Andy's 2019 Blue SZ5

What does the tyre pressure plate inside the door say?

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But the new ones are pretty much the same size?

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So close enough to be the same on the plate

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On the vin plate it will give you the individual axle weight front and rear. On the side of the tyre it will have the maximum weight that the tyre can take at a maximum pressure. So using mathematics you know what they maximum weight that the axle will carry, divide that by the 2 tyres. You now know how much maximum weight each tyre is going to experience. So now with the information off the tyre you can work out how many psi the tyre needs to support 1 kg. Knowing that you can then multiply it by the half axle weight you worked out first. This will give you the correct psi for your tyres at maximum vehicle weight. It will be within 1 or 2 psi of the standard 26 psi all round. Simples.

Volume and pressure are two different things. Yes a bigger tyre holds more air than a smaller one but that just means you have to have more air to achieve the same pressure. The same amount of air in a smaller space will be under more pressure but by releasing some of the air you can regulate the pressure. If that makes sense.

Lambert wrote: Volume and pressure are two different things. Yes a bigger tyre holds more air than a smaller one but that just means you have to have more air to achieve the same pressure. The same amount of air in a smaller space will be under more pressure but by releasing some of the air you can regulate the pressure. If that makes sense.

The volume of a tyre is consistent regardless of the volume of air you put into it. What changes is the pressure of the air as you introduce more volume of air into the fixed volume of the tyre.