Hello all,

It was about 15 degrees Fahrenheit this morning, and the Tire Pressure warning came on when I started the car. I remember reading some posts on the site that indicated that this happens in colder weather, so I just motored on. When I arrived at work about an hour later, the light was still on, but I walked around my tires and nothing seemed low.

However, it occurs to me that this is the first time I've had run-flat tires and I'm not sure what a flat run-flat looks like.

Is it possible I do, in fact, have a flat tire? How could you tell with the run-flats if the tire pressure monitor is malfunctioning?

Should I go get some air in my tires? Or is there some problem with setting air pressure below freezing?

Those of you that live in climates more accustomed to super-cold weather, is this a common problem? How do you deal with it?

Thanks!

 

If you check the pressure, it should be down several pounds because of the cold. Air expands when it's hot. I would go ahead and put a little air in to bring the pressures to around 28-29 psi. But, when it warms back up in the spring, don't forget to let the air out so you'll be back where you want to be.

 

I usually keep my tires at the recommended 33 PSI. That brings to mind a question: what is the minimum tire pressure to keep the TPMs from tripping the alarm?

 

Tire pressure varies greatly with temperature and season. In areas where winter is real this can be quite a bit. It is only now with TPM that people are seeing this. You really need to check and adjust pressure several times a year - add in winter and let out in summer.

 

Agreed, your tire pressure should be kept at the PSI shown on the driver's door post. You should check it occasionally, because you cannot tell by looking at the runflats whether or not they are low on air. Always check tire pressure when the car hasn't been driven in several hours and the tires are not in the direct sun.

When the average daily outdoor temperature drops, your tire pressure will drop, even if no air has leaked out. That's why it is necessary to check the pressure when it gets cold in the winter. Same in summer: the air will expand and the pressure increase, so you'll need to let air out to get pressure back to 33 PSI (which is what my doorpost says). Again, always check tire pressure when tires are cold, not after just driving it or tires have been in direct sun.

 

I usually run 38 PSI all around and my tire pressure warning light did not come on so far. We are also having cold temperatures in north Florida these days. I check my tire pressures usually once a week.

 

This has happened to me a few times this winter season. Whenever the TPMS light went off the sensor went "INACTIVE" even though the tire pressure was OK. That said I wouldn't necessarily attribute the light going off to low tire pressure. Check your pressure, adjust if necessary, reset the TPMS and motor on...

 

How do you reset the TPMS?

 

It's in the manual, but if I remember correctly you need to press the stalk button until it reads SET/INFO, then hold down the button until you get into the sub-menu. Then press the stalk button again to rotate thru the menus until you get to the tire symbol, and the RESET option. Then hold down the stalk button again until it reads RESETTIING. The drive around until the light goes off. HTH.

 

mine came on too, but its neg 15 today. Im just going to wait it out (ill add a tiny bit to kill the light). I had them all at 38, and they read from 33-35 yesterday. I figure if i put in 38 at these temps theyll be way overfull come a 30-40 deg day.

 

If your TPM is working and you have a flat it will feel as if the tire is not centered on the hub. Also there will be a noticable difference in the tire that has no air, so don't worry about not being able to identify which tire has no inflation, Unless you are always driving in the snow...then you might have an issue with seeing the tire.

 

kk, so I just went out to lunch and filled the tires back to 33 PSI then reset the warning light.

Anyone know the formula for the ratio between air pressure and temperature? That way I can figure out if I need to release any air when it gets back up to 35-40 degrees...

 

I got my MCS in Dec 2007 (17" all-season run flats) and never checked my tire pressure until (late?) Spring 2008. It got down to close 0 degrees (F) here last winter, but oddly the TPMS never went off.

Last Spring, I bought a tire pressure gauge and bike pump (my door says the tires should be 38 PSI) and when I checked the tires the first time, they were 35 PSI or lower. I've been keeping them properly filled ever since (always check at least every few weeks).

This week the TPMS alert came on briefly, just once, on 3 separate occasions. The temps were only down to the 20's or teens. So yesterday morning before I left for work, the temp was around 10 (F) and I checked the pressure. All were around 35-36 PSI. Pumped them all up to 38 or just below, figuring it will warm slightly over the coming week.

 

You should just use a tire gauge. There'll have been some leakage by the time you get to warmer temperatures.

I have 16" all-season run-flat tires. I'm not sure why some people with the same tires keep them at 38 PSI. My doorpost says that's only for speeds over 100 MPH. If you're doing that regularly, then 38 PSI is fine. But whereas 38 PSI for everyday driving may get you slightly better gas mileage, the car rides really rough and you reduce your braking ability.

MINI owners wash and wax their cars every 24 hours, change their oil every 150 miles, but can't be bothered to use a tire gauge? Go figure...(not referring to you, jasonite, you obviously have the right idea).

 

What's a "tire gauge"?

Brb, going to wax my car...

 

1 psi per 10 degrees F

 

We were out on a major motoring trip to Tennessee near the "Dragon" and it was 12 degree's when we got up for a return home and had the Tire Warning on start. I just drove a little and everything felt normal. Got on the freeway and took it easy for the first 50 miles or so with no issues or tire noise not out of the ordinary. When we got to an area that was in the 20's I reset the tire alarm and motored on. After 845 miles no alarm and one happy Mini owner.
This 1,600 mile round trip in 4 days really showed the Mini is solid!

 

1. Buy a tire gauge. Get a good one, not the 99-cent pen type.
2. Check your tire pressure each month, and fill to the recommended amount indicated on the driver's door sticker, or the owner's manual.
3. Reset your tire pressure warning as per the manual.

 

Unless very cold weather increases air leakage around the rim, temperature changes contribute very little to tire pressure changes, maybe a pound or two at most.

 

Most low tire pressures are probably caused by increased air leaking around the rim, not changes in pressure. It's not easy to figure how that affects the average car, as it's dependent upon the specific tires and rims, and their condition. About 1 PSI per 10 degree change is close to the physics calculation, but real world differences can be much more if the rim seal leaks more.

 

I got the "low tire" warning light the other morning as I left for work. Checked all the tires and they were fine. Reset the warning and it has not come back. I suspect it was because of the cold weather we are currently having but I can't imagine it got below 40 in my garage.