eddieo45

Was getting a "correct tire pressure" warning over the weekend, left front down one pound (!) but I forgot to take care of it. Wife goes to work this morning and sends me this:




I tell her to remind me when she gets home, but then after luch she sees this:




72° day, parked indoors and nobody touched the tires. What gives?

ManiacGT

Those values seem low. In addition if the car is used, tyres and their air will heat up and expand causing increased pressure. Add that to ambient temp increases.

StanNH

Tire pressure readings on any car will vary widely during a day. Sun, temperature, road friction, and speed all effect it. The time to check pressure is when the car is in the shade and the tires are cool.

parkwood

I have checked the tyre pressure via the tpms and they are quite variable and usually uneven. I asked my garage to check the pressures and they said they were all fine. They will vary dependent on ambient temperature, and car use and load. Am ordering my winter wheels and tyres tomorrow so will get them checked again.

eddieo45

Car is new and parked indoors all day, mild temps today. The run-flats run pretty hard; what are you guys filling them to? (I run my 2009 CLK550's 18's at 40 PSI).

I'll go around with my compressor tonight.

rbrylaw

Check your fuel filler door. That's where the recommended tire pressures for front and back are for the tires on your car.

abmims

I have mine set at 36. I tried 40 but the ride was harsh.

CO2010

I have the 19 inch RFT's and my recommended settings are 39 PSI for the fronts. 45 for the rears. Which I think is way too high.

xMB007x

That is for a heavy load.



Check your fuel filler door for the normal operating pressure.

eddieo45

I have that same door label for my 17" tires, and I filled them all to 40 PSI this morning before seeing this subsequent post (they were all slightly under 30 PSI!)

As my wife is off to work with the car, can someone post the fuel filler door label? I'm guessing I (slightly) overinflated....

CO2010

Here you go

eddieo45

Thanks!

miketc

What does 'For driving less than 100 mph: - 4 psi' means? 36 - 4 psi = 32 psi at normal load under 100 mph?

StanNH

Who drives less than 100 mph?

Seriously, I never noticed that before. I know my dealer recommends 34 psi all around, but I always thought they were wrong. Maybe not. For normal driving, that would indicate a cold pressure of 32 psi and a warm one of 36. I might try that just to see if I can feel any difference. That might just turn out to be the sweet spot for the car.

That would also indicate that most of us are driving with over inflated tires.