petrol garage air pump pressure

[slowmotion]

AFAIK petrol station ones should be kept accurate IF they are charging for it as it then comes under weights and measures. If it is rated below the max pressure of tyre/tube combo it shouldn't make any difference how fast it fills. Flow and pressure are 2 different things. I've filled the ships bike tyres with a 8 bar pressure supply line without problems, and the compressors are a lot bigger than anything on a forecourt.

I would still be a bit concerned about how responsive the pressure cut-off was when filling the tube very fast. You are far more savvy than the average cyclist who may attempt to fill a tube like a car tyre.

 

[classic33]

AFAIK petrol station ones should be kept accurate IF they are charging for it as it then comes under weights and measures. If it is rated below the max pressure of tyre/tube combo it shouldn't make any difference how fast it fills. Flow and pressure are 2 different things. I've filled the ships bike tyres with a 8 bar pressure supply line without problems, and the compressors are a lot bigger than anything on a forecourt.

The thing you have to take into account is that they are designed to fill a larger volume. Often to a lower pressure, but still a larger volume. The same amount of air into a smaller volume will result in a larger pressure.

 

[Piemaster]

The same amount of air into a smaller volume will result in a larger pressure.

True, but that isn't whats happening as its being connected to an air supply and thats an important difference to being connected to a compressor or track pump.
The compressor will operate between a couple of different pressures, you can usually hear it cutting in and out, then discharge into a receiver, an air bottle. The tyre is connected to the receiver. The pressure going into the tyre cannot exceed the pressure in the receiver, it's fixed (which is why the OP wants a different garage). As connecting and filling the tyre will very slightly increase the total volume of the system there will actually be a slight decrease in the pressure as the tyre fills.

And how about helium balloons? Doesn't seem any problem filling them from a big bottle of gas.

 

[classic33]

True, but that isn't whats happening as its being connected to an air supply and thats an important difference to being connected to a compressor or track pump.
The compressor will operate between a couple of different pressures, you can usually hear it cutting in and out, then discharge into a receiver, an air bottle. The tyre is connected to the receiver. The pressure going into the tyre cannot exceed the pressure in the receiver, it's fixed (which is why the OP wants a different garage). As connecting and filling the tyre will very slightly increase the total volume of the system there will actually be a slight decrease in the pressure as the tyre fills.

And how about helium balloons? Doesn't seem any problem filling them from a big bottle of gas.

The system is built to cater for the larger volume, lower pressure vehicle tyres though.
Filling helium balloons from a larger gas cylinder is usually done from a cylinder that has a regulator & special valve fitted.
Still some manage to overinflate the balloons though!

 

[Piemaster]

I would still be a bit concerned about how responsive the pressure cut-off was when filling the tube very fast. You are far more savvy than the average cyclist who may attempt to fill a tube like a car tyre.

It's actually not that difficult. As you get the tyre closer to whatever the supply air pressure is the difference in pressure between the two reduces and the tyre fills slower.

I would still have used a track pump if I'd had one handy though!

 

[Piemaster]

The system is built to cater for the larger volume, lower pressure vehicle tyres though.
Filling helium balloons from a larger gas cylinder is usually done from a cylinder that has a regulator & special valve fitted.
Still some manage to overinflate the balloons though!

Despite my posts, I'd still use my Joe Blow track pump myself - best option. It hangs up next to the bike and i don't have to go to a garage to use it. And how do you get the bike to the garage if you've changed a tyre or fixed a flat?

 

[slowmotion]

It's actually not that difficult. As you get the tyre closer to whatever the supply air pressure is the difference in pressure between the two reduces and the tyre fills slower.

I would still have used a track pump if I'd had one handy though!

I had a tube and a tyre wall blow out when riding a couple of months ago. I made quite a noise. Not quite as much as the fully-laden quarry truck that blew a tyre three metres away from my seat at a cafe on Naxos a long time ago. That noise was impressive. I think I read subsequently that people get killed by exploding truck tyres.

 

[vernon]

AFAIK petrol station ones should be kept accurate IF they are charging for it as it then comes under weights and measures. If it is rated below the max pressure of tyre/tube combo it shouldn't make any difference how fast it fills. Flow and pressure are 2 different things. I've filled the ships bike tyres with a 8 bar pressure supply line without problems, and the compressors are a lot bigger than anything on a forecourt.

Petrol station pressure gauges are notoriously inaccurate with large variations in indicated pressures when tested with a calibrated gauge. Most of the motoring organisations and motoring publications recommend that motorists and motorcyclists carry their own pressure gauge.

Weights and measures legislation does not cover pressure gauges. From the Motorcycle Action Group (MAG), web site in an article about accuracy of forecourt pressure gauges:

· Tyre pressure gauges are not regulated under any UK legislation.

· Local Trading Standards Officers (TSOs) could inspect air pumps on garage forecourts but they have no legal powers to force operators to put right any defects. Only forecourt operators are responsible for ensuring that the equipment is in good working order.

 

[threebikesmcginty]

You shouldn't rely on the forecourt ones with the gauge on the hand held bit as these go out of calibration when they get bumped, knocked, dropped, etc., which is all the time.

 

[subaqua]

I have used the adaptor on my LP ( 10 Bar ) hose on my scuba set to inflate bike tyres before . no problems

 

[jnrmczip]

After all the input I'm off to my lbs to get a track pump which sounds better and I will avoid the garage

 

[vernon]

Has the OP exploded his tyres yet?

After all the input I'm off to my lbs to get a track pump which sounds better and I will avoid the garage

Yep.

 

[raleighnut]

A lot of Petrol stations use a small post mounted compressor which will struggle to reach 55psi (20p coin op jobbies) A garage compressor can easily reach 175 psi ( the place I worked at, Status Garages, in 1975 had theirs set to cut off at 260psi which is now completely illegal although the tank was safety tested to 300 psi and the blow off safety set to 280)
As others have said though Track Pump.

 

[vernon]

A lot of Petrol stations use a small post mounted compressor which will struggle to reach 55psi (20p coin op jobbies) A garage compressor can easily reach 175 psi ( the place I worked at, Status Garages, in 1975 had theirs set to cut off at 260psi which is now completely illegal although the tank was safety tested to 300 psi and the blow off safety set to 280)
As others have said though Track Pump.

20p coin operated pumps??!! I haven't found one that takes less than 50p.

 

[fossyant]

Get a good track pump and a good pocket one. Simple.