Run Flat Tyres - flat - then reinflated!!

[Pongobongo]

Morning Everyone,

What am I doing up at this unearthly hour!!

Anyway, I recently bought an MCS - loving it.

The problem lies with the tyres. This morning, I got in the car and immediately noticed a bumping sound from underneath. I pulled over and inspected the tyres (must have drove 30metres).

To cut a long story short, the tyres were fine except the passenger front. The car was facing down hill (maybe this tyre was exposed to the elements more). There was a definite flat spot on the tyre (e.g. Tyre not completely round) which was making this bumping noise.

I turned the car around and headed by up the hill (expecting to call the RAC as they are run flats).

I told the missus and went back out to the car..... they had somehow re-inflated!!!?? and off I went to work without a hitch.

At no point did the dash say I had a problem.

Looking at the tyres now, there does seem to be a little less pressure in this tyre. I'm wondering if it could be something to do with tempreture (-6c last night) such as frozen rubber/sealing solution or possibly a hole has been resealed??

Any suggestions?

Thanks

[Pongobongo]

So now its a bit lighter and I can see what I'm doing.....

There is no sign of a nail etc in the tyre, however there was no air either (zilch!).

I presume that because the tyre had deflated, the run flat had to do a few rotations to gain its shape.

I've re-inflated and it seems to be holding (for the time being)

However, my dashboard sensor didn't alert me to any untoward problems.

Any ideas?

Ta

[minicore]

Quote: Originally Posted by Pongobongo (original)

I presume that because the tyre had deflated, the run flat had to do a few rotations to gain its shape.

I'd say so.

Possibly a leaking valve? Although you'd expect that to be gradual, rather than an overnight thing... I'd keep an eye on it, and check pressure before you get back in it or drive anywhere. If it remains the same, you could put it down to "one of those things" - but it may be worth getting it looked at either way?

As far as I'm aware, the dash warning only comes on while a loss of pressure is detected while you're actually driving?

[craig71u]

Quote: Originally Posted by minicore (original)

I'd say so.

Possibly a leaking valve? Although you'd expect that to be gradual, rather than an overnight thing... I'd keep an eye on it, and check pressure before you get back in it or drive anywhere. If it remains the same, you could put it down to "one of those things" - but it may be worth getting it looked at either way?

As far as I'm aware, the dash warning only comes on while a loss of pressure is detected while you're actually driving?

Got to agree with you on this one, had the same problem myself a while back and this was it. Get a proper mechanic to look at it for you.

[Pongobongo]

Thanks guys.

Well the pressure is holding in the tyre - dash reset after reinflating.

It's been standing for 8hrs - plus 10 miles of driving with no loss whatsoever.

Wonder if it's self sealed. Very peculiar.

[Macguyvic]

You probably had an intermittent leaking valve. Cold weather will reduce the pressure in the tires. The warning may not have come because the monitoring system hadn't been re-set after the last inflation. Any time you adjust the air pressure in the tires you need to let the monitoring system know.

[Pongobongo]

Quote: Originally Posted by Macguyvic (original)

You probably had an intermittent leaking valve. Cold weather will reduce the pressure in the tires. The warning may not have come because the monitoring system hadn't been re-set after the last inflation. Any time you adjust the air pressure in the tires you need to let the monitoring system know.

Would the valve reseal by itself? Unsure if theres any "goo" in these run flats.

The tempreture was low - but not to completely deflate the tyre (0psi).

No alerts from the dash this am. Its most odd!

Thanks for the replies.

[sidewaze samm]

The tyre pressure warning doesn't detect the actual pressure in the tyre - as far as I'm aware, it measures the number of wheel revolutions over a given distance and compares this to what it was doing previously. So if a tyre loses pressure it will have a smaller rolling circumferance and make more revolutions than if fully inflated. That's why the warning didn't trigger - the car hadn't travelled far enough.
I think...

[m1ke823146]

Quote: Originally Posted by Macguyvic (original)

You probably had an intermittent leaking valve. Cold weather will reduce the pressure in the tires. The warning may not have come because the monitoring system hadn't been re-set after the last inflation. Any time you adjust the air pressure in the tires you need to let the monitoring system know.

how do you let the monitoring system know you've adjusted the tyre pressures?