Tire pressure query

[omodos]

Hello all, happy new year, well been happily inflating my tires at the nearest garage to me and doing so to spec for the tire size i have 17" 235.65

In bar I set for normal driving (90% of the time just me) 2.2 bar up front and rear...

Just so happened I was not near my local gas station and filled up at brand new garage, checked my tire pressure and it was 2.0bar according to their machine....so pumped upo to 2,2 and out of curiostiy checked at another gas station and again 2.2bar, so seems my local gas station compressor erading is wrong and i have for years been underinflating!

Dangers I guess are tires overheat and blow? and out of curiosity what if I inflate to 2.3 or 2.4 bar for example instead of 2.2?

[StephenVA]

Never assume that the tire gauge attached to a public air pump would ever be accurate, as it is used and abused by everyone. Buy a dial gauge and use it monthly.

[Qsilver7]

And, the tires heat up the more you drive, which will also affect the air pressure reading. I always check tire pressure on a cold tire.

Air (gas) expands as it is heated and contracts as it is cooled. Thus driving, sunny days, etc...will expand the air pressure in the tire. Just like cold weather can cause tires to go flat (ask about 4 of my female coworkers that ignored their tire inflation light...as temps began to drop...and they all ended up with flat or nearly flat tires in the parking lot).

[StephenVA]

Found the actual ratio on ambient temps vs tire pressure changes
"Your tire pressure will decrease about 1 psi for every 10 degrees Fahrenheit the outside air temperature drops. (Likewise, it increases about 1 psi for every 10 degrees when the temperature rises.)"

Note: This is not a chart for measuring or gauging temp increases of driving with low tire pressures, as that will way too often result in premature tire wear and the possibility of catastrophic tire failure as the sidewall flexing will create internal temps well beyond tire structure ability to survive. See Ford SUV tire recall campaigns from a few years ago where FORD recommended tire pressures, to provide a soft and compliant ride to resolve customer complaints, which were well below the tire manufacturer's recommendations. The results were tire failures at high speeds during long trips. Not a pretty event.....

Bottom line: Inflate tires to maximize tread footprint, driving styles, trips durations, leveraging recommended PSI/BAR by BMW, by tire type and size. Qsilver7 will provide the chart....... cue the posting!

[omodos]

thanks gents....gonna get my self a half decent gauge to measure the tire pressure...and make sure I inflate when cold and after minimal driving,....one thing i did fail to mention was I had the 2 front tires swapped asked the garage to pump up to 2.2bar(and being a tire fitting shop they did have a more accurate gauge than a gas station) yet when I went a few days ago to check at the gas station the reading on the machine was over 2.5bar......

Moral is keep to spec of what BMW suggest obviously thet have factored in fluctuations in pressure due to fluctuation in temps whilst driving,,,,,thanks to all again...

[Qsilver7]

Originally Posted by StephenVA

Bottom line: Inflate tires to maximize tread footprint, driving styles, trips durations, leveraging recommended PSI/BAR by BMW, by tire type and size. Qsilver7 will provide the chart....... cue the posting!

LOL LOL