Tyre Pressures

[Bazile]

When you put air in your tyres and then remove the hose , there is a decrease in pressure as the connection is removed from the valve .

Is the best solution to set the machine at say, 1 bar above what it should be , in order to compensate for the decrease in pressure , when the hose is removed ?

[Baldric]

I might be wrong but isn't 1 Bar about 14 PSI?

[TWR]

I check my tyres on a weekly basis, after checking I recheck to see if it's correct, I'm still in lbs, that's including the spare.

[TWR]

To add, yes you are correct Balders.

[Bazile]

Ok - so it might not be bar , but llbs

Is my solution the best ?

[TWR]

Go for lbs Bazile, you know where you are with that, whilst your at it, Visual check your tyres for Cuts etc.

[andy-hughes]

If you are putting air into a sealed valve, the noise you hear when you remove the hose is air escaping from the hose pipe, not from the tyre.

Therefore, when your pressure is reached, the air stays in the tyre, so no need to over-fill it.

[Baldric]

I do our Motors once a week in the drive with a good footpump, the connection screws onto the valve like a dustcap, never have any problems.

[Bazile]

What andy describes is what i was referring to - i thought the hissing sound that you hear when the hose connection is removed from the valve was air escaping from the tyre .

Balders - i'm using a garage forecourt pump

[vulcan42]

When a car has been driven for a few miles the air in the tyres gets hot and the pressure increases by 3 or 4 lbs anyway.

[Islay]

Lol I don't know the answer I will ask my garage next time I get them to check them!!

[TWR]

Vulcan, you will only get that on High Speeds, Eg Motorways.

[bhg481]

TWR - no you won't. I have tyre pressure monitors and can see the pressures increase whatever type of driving I do. The heat is generated by the tyre walls flexing, so you could argue the increase would be greater on rough country/city roads.

[vulcan42]

TWR,
I beg to differ as I tested it once. I drove to my local garage, 1 mile way, used their machine to put the correct pressure in and checked with a digital pressure gauge. Then drove 12 miles to next garage and rechecked, all tyre pressures had increased by a couple of pounds.

[Bazile]

Funnilly enough i was watching an old episode of 5th Gear last night and Tiff Needell was doing a piece on air versus nitrogen in the inflation of tyres .

In his subjective opinion he could not tell any difference between the feedback coming from the tyres filled with either .

F1 uses nitrogen to inflate tyres .

Apparently because the molecules in air is smaller than in nitrogen , they can escape through the rubber of the tyres - whereas the molecules in nitrogen being bigger don't escape through the rubber ; thus enabling the tyre to stay inflated at the set pressure

[bhg481]

Air is approx 80% nitrogen, 20% oxygen. Oxygen molecules are bigger than nitrogen molecules. Whenever you check your tyre pressures you can only add air yourself. I don't see any point in putting nitrogen in tyres.

[ToraToraTora]

that's what I do bazille.

[MantaRay]

That small hiss of air represents very little in terms of tyre pressure. Sometimes I have to reset the pressure if I've not disconnected the inflation nozzle swiftly which has caused a second or so of air to be released.