I am asking this because the first time I checked my less than one year old car's pressures they were around 32 or 33 PSI - I cant remember exactly, but I noticed the recommended pressures, which are found on the inside of the fuel flap, are 2.7 bar for the fronts (that's 39 PSI) and 2.9 bar (42 PSI) for the rears. Are they recommending such high pressures because it makes the official fuel economy figures better? I believe Porsche do this with the latest 911.

Edited 27 October, 20241 yr by mccririck

I just go with what it says on the fuel filler flap. That way if there's an accident I'm complying with the tyre pressures supplied by the manufacturer.

6 minutes ago, TheWanderer said:

I just go with what it says on the fuel filler flap. That way if there's an accident I'm complying with the tyre pressures supplied by the manufacturer.

Fair enough, I'd rather set mine to the best level for driving rather than fuel economy.

I just see it as protecting one's backside from ambulance chasing and where there's a blame crooked lawyers.

3 minutes ago, TheWanderer said:

I just see it as protecting one's backside from ambulance chasing and where there's a blame crooked lawyers.

I've never heard of anyone being done for having their tyres lower than spec but not obviously low. I mean, it looks like the car was supplied to me with the pressures set to 33 PSI. And 39 seems very high.

Edited 27 October, 20241 yr by mccririck

If there's a serious collision and someone suffers life changing injuries or dies, and the police accident investigation team start examining your car for faults and stuff, then they check the tyres and they're found to be under or over inflated they would more than likely put it as part of the attributable cause, leaving you open to charges and a claim against you for failure to keep it in a roadworthy condition.

 

I wouldn't trust the police to run a kids bath these days.

The answer is surely "Do the tyres have edge wear (pressure too low) or centre wear (pressure too high) at your preferred pressure?"

Relative tyre pressures are very dependant on vehicle load and speed, but should match on the same axle - any tyre pressure label fitted on a vehicle is only a recommendation, not a legal requirement.

IIRC, maximum pressure permitted is usually moulded into the sidewalls.

There are usually several recommended tyre pressures shown on the fuel flap for different loads (one person, 3 people, three people plus luggage IIRC).

 

@mccririck Which recommended tyre pressure were you comparing against?

I've been running mine at the pressures indicated on the label under fuel filler flap as @TheWanderer suggests; and adjust according to load (full load is 49psi at the back IIRC) and I have no complaints wrt grip, ride or handling. The original fit tyres lasted over 45k miles with even wear across the tread width.

 

All of which implies that the pressures on the label are perfectly fine.

1 hour ago, PetrolDave said:

There are usually several recommended tyre pressures shown on the fuel flap for different loads (one person, 3 people, three people plus luggage IIRC).

 

@mccririck Which recommended tyre pressure were you comparing against?

The lightest one.

56 minutes ago, SteveTheElder said:

I've been running mine at the pressures indicated on the label under fuel filler flap as @TheWanderer suggests; and adjust according to load (full load is 49psi at the back IIRC) and I have no complaints wrt grip, ride or handling. The original fit tyres lasted over 45k miles with even wear across the tread width.

 

All of which implies that the pressures on the label are perfectly fine.

My issue is with road noise which I'm sure increased when I upped the pressures.

8 minutes ago, mccririck said:

My issue is with road noise which I'm sure increased when I upped the pressures.

What tyres do you have?

10 minutes ago, SteveTheElder said:

What tyres do you have?

Pirelli P7 I doubt it's the tyres.

After 18 months of driving and about 7,000 miles  I got a low pressure warning (car was 6 months old with 40 miles on it when I bought it).  When I checked, all of the tyres were at 2.0 bar and the fuel filler cap suggested 2.5 bar.  2.5 bar seemed high, but I have no idea what the pressures were when I bought the car, and therefore what pressure drop is required to trigger the low pressure warning.  I topped the tyres up and will now see how long it takes before I get the next low pressure warning.

Is it showing a low pressure or just a change in pressure? when I was towing and the tyres got warm I would get a warning.

You still have to check all four tyres to see if you do have a problem though.

1 hour ago, mccririck said:

The lightest one.

My issue is with road noise which I'm sure increased when I upped the pressures.

 

I just ignore it, turn the radio up slightly or have the window open slightly like I do as I hate air con as it knackers my sinuses.

1 hour ago, mccririck said:

Pirelli P7 I doubt it's the tyres.

I’ve had Michelin Primacy 4 and now Goodyear Efficient Grip. Both quiet (enough). Not driven on P7s though.

 

Not noticed any increase in noise with pressure increase.

35 minutes ago, avi4tor said:

After 18 months of driving and about 7,000 miles  I got a low pressure warning (car was 6 months old with 40 miles on it when I bought it).  When I checked, all of the tyres were at 2.0 bar and the fuel filler cap suggested 2.5 bar.  2.5 bar seemed high, but I have no idea what the pressures were when I bought the car, and therefore what pressure drop is required to trigger the low pressure warning.  I topped the tyres up and will now see how long it takes before I get the next low pressure warning.

I think I was the same actually. I cannot believe all four tyres would lose that much pressure though.

It's all those darn potholes & speed humps that litter our roads!

2 hours ago, gumdrop said:

Is it showing a low pressure or just a change in pressure?

Delta P. VAG standard TPMS uses derived pressure from the ABS sensors and not actual pressure.

I'm pretty fanatical about checking tyre pressures and the day after collecting my Skida Approved Used 1.0TSI Estate I checked to see what the pressures had been set to by the dealer. All 34psi which is what I would have expected for an unladen car with just driver and passenger (out old Fucus was 33psi all round). Checked the recommended pressures on the fuel flap and there are none given for only driver or driver and passenger, only 3-up with some luggage and fully laden. The quoted pressures are as you say. I tried then at the lower of the two for a day and the ride was awful with just me and the dogs in the boot. Far too choppy. Ever since I've set them at 34 psi all round unless loaded up and the ride is much better.

 

The Tyre pressure sensor has to be set by you once your happy with them and just warns of any change outside a set difference. AFAIK it does not tell you if the pressures are correct, just uses wheel rotation to determine any changes from those set.

14 hours ago, avi4tor said:

After 18 months of driving and about 7,000 miles  I got a low pressure warning (car was 6 months old with 40 miles on it when I bought it).  When I checked, all of the tyres were at 2.0 bar and the fuel filler cap suggested 2.5 bar.  2.5 bar seemed high, but I have no idea what the pressures were when I bought the car, and therefore what pressure drop is required to trigger the low pressure warning.  I topped the tyres up and will now see how long it takes before I get the next low pressure warning.

I really worry when I hear how infrequently some drivers physically check tyre pressures - and all fluid levels!

4 minutes ago, Warrior193 said:

I really worry when I hear how infrequently some drivers physically check tyre pressures - and all fluid levels!

In the bad old days I would agree with you, but in those days I did everything including the minor services.  With modern cars you can go between major services without lifting the bonnet.  There are sensors everywhere to tell you if anything needs attention and a visual check of the tyres will soon highlight a problem there.

4 hours ago, Scrumpy1 said:

I'm pretty fanatical about checking tyre pressures and the day after collecting my Skida Approved Used 1.0TSI Estate I checked to see what the pressures had been set to by the dealer. All 34psi which is what I would have expected for an unladen car with just driver and passenger (out old Fucus was 33psi all round). Checked the recommended pressures on the fuel flap and there are none given for only driver or driver and passenger, only 3-up with some luggage and fully laden. The quoted pressures are as you say. I tried then at the lower of the two for a day and the ride was awful with just me and the dogs in the boot. Far too choppy. Ever since I've set them at 34 psi all round unless loaded up and the ride is much better.

 

The Tyre pressure sensor has to be set by you once your happy with them and just warns of any change outside a set difference. AFAIK it does not tell you if the pressures are correct, just uses wheel rotation to determine any changes from those set.

Thanks for checking when you got the car. I knew I wasn't imagining the change in comfort.

4 hours ago, Warrior193 said:

I really worry when I hear how infrequently some drivers physically check tyre pressures - and all fluid levels!

An important issue with the indirect TPMS system most commonly used by Skoda and others, is that it may never flag pressure loss before tyres fall to unsafe levels if the loss is roughly equal over the set. It is a fact that ALL tyres will lose pressure to some extent over time.