Mystery of tire air pumps at gas stations....

[thcosh]

On 12/14/2020 at 2:55 PM, Trujillo said:

Of course with external gauges, you have to wonder if they themselves are accurate. 

 

 

 

The day when people will wonder and understand how wrong they think, the world will be full of smart people. Not yet to happen.

 

 

[Andrew Dwyer]

39 minutes ago, Dante99 said:

It is great you check the temp but why is that releveant to this thread about pressure?

Just a little test to see if anyone actually reads my posts, thanks for being attentive . ????

[jvs]

1 hour ago, boonchu said:

I filled my tyres with nitrogen, 400bt first time after that free top ups. I just drive to the tyre shop where I filled the tyres and get the free tyre pressure check and free top up of nitrogen. Don't even have to get out of the car.

Yes they ought to do that after they took 400 baht pressure out of your wallet!

You got scammed!At least in my opinion.

 

[EVENKEEL]

Can't be bothered with the air at stations so I bought my own compressor. Only 4500 bht and can be had for cheaper. I don't understand why the service stations have these electronic gismos.

[Slain]

I the UK the advice is always check with your on pressure gauge  because the petrol station one is probably out due to heavy use.

[whaleboneman]

7 hours ago, Dante99 said:

It is great you check the temp but why is that releveant to this thread about pressure?

Boyle's law? 

[Dante99]

4 hours ago, whaleboneman said:

Boyle's law? 

Science is great but you do need to understand when it is applicable and Boyle's Law is certainly not useful in this situation.

[dingdongrb]

12 hours ago, EVENKEEL said:

Can't be bothered with the air at stations so I bought my own compressor. Only 4500 bht and can be had for cheaper. I don't understand why the service stations have these electronic gismos.

I bought one years ago. It's great not just for tires but I use mine to blow out all the dust from my PC and NAS.

[KhaoYai]

Service station gauges have been suspect for many years - just blow them up over the required amount and use your own gauge to correct the pressure as you let it out.

[whaleboneman]

1 hour ago, Dante99 said:

Science is great but you do need to understand when it is applicable and Boyle's Law is certainly not useful in this situation.

I guess humour not allowed now? But in fact, Boyle's law is applicable and it is why you should check tire pressure when they are cold.

[Bill97]

1 hour ago, dingdongrb said:

I bought one years ago. It's great not just for tires but I use mine to blow out all the dust from my PC and NAS.

Plus to blow dry your motorcycle, truck and hairy regions.

[Bill97]

1 hour ago, whaleboneman said:

I guess humour not allowed now? But in fact, Boyle's law is applicable and it is why you should check tire pressure when they are cold.

What does it have to do with variations in the pressure readings on gas station air filling equipment?  Our topic

[trevoromgh]

On 12/13/2020 at 1:29 AM, Trujillo said:

If you go to a gas (petrol) station and put air in your tires, the first reading seems to indicate what pressure is currently in the tire (before the pump starts). 

 

So, when you hit your target air pressure -- let's say 32 psi -- the pump beeps and you remove the air chuck from the tire stem. Okay. The tire ought to have the pressure now that you just put in and was recorded on the digital display, right? 

But if you immediately put the chuck back on the tire stem, the display reads far less (like 27 psi) than it just did when the tire was "full" to the pressure you programed in. Shouldn't the tire read the same as what it just registered immediately after you finished "filling" it? 

 

Mystery....

 Smile you're going to be on next months "Candid Camera" episode 

[chilly07]

If you  can  hear air going  into the tyre it should  stay at that pressure. I always  check with  my own gauge as those tyre towers are often innacurate 

[Trujillo]

Thanks Russell17au for solving this question. It all makes sense now. 

 

By the way, I don't know if it's just me but the tires in my car deflate on their own. The tires on my scooter deflate on their own. The tires on my chopper deflate on their own (although not as badly as all the other vehicles). The tires on my bicycle deflate on their own. 

Paying to put nitrogen in the tires of my car would be silly. Every two weeks I'd have to refill them. 

[GregTN]

After reading this thread I went to fill my tires at the local PTT and after reaching the desired PSI of 36 I reattached the hose and it was still reading 36. Apparently certain designs of air pumps cause that issue as previously stated.

[thailandbeachisland]

1 hour ago, GregTN said:

After reading this thread I went to fill my tires at the local PTT and after reaching the desired PSI of 36 I reattached the hose and it was still reading 36. Apparently certain designs of air pumps cause that issue as previously stated.

 

clearly, it has always been like this for me ! I wonder if the OP could understand how wrong he is ?!

 

[KhaoYai]

8 hours ago, Trujillo said:

Thanks Russell17au for solving this question. It all makes sense now. 

 

By the way, I don't know if it's just me but the tires in my car deflate on their own. The tires on my scooter deflate on their own. The tires on my chopper deflate on their own (although not as badly as all the other vehicles). The tires on my bicycle deflate on their own. 

Paying to put nitrogen in the tires of my car would be silly. Every two weeks I'd have to refill them. 

If any of those are tubeless (probably only your car), it is very likely a bead leak.  That is where corrosion or dirt is causing a leak on the bead of the tyre (where it seals).  This is very common on alloy wheels.  I have even found a minute crack on an alloy before that was causing a slow puncture - kerbing is the usual culprit.

 

However, on tubed tyres -  I had a similar problem with my Honda Scoopy - it seemed to puncture regularly and the tyres deflated slowly in between punctures.  I got sick of it and took a closer look at what was going on - it turned out that when I'd had a 'genuine' puncture, the bike shop up the road kept replacing the tubes with cheap rubbish ones. Both back and front tubes were leaking very slowly from the 'rubber weld' where the valve stem is attached to tube.  I went to a bike shop and asked if there was more than one quality of tube - there was.  I bought a pair of decent quality tubes and I've never has a problem since.  In future I'll repair punctures myself.

[Monkeyrobot]

Just buy one of those tyre pressure gauges at you local auto store the ones about 6 inches long and look like a pen , I always keep one in my  glove box , also always check your tyre when they a cold; those gauges at the gas stations are not that accurate if they have been dropped and un calibrated. Fill you tyre then use the gauge to check against the gas station gauge.