Car tyre pressure/tread depth gauge accuracy

reeac

Iceweasel wrote: »

I've had no less than 3 of these cheapy digital gauges - my grandchildren give me them as presents.

They have all given up the ghost and are now in the bin.

The gauges that is - not the grandchildren! LOL

I'm still using my old Motometer analogue one.

It's got a round dial approx 2" (50mm) diameter and is bomb proof.

Looks like this:

https://www.google.ba/search?q=motometer+tyre+pressure+gauge&tbm=isch&tbo=u&source=univ&sa=X&ei=RUFBUsTGKsfKtAa-3oAo&ved=0CD0QsAQ&biw=1366&bih=667&dpr=1

Porsche used to supply one in the car tool kit.

Pricey - but plenty similar style copy versions on the Bay of E.

The Motometer pictured there is reading 4 Kg/sq.cm. without being attached to anything. Not a good sign.

Iceweasel

reeac wrote: »

The Motometer pictured there is reading 4 Kg/sq.cm. without being attached to anything. Not a good sign.

Ha ha - I just noticed that - but some of those are from the 1930s and are now collectors items!

Mine is a 1973 vintage and works perfectly - the digital ones agree with it but they either fade away or don't survive being dropped. They are also difficult to read in bright sunlight.

You should see how much old Motometers fetch on eBay - especially if they still have the soft leather pouch.

Weird_Nev

reeac wrote: »

The Motometer pictured there is reading 4 Kg/sq.cm. without being attached to anything. Not a good sign.

They have a "reading hold" function, which holds the measured reading until you press the reset button. This means you just press the meter onto the valve, lift it off, make the reading at eye level in comfort, and then press the button to reset it back to zero.

I use a cheapy Analogue gauge with similar function. When 4x4'ing we adjust tyre pressures many times a day, and need accurate readings from 10psi up to 40+Psi. I've always found the analogue gauges far easier to use. It's quick and as accurate as anything else. How many people have access to a calibrated pressure gauge? So long as it's accurate relative to itself, and holds accuracy over time, that's as good as it gets with handheld tyre pressure gauges. Digital gauges aren't necessarily more accurate, just more precise. And they can be hard to read in bright or low light.

Tread depth? Use the visual wear indicators, and put a 20p piece on edge into the grooves of the tyres. If the edge of the "rim" disappears completely, then you have enough tread (for legal purposes).

scotsbob

Ultrasonic wrote: »

Out of interest, how do you know that it is accurate?

The engineering dept at the university have an extremely accurate calibration unit, my nephew tells me it tested to 99.84% accurate.

That is how I know and it's good enough for me.:D

Jamie_Carter

Iceweasel wrote: »

I've had no less than 3 of these cheapy digital gauges - my grandchildren give me them as presents.

They have all given up the ghost and are now in the bin.

The gauges that is - not the grandchildren! LOL

I'm still using my old Motometer analogue one.

It's got a round dial approx 2" (50mm) diameter and is bomb proof.

Looks like this:

https://www.google.ba/search?q=motometer+tyre+pressure+gauge&tbm=isch&tbo=u&source=univ&sa=X&ei=RUFBUsTGKsfKtAa-3oAo&ved=0CD0QsAQ&biw=1366&bih=667&dpr=1

Porsche used to supply one in the car tool kit.

Pricey - but plenty similar style copy versions on the Bay of E.

And those are the type I used to use in motor racing, where tyre pressures are critical.

Bongles

Hintza wrote: »

Why do you need a depth gauge? The tyres are marked and fingertips will soon tell you if you are below the minimum.

A simple "am I at the minimum tread depth yet or not?" is not the only question I might want to answer. I do use my gauge to answer that question, but I also use it to more generally keep an eye on tyre wear - both the overall level of wear and how even it is across the tyre width - as well as specific things like checking how quickly a new type of tyre starts to wear or whether I'm close to the 3mm threshold beyond which performance supposedly degrades more markedly.

If all you're interested in is the legal minimum then the wear indicators on the tyre are all you need.

daveyjp

I use the Halfords analogue. Easy to use and as far as I'm concerned it is accurate. I had two new tyres fitted, told the garage they needed to be 34 PSI, checked when I arrived home and it read 34.

Pressures are only accurate at the time you do them anyway. A few degrees temeprature change and the pressures will change.

Bongles

daveyjp wrote: »

I use the Halfords analogue. Easy to use and as far as I'm concerned it is accurate. I had two new tyres fitted, told the garage they needed to be 34 PSI, checked when I arrived home and it read 34.

Pressures are only accurate at the time you do them anyway. A few degrees temeprature change and the pressures will change.

Indeed it will. If I was feeling pedantic I might point out that your first paragraph implies that your gauge perhaps underreads (or the garage didn't really give you 34psi). Driving home from the garage you'd expect the tyres to heat and the pressure to increase. Do you live very close to the garage?

daveyjp

Garage is 100 yards away.

Ultrasonic

Hintza wrote: »

Why do you need a depth gauge? The tyres are marked and fingertips will soon tell you if you are below the minimum.

I never felt the need to have one, but after buyig a pressure gauge with one built in I do think one is useful. They allow you to:

1) Spot uneven wear earlier (I did this on my rear tyres).
2) Monitor wear, particularly useful if you choose to change tyres at around the recommended 3 mm tread depth rather than waiting for the legal minimum to be reached.