Tire Pressure Monitors - which do I have?

[haygood]

I'm considering buying some takeoff rims and tires from a MINI to go on my brand new MCSC - so new I haven't seen it yet.

I read that the TPMS has been changed, and that the new sensors and old sensors are not compatible with each other. Can I look at these wheels without dismounting them and tell which TPMS system the take-off rims have?

Will my new '08 MCS convertible have the old system (because it is a 1st gen car) or the new system (because it is an '08)?

The rims I might buy are 16" 7-fin spoke R92's in silver.

Thanks.

Brian

[ScottRiqui]

I think the requirement for the new TPMS system came online in September of 2007, so I think you'll have the new system even though your car is an R52 and not an R56.

When you pick up the car, compare the valve stems to a new hardtop on the lot. I know the stems on the new TPMS system are distinctive, but I don't know exactly what they look like off the top of my head.

[Trock]

The valve stems will be metal all the way into the wheel. Thats the way most are anyway.

[MINIFVR]

My RFT wiring was somehow completely destroyed upon report from the state inspection.

luckily I dont have RFTs anymore, so Im just going to have it ripped out!

[Davidf]

I believe the TPMS is of the DWS (as opposed to RDS) design. What this means is that the wheel speed sensors are used to determine if a tire has deflated sufficiently to cause it's diameter to be reduced and thus its speed to be increased relative to the other wheels. When the WDS senses this discrepancy in wheel speed, the warning light is illuminated.

So, what does this mean? It means there is NOT any device related to TPMS installed within the tire, wheel, or valve stem. So when changing tire and/or wheels, no worries.

BTW, it takes about a 30% pressure difference before the tire defect light will be illuminated. It also takes a few miles before the DWS module can determine the problem is not due to normal wheel speed differences.

FWIW: The RDS design uses pressure sensors within each wheel and a radio receiver behind each fender liner. The RDS is more sensitive to pressure fluctuations and operates at real time. Thus the RDS design is more costly. Generally, BMW has gone away from the RDS systems and favors the DWS approach as first used on the E39 M5 (I think).

[bobj]

Originally Posted by Davidf

I believe the TPMS is of the DWS (as opposed to RDS) design. ......

So, what does this mean? It means there is NOT any device related to TPMS installed within the tire, wheel, or valve stem. So when changing tire and/or wheels, no worries.

Generally, BMW has gone away from the RDS systems and favors the DWS approach as first used on the E39 M5 (I think).

I have a 2008 cabrio with TPMS. It has valve sensors. Below is an excerpt from Tire-Rack:

Originally Posted by TireRack

Tire pressure monitoring systems (TPMS) are now impossible to run from when buying a new vehicle. Every new vehicle made for sale in the USA has a direct TPM system as standard equipment. There are several exceptions though: the vehicle must have only four wheels (so no dual-wheeled trucks or motorcycles), and the GVWR must be less than 10,000lbs.We carry all sensors and valves for every model of BMW and Mini up to the 2008 model year. The older model BMW’s and Mini’s that have an indirect system do not need TPMS valve sensors.
The basics of the direct TPMS is that it uses a sensor in the wheel/tire to wirelessly relay pressure back to the driver on some sort of display. Some vehicles have a digital info screen that will show all four tire pressures (five pressures if spare has sensor) all the time. While others might just flash a low-tire-pressure light on the dash. There are also two different styles of sensors for this system: a valve sensor and a strap/band sensor. Only valve sensors are used by the direct system-equipped BMWs, although if you bought an aftermarket SmarTire TPM system, those use the sensors held on by a strap around the barrel of the wheel.
BMW’s indirect system will not affect the choice of switching aftermarket wheels or tires. The system runs off of the ABS/wheel-speed sensors which “count” the number of revolutions of each tire. If the right-front tire is low (25psi) it will spin faster than the left-front tire (35psi), so the ABS system will recognize this change and alert the driver with a flashing light near the gauge cluster and possibly a loud chime.
All BMW valve sensors are currently being produced by BERU and are sold by us in two parts: the sensor component and the metal valve. The size of the sensor shouldn’t be a problem for many wheels, but if the valve hole is in the middle of the wheel’s barrel, then obviously the sensor will not fit properly. The wheel industries are aware of the valve sensors and are rushing to get most of their wheels TPMS-compatible. If you have any questions about the TPMS-fitment on a wheel that The Tire Rack sells, I can look up the wheel and confirm if it will work with your vehicle.
When placing an order please reference Connor @X269Thanks and have a great day,
Connor
877-522-8473 X269
Connor@tirerack.com
Tire rack performance specialist
7101 Vorden Pkwy
South Bend, IN
46614

[Davidf]

Well then, my bad. I guess I should not have assumed that since on '08 was still first gen it would not have changed.

[MINIAC]

I think all MINIs built Week 32 2007 onward have the direct TPMS.

[haygood]

Still, as I understand it, there are two types of DIRECT sensors that have been used in the wheels. So that's three different systems, two direct, and one, earlier, indirect (rotational speed, not pressure sensing).

I'm wondering which of the two direct systems my car will have, when they changed, and whether they are interchangeable within a car and without tinkering.

In general, do you have to reprogram something to have sensors from other original MINI wheels work on your car, or does any like sensor get picked up by the fender liner receiver? I'm asking whether it is like alarm system remotes where each one has to be programmed in to be recognized. I'm expecting not. Maybe the tire forum folks know better.

[bobj]

By two types are you referring to strap or valve? The new MINIs have valve type pressure sensors.
What do you mean by "interchangeable within a car"? You can rotate your tires.

[haygood]

My friend who manages a Discount Tire showed my two types of valve stem sensors he says are used in MINI's. Was this unreliable info?

[BunsenH]

Pardon the slight tangent, but since you're talking about TPMS on an 08 Cabrio:

On of my valve caps went "missing". Is there something special about them due to their odd shape? Should I buy a direct replacement and some spares? At the moment, I just put an old metal cap on it.

Thanks

[bobj]

Here is an article from Tire Rack that says it is important to retain the original valve cap. Also it is important to use the correct valve stem if replacing that part. I have seen two reasons for this at different times:
1 - you get wrong readings, the TPMS cap has to be able to "breathe"
2 - the different metals cause galvanic corrosion and the parts seize together.
http://www.tirerack.com/tires/tirete...jsp?techid=152

[BunsenH]

bobj, thanks for the link.

My caps are shaped more like the rubber grommet than the cap shown. I'm still confused and will do some more research.

[bobj]

Do they look like this?
CLICK HERE TO ENLARGE

[haygood]

I don't have the car yet, but I'd be surprised if my '08 Cabrio is different from your '08 Cabrio, bob. Thanks for the pic.

[BunsenH]

Originally Posted by bobj

Do they look like this?
CLICK HERE TO ENLARGE

Them's the ones!

I'm going to switch a plastic substitute for my metal one until I get a replacement.