Twice recently my dashboard tire pressure icon has notified me of a problem. Turns out I wasn’t losing pressure but the same tire had a pressure of 57lbs (normal is 36). My tire shop says they’ve never heard of this happening. In fact I can tell they don’t believe me but I measured the pressure myself. Any suggestions?
Are you checking the pressure with tires cold or hot? Makes a difference.
OK, you measured the first time and saw 57 psi. Then what? Did you release air? To what pressure? Did you check your gauge by checking the other tires too? There’s a lot missing here.
Not THAT big a difference! It’s typically considered to be 1 pound for every 10 degrees.
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=73
I’m wondering whether the OP used a reliable gage. The “pencil” gages are pretty terrible.
I’m wondering what both mountainbike and SteveF are wondering. After you measured it the first time, did you let air out & down to the recommended pressure?
And…what are you using for a gauge?
And one more…do you have any neighbors that don’t like you? This would be a very weird thing to do to someone, but IF the pressure was right, the only way to get more in there is for someone to put it there. Does anyone else drive the car?
Has someone else checked the tire pressure? I would buy an accurate tire gauge and keep check of the pressure on my own. I don’t really trust a TPMS to accurately monitor tire pressure.
I wonder if you have a sticking brake caliper on that wheel or a bearing problem. This could generate heat and transfer it to the rim and tire. I had that happen on a 1983 Mercury Marquis. Feel the wheel and if it is hot, you haver a problem.
That’s an excellent question daq. But that wheel would have to be one hot mama to raise the pressure 21 psi.
the same mountain bike–
I know that when I had the problem, I had picked up a car that my son had purchased to use during the summer. He was about 100 miles from where we lived and the car hadn’t been driven for a couple of months. I started the car and the tires looked low. I drove to a service station and checked the tire pressure. Three were about 18 pounds, but the right front was 40 pounds and the wheel was very hot. I did get the car home , but had to replace the front pads and calipers. The right caliper was stuck.
Ouch! Yup, that must’ve been one hot mama!
Your suggestion was a good one.
The OP never mentioned anything hot…The answer to this thread is to buy a decent tire gauge and check your tires yourself…
Good comments from everyone. Thanks!
When I first noticed the problem I was on the highway so I had to check the tires hot. All were normal but the problem one (right front). I released air to 36 lbs and drove the rest of the way home. Checked them cold the next a.m. and they were all normal.
I confess, my tire gauge is a cheapy but the other tires checked normal compared to the one.
I did notice increase pulling to the right when braking while the tires were still hot.
I do have a few nutty neighbors but I don’t let them drive my cars. And I have to wonder how they’d classify me if they knew I was posting to Car Talk? I mean Tom and Ray aren’t known as totally stable, right?
Cheap pencil style tire gauges are NOT very reliable…Some can work reasonably well, but over time, they become unreliable and can give false readings leading to problems like the one you describe…
With tires costing what they do today, a decent dial type gauge is a wise investment…
My dad had a dealer service department leave the tires on his Caddy STS at 15 PSI twice! I finally took the dang thing to a gas station and put the proper pressure in them myself. I now have a compressor and won’t trust anyone to inflate my tires. I got an Accutire MS 4021B gauge for about $15 and it is superb.
The trouble with those cheap pencil gages is that you can check the same tire four times and get three good readings and one bogus one. The work based on friction…and they’re notorious for “hanging up”.
A decent bourdon tube dial gage with a dial is inexpensive and reliable. A bourddon tube is a banana shaped tube inside the gage body that straightens with pressure, just like the party favors that you blow into. They’re durable, reliable ,repeatebl, and worth the cost.
Someone disagrees with my statement about checking tire prsessure hot or cold makes a difference? Granted not this much, but it does make a difference. Possibly as much as 5-6psi combined with air temp.
“Additionally, the difference between cold nighttime temperatures and hot daytime temperatures in most parts of the country is about 20° Fahrenheit. This means that after setting tire pressures first thing in the morning, the vehicle’s tire pressures will be almost 2 psi higher when measured in the afternoon.”
“Next we evaluated the effects of heat generated by the tire’s flexing during use. We tried to eliminate the variable conditions we might encounter on the road by conducting this test using our “competition tire heat cycling service” that rolls the tires under load against the machine’s rollers to simulate real world driving. We monitored the changes in tire pressure in 5-minute intervals. The test tires were inflated to 15 psi, 20 psi, 25 psi and 30 psi. Running them all under the same load, the air pressure in all of the tires went up about 1 psi during every 5 minutes of use for the first 20 minutes of operation. Then the air pressures stabilized, typically gaining no more than 1 psi of additional pressure during the next 20 minutes.”~from Tire Rack website
No. D, that’s not what I said. I did not disagree that checking pressure hot will yield a higher result than checking pressure cold. What I said was that it will not make THAT big a difference (21 psi difference). It’s clear that some other cause was at work here.
“Someone disagrees with my statement about checking tire prsessure hot or cold makes a difference?”
No, they just like to hit the buttons and see the pretty colors.
Someone’s fave is purple (lavender?).
Agreed 100% tsb, and I wasn’t referring to your comment : )
Looks like it, CS.
Sorry, D. Didn’t see the little purple button.