Monday, October 3, 2016

Check your own tyre pressures - no garage will ever get it right.

In my 28 years (and counting) of driving, in six different countries, I've yet to come across anywhere that knows how to set car tyre pressures properly. I've not yet found a garage, dealership, oil-change shop or tyre store that understands what the sticker inside the driver's door means, nor how to use a pressure gauge.
At this point I'm convinced such a place doesn't exist. Generally, when someone else has worked on my car, I get it back with tyres that are anything from 5psi below the recommended pressure to 10psi above. My current Range Rover dealer is about the closest I've seen with all four tyres consistently 2psi above where they're supposed to be.
Underinflated tyres are bad, but on the occasion where I've had overinflated tyres, it's been dangerous. All tyres have a maximum inflation pressure and on one extreme occasion, a Subaru dealer gave me my car back with all four tyres inflated to 62psi. That was 7psi above the max pressure rating on the tyre and a full 34psi higher than the door sticker.
You can normally tell instantly. You'll get in your car and it will either feel like you're driving on grease, or on granite wheels. The greasy feeling means the tyres are underinflated. Rock-hard spinal re-adjustment feeling means the tyres are overinflated.
Spend a tenner and buy a decent dial pressure gauge (not one of those cheap pen type ones) and always check your own pressures when you get your car back from anywhere that's touched the wheels.
The same holds true for the lug nuts or bolts. If ANYONE touches them for ANY reason, check the torque yourself a day later, because as with tyre pressures, in 28 years I've yet to find a single place that knows what a torque wrench is.
I know you shouldn't need to do this but such is life.


Paul Canciu said...

There is also the issue of running tyres of a different size than the ones the sticker is meant for (original tyres). Then most surely the sticker doesn't apply anymore.
For example, for my Golf GTI, the original tyres are 225/40R18, but I run 225/45R17 in the summer and 205/55R16 in the winter. I have found that the pressures on the sticker are too high for my tyre sizes, so I experimented a little until I found something hard enough but which does not feel like "rock" wheels, as you called them. The winter tyres are inflated, let's say, more on the soft side, so that they absorb the bumpy winter conditions and also for better grip in snow and ice.
I also wouldn't say no to a "pen" pressure gauge, as long as you know the inaccuracy for it. You can still use it for checking, you just need to add or subtract whatever value you know it to be off by.

Oto said...

Regaring torque wrench it is only needed once. You tighten by hand and check with torque wrench then you will feel how much is enough for future. Also grease wheel nuts as otherwise the reading will not be correct. And no, applying grease won't make nuts to loosen themselves.

Skip92 said...

ambient temp. effects tires (yes i know i missed spelled it) about +/- 10 degrees F is good for 1 psi in change. some tire companies recommend checking tire presuures monthly unless your car does it for you(law in Yankyville, USA). So just maybe the autotech checked your tires in cold early morning and when you picked up your car you pulled a jackie stewart and did some motor car racing to get home and really heated up the rubber. I've always torqued with torque wrench because i was told torque sticks don't work on double hammer air guns and almost all air guns are double hammering, I could be wrong on this because i've never bother to fact check it. I also always re-torque all wheels after 100k's especially on aluminum rims, lots of corrision on rims maybe because of two dissimilar metals reacting to each other. Just don't go to the extreme and torque your rims to much or you will stretch the lugs over time.