I have had my Cooper-S with JCW engine kit, for coming on 4 years. I drive the car 9 months of the year, and the remainder I drive my Land Rover (Fun in New England). Because of the Run Flats, and Tire pressure system, I have never given the tires much thought, until this weekend.

My wife bought me a Sears Craftsman compressor, so I was testing it out, filling up the air in everything (Bikes, Tractor, Land Rover, then the Mini). I was shocked to see that the pressure was down to about 22 lbs in all 4 tires. Yikes! Because of the run flats, I never noticed it.

Should the Tire pressure system have alerted me? or does it only do it when there is zero pressure?

 

Might want to check tire pressures on occasion. And fluid levels. The TPM on a MINI is more about sudden loss. Now GM vehicles will show you psi of each tire on the dash display - that I like on my 2008 GMC truck.

Related thread.

 

I ran into a similar instance on my 2010 MCS. The low tire light came on, and when I checked pressures, I found that they were quite low, as you described.

That's the funny thing about run-flats. They still look round even when they're low! I try to remember to check mine periodically.

Spridget

 

On my 1st gen, I had new tires installed and assumed they had been properly mounted and sealed. A few days later I got the low pressure light, I was at under 10psi. Of course, this is a different sensor system but I still would not generally trust these systems implicitly and now I check pressures weekly.

 

Im under the impression the 2011 is like on my VW. Anything lower then a certain pressure sets off the system.

 

I have had the TPM light come on on a very cold morning. In my instance it was -20c outside when normally I drive my mini when it is at least 12c. So I am thinking the computer compared pressure between when I put the mini away for winter and when I needed my "mini fix" in the winter and saw it as a sudden drop.

I agree with the OP, I have also not seen it respond to a slow loss in pressure. I contribute these to what I call bump leaks.

 

Many 2007 models don't have TPMS (I've got one too). What it has is a sensor that's involved in the ABS system that will go off if one wheel is turning at a different speed than others. If a tire pressure drops then it will turn slower. The system is different from TPMS, where a sensor in the wheel sends a message to the car about the tire pressure. If all 4 tires were the same low pressure they all turn at the same speed, so no warning. I had it warn me twice with my runflats, and I had a nail each time, but there was still about 20 lbs of pressure in the tire. The TPMS started being required in late 2007 model year I think. My wife's 2010 car has it, and the PIA is when it gets cold the thing goes off. Using nitrogen will fix that annoying problem, because there's no water in bottled nitrogen, and it's the moisture in the air in the tire (not the gas) that makes the pressure go up and down with the temp. The other PIA is that you have to buy the stupid sensors if you change wheels, and they cost about $50 per. My car is good to go no matter what's on there (I have nonrunflats now).

 

the TPMS changed during the 2007 model year. When my car came off the truck in Aug some cars had the old ABS based system - mine did - and some had the new active sensor version. Both systems are technically TPMS but the ABS based system was determined not to meet all US requirements.

mine left the port of arrival - Charleston, on 8/24 and was delivered to me on 8/29

 

Re-read the are in the manual about the TPMS on the 2011. It reads like it only will tell you of a sudden drop in pressure.

 

Legally it is not supposed to be a sudden drop in pressure it is supposed to be if one or more is lower than a percentage of the set pressure. I.E. if I set it at 35 psi and any tire drops to less than 31 for any reason then the TPMS should notify you.

I know the ones on my 08 work that way and those on a friends 09 work that way.

So I would be willing to bet that the 2011's work the same way. on a % of set pressure drop no matter how long it takes.

 

On my 2008 GMC truck it's 15 psi too little or 15 psi too much to get a warning on any tire. No clue when the MINI will flag it........ Have free nitrogen in them from Discount tire so don't expect much loss normally anyways......

 

Hmm I will have to inquire next time at the dealer. I did check mine today, spot on 38PSI all around.