2014 Mercedes-Benz CLA250: Low Tire Pressure. Or Not?
August 14, 2014
Not soon after I left our Edmunds editorial offices for the day in our 2014 Mercedes-Benz CLA-Class the car's tire pressure warning light illuminated. "Oh great," I thought. "I probably drove over a nail or something, so one of the tires has a leak. There goes my afternoon."
Thankfully, the CLA's gauge cluster display also has a readout for individual tire pressures. That's considerably more useful than just having the one "exclamation point in a tire" warning light, which is all you get in a lot of cars. I brought that tire display on the screen to see what was going on. Oddly, the display indicated that both the rear tires were low.
Now I was curious. Forty psi up front and low 30s in back? That seemed weird. Maybe that's what they were supposed to be? I was still driving at the time, though, so I couldn't check the car's door jamb to see what the recommended pressures were. Oh, and I didn't have a tire gauge on me, either. I decided to just keep driving but leave the pressure display on and observe the pressures to see if any of the tires kept dropping.
One hour later, the pressures hadn't changed. It seemed more likely now that the rear tire pressures were low for some reason and one or both of them had finally dropped enough to trigger the car's warning light threshold.
When I finally got home, I adjusted the tires to the recommended spec.
I also asked my coworker who had driven the CLA the day before. He hadn't had a warning light at all, nor did he know how the rear pressures had gotten so off. For now, I'm just going to assume that everything is back to normal.
UPDATE: As noted in the comments, the tire pressures pictured above from the door jamb are actually the maximum load pressures. On the fuel cap door, Mercedes also lists the "Normal Load" tire pressures, which are 36 psi front and 32 psi rear. So the tire pressures were "correct," though the tires were: 1) heated up from driving; and 2) still suffering from low enough pressure in one or two tires (over time) to trigger the tire pressure warning light. Presumably as a real CLA owner, I would have actually paid attention to the big, yellow "See Owner's Manual For Additional Information" warning on the door jamb label to learn about the different tire pressures. That said, it would be nice if the door jamb actually noted what those 39 psi numbers were.
Brent Romans, Senior Automotive Editor @13,462 miles