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10-17-2009, 02:38 PM | #1 |
Is now a Corolla S Owner
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Check your air pressure!
You know, it should be a very simple thing for the technician who performs your oil change to check your tire pressure and inflate the tires to the proper pressure. This is supposed to be included in the service when the oil is changed.
Well, I had my oil changed this past Monday at the dealership where I bought the car, and guess what? When I checked my air pressure today, five days after the dealership's service department performed the oil change, I found that the tires were inflated to 27 psi! I aired them up to the recommended 32 psi myself here at home. I wonder if the pressure had leaked-off to 27 psi, or if the technician thought they were supposed to be at 27 psi. If the tires had been running at 27 psi for a while, that might explain some of my lower than expected MPG on the last few tanks of gas. That was the second oil change for my Yaris, and the first one was also done at the dealership. The first one was free. I don't remember if I checked air pressure between the first and second oil changes or not. This just goes to show you that you should check that pressure on a regular basis and that you cannot count on the service department to inflate them to the proper pressure all the time. Tom |
10-17-2009, 02:53 PM | #2 |
TRIM HUNTER
Drives: 2007 BLAZIN BLUE YARIS 3 DR Join Date: May 2006
Location: ROCKLAND COUNTY NY
Posts: 2,088
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YOUR 2009 doesn't have TPMS? Also if the tires were set to that 27 psi your light would have been on.....
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10-17-2009, 03:03 PM | #3 | |
Is now a Corolla S Owner
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Quote:
There was no warning light. Don't those sensors look for DIFFERENCES in tire pressure among the four tires, rather than look for some specific minimum pressure threshold? The tires were very uniform in pressure when I checked them this morning. They were all kind of in between the 26 psi mark and the 27 psi mark. That's what makes me think they were set that way. Tom |
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10-17-2009, 10:55 PM | #4 |
Half a Bubble Off Plumb
Drives: 2009 Yaris Sedan Join Date: Mar 2009
Location: Bristol, Tennessee, USA
Posts: 1,593
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They measure "gauge pressure" in each tire. I think they go off when the pressure drops below 24 PSI, which is down 25% from the recommended 32 PSI. The Yaris has a basic TPMS system that can't tell you which tire(s) went down, only that one or more is low.
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10-18-2009, 02:25 AM | #5 | |
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Air pressure changes throughout the day. Especially after a brisk drive. It can raise the pressure by a few pounds. For example it was a warm day. You been maybe driving little agressively enough to heat up the tires a bit. Then the technician checks your tire pressure and its at about 32. On a tire check they are not really that accurate so anything between 29-32 looks almost the same. Then you check it some time later and its a cold day maybe morning time and the car hasnt been driven yet and now the tire pressure is at its ultimate low. Or just the mechanic is lazy and hasnt checked tire pressure. I honestly as a mechanic have been guilty of that once or twice. Especialy on a really long day when your busting out 15 oil changes nonstop. You tell yourself well its got tire pressure monitoring system. I checked one tire and its decent i guess its safe to say the rest are good. And then ship the car. Your car could have come at the end of the day of a mechanics shift. Maybe hes working flate rate and trying to get the car out as fast as possible, new or just really lazy. I tell you EVERY single day atleast once i get asked by a customer to check thier tire pressure. Even though it says we do on our paperwork, for every oil change we perform at my shop. And then they go to pay they quiz me on what it was and what it is now. That tells me unfortunately it seems to be a common practice to skip tire pressure checking once and awile. I am looking into getting a cordless tire chuck. Its pretty much a small motorized tire chuck that runs off a 12v battery that has its own minature air compressor. So you can walk around the car and fill air much faster without having to drag that annoying air hose around the car. Also good for filling air on the go at home without the use of a air compressor.
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10-18-2009, 07:24 AM | #6 |
DWEED
Drives: 3DR 2008 Metorite Metalic Join Date: Oct 2008
Location: Arizona
Posts: 1,161
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Just did my 5,000 mile oil change and rotate the tires. Always check pressure at this point. I lost 1-2 psi per tire in 6 months.
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10-18-2009, 07:29 AM | #7 | |
Is now a Corolla S Owner
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Yeah, I am aware that the pressure changes with the temperature of the air in the tire. I drove 25 miles to get to the shop, so I asked them to inflate the tires to 35 psi, hoping that that would equate somewhere close to 32 psi cold pressure. Tom |
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10-18-2009, 07:51 AM | #8 |
Drives: yaris 08 sedan Join Date: Oct 2008
Location: Montreal Canada
Posts: 1,286
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Teaches you to always recheck what you can after having your car serviced,on rare occasions they will actually forget to put the new oil in the car.,27psi isnt out of the ball park for operating parameters for your car,i usually run 28psi in winter to get a bit more traction.
Then theres always the possibility that the mechanic did in fact fill your tires to the correct pressure and your tire pressure gauge is misreading the correct psi. i once had a digital pressure gauge that was 10psi off. I've since bought my tire pressure gauges at the local speed shop and try to get the ones the racers use heres my current gauge http://stefsperformance.com/bandb/pr...ge%2040540.jpg Last edited by jambo101; 10-18-2009 at 08:01 AM. |
10-18-2009, 08:05 AM | #9 | |
Is now a Corolla S Owner
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Quote:
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10-18-2009, 08:41 AM | #10 | |
DWEED
Drives: 3DR 2008 Metorite Metalic Join Date: Oct 2008
Location: Arizona
Posts: 1,161
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Quote:
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Making a decision without following it with an action is still a fantasy. |
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10-18-2009, 08:55 AM | #11 |
Is now a Corolla S Owner
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10-18-2009, 09:44 AM | #12 |
Drives: 2010 Toyota Yaris 2 DR LB Join Date: Oct 2009
Location: Pennsylvania
Posts: 49
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When I first started driving, I remember my Dad telling me to always over-inflate by about 2 pounds, particularly if your drive to an air supply was a short one. I understand that both under and over-inflation can lead to specific (bad) wear patterns, but the 2 lb rule hasn't ever done me wrong (along with periodic tire rotation). And, of course, check it as you inflate with a known good gauge of your own, not the indicator on the compressor/air-pump (unless you know it's accurate).
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10-18-2009, 12:09 PM | #13 |
Audio Junky
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I went in for an oil change once, had tires at set to 43-44psi just to keep them below the max psi rating.... dealership told me the tires were at 49psi. I was a bit shocked, but then stated that the weather was much colder when I set them to 43-44, and that maybe the 35F increase in heat was to blame.
Guy said that temp differences would only make a change of 1 or 2 psi... I don't know if I should believe him or not... I don't really care.... but the random high psi did explain why my ride had more rattling going on at the time. Anybody know how much of a temp change it takes to increase temps by 1psi? |
10-18-2009, 12:19 PM | #14 | |
Is now a Corolla S Owner
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Quote:
Tom |
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10-18-2009, 01:58 PM | #15 |
Banned
Drives: 2007 4 Door Yaris Join Date: Jan 2009
Location: Southern California
Posts: 1,357
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ideal gas law: PV=nRT
(V)olume, (n)umber of particles, and R which is a gas constant, will be constant for what we're doing. T is an absolute temperature, so we have to use Kelvin. Assuming 32 psi at 50 Celsius(322 K), you get 32psi(V)=(n)(R)(322) which is right about a 10 to 1 Celsius ratio. The rule of thumb Tom just gave is probably pretty close for standard temps and pressures. If you pump 50 psi at 0 Celsius, you get 50psi(V) = (n)(R)272K which is closer to 5 to 1 C. And then since rubber is such a good insulator, most ambient temperature transfer(not talking friction) is transferred through the wheel, not the tire. So the speed at which the air in your tires heat up standing still will depend on the material of your wheel. So basically, every combination of pressure and temperature - when you fill your tires - has a different rate of changing pressure with temperature, and every different wheel will change temperature at different rates in relation to the ambient temperature. Rules of thumb generally get you in the ballpark but ultimately prove useless. Whatever ratio you pumped at will be the ratio it stays at, provided you don't have a leak |
10-18-2009, 05:06 PM | #16 |
Audio Junky
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very nice.
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10-18-2009, 05:07 PM | #17 |
Half a Bubble Off Plumb
Drives: 2009 Yaris Sedan Join Date: Mar 2009
Location: Bristol, Tennessee, USA
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10-18-2009, 08:55 PM | #18 |
Drives: yaris 08 sedan Join Date: Oct 2008
Location: Montreal Canada
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