Do I have psi sensors or not?

[yj bill]

Does my 07 328i have pressure sensors in the rims or does it have the system that works by just comparing the different rotational speeds of each wheel?

We are thinking of getting another set of wheels and may keep the old set for standby.

[Amalan]

you can check that by looking for a circle with the letters rsc on the side wall of the tire or just check and see if you have a spare wheel. no spare wheel means you have run flats. the 3 series with run flats i believe come with the tpm so if you have run flats then youll have the tire pressure monitor. its measured by measuring and comparing rotational speeds tho

[The HACK]

If you have a big round grey cover for your valve stem, you have a physical sensor in the wheel.

[yj bill]

Thanks Hack, the stems are rubber so I assume no sensors in the wheel

[Amalan]

if the car has run flats then it has tpm so check to see if it has run flats

[yj bill]

Yup, it's got runflats but I've been told that some models came with external sensors, ie no sensor in the wheel.

[The HACK]

if the car has run flats then it has tpm so check to see if it has run flats

Run flats does not determine whether or not the wheel has a physical sensor. Pre '07 models use the ABS sensor to determine if the tires are losing pressure. Post '07 models use a physical pressure sensor attached to the valve stem to determine if you're losing pressure. Only way to tell, is the newer style physical sensors has an aluminum valve stem core and is denoted by a large, round, grey plastic cover instead of the traditional black valve stem cover.

[Jim@tirerack]

The Coupe uses a sensor and the sedan uses the ABS system.

[TambourineMan]

Do '07 and '08 335xi sedans have physical pressure sensors, or do they rely on rotational speed difference calculations or the ABS sensor?

If they have a physical pressure sensor, how does the information get transmitted from the "large, round, grey plastic cover " ("instead of the traditional black valve stem cover") to the car's electronic instrument system?

[Jim@tirerack]

They have direct tire pressure monitors.