Hi

I've had my new (third) Mini, a 2011 Coop, for three months and just under 2500kms.

For the first time in three cars, I had the red run flat indicator appear and sound a tone.

I pulled the car into a service station and inspected the tyres with no evidence of a flat: all tyres seemed to be the correct shape, no bulging at the walls, and all at the same height. There was also no softness when I gave a hard press on the tread surface of each tyre.

Hooking up the air hose to each tyre, I got some very odd readings: 39psi in the front drivers, 28psi rear drivers, 32 rear passenger, 39 front passenger.

I inflated and deflated all tyres to 32 and reset the run flat indicator as per the manual.

Admittedly it's the first time since ownership of the car I've checked the tyre pressure, but 39 seems insane to me.

I'm waiting overnight to see if any evidence of a flat presents itself and will go double check the pressure at a different station just in case the pump was off.

A couple of questions:

1) is a flat run flat easy to spot? I certainly didn't notice driving over anything sharp, and all tyres appear OK. I've actually never had a flat before. Ever.
2) if there is a flat, and having reset the system, will it detect it again or not? I'm vaguely aware of the revolution counting method the system works on.

I'm hoping it was the 28psi tyre that tripped the system and not a flat. Being a week out from Xmas, it'll be a pain getting it into the dealer (plus it'd be nice not to have to fork out $450 for a new one :P)

Hooking up the air hose to each tyre, I got some very odd readings: 39psi in the front drivers, 28psi rear drivers, 32 rear passenger, 39 front passenger.


If you'd been driving for more than about 20 minutes, the tire (oops, sorry, "tyre" ;)) with 28psi was about 8psi low. I don't know how the TPMS figures low pressure, but after running that long, you should have been seeing about 36 psi in each tyre. The pressures the manual gives you are for cold tyres - if you've driven on them for even 5 minutes they should be showing more pressure than the book quotes.

With all the different pressures in the tyres, I suspect they'd been checked at random times - one cold, one after a little driving, one on a cold day, one on a warm day, etc.

The system won't let me post a URL yet, but if you go to tirerack dot com and do a search for "Air Pressure: When and How to Set" it'll take you to a good article that explains the details. Based on the article, the tire you measured at 28psi was probably about 24psi cold.

Keep in mind that run-flat tyres have very stiff sidewalls that allow you to drive short distances with no air in the tyre at all. It would be very hard to detect low tyres without actually checking the air pressure.

Hope that helps...

Thanks. Good article and seems to explain why I was getting hugely different readings in the front. Now my issue may be in deflating the front tyres.

The weather has been very warm the last few days, so that might also affect readings.

Quick update after being able to properly inspect the tyres in the morning light: it's most definitely a puncture. Can add "screw stuck deep in the tread" to the list of signs you have a puncture.

Unfortunately since the car was left overnight it's in no state to drive, despite the accursed run flat technology. Add to that it's Sunday so there's no place open to drive it to anyway.

So far I've had to call BMW Roadside, who sent out a repairer, who advised against a patch repair and called a tow, the tow then called me to say "it's Sunday, there's nowhere to tow it, we'll grab it Monday morning". Just as well the car is at home and not an actual emergency, that's all I can say.

The beauty of run flat tyres, hey. :confused: