I was driving in the snow last night, when my flat tire light came on and started blinking. I read the manual and it said that this could be due to low pressure and not always an actual flat. I looked at my tires and none seem flat, so I refilled them with air and reset the flat tire button. My question is how do I know if I have a flat or not with run flats? Would the light come back on again if that was the case? All the tires look fine but Im wondering if I have a leak or something. The book says the light can not detect tire damage, so whats the point of run flats if you dont know you even have a flat? Please help as my damn service advisor has not called me back.

 

I woudl think that if you had a leak then the light would have come back on once you reset the pressure monitor and drove for a little while. Also, I've heard that this light will sometimes come on if you hit a severe bump in the road.

 

yeah the book also says it can come on falsely in the snow, which there is a lot of here in NY right now. Thats makes no sense to me though.

 

The tire inflation light is actually responding to slight variances in the rotational speed of each wheel (less air, different circumference, different rotational speed...middle school geometry ). So, it seems to me that it's possible that if you hit a slippery patch with one wheel while 2 or 3 other wheels were on dry pavement...and this went on for more that a fraction of a second, you may get a inflation light warning. A bump in the road -- a big, long bump that you hit with just one wheel -- may do the same thing. Then, once that happens, you'd need to reset the thing.

I'd say carry a good tire pressure gauge with you, and check the pressures manually.

 

That sounds like a good idea.

Also, wait until you get to replace one of these puppies at $220 a pop!

 

use a tire pressure gauge

 

i did and they were all around 35 to 40 PSI. So i dont get why the light came on. Also how would you ever know if you really had a flat on run flat tires?

 

I recently spoke to my service advisor on this very issue. I had gone over one of those steel plates in the road covering a dig. Only one tire actually went over this plate. It was raining at the time and I hit the grate a bit hard. Since it was a smooth wet plate the tire that contacted it spun out, while the others did not. This caused my tire light to come on.

The core of this is that if one tire rotates faster than another, the light will come on....regardless of the tire pressue. The sensors are only looking at whether one wheel rotates faster than another. If so, the diameter must be smaller, aka less air/deflated. But a single slipping wheel, like in slick/snowy conditions can "trick" the sensor.

If this happens, check the tire pressure in each tire for accuracy and then reset the light with the button under your hand brake. Nothing to worry about at all.

R

 

Thanks for the help everyone. I feel much better now. lol.

 

NYIllustrator, since noone else has directly answered your questino about run-flats, I'll pop a quick opinion...

The only way I can think of you being able to tell is, one, yes, the light should come on... and two, when it does, just park the car on a flat spot, and check to see if any corner of the car is leaning, the tire will look bulged. It may be a run-flat, yes, but the car is still heavy for an airless tire, so it should be fairly obvious. As for the snow, I agree with the wheelspin issue, when I put my car on a dyno, all the warning lights went nuts, including the flat tire... since the front wheels were spinning and the rears weren't. (141 mph, btw... lol)

Hope that helps.

 

I would recommend that you carry a small tire pressure gauge in the car. If the light comes on, you can measure the pressure in each tire to find out which one was losing air. In my case, when I had a slow leak with the run-flats (nail) the tires still all looked the same. It was only with the tire pressure gauge that I found the affected tire, and then found the nail.

The tire pressure light will come on if the surface is uneven. It's not just snow, that can cause problems (because of slippage), but also driving on dirt roads.

Dave

 

DID
How many pounds off? When I had the nail
in my non-runflat the tire was only off by like
four lbs. I was pretty impressed with the system.
2

 

As I recall with my run-flat it was more like 6 psi different in the one corner. Which makes sense that it would take a little more pressure difference with the run-flats since the sidewalls are stiffer.

 

>>
>>Also, wait until you get to replace one of these puppies at $220 a pop!


Is this for real? I expected them to be expensive but $220 per tire? egad.