The tyre's were set at a tyre dealer at 35lb Then I tried a digital gauge from Argos which is incorporated in a 12V pump from Argos. .The Argos pump reads 33lbs, a friends digital meter read 36.5lb, a difference of 3.5lb. Not alot of difference, but I had to change 2 worn tyres due to low tyre pressure which I thought was set at 33lb originally so I want to set them as accurate as I can. The tyre's were all checked when cool. Anyone have any idea where to buy an accurate gauge and what manufacturer.
How do you define accurate???? An 'accurate' gauge is one that reads within a set tolerance of the actual value. Any of the above are most likely accurate to a degree and if the set tolerance is, for arguments sake, ± 2 PSI of the true value then all of the above would probably be defined as within the required level of accuracy. An accurate gauge this week might not be accurate next week after it has been used, abused etc and would therefore need to be verified against a standard to ensure it was still within defined tolerance levels. These levels would most likely be ± 1 or 2 PSI anyway. I really wouldn't worry about but if you must then take the average of 3 readings oobtained from 3 separate sources!
A while ago I had access to a piece of test equipment at work that could very accurately measure and create pressure. It had a calibration certificate. Purely out of interest, I made a rig to test pressure gauges.
I already had an expensive bourdon tube gauge. I bought a really cheap digital one from Halfords. I borrowed a few other gauges from colleagues and tested them in 1 psi steps from 10 to 30 psi. I repeated the test on each gauge three times. (I'm glad my employer doesn't read Usenet!)
Briefly, some of them, including my posh one, were misreading by more than
10%. The most accurate one was the one from Halfords that was less than a fiver! It was within 2% throughout the tested range.
Clearly, the next one on the shelf of the same type might be way out. My conclusion was that it is not possible to know how accurate a gauge was without being able to test it. I'm sorry, I'm sure that was not what you wanted to hear.
As an aside, if I back my car out of the garage on a sunny day, spend ten minutes checking fluids and cleaning the windscreen and then check the tyre pressures the tyres on the "sunny" side of the car will be 2 or 3 psi higher than the side in the shade. It really can't be an exact science it seems.
It doesn't really matter. Digital guages IME are reasonably accurate. Just use the same guage and pressure the tyres by trial and error, starting at the manufacturers recommended pressure, and initially keep an eye on the wear pattern. 1-2 psi either way is not likely to make much difference, but if the tyre shows an uneven wear pattern, adjust the air pressure to correct it. More wear across the middle, reduce the pressure. More wear on the outside of the tread increase the pressure. Adjust it by 1 or 2 pounds until the wear pattern is even across the tread. As long as you use the same guage, it wont matter what the actual reading is. Mike.
The important thing is the pressure differential in each tyre as opposed to the actual value of that pressure (within reason obviously). Don't worry too much about it - I always use a couple of psi more pressure than recommended anyway.
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