I'm Guessing Tyres Are Not Meant to do This

[Wolfgang]

Thanks for the advice Brad. Will give them a ring in the next few days.

I'm running the factory recommended 2.4 bar (35-6 psi), will up it to 38psi and see how the car rides.

[Diesel_vert]

Thanks for the advice Brad. Will give them a ring in the next few days.

I'm running the factory recommended 2.4 bar (35-6 psi), will up it to 38psi and see how the car rides.

The OEM spec pressures are almost always cold figures, i.e. before the tyres have warmed up.

Gases expand when heated, so you need to add 0.2 - 0.3 bar (3 - 4 psi) to the pressures listed in the fuel flap if you need to drive the car anywhere in order to add air.

I suspect the previous owner didn't really check the pressures often, or used the cold pressure figures whenever they added air at a service station - which means by the time the tyre has cooled down, it would be underinflated.

[brad]

It takes at least 15 minutes of "normal" suburban driving to get enough temperature into a tyre to make a noticeable difference in pressure unless the tyre is grossly (like <20psi) under-inflated.

Previous owner possibly never added air or checked the pressure. I have plenty of friends of both genders that never do anything to their car beyond adding fuel. They rely soley on the Service Centre to look after their cars. One of the dingbats is trying to get warranty on the paintwork of their 8yo Mazda because the clearcoat is peeling. Don't mind the fact that it has never been garaged, washed or had any body maintenance in the whole time she's owned it.

[Diesel_vert]

It takes at least 15 minutes of "normal" suburban driving to get enough temperature into a tyre to make a noticeable difference in pressure unless the tyre is grossly (like <20psi) under-inflated.

The relationship between air pressure and temperature, brought to you by Tire Rack:

Tire Tech Information - Air Pressure, Temperature Fluctuations

Tire Tech Information - Air Pressure: When and How to Set


The gist of it being...

... even a short drive to inflate your tires will result in tires that will probably be under-inflated by a few psi the following morning.

Some conversions (change in air pressure per difference in temperature)

Imperial: 1 psi per 10°F

Metric: 0.1 bar per 10°C

Hybrid: 1.5 psi per 10°C

Previous owner possibly never added air or checked the pressure. I have plenty of friends of both genders that never do anything to their car beyond adding fuel. They rely soley on the Service Centre to look after their cars.

One of the pitfalls of long service intervals.

A proactive attitude towards maintenance is needed in order to benefit from such a regime, otherwise it can end up costing the owner more money than would otherwise be saved.

[brad]

The change in pressure is fairly easy to check - simply record the pressure before leaving home & then when you get to the service station. I've done it several times & under the conditions I drive there is no significant change in the 3km between my house & the servo.

I think you'll find the heat cycling machine Tirerack uses puts a bit more stress on the tyre than a 5-10 minute drive up the road does. Also you'll note they didn't test on a more typical pressure (these days) of 35psi. I don't believe it would have experienced the same increase in temp/pressure.

I'm fairly anal about this stuff but based on experience, I'll even check my tyres after doing a 45minute trip from Campbelltown to Hurstville. I figure it's better to do the monthly check rather than let it go. I know how much I inflated it to the last time & I'm using the same guage, so i adjust how much air I put in based on the highest reading i get from all 4 tyres (eg: if I get 38psi from the first tyre I do I inflate them all to 38 & I'm happy that all the tyres are inflated within a pound or 2 of each other & above the vehicle manufacturers recomendation (Skoda says 31psi FFS). That's probably better than 70% of the cars on the road