-15 tires seems way high. That translates to 41 psi when hot. That big suv territory. I am used to running much lower than that with my last car.

Currently on the Sonic I am running 38 ft and 36 rear.
Will probably change to 37 ft/35 r and see what happens.