[Matthewjlove]

So now that I went with new tires and wheels I wanted to dial in my air pressure.

I checked through the cars TPMS report (cold tires) and they were all dramatically different. Didn’t snap a picket but example would be 44psi from left. 36psi front right, etc.

Felt like that was a little weird since I had a reputable shop to the tire / wheels.

Checked with my own gauge and got 38psi for
both front wheels.

Anyone else see off numbers wkth their TPMS?

 

[RRToadHall]

a: never check tyres cold go out 10-15 drive and get them up to temp. Every winter we have slew of repeat threads that folks think they have air escaping from their tyres... the difference between cold air readings and road temp readings an be 5-7 PSI.


now the EAS sytems... yes. Orings shrink, bladders have a lot less flexibility.

 

[Noreaster]

a: never check tyres cold go out 10-15 drive and get them up to temp. Every winter we have slew of repeat threads that folks think they have air escaping from their tyres... the difference between cold air readings and road temp readings an be 5-7 PSI.


now the EAS sytems... yes. Orings shrink, bladders have a lot less flexibility.

Ok, i have not been on this forum very long, and i am sure there are a ton of WTFs with cold temps and tire pressure, seeing that cold air takes up less space than warm air. However, have never heard someone say never check tire pressure cold. Recommended tire pressures are a cold reading with the expectation that when they get warm the pressure will be higher. Curious where the - dont take cold readings - comes from?

OP, TPMS requires the car to be driven a little bit for the dash info to be (somewhat) correct.

 

[dwboston]

I agree with Noreaster. Advice has always been to check tire pressure (with an actual pressure gauge) when the tires are cold. Tire pressure increases with temperature (and vice versa) so to know what the real pressure is, you need to check when the tires are cold.

 

[Matthewjlove]

Yeah. Very odd.

I grew up racing bikes and we always did a cold tire check before using the tire warmers.

 

[bill2019]

come on guys, use common sense what RRTOADHALL said is true for several reasons.

If you have a desired driving tire pressure of say 40psi how in the world are going to be able to tell how much expansion is going to take place once they warm up? you can try to guess at it but you would be wrong. so the proper way is to drive it a bit to warm up tires and then check and fill.

if you desire to go by manufacture cold tire recommendations than you will have a different driving pressure. I would think we all desire a driving temp not a cold temp.


To matthewjlove: one of the reasons one side of your vehicle may be showing a slightly different pressure is sun load, if your car is sitting outside with one side in the shade that side will show a different temp the sun does in fact heat up tires. If you check them when hot you wont have to worry about the difference of sun load on some tires.When you use a tmps programmer it not only shows you tire pressure but also will tell you the temp of the tire. All the dash reader does is read the output signal from the tires if anything at all would be off it would be the tpms used in each tire.

keep in mind that not all pressure meters are equal.

 

[dwboston]

come on guys, use common sense what RRTOADHALL said is true for several reasons.

If you have a desired driving tire pressure of say 40psi how in the world are going to be able to tell how much expansion is going to take place once they warm up? you can try to guess at it but you would be wrong. so the proper way is to drive it a bit to warm up tires and then check and fill.

if you desire to go by manufacture cold tire recommendations than you will have a different driving pressure. I would think we all desire a driving temp not a cold temp.


To matthewjlove: one of the reasons one side of your vehicle may be showing a slightly different pressure is sun load, if your car is sitting outside with one side in the shade that side will show a different temp the sun does in fact heat up tires. If you check them when hot you wont have to worry about the difference of sun load on some tires.When you use a tmps programmer it not only shows you tire pressure but also will tell you the temp of the tire. All the dash reader does is read the output signal from the tires if anything at all would be off it would be the tpms used in each tire.

keep in mind that not all pressure meters are equal.

To use your own logic back on you, how will you know exactly when to measure the warm tire pressure? After 5-10-20-30 or 60 minutes? After a drive around town or one on the highway? Tires after a 60 minute run at 65+ mph will be warmer than one driven about town at 30-40 mph for an hour, and hence have higher pressure.

There's a mix of art and science when it comes to tire pressure, but it's unwise to make a blanket statement that you should never measure tire pressure cold, when that has always been the prevailing advice. You measure the cold pressure and assume a rise of 3-5 psi given typical driving conditions/ambient temp and add/remove air to get to your desired pressure within the recommended range for the tire and car.

 

[Noreaster]

come on guys, use common sense what RRTOADHALL said is true for several reasons.

If you have a desired driving tire pressure of say 40psi how in the world are going to be able to tell how much expansion is going to take place once they warm up? you can try to guess at it but you would be wrong. so the proper way is to drive it a bit to warm up tires and then check and fill.

if you desire to go by manufacture cold tire recommendations than you will have a different driving pressure. I would think we all desire a driving temp not a cold temp.

Your point of view is absolutely correct for people who set up cars for the track or armature racing, or have even collected their own data for temperature and road wear patterns on their own tires.

However the commoner does not know what the optimum pressure is for their vehicle on the common roads they drive. Therefore the only data we have to work with is the cold temperature recommendation from the vehicle manufacturer.

General advice, Dont mess with tire pressures unless you really know what you are doing.

"A tire's operating temperature will increase with higher vehicle load, speed, air temperature and with lower tire inflation pressure. The combination of inflation pressure, speed, and vehicle load could increase the tire temperature as much as 50 degrees C above the ambient air temperature.[SUP][39][/SUP] Higher operating temperatures will increase the rate of oxidative aging.[SUP][39][/SUP]"

https://en.wikipedia.org/wiki/Firestone_and_Ford_tire_controversy#Operating_Temperature

 

[RRToadHall]

Curious where the - dont take cold readings - comes from?

OP, TPMS requires the car to be driven a little bit for the dash info to be (somewhat) correct.

Okay, then try an experiment go for you normal drive with the TPMS readings on you screen. the tyres will come way up in PSI and not necessarily all at the same time. If you stick to cold readings and add more air you are going to be way over inflated which is a safety issue.

 

[dwboston]

Okay, then try an experiment go for you normal drive with the TPMS readings on you screen. the tyres will come way up in PSI and not necessarily all at the same time. If you stick to cold readings and add more air you are going to be way over inflated which is a safety issue.

It all depends on what the cold readings are. No one is suggesting to blindly add air. Tire manufacturers and auto makers virtually all recommend checking the tire pressures when cold. Most people know that tires will increase in pressure when warm. Whether those pressures are "way up in PSI" when they warm up depends on a range of factors, and most tires have a decent range of recommended PSI. The range of PSI for normal vs. full loads is pretty wide, and adding say 4-5 PSI (for example) to tires that are at the low end of (or below) the recommended range when cold is unlikely to introduce safety issues unless driving from extreme cold to extreme hot temperatures is a short period, which is unusual. And under-inflation is more dangerous, and likely to happen, than over-inflation.

 

[dwboston]

Right out of the RRS owners manual:

"All tire pressures, including the spare, should be checked regularly using an accurate tire pressure gauge, when the tires are cold. Failure to properly maintain the tire pressures could increase the risk of tire failure, resulting in a loss of vehicle control and potential personal injury."

"Pressure checks should be carried out only when the tires are cold and when the vehicle has been stationary for more than three hours. A hot tire at, or below the recommended cold inflation pressure is dangerously under-inflated."

 

[bill2019]

Ok guys once again if you think about why the manufactures are telling you this it will make sense.

Their goal is not to offer you optimal driving pressure but to make sure you do not go below the minimum recommended pressure. This is the one and only reason that you are told to check them when cold.

most people only fill to the minimum pressure and of course of if that is done on a hot tire as soon as it cools down you will be below the safe driving pressure for that tire.

 

[dwboston]

Ok guys once again if you think about why the manufactures are telling you this it will make sense.

Their goal is not to offer you optimal driving pressure but to make sure you do not go below the minimum recommended pressure. This is the one and only reason that you are told to check them when cold.

most people only fill to the minimum pressure and of course of if that is done on a hot tire as soon as it cools down you will be below the safe driving pressure for that tire.

No one is debating that point. There's a reason why you check when the tires are cold and adjust from there.

 

[Noreaster]

Their goal is not to offer you optimal driving pressure but to make sure you do not go below the minimum recommended pressure. This is the one and only reason that you are told to check them when cold.

Cold pressure is used because warm pressure has too many variables. Warm tires should be about 4psi above the cold pressure, and a tire that has been driven extensively should read about 6psi above cold temp.

Just like low pressure is bad, high pressure is bad as well. there is a predetermined recommended range (best fuel economy and ride) and a safe range.

These ranges are set by engineers that consider the tire size, width and weight of the vehicle, which is why a vehicle that weighs 2k lbs lighter will have a different recommended pressure on the same exact tires. The math is rather simple, vehicle weight divided by 4 x P = square inches of required contact area of the tire to the road. P = tire pressure. Contact area would be at the advice of the tire manufacture. This also works on the beach. You lower your tire pressure to not sink in the sand. If you lower to 15psi, you are literally putting 15lbs of pressure on every square inch of sand.

 

[Old&Bald]

It is possible that pressure readings shown after your RR has been parked are actually the readings from when the RR was last driven. This could depend on how the actual TPS sensor is powered. There are two ways these TP sensors are powered. First, and what is probably now the older way, the TP sensor contains a small battery. Secondly, the TP sensor might contain a so called "energy harvestor". In this second case an operating voltage for the TPS is developed from vibration and/or rotational forces experienced by the sensor when the RR is driven. So you may have to drive a few miles, not only to warm up the tires, but to power up the TP sensor.
Here is a link to a discussion on this very topic:
https://www.sensorsmag.com/embedded/powering-tire-pressure-sensors

Cheers

 

[nar]

I always check the tire pressures when they are cold and only if there is shade in the mornings. If you have one tire in the blazing sun all day the cold pressure will be dramatically higher in that tire as well. I don't except the pressures to change too dramatically and even if it's a lot colder the pressure drop isn't going to be that much of a problem. There is no need to constantly adjusting your pressures. I check it once a week in the aforementioned conditions, usually only adjust them once every month or so at most. I go off my air compressor gauge for consistency.

Use the TPMS as a reference for flat tires or leaks, not when you need to add air to your tires.

 

[gpiotras]

I’m one of those odd individuals that read almost every page of the owners manual for my vehicles, and the instructions for products I purchase, including tires. Every single manual I read over the las 30+ year always emphasizes to set the tire pressure when they are cold. I do respect other people’s preference to softer rides, but to say that the proper way to set the recommended tire pressure when the tires are not cold is quite frankly incorrect, IMO. Read you manual and follow those instruction. That is the correct method to set the recommended tire pressure. What you do after that (or any method you come with), that’s your own personal preference and you are free to do that. That said, if you decide to do something different, then ignore the recommended pressure for your vehicle or tire too, as those values are provided assuming that you follow the recommended procedure to inflate. In other words, if your manual says to inflate to 44 when they are cold and you decide not to measure when cold, then inflate to any arbitrary number you want, because using 44 no longer applies to you.

 

[MarkinMaine]

My truck was in the dealer for recall work. When the shop did their basic checks (fluid, and basic safety check) they adjusted the tire pressures. This seemed like a good idea to them, but... The truck had been sitting in their 68F shop all day, and ambient temps outside were averaging 5-10F. The next morning when I started up in the drive (it stays outside) guess what? All the tires were low (way low) on tpms monitoring. I figured that even MY wife couldn't hit nails on all 4 tires at once. Dealer didn't take that into consideration that it is winter outside of their nice 68F garage. Shame on them for messing with my correctly adjusted tires.

 

[Noreaster]

My truck was in the dealer for recall work. When the shop did their basic checks (fluid, and basic safety check) they adjusted the tire pressures. This seemed like a good idea to them, but... The truck had been sitting in their 68F shop all day, and ambient temps outside were averaging 5-10F. The next morning when I started up in the drive (it stays outside) guess what? All the tires were low (way low) on tpms monitoring. I figured that even MY wife couldn't hit nails on all 4 tires at once. Dealer didn't take that into consideration that it is winter outside of their nice 68F garage. Shame on them for messing with my correctly adjusted tires.

You would think the dealer would know better.