Tire pressure wtf

P

Palo Verde

Active member
Fellow Frogger
Joined
Oct 2, 2017
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441
Location
Sydney NSW
Hey everyone,

As many of you know, I got a new car from a dealer not too long ago and have been happily driving it since August 2023. Recently, though, with all the rain in Sydney, the roads are like a minefield of potholes. I've tried my best to dodge them, but sometimes you just can't see them until it's too late.

Tonight, my tyre pressure monitor decided to make my evening interesting by flashing a 'low pressure detected' warning. I immediately thought, "Great, must be from that pothole I hit earlier today." So, I rushed to the nearest servo to check things out. The tyres looked fine—no flats or anything—but I figured I'd better top them up just in case.

Now, here's where it gets interesting. I checked the door sticker for the recommended pressure, and to my surprise, it was all in kPa and bar, no PSI. Luckily, the servo had kPa measurements. The sticker said 250 kPa for minimal passengers, so I went with that since I'm usually driving solo.

To my shock, it took forever to fill up the tyres. Turns out, all four tyres were at 180 kPa—grossly under-inflated! This whole time since I left the dealer, I'd been driving around on under-inflated tyres. Apparently, the dealer must have rushed the prep and set the pressure way too low, and the tyre pressure monitor just accepted that as the norm.

So, lesson learned: when you drive off the dealer's lot with your new car, head straight to the servo and check the tyre pressure. Chances are, it might be all wrong like mine was. Fingers crossed I didn't cause any damage to these pricey 18' continentals!

Stay safe and check those tyres, folks!
 
Tyres do go down by themselves in 9 months. You don't have good evidence against the dealer.
180 kPa is 26 psi. I've had worse than that.
 
You’re right, tyres do lose pressure over time. I guess it’s possible they deflated a bit over the months. Still, driving around with 26 psi in all four tyres was quite the surprise for me! I appreciate the perspective, though—sounds like you've seen worse.

Under-inflated tyres definitely aren’t doing my fuel economy any favours, meaning all my fuel consumption were incorrect for months. Guess I’ll just chalk this one up to a learning experience and keep a closer eye on those tyres from now on. Thanks for the insight!
 
I've known dealers to lower tyre pressures to give a smoother, non-jarring ride with those skinny tyres.
 
26 psi isn't drastically low. As seasink said, they've probably also gone down a bit in 9 months.
All new cars run high tyre pressures, primarily for fuel economy reasons.
Obviously your pressure monitoring system's parameters deem the lowest acceptable pressure to be 27 psi?
You also seem to have more confidence in the accuracy of a service station pressure gauge than I would?
 
I guess 26 psi isn’t too drastic, especially over nine months. It’s interesting to learn that new cars typically run higher pressures for fuel economy.

My tyre pressure monitoring system probably has its lowest acceptable limit set around 27 psi, which explains the alert. And you’re right about service station gauges—maybe I should be cautious about relying solely on them. But if not for servos, where would one find a convenient, accessible, free, and accurate way to check tyre pressure?

I appreciate the insights and will definitely keep these points in mind moving forward.
 
Palo Verde said:
I guess 26 psi isn’t too drastic, especially over nine months. It’s interesting to learn that new cars typically run higher pressures for fuel economy.

My tyre pressure monitoring system probably has its lowest acceptable limit set around 27 psi, which explains the alert. And you’re right about service station gauges—maybe I should be cautious about relying solely on them. But if not for servos, where would one find a convenient, accessible, free, and accurate way to check tyre pressure?

I appreciate the insights and will definitely keep these points in mind moving forward.
Click to expand...
You can buy a hand held battery powered digital gauge for minimal expenditure.
 
IF your Skoda is like my (older) Skoda, it may not actually have tyre pressure sensors. Our Skoda just monitors the rotation of the ABS sensors on each wheel and turns the warning on if there is anything that seems wrong, such as one wheel turning faster than the others when driving straight ahead. It is remarkably sensitive, it has reported a tyre pressure "fault" several times after simply having all tyres brought up to correct pressure when they had been a tiny bit different; and has also reported a "fault" when I rotated the tyres to even out wear - the computer had adapted to one pattern of wear, when I moved tyres around, the relative speeds changed (due to fractionally different diameters) which was detected as an unexplained change and the tyre light came on...

Two bits of advice:

1. You should check your tyre pressures and tread wear much more frequently - at least once a month. Expect to have to add more air every couple of months. This is perfectly normal. If your tyres are varying in wear (generally on Australian roads, left tyres wear faster than right) or pressures are changing slowly over time, then you are likely to get the error.

2. In Skodas (*and other cars) with this typer of tyre pressure "calculated monitoring" (my term) rather than actual tyre pressure sensors, you need to reset the tyre pressure monitoring each time you do anything to the tyres - add air; rotate tyres to new positions; get new tyres fitted. The car's computer maintains a "memory" of the relative speeds of each wheel when the monitoring was last reset - each time something is changed, you need to press the reset button (or select tyre pressure reset in a menu) to tell the computer that this new reading is "correct" and should be accepted as normal. Otherwise it will detect changes, compare them to old stored values and falsely report a fault.

In our car it can be a bit temperamental, sometimes it had put on the warning, I have checked tyres and found them all OK or adjusted pressures, pressed the reset button and the warning just comes straight back on again. I have variously found at different times that I have had to hold the rest button down for a few seconds to get it to reset properly, at other times I have had to press the button while the car is being driven for it to register, it wouldn't accept a reset if the car is not moving. Sometimes... at other times it will accept a reset while not moving.
Our Skoda has a button on the centre console with a picture of a tyre and the word "RESET" but I think on newer ones, it is done through the on-screen menu. (?)

I hope this is useful for you.

here is a cheap digital tyre gauge...

Loading…

www.repco.com.au

This dial type gauge is on clearance for $5:

Loading…

www.repco.com.au
 
One other point which may be relevant

If you have the nasty licorice strip tyres 26psi may be too low for some conditions. I am thinking particularly of rough roads with potholes and dodgy edges - they do not have the sidewall space to handle hitting anything much unless properly inflated

Partner has just got rid of her much loved Audi S3 as she got sick of 2-3 new tyres / year ( we live on dirt ). Grief partly assuaged by fact that she is v impressed with new Subaru, which handles it all with aplomb, if a good bit less power .

Andrew
 
simca1100 said:
IF your Skoda is like my (older) Skoda, it may not actually have tyre pressure sensors. Our Skoda just monitors the rotation of the ABS sensors on each wheel and turns the warning on if there is anything that seems wrong, such as one wheel turning faster than the others when driving straight ahead. It is remarkably sensitive, it has reported a tyre pressure "fault" several times after simply having all tyres brought up to correct pressure when they had been a tiny bit different; and has also reported a "fault" when I rotated the tyres to even out wear - the computer had adapted to one pattern of wear, when I moved tyres around, the relative speeds changed (due to fractionally different diameters) which was detected as an unexplained change and the tyre light came on...

Two bits of advice:

1. You should check your tyre pressures and tread wear much more frequently - at least once a month. Expect to have to add more air every couple of months. This is perfectly normal. If your tyres are varying in wear (generally on Australian roads, left tyres wear faster than right) or pressures are changing slowly over time, then you are likely to get the error.

2. In Skodas (*and other cars) with this typer of tyre pressure "calculated monitoring" (my term) rather than actual tyre pressure sensors, you need to reset the tyre pressure monitoring each time you do anything to the tyres - add air; rotate tyres to new positions; get new tyres fitted. The car's computer maintains a "memory" of the relative speeds of each wheel when the monitoring was last reset - each time something is changed, you need to press the reset button (or select tyre pressure reset in a menu) to tell the computer that this new reading is "correct" and should be accepted as normal. Otherwise it will detect changes, compare them to old stored values and falsely report a fault.

In our car it can be a bit temperamental, sometimes it had put on the warning, I have checked tyres and found them all OK or adjusted pressures, pressed the reset button and the warning just comes straight back on again. I have variously found at different times that I have had to hold the rest button down for a few seconds to get it to reset properly, at other times I have had to press the button while the car is being driven for it to register, it wouldn't accept a reset if the car is not moving. Sometimes... at other times it will accept a reset while not moving.
Our Skoda has a button on the centre console with a picture of a tyre and the word "RESET" but I think on newer ones, it is done through the on-screen menu. (?)

I hope this is useful for you.

here is a cheap digital tyre gauge...

Loading…

www.repco.com.au

This dial type gauge is on clearance for $5:

Loading…

www.repco.com.au
Click to expand...
Thanks for the detailed advice—this is super helpful!

It turns out my 2023 Skoda might be using different technology for tyre pressure monitoring. While previous models prior to 2023 may have used ABS sensors, mine seems to use actual tyre pressure sensors, which would explain why it alerts me with precise readings. Still, your tips about resetting the system after any tyre adjustment are spot on and something I’ll definitely keep in mind.

I’ve learned my lesson about tyre maintenance—I'll be checking pressures and tread wear monthly from now on. And thanks for the tip on the pressure gauges; I’ll grab one for more accurate readings.

When I left the dealer, they must have eyeballed the tyre pressure instead of measuring it. Now that I've set it to the recommended 250 kPa, the difference is huge—better tyre appearance, less cabin noise, improved pick-up speed, and smoother start-stop. It feels like a whole new car!

It's frustrating to think I’ve been driving with under-inflated tyres all this time, affecting the car’s performance and potentially wearing out my Continentals faster. And with a tyre rotation due in 10,000 km or 12 months, I shudder to think what the tyre shop will say about the wear and tear. All this because I assumed the dealer was diligent in checking these little details!

Thanks again for the great advice and pointing me to those gauges. I’m definitely going to stay on top of tyre maintenance from now on. And yes, a visual indicator for tyre pressure would be a game-changer—someone needs to invent that!
 
Andrew Watkins said:
One other point which may be relevant

If you have the nasty licorice strip tyres 26psi may be too low for some conditions. I am thinking particularly of rough roads with potholes and dodgy edges - they do not have the sidewall space to handle hitting anything much unless properly inflated

Partner has just got rid of her much loved Audi S3 as she got sick of 2-3 new tyres / year ( we live on dirt ). Grief partly assuaged by fact that she is v impressed with new Subaru, which handles it all with aplomb, if a good bit less power .

Andrew
Click to expand...
Thanks for the additional point—very relevant indeed!

I do have those licorice strip tyres, so 26 psi might have been too low, especially with the rough roads and potholes around here. They definitely need to be properly inflated to handle any bumps or dodgy edges.

Your partner's experience with the Audi S3 resonates—I can see how those low-profile tyres would struggle on rougher surfaces. Glad to hear the Subaru is handling it well, even if it has a bit less power.

As mention in reply to simcar, with my tyre rotation due in 10,000 km or 12 months, I’m really hoping I haven't incurred too much wear and tear. It's frustrating to think I’ve been driving with under-inflated tyres all this time, just assuming the dealer had checked these details.

Thanks again for all the great advice and insights. I’ll definitely stay on top of my tyre maintenance moving forward. And yes, a visual indicator for tyre pressure would be a game-changer—someone needs to invent that!
 
Palo Verde said:
Hey everyone,

As many of you know, I got a new car from a dealer not too long ago and have been happily driving it since August 2023. Recently, though, with all the rain in Sydney, the roads are like a minefield of potholes. I've tried my best to dodge them, but sometimes you just can't see them until it's too late.

Tonight, my tyre pressure monitor decided to make my evening interesting by flashing a 'low pressure detected' warning. I immediately thought, "Great, must be from that pothole I hit earlier today." So, I rushed to the nearest servo to check things out. The tyres looked fine—no flats or anything—but I figured I'd better top them up just in case.

Now, here's where it gets interesting. I checked the door sticker for the recommended pressure, and to my surprise, it was all in kPa and bar, no PSI. Luckily, the servo had kPa measurements. The sticker said 250 kPa for minimal passengers, so I went with that since I'm usually driving solo.

To my shock, it took forever to fill up the tyres. Turns out, all four tyres were at 180 kPa—grossly under-inflated! This whole time since I left the dealer, I'd been driving around on under-inflated tyres. Apparently, the dealer must have rushed the prep and set the pressure way too low, and the tyre pressure monitor just accepted that as the norm.

So, lesson learned: when you drive off the dealer's lot with your new car, head straight to the servo and check the tyre pressure. Chances are, it might be all wrong like mine was. Fingers crossed I didn't cause any damage to these pricey 18' continentals!

Stay safe and check those tyres, folks!
Click to expand...
No you should definitely call fair trading or the police maybe the A team but being a VAGina car just set it on fire all problems solved.
 
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Palo Verde said:
And yes, a visual indicator for tyre pressure would be a game-changer—someone needs to invent that!
Click to expand...
You can buy a set of these valve caps for under $10 off EBay.
But if your tyre pressure monitoring system isn't ABS based, I'm guessing your present valve caps have transmitters in them?


20240526_205237.jpg
 
Transmitter TPMS uses radio transmitters inside the battery moulding, so they transmit from inside the tyre. One of mine triggered a fault today. I measured the tyre at a lick under 30 psi.
 
Michelin's system just uses transmitters in the valve caps.


20240526_221124.jpg
 
Used to have a "Tyredog" system that looked like that on our Landcruiser - like your Michelin system, it was an aftermarket add-on, not a factory OEM system, which is what seasink is describing (& Palo Verde almost certainly has).
 
But who doesn't check their tyres at least once every few months? Certainly at least in a 10 months!

@Palo Verde I presume you have stored the new and correct pressure in the cars system?
 
Armidillo said:
Used to have a "Tyredog" system that looked like that on our Landcruiser - like your Michelin system, it was an aftermarket add-on, not a factory OEM system, which is what seasink is describing (& Palo Verde almost certainly has).
Click to expand...
I believe most of the factory system transmitters are now incorporated in the valve stem?
I also believe back in the early days of mandatory TPMS' that some manufacturers resorted to using the "add on" style systems as standard equipment.
The US has had mandatory TPMS monitoring since the Firestone debacle in the mid 2000s.
The add on systems are popular in the UK as a non functioning factory TPMS is an MOT failure, and often the factory parts to repair them are either unobtainable or prohibitively expensive.
 
A tyre and exhaust mechanical workshop I use always pump the tyres up to around 39 or 40 psi on any vehicle I've sent there.
Whenever I pick the vehicle up now, straight to a nearby servo.
Press the needle in the valve for about 30 seconds at least, then put the pump on it to sort it out.
Nuts.
 
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