LIES,DAMN LIES,AND TYRE PRESSURE GAUGES Whilst on the subject of checking your
tyres,you really ought to check the pressures once every couple of weeks too.
Doing this does rather rely on you having,or having access to a working,accurate
tyre pressure gauge. If you've got one of those free pencil-type gauges that car
dealerships give away free,then I'll pop your bubble right now and tell you it's
worth nothing. Same goes for the ones you find on a garage forecourt. Sure
they'll fill the tyre with air,but they can be up to 20% out either way. Don't
trust them. Only recently - since about 2003 - have I been able to trust digital
gauges. Before that they were just junk - I had one which told me that the air
in my garage was at 18psi with nothing attached to the valve Autel
MD702. That's improved now and current-generation digital gauges are a lot
more reliable. One thing to remember with digital gauges is to give them enough
time to sample the pressure. If you pop it on and off,the reading will be low.
Hold it on the valve cap for a few seconds and watch the display (if you can).
Generally speaking you should only trust a decent,branded pressure gauge that
you can buy for a small outlay - $30 maybe - and keep it in your glove box. The
best types are the ones housed in a brass casing with a radial display on the
front and a pressure relief valve. I keep one in the car all the time and it's
interesting to see how badly out the other cheaper or free ones are. My local
garage forecourt has an in-line pressure gauge which over-reads by about 1.5psi.
This means that if you rely on their gauge,your tyres are all 1.5psi short of
their recommended inflation pressure. That's pretty bad. My local garage in
England used to have one that under-read by nearly 6 psi,meaning everyone's
tyres were rock-hard because they were 6psi over-inflated. I've yet to find one
that matches my little calibrated gauge maxisys.
One reader pointed something else out to me. Realistically even a cheap pressure
gauge is OK provided it is consistent. This is easy to check by taking three to
five readings of the same tyre and confirming they are all the same,then
confirming it reads (consistently) more for higher pressure and less for lower
pressure. One last note : if you're a motorcyclist,don't carry your pressure
gauge in your pocket - if you come off,it will tear great chunks of flesh out of
you as you careen down the road....
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