2015 BMW M235i: Tire Pressure Monitors Do More Than Monitor Pressures
by Jason Kavanagh, Engineering Editor on November 23, 2015
Like several of the cars in our fleet lately, our long-term 2015 BMW M235i flashed up a low tire pressure warning the other day. Not all that surprising given the drop in ambient temperature lately.
But what I observed next shocked me.
Not really, I just wanted to try a clickbait-y sentence. Feels...slimy.
Anyway, I did notice an unexpected side effect of the M235i's TPMS warning.
First of all, look at that display. It's terrific, with color-coded tires based on the current pressure and temperature in each tire. The temperature bit is clever, since it means that this car realizes that a tire's inflation can be off even if the pressure is within the happy range. Smart.
I pulled into a gas station and checked the tires with a brand-new tire gauge purchased from a FLAPS. All pressures were 3 psi higher on the gauge than what the TPMS said. Hmm. I then set the gas station's compressor to the BMW's set pressure on the doorjamb sticker and inflated all four tires.
When I set off, the TPMS readout said the tires were, again, 3 psi lower than the doorjamb numbers. Call it gauge-to-sensor variability. But at least the tire pressures were now within the car's happy zone.
So now, the unexpected part. While the TPMS warning you see above was active, the car would not allow me to switch into 'Sport' mode. Once the tires were inflated and the TPMS alert extinguished, Sport mode was back on the table.
Apparently the car wants to safeguard against potential hooliganism when the tire pressures aren't set correctly. While I would have liked to enjoy the more responsive powertrain calibration, I appreciate that this is a reasonable strategy.
Jason Kavanagh, Engineering Editor