[Bruthal]

Originally Posted by RoverJames

JUst saw your edit

Is that good or bad

[RoverJames]

Dunno still think jacking it and using the same pump might work.

[Bruthal]

Originally Posted by RoverJames

Dunno still think jacking it and using the same pump might work.

Well if the pump wont pump the tyre beyond 24psi, how would taking the weight of the car off it now allow it to reach 30psi?

After all, all the pump senses is 24psi from the tyre valve.

Even if there was a 20 ton car on the tyre, the pump should still pump the pressure in the tyre to 30psi as easily as if it was a spare wheel with no load on it. It just wouldnt lift the 20 ton load up very much, if at all, so the tyre would remain like a flat.

This is assuming a properly working pump that is able to inflate to 30 psi.

[RoverJames]

Dunno, I don't think the pumps the OP used are working properly though.

[Bruthal]

Originally Posted by RoverJames

Dunno, I don't think the pumps the OP used are working properly though.

Possibly. Its either that, or the tyre valve. Dont think i seen a valve do that, but had pumps that wouldnt pump the tyre up to pressure myself alright.

Just in the OP`s case, it seemed to pump his other tyres up ok.

[2 stroke]

I would say bs but I had a similar experience last week. Compressor at petrol station would inflate every tyre except the one with a slow leak. I went up the road to tyre shop and no problem inflating it there, guy could make no sense of it except he said I wasnt the first to have the same problem recently. I wonder is there a faulty batch of forecourt gauges. The weight of the car on the tyre is irrevelant unless compressors have developed intelligience, and 30psi would pop a baloon.

[RoverJames]

Originally Posted by 2 stroke

I would say bs but I had a similar experience last week. Compressor at petrol station would inflate every tyre except the one with a slow leak. I went up the road to tyre shop :............ and 30psi would pop a baloon.

the balloon was a hypothetical example, the experience you had is similar to mine.

[Bruthal]

If you take a car tyre as having 1000 square inches( just as example), and inflate the spare to 30psi.

Now put 1000 pounds weight on the tyre by putting it on a 4000 pound car (assuming equal load on each wheel which it wouldnt be). Its pressure will now go to 31 psi.

If you however put the flat tyre on the car, and pump to 30 psi, removing the wheel will drop the pressure to 29 psi. So as said earlier, it will be inflated slightly less when pumped to 30psi with the weight on it, than when pumped unloaded. It is still reaching 30 psi, but slightly quicker. (With the weight of the car on it, there is slightly less volume to fill to reach the same pressure)

So Pumping the tyre while on the car would need 31 psi so that its 30 psi when removed. Or to pump the spare so it was 30psi when then fitted to the car would only need 29psi.

As you said, these differences wouldnt be seen on a forecourt pump gauge.

So the pump not going beyond 24psi is possibly the pump alright, if not the wheel valve. Maybe the gauge sticking, although the user should still hear the air going in.

[toe2toe]

check to see i there is a collar type of thing slid over the tyre valve ,sometimes used to match alloys? they can restrict the connector on compressor pushing down enough on valve if there is one it can be slid off