Runflat warning - possible fault?

shamalive

I was driving to Dublin at the weekend, 2006 320CD,
the runflat light came on (red) while on the motorway.

I pulled in and checked the 4 tyres, they all seemed to have plenty of pressure.
The manual says a yellow light = system fault,
while red light = runflat initiated.

Pulled off motorway at next exit and went to a garage to check the pressure.
All four were fine, so I reset it, kept button on centre console pressed for 10 seconds.

Drove onwards to Dublin, checked again when I arrived and all still fine.

Strange that it would fault out, and not happen again.
Is it worth getting it check out, or does anyone have any suggestions
as to what might have caused it?

TheBazman

That happened a couple of times in my previous car a 520d - sometimes if you hit a bump it might trigger the warning. I'd imagine just check all the tyres again in a few days to make sure

Anan1

AFAIK, the system is activated through the ESP - it detects when one wheel is rotation faster than it should be. As TheBazman says, a bump or a slippery patch could activate it. I wouldn't worry, unless it happens again shortly.

shamalive

Thanks for replies.

Anan1 wrote: »

AFAIK, the system is activated through the ESP - it detects when one wheel is rotation faster than it should be. As TheBazman says, a bump or a slippery patch could activate it. I wouldn't worry, unless it happens again shortly.

I thought it was based on the actual pressure?
But the above would make sense anyway.

Cheers.

Anan1

shamalive wrote: »

I thought it was based on the actual pressure?

The more expensive ones are, the BMW system is based on speed differential. At least the one in my mother's E90 is.:)

crosstownk

shamalive wrote: »

I thought it was based on the actual pressure?
Cheers.

So did I I (incorrectly) assumed that they were all like the Renault system in the Laguna II.

Anan1 wrote: »

The more expensive ones are, the BMW system is based on speed differential. At least the one in my mother's E90 is.:)

Everyday's a schoolday - cheers Anan1!

bazz26

On a side note folks, my next motor is looking more likely to be a 320d and most if not all come with run flats. The plan would be to eventually replace the run flats with conventional tyres due to both the cost and more importantly poor ride comfort of run flats, my question is can the run flat warning be disabled or is it just something to live with?

crosstownk

I drove a 320d (2005) with runflats. I wasn't impressed. Very giddy on rough surfaces. I didn't like them at all. For ride quality I'd sooner have standard tyres.

bazz26

Yeah my cousin has an E90 with them, even with standard suspension setup I couldn't live with them for long. Definately not designed with Irish roads in mind. Can only imagine what it is like with the M Sport suspension and 18" rims.

Voodoomelon

Here's a bit of info on BMWs tyre pressure monitoring systems:

BWM used two different types of tire pressure monitoring systems the Tire Pressure Control (RDC) system, and the Tire Defect Indicator (RPA) system (formerly know as the “DWS” system). The RDC system uses pressure and temperature sensors installed in each wheel as part of the valve stem. The sensors transmit their individual tire data to antennas mounted in each wheel well that feed to the RDC controller. This system is technologically superior, because it can alert you to absolute pressure changes (like when all four wheels decrease pressure over time), it is more sensitive to slight changes, and it can react faster. The disadvantage to the RDC system is that it puts a few ounces of extra weight in each wheel, and the system is more expensive and labor-intensive to retrofit. The RPA system uses the speed pulses from the ABS controller to calculate their relative rolling diameters. The advantage of this system is that it is passive (does not add “stuff” to your wheels and lots of extra wiring) and less expensive and easier to retrofit. It’s down side is that it is not as sensitive to pressure changes.

BMW introduced the RDC system in the E38, and they may have used it in the E65/E66. However, the RPA system is clearly BMW’s preference, because they switched to the RPA system for all other models. The RPA is better suited to a high performance vehicle, and I suspect that BMW has similar priorities, since they dropped their absolute pressure system for the ABS wheel speed version. According to the BMW WDS, the RDC system will detect about 5 PSI pressure change. The RPA system will detect pressure drops of about 30% (roughly 10 PSI, depending on tire pressure).

shamalive

Thanks to all for your replies.