man the most wackiest thing happened to me yesterday! my tire pressure light came on while driving down the highway. i went to a gas station and checked my tires. one tire was 48psi, the next 42psi, and the other 2 where 38psi each! didnt know what caused my tires to do that. the manual says to maintain 32psi for tire pressure but i kept mine at 36psi for now. what tire pressure do you guys recommend? i will probably drop mine to 32psi to be safe.

 

They should be at 32psi cold. The pressure will be higher when they're warm. But that's a wide range of pressures you had!

 

The pressure goes up in summer and down in winter due to changes in ambient air temps. For instance, 32 PSI pumped into a tire at 5 degrees farenheit will be far more air by volume than 32 PSI pumped into a tire at 80 degrees farenheit since air, like most things, expands as it is heated. That's normal.

I usually use around 31 PSI in the RX 8, but I'm not wedded to it.

 

yeah i know hot air expands but i dont have a clue what the dealer had the tire pressures set at before i bought the car. would have been ugly if i had a blow out.

im gonna drop them to 32psi cold and see how they go

 

you never changed/checked your tire pressure when you picked up the car? the tires are purposely over inflated for shipping. the dealer is supposed to correct the pressure during the pre-delivery inspection (PDI) many of them for some reason miss this step, hence the high pressure you are seeing.

 

The tire pressure sensor detects both low and high pressure (also temperature). Probably, as already stated, the dealer forgot to lower the pressure to 32 before you picked up your 8. Mazda uses high pressure during transport to reduce any flat spots or damage.

As for high pressure when a tire is hot - watch out. The reason could be low cold pressure causing more side wall flex and more heat in the tire resulting in higher pressure. To lower the hot tire pressure you actually ADD air to the tire. Anyone that has done some racing has learned this. If you need more heat in the tire to get the best traction you lower the pressure. To lower the heat you increase the presure. Many stock 70 ratio or larger side wall tires are raced with high presure to reduce side wall flex. But the low ratio tires the 8 uses has small side walls, so too much pressure can reduce your heat, contact patch, and traction. So I recomend the 32 psi unless you really know what you are doing.

 

had my oil changed last week at the dealership and requested them to let the air out of each tire to make sure the light was working. i'm putting my spare tire in the garage to make more room in trunk. they was happy to do that and they all work fine

 

Hmmm, I'd never thought about why it was more likely to blow out an underinflated tire, but that makes sense, TRZ750. That's some good info.

 

My Tire pressure light came on once, during the one and only day we had snow in Austin this winter. Put 4 lbs. of pressure in each one so they were at 32 again and let 4 lbs. out the next week when it was 70 again.

Ahh chemistry and noble gas theory to the rescue. 1/273 increase in pressure per degree Celcius.

I wonder how hot the tires get running on 140degree pavement at 80MPH for long periods of time during the summer.

 

Pretty hot. It's a good thing we have "Z" rated tires to handle the heat and pressure .

 

thanks for the info. i didnt know about the dealership over inflating the tires for shipment. my car had 74 miles on it before i purchased it so i take it that they test drove it alot like that. i checked my tire pressure before i drove my car today and they were maintained at 36psi from yesterday and i dropped them all to 32psi. i checked them after driving today (just now) and they are still 32psi. still good to go

thanks for the info! ill tell the dealership to watch the tires. i gotta go back to them anyways for another drive away slip.

 

check the tire at 48 psi. the monitor will trigger if the pressure is too high. hope this helps.

 

My light came on this morning accompanied by the beeping. Before I could take it to check the pressure/tires it went off. I'm going to check again later but thought it was strange. Maybe the pressure is low and with the driving it increased enough to turn the sensor off again?