Check your air pressure!

[YarisOwnersDad]

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

[ROCKLAND TOYOTA]

YOUR 2009 doesn't have TPMS? Also if the tires were set to that 27 psi your light would have been on.....

[YarisOwnersDad]

YOUR 2009 doesn't have TPMS? Also if the tires were set to that 27 psi your light would have been on.....

Don't know if I have the tire pressure monitoring or not. I didn't specifically ask for it, so unless it is standard, I don't have it.

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

[Yaris Hilton]

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.

[YarisSedan]

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



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.

[nemelek]

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.

[YarisOwnersDad]

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.

Thanks for the reply.

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

[jambo101]

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/products/productimages/images/112%20tire%20gauge%2040540.jpg

[YarisOwnersDad]

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/products/productimages/images/112%20tire%20gauge%2040540.jpg

How much "lettuce" we talkin' for one of those puppies?

[nemelek]

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/products/productimages/images/112%20tire%20gauge%2040540.jpg

That won't work for the hypermilers that put 50 psi in each tire.

[YarisOwnersDad]

That won't work for the hypermilers that put 50 psi in each tire.

Ah, I had not noticed that the max pressure for that gauge is 40 psi.

Well, I only plan to run the recommended 32 psi, so that gauge would work for me.

Tom

[msmitka]

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).

[talnlnky]

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?

[YarisOwnersDad]

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?

Found something on the Internet that says the rule of thumb is 1 psi change for every 10°F change in ambient air temperature.

Tom

[supmet]

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

[talnlnky]

very nice.

[Yaris Hilton]

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.

Or that the mechanic's gauge was off. Tire gauges and scales are immensely variable.

[jambo101]

How much "lettuce" we talkin' for one of those puppies?
Between $30 to $40
As for the 40psi max on that particular model they do make others
http://www.rpmcat.com/images/P89-11103.jpg

[TinyGiant]

i havent checked mine in a while . i'll have to do that tomorrow !

[bronsin]

Never heard of anyone offering to check and inflate your tires as part of an oil change. Thats totally your responsibility. I find once a month is good if the tires arent leaking. When my kids show up for a visit theres often no oil on the dipstick and 18 psi in their tires. They got fancy wheels and air intakes though.

[talnlnky]

Never heard of anyone offering to check and inflate your tires as part of an oil change. Thats totally your responsibility. I find once a month is good if the tires arent leaking. When my kids show up for a visit theres often no oil on the dipstick and 18 psi in their tires. They got fancy wheels and air intakes though.

glad I don't live in nj.... thats pretty much expected on the west coast.

[TinyGiant]

they usually top off the air at the walmart service center i usually bring the car to.. they also vacuum the car :) all for $20 bux :)

[YarisOwnersDad]

Yeah, I thought that ANYWHERE that you might get your oil changed the folks would check your tire pressure for you, and especially if you went to the dealership.

Tom

[H3LlIoN]

Don't know if I have the tire pressure monitoring or not. I didn't specifically ask for it, so unless it is standard, I don't have it.
Tom

If it's a USDM, then it has TPMS. (TPMS became mandatory in 08)

The Yaris TPMS is set to go off at 28/29 psi.


This info is as provided by my roomate, who is a Toyota/MCEP certified master mechanic, currently employed with Toyota.