Tyre Pressure guage measurements

[Geez Louise]

Hi,

Okay this may seem like a silly question, however I was doing a bit of weekly maintence on our cars and noticed that the tyre pressure guage/pressure meter, has two measurements on it. PSI (pounds per square inch) and KPA. (kilopascals)

My question is....why?

Is it like imperial and metric? Do different countries use different measurements?

I have never heard anyone say..."Yes I put such and such kilopascals in my tyres. So why do they have it? and who would use kilopascals?

It just had me curious as to why it is on there.

Cheers
Col

[K10wN]

You got it in one, imperial and metric. Both measurements are usually on the tyre sidewall too.

[xisled]

Read this, it may give you an idea.

http://en.wikipedia.org/wiki/Pascal_(unit)

[Geez Louise]

Thanks for that.

So PSI is imperial and KPA is basically metric?

I never noticed both were written on the side wall of the tyre, so I have learnt something new today.

Cheers
Col

[galaxy xr8]

Originally Posted by Geez Louise

Thanks for that.

So PSI is imperial and KPA is basically metric?

I never noticed both were written on the side wall of the tyre, so I have learnt something new today.

Cheers
Col

Your not the only one, thank's for the question and thank's to those that replied with the answer.

[Franco Cozzo]

I use metric for everything, but it seems easier to put 32 psi in my tyres than 220kpa

[svo supporter]

I'm fairly confident saying, our Aussie cars have a KPA measurement on the tyre placard, for pressures, rather than the ol' PSI.

[Bossxr8]

Originally Posted by svo supporter

I'm fairly confident saying, our Aussie cars have a KPA measurement on the tyre placard, for pressures, rather than the ol' PSI.

I'll think you'll find they have both.

[2011G6E]

I can assure you that even in new cars (like the placard I checked the other day in our G6E) still list simple psi figures...the kpa figure does come above it and the psi is in brackets underneath, but it's there..much easier to remember, in our case, 38psi than whatever that is in kpa...


Metric is great, don't get me wrong, but for tyre pressures they still stick to a simple two digit number that everyone can remember.

There's also a practical aspect...no tyre gauge is very big...some are rather small...and the increments for the huge number range of kpa has the divisions spaced close together, while the good old psi is spaced at a nice easy-to-read distance apart. If you depended on solely kpa gauges, there would be a very common problem with people over or under inflating thier tyres when they read the gauge slightly wrong.

[svo supporter]

Originally Posted by 2011G6E

If you depended on solely kpa gauges, there would be a very common problem with people over or under inflating thier tyres when they read the gauge slightly wrong.

I don't think I've ever came across 2 gauges that read the same pressure in either measurement. So I doubt this would be a reason.

Personally I think it's because the majority of things are in metric, so they're trying the same with tyre pressures

[superfly]

Originally Posted by Bossxr8

I'll think you'll find they have both.

Mine definitely has psi on the card. Can't remember if it also has kpa.

[Tha Jack]

I use psi for tyre pressure as well as blowers and turbo pressure instead of bar.
Torque wrench- I use Newton metres instead of Lbs.
Measurements- I tend to use a mixture of inches and centermetres.
It confuses the heck out of Col but I know what I mean

[monzie]

Tyre sizes have both as well. E.G. 235 mm metric/ 45 x 17 inch imperial
Wheels are still imperial. Some european cars tried a "390"mm size back in the late 80's but it died a natual death.

Pete

[svo supporter]

Originally Posted by monzie

Tyre sizes have both as well. E.G. 235 mm metric/ 45 x 17 inch imperial
Wheels are still imperial. Some european cars tried a "390"mm size back in the late 80's but it died a natual death.

Pete

An Aussie made car tried the same too. Ford. And yes, it died a natural death

[BigBlue]

Col,
Basically so the gauge can be sold in all countries without having to make a different "metric" version and an "non metric" version.

Just an aside...my idiot brother "borrowed" my tyre gauge recently and I am not sure what he did with it but accurate it ain't any more.

Knowing what he does with his tools (like throwing a torque wrench back on the bench over the bonnet because he was too freakin' lazy to walk around the front of the car and put it there!) I am not totally surprised.

I now keep ALL my tools under lock and key and he has paid for a new gauge.

Peter.

[Ben73]

According to my cars tyre pressure monitoring system, my car has abut 2.8 BAR. I don't know what BAR is I have only used PSI and KPA before.

[svo supporter]

Originally Posted by Ben73

According to my cars tyre pressure monitoring system, my car has abut 2.8 BAR. I don't know what BAR is I have only used PSI and KPA before.

Another form of tyre pressure measurement. Alot of more expensive gauges have this on them.

For what it's worth. PSI is a lot easier to remember than all the other measurements

[Franco Cozzo]

Originally Posted by Ben73

According to my cars tyre pressure monitoring system, my car has abut 2.8 BAR. I don't know what BAR is I have only used PSI and KPA before.

Fairly sure 1 BAR is 1x "atmospheric pressure" at sea level.

[Geez Louise]

Thanks to Jack and his mad measuring terms confusing the heck out of me....I have read a lot today about measurements. May as well fill my head up with 4000 more useless facts that I will use once in a lifetime...Like the fact that all cows walk left foot forward first...that kind of thing.

I will probably never use in a conversation, half or even 3/4 of what I have read today....EVER...but at least I have learnt something.

Definition of BAR:
The bar is a measurement unit of pressure, equal to 1,000,000 dynes per square centimetre (baryes), or 100,000 newtons per square metre (pascals). The word bar is of Greek origin, báros meaning weight. Its official symbol is "bar"; the earlier "b" is now deprecated, but still often seen especially as "mb" rather than the proper "mbar" for millibars

Thanks for all the replies guys. Appreciate the input.

Cheers
Col

[2011G6E]

Originally Posted by Geez Louise

Thanks to Jack and his mad measuring terms confusing the heck out of me....I have read a lot today about measurements. May as well fill my head up with 4000 more useless facts that I will use once in a lifetime...Like the fact that all cows walk left foot forward first...that kind of thing.

I will probably never use in a conversation, half or even 3/4 of what I have read today....EVER...but at least I have learnt something.

Definition of BAR:
The bar is a measurement unit of pressure, equal to 1,000,000 dynes per square centimetre (baryes), or 100,000 newtons per square metre (pascals). The word bar is of Greek origin, báros meaning weight. Its official symbol is "bar"; the earlier "b" is now deprecated, but still often seen especially as "mb" rather than the proper "mbar" for millibars

Thanks for all the replies guys. Appreciate the input.

Cheers
Col

...which is why it's easier to remember "32 psi" instead of bar, kpa, or whatever...

[sneaky]

from memory 1 bar = about 14.7psi.. or was it 14.2psi

[Mechan1k]

Originally Posted by sneaky

from memory 1 bar = about 14.7psi.. or was it 14.2psi

without looking ... 14.7 looks about right to me.

I remember seeing all the old Telstra HIACE vans with the specified kPa reading for each tyre written on the guard. That was a while ago though.

[superpursuit83]

Originally Posted by sneaky

from memory 1 bar = about 14.7psi.. or was it 14.2psi

Yep. 14.7psi (i think) is one bar or 100kpa. Base atmospheric pressure

It will be a sad sad day the day you stop learning people.

[Ben73]

Internet has said 1 BAr is 100kpa.

[Phytho]

What's the most accurate way of measuring tyre pressure? I've been told that the electronic pumps at the servo are pretty unreliable, so bought myself a $10 pressure gauge from autobarn. Measured this morning (FG XR6 LE) and the tyres were around 29-30, so took it down to 7-Eleven and the pump there said the same. Filled them to 39, but when I crossed checked with my gauge, it read only 36. Which to trust?

[GasoLane]

Originally Posted by Phytho

What's the most accurate way of measuring tyre pressure? I've been told that the electronic pumps at the servo are pretty unreliable, so bought myself a $10 pressure gauge from autobarn. Measured this morning (FG XR6 LE) and the tyres were around 29-30, so took it down to 7-Eleven and the pump there said the same. Filled them to 39, but when I crossed checked with my gauge, it read only 36. Which to trust?

I went to my friendly tyre dealer and had them checked then compared it to my 'Autobarn' gauge and went from there.

[Phytho]

Originally Posted by GasOLane

I went to my friendly tyre dealer and had them checked then compared it to my 'Autobarn' gauge and went from there.

So did your autobarn gauge compare well against the tyre dealers? And had you had similar differences between your gauge and electronic air at servo's?

[GasoLane]

Originally Posted by Phytho

So did your autobarn gauge compare well against the tyre dealers? And had you had similar differences between your gauge and electronic air at servo's?

Not enough to worry about, only a couple of pounds difference and I've never used an electronic one, sorry.

[svo supporter]

Originally Posted by GasOLane

Not enough to worry about, only a couple of pounds difference and I've never used an electronic one, sorry.

No offense towards you, but a couple of PSI can be the difference between wearing tyres unevenly and wearing evenly.

The best way to do pressures is once the tyres have been fitted, check them with what ever guage you have on hand and remember the pressure on THAT one.

When re-pressuring, from where ever you get it done, double check the pressure with your gauge. Then you know the pressure is correct, because all guages read differently.

[superfly]

Originally Posted by Phytho

So did your autobarn gauge compare well against the tyre dealers? And had you had similar differences between your gauge and electronic air at servo's?

I use a PCL pencil gauge and I find it to be very accurate. I had someone try and rubbish it claiming they were most inaccurate but when compared to his you-beaut expensive gauge, mine read exactly the same

You need to buy a good quality gauge and trust it.