How to correctly inflate tyres

deaston

I have a van which has two sets of tyre pressures - for light loads or heavy loads. I generally have a lot of stuff in my van.

Do I set the pressure depending on how much will be in my van or how much is in my van? Should I empty the van, fill the tyres for a full load, then reload it...?

molerat

You set the pressure to the conditions you will normally drive under. The load does not have to be in the van at the time, it makes no difference if it is or is not. You only need to change the pressure if you are going to do a long journey loaded differently.

deaston

molerat wrote: »

You set the pressure to the conditions you will normally drive under. The load does not have to be in the van at the time, it makes no difference if it is or is not. You only need to change the pressure if you are going to do a long journey loaded differently.

So how much load is in the van at the time of checking the pressures won't skew the reading?

I assumed having several hundred kilos of stuff in the van would make the pressures read higher.

debtdebt

It has no bearing whatsoever. When changing tyres, garages inflate the tyres when they are off the car with no load on them.

m_c

Technically whether the tyre is loaded or not does have a bearing, however the change is negligible in the grand scheme of things. An uncalibrated pressure gauge will likely have a far larger margin of error, than whether the tyre is loaded or not.


As to the OPs question, set it to what you would normally expect to carry. There are pros and cons to being over and underinflated, but it's probably best to verge on the side of overinflated to minimise problems.

System

deaston wrote: »

I have a van which has two sets of tyre pressures - for light loads or heavy loads. I generally have a lot of stuff in my van.

Do I set the pressure depending on how much will be in my van or how much is in my van? Should I empty the van, fill the tyres for a full load, then reload it...?

If it spends most of its time being driven with a lot of WEIGHT in it then you go for the heavier loaded. If it doesn't then you go for the light loaded. It is the WEIGHT of what is being carried, not the amount that matters so if your vehicle is ram packed full but the stuff weighs nothing you'd go for the lightly loaded option.

Car_54

molerat wrote: »

You only need to change the pressure if you are going to do a long journey loaded differently.

Indeed. These clever tyres instinctively know that you're only popping down to the shops, and adjust the pressure automatically.

deaston

Car_54 wrote: »

Indeed. These clever tyres instinctively know that you're only popping down to the shops, and adjust the pressure automatically.

How do I know if I've got this type of tyre? Are they the same as 'run flats'?

facade

deaston wrote: »

How do I know if I've got this type of tyre? Are they the same as 'run flats'?

Car 54 is joking.

Incorrect tyre pressures are actually an offence under construction & use regulations, and really you should adjust the pressures before each journey, no matter how short, to match the load.

The weight won't affect the pressure reading, what happens is the tyre squashes out more with more load as

weight on tyre = pressure x area in contact with road

So with pressures that are too low, the tyre squashes out more, and the sidewalls flex too much, get hot and explode on a long journey.

With too high a pressure, not enough of the tyre area contacts the road and there is less grip available.