Air Gauges
Submitted: Saturday, Jul 29, 2006 at 17:14
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ZUKSCOOTERX90(QLD-MEMBER)
Good Evening All,i have four air gauges,one is for work compressor,one is portable Dr Air & two hand held all of which give a different reading.The two hand helds show about 6/8 psi lower than the two compressor ones.The dilema is if i go by the hand helds this will make the tyres too low for h/way travel & just about right for off road or do i go the other way as in too high for h/way & off road.
There must be a right air gauge out there somewhere if there is can i be pointed in the right direction,i.e. type,brand & cost but it must be accurate.
Thanks to all in advance.
Cheer's Bob.
Reply By: Max - Sydney - Saturday, Jul 29, 2006 at 17:50
Saturday, Jul 29, 2006 at 17:50
Hi Bob
All the experts who tell you that you should only measure tyres with accurate gauges NEVER tell you where you can get them checked. And you can't buy a new one every year!
I work on two ways to deal with that:
1. I don't trust gauges on compressors - the gauge is pounded by the fluctuating pressure they are subjected to, and can reasonably be expected to lose calibration.
2. I use the 4 psi rule - put tyres to the pressure you want when cold, then drive for a few tens of km until they are warmed up, then measure pressure again. If the pressure is about right, they will have gone up by 4 psi. If too low, they will have gone up by more, and if too high they've gone up by less, so adjust pressures to suit. Then you can use the pressure read by that gauge when the tyre is cold as your guide.
The NRMA web site says 4 psi rise for cars and 6 psi for 4WDs, but I cannot understand why. I have had good luck with tyres using the 4 psi rule - current tyres are just coming up to 100, 000 km (set of 5) on my 80 series with a range of loads including caravan and camper trailer hauling, on bitumen and off. I do fuss about tyre pressures, have regular wheel balances, rotate as per the owner's manual and a wheel alignment if it feels "funny".
That's my prejudice - bet you get lots of conflicting advice!
Cheers
Max
AnswerID:
186003
Follow Up By: Crackles - Saturday, Jul 29, 2006 at 19:45
Saturday, Jul 29, 2006 at 19:45
Agree with you Max that in general the hand held gauges are more accurate than those connected to a compressor, particularly those at service stations but I'm yet to be convinced that the 4 psi rule is particularly accurate as there are far too many variables like when you go for your 10 min drive is it on dirt or tar, at 60 or 100kph, is it the same on a 6 ply or 12 ply radial or for a bias ply tyre with a tube? What if it's a 40 degree day, do you still only get a 4 psi rise? What if the road you're driving has lots of corners, doesn't that increase the pressure more? Even driving in a straight line the tyres facing the sun can be 2 psi higher than the shaded side. And really how many people pump their tyres up each & every time we add 300kg as that will increase the rise in pressure as
well?
Cheers Craig.............
FollowupID:
442985
Follow Up By: Max - Sydney - Sunday, Jul 30, 2006 at 09:54
Sunday, Jul 30, 2006 at 09:54
Craig
Agree with all you say - its just that this has worked for me, when nothing else has.
Yes, I am fussy enough to try to do the testing near the start of the trip - I just blow them up to what I reckon when I inflate the Polyairs before packing, then at morning tea on day one, hop out and check them all. I generally make my decisions based on the tyres that are on the shade side.
That lasts for the trip then - though I feel all tyres & bearings (including caravan) every now and again when I pull up just to know nothing is going wrong.
According to the gas laws (learned a million years ago at Uni and vaguely remembered) the 4 psi rise will hold true in any ambient temperature.
I generally work at or just above the tyre placard pressures around town, and a bit more depending on load on a trip. But the 4 psi rise avoids having to get the gauge calibrated, and certainly I am happy with tyre life doing it that way.
I certainly have only experienced a limited a range of tyres - but would fiddle around and find out with any others if I had to.
Its all good fun!
Max
FollowupID:
443053
Reply By: Member No 1- Sunday, Jul 30, 2006 at 10:59
Sunday, Jul 30, 2006 at 10:59
i find the digtal ones at servo's to be very close to being true.
AnswerID:
186057
Follow Up By: Shaker - Sunday, Jul 30, 2006 at 11:26
Sunday, Jul 30, 2006 at 11:26
Compared to what?
FollowupID:
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Follow Up By: Member No 1- Sunday, Jul 30, 2006 at 14:19
Sunday, Jul 30, 2006 at 14:19
my NATA certified data logger..pressure, temperature, etc etc
anything else you would like to know?
FollowupID:
443074
Follow Up By: Shaker - Sunday, Jul 30, 2006 at 15:07
Sunday, Jul 30, 2006 at 15:07
No that's all.
I have several air pressure gauges & have absolutely nfi how to determine which one, if any, is correct. So I was just wondering how you had.
FollowupID:
443075
Follow Up By: Member No 1- Monday, Jul 31, 2006 at 08:08
Monday, Jul 31, 2006 at 08:08
toss your spare tyre in the back and measure and record the pressure at say 5 or more servo's..the ones with digital readout prefered...discard those readings that are more than 5% out of the norm, & then average the remainder...., this will be more than close enough for what we want
FollowupID:
443224
Reply By: D-Jack - Sunday, Jul 30, 2006 at 20:57
Sunday, Jul 30, 2006 at 20:57
The most accurate hand guage I think I have ever had and still have is the pencil type one. Small, light, quick and easy to use. When it says 40psi so too does the one at BP digial station - either it's accurate or the BP ones and
mine are both out exactly the same amount. It cost me $10. The dial type ones which can cost up to $30 (I have had 2) break easily, are bigger, and didn't seem to be as accurate compared to the BP digital ones. Dunno if this helps you or anyone, but I said it anyway!
D-Jack
AnswerID:
186146
Reply By: HJ60-2H - Sunday, Jul 30, 2006 at 21:14
Sunday, Jul 30, 2006 at 21:14
You can accutally buy very accurate gauges if you look at specialists that sell pressure gauges and don't just look at ready made tyre gauges from auto outlets.
I bought a box of them a whiie back and made up a heap of inflation assemblies to run of my car and home compressors. I still have some of the guages around if anybody is interested.
I think they average out at around $10 per guage. To that you need to add a T, valve coupler, hose etc. About $50 per assembly I made up.
AnswerID:
186150