I know that it's suppose to be 35 psi when they are cold, but last wednesday, I think the dealer adjusted them down below that. This morning, the tire pressure light came on because they were showing 27-28 psi. After driving for about 40 minutes, they went up to 29-30 psi. Light still stayed on, so took it to the dealer. The dealer did something and the warning light went away, but they will still only showing 31-32 psi. So, I took the car right back, the service manager says it's the correct settings. They don't want to put more, because when it gets hotter, I might be riding with 50 psi at 80 MPH. Sounds right, but is it? I am thinking the warning light will re-appear tomorrow morning when the tires are cold.

 

The most I've ever seen is an increase of ~8psi (highway speeds on a hot day) per tire. 35psi cold caps out at 43 psi on mine. This is still under the 45psi recommended max.

 

TPS is a guide. Do not put too much faith in it.


Buy a tire pressure gage. Check pressure when cold. There is a common misunderstanding that hot tires increase pressure, and increased pressure is bad. Under-inflated tires lead to tire failure.

 

I would strongly suggest getting a new tire pressure gauge. I use one with an analog face and a bleed valve built in for easily draining air if I overfilled. I fill my rears to 38 cold and 42 psi up front and have never had a problem with treadwear issues or explosions. :P I remember I popped my rear falken once when I decided to run 35 psi, then again the tread was kind of low.

 

The TPS sensors are accurate to within ±1 psi so that should be a very good indication of your pressures. But you should always use an accurate gauge when filling the tires. Not the cheap $1 pencil type gauge, get a real dial indicator gauge and expect to pay $20 or more.

My guess is that the dealer's gauge is out of whack or they just put the wrong pressure in. They did it to me once, set the pressures to 30psi. The next morning the TPS warning went off because the pressure was below 28.

 

Don't think it's a mistake. When I took the car back, told the service manager it's still showing only 31-32 and recommended psi, on side of driver door, says 35 psi cold. He said "Trust me." Supposely, they change tire pressure during hot and cold months. I been riding around since October at 34-35 psi cold and max 40 hot before last oil change. I am about to take long road trip too. Should I just add more pressure myself?

 

So the dealer is claiming the pressure is correct (35) but the sensors read 31-32, right? Based on my past experience with tire pressure gauges, I wouldn't trust his reading. I'd bet the TPMS reading are closer to the true pressure.

Naturally, the tire pressures fluctuate with temperature changes. That's why it's a good idea to check the tire pressure weekly with either with a gauge or the TPMS to make sure you're close to normal.

The 35 cold to 40 hot sounds about right for the stock tires.

Or, is the service manager claiming the pressure should be set to 31-32?

 

Yes. He's pretty much saying it should be set at a lower range during hot days (summer), and thus, why tires are only at 31-32 psi when I came back. No mention of problems and/or incorrect data showing through the TPS.

 

The service manager is an idiot. The tire pressure recommended by the manufacturer and every tire maker in the world is a "cold" pressure. You set it when the tire is at or close to the ambient temperature. You never make adjustments for temperature.

Set it to 35psi and avoid that dealership if you need work done to your car.