[rich1068]

From what I understand the system monitors for a significant drop in pressure indicated by a reduction in the rolling circumference of the wheel/tyre. A natural reduction in pressure may not show up.

[Red Ice BMW]

Originally Posted by rich1068

From what I understand the system monitors for a significant drop in pressure indicated by a reduction in the rolling circumference of the wheel/tyre. A natural reduction in pressure may not show up.

The tyres look ok, doesnt look to be a flat tyre as such, again this is only a visual inspection and I'm not sure how run flats look when they have lost pressure. Would they look the same or would they look flat?

[Brian mc21]

Hate to Worry you pal but Check the back of the rims for cracks. This is a well documented problem with some standard alloys.

[Red Ice BMW]

Originally Posted by Brian mc21

Hate to Worry you pal but Check the back of the rims for cracks. This is a well documented problem with some standard alloys.

God damn it, hope not but thanks for the heads up. Whats the tell tail signs if its cracked? If i check pressures and they all seem ok etc.??

[Falmouthboy]

If you have done a visual inspection, make sure your pressures are right, re set the monitoring system and checkr your presssures every few days for a few weeks to see if any tyres have lost air, if so it could be a puncture, cracked rim or leaking valve - either way, you will need to get it checked and sorted.

The tyre pressure monitoring system on BMWs is quite crude and can give the odd false alarm. But if the light keeps coming on with no evidence of lost air you have a problem with it.

[Statler]

Check the inner edges of the rear tyres for excessive wear. Last time I had this mine were down to the cords.... nothing to panic about really ;-)

(I should really read the whole thread...)

Get the pressures up all round and monitor over a few days, if one is going down you'll spot it.
Runflats don't look much different inflated than they do flat so take care.

If you are on 225M rims like me then you may have a cracked rim, only the manual pressure checking will reveal this if the tyres are OK.

Oh, and keep below 50mph until you work out what's wrong (recommended max speed on a flat RFT)

[Red Ice BMW]

I reset the light last night and I've done 20 miles without the light returning. Visually checked again and everything "seems" ok. I will manually check all pressures.

[Stringbag]

Great. Hope it is just spurious.
read this to see what a cracked alloy looks like
http://www.e90post.com/forums/showthread.php?t=693164

[Red Ice BMW]

It was a cracked alloy in the end and its happened again! Can I do anything to prevent this like change profile size of the tyres etc? Really need to resolve this before I get rid of the car!