Run Flat Waning...Sensor Issue or Puncture :-(

[bigfish]

Got delivery of 325 yesterday (55 plate) & covered about 50 miles when told I have a puncture by BMW computer

I also think a "non BMW" dealer put a new tyre on it a few days ago. They all have RSC on the tyres

So, how do I know if it really is a puncture (normally I would see a flat tyre!) or its just a sensor misbehaving?

Could take it to BMW but....my experinence will be "oh yes sir....four new tyres sir!" :-)

[DSM2]

Have you checked the tyre pressures? That might give a clue.

[bigfish]

Just have.....

so...Front RHS is 21.....Front LHS is 30

Looks like just need some puff in RHS then?

[DSM2]

bigfish said:

Just have.....

so...Front RHS is 21.....Front LHS is 30

Looks like just need some puff in RHS then?

That will probably reset the TPMS, the question now is why such a loss of pressure? Anyhting obvious? If not see if it happens again.

OT, a lot of users seem to think that the TPMS obviates them from regular tyre pressure checks but often the gradual presure loss in RFTs is signiicant and, of course, if the pressure across an axle falls roughly in line, the TPMS doesn't recognise it.

I have seen examples of tyres down by 7 or 8 psi in pairs but the owner had no idea.

[Roger645]

DSM2 said:

bigfish said:

Just have.....

so...Front RHS is 21.....Front LHS is 30

Looks like just need some puff in RHS then?

That will probably reset the TPMS, the question now is why such a loss of pressure? Anyhting obvious? If not see if it happens again.

OT, a lot of users seem to think that the TPMS obviates them from regular tyre pressure checks but often the gradual presure loss in RFTs is signiicant and, of course, if the pressure across an axle falls roughly in line, the TPMS doesn't recognise it.

I have seen examples of tyres down by 7 or 8 psi in pairs but the owner had no idea.

Surely a change of that magnitude across a pair is normal behaviour for cold to warm tyres in normal use.

[bigfish]

Thanks all....just put some air in tyre & reset system

Lets see what happens, but as I have only just got the car, cant tell what previous owner did

[Sticks.]

Gd luck. My experience is that a lot of dealers will just keep topping up a leaking tyre until the car is sold. Even some main dealers, I'm told. Then you picked up a puncture since you bought it, didn't you?

[DSM2]

Roger645 said:

DSM2 said:

bigfish said:

Just have.....

so...Front RHS is 21.....Front LHS is 30

Looks like just need some puff in RHS then?

That will probably reset the TPMS, the question now is why such a loss of pressure? Anyhting obvious? If not see if it happens again.

OT, a lot of users seem to think that the TPMS obviates them from regular tyre pressure checks but often the gradual presure loss in RFTs is signiicant and, of course, if the pressure across an axle falls roughly in line, the TPMS doesn't recognise it.

I have seen examples of tyres down by 7 or 8 psi in pairs but the owner had no idea.

Surely a change of that magnitude across a pair is normal behaviour for cold to warm tyres in normal use.

No it isn't an increase of more than 3 or 4 psi maximum would be odd.

Anyway that's not what I meant. What I am saying is that if a pair of tyres, on the same axle, lose pressure at about the same rate, the TPMS will never pick up the loss, as it works on the ABS system, measuring rotational speeds which vary with rolling diameter.

[Roger645]

DSM2 said:

Roger645 said:

DSM2 said:

bigfish said:

Just have.....

so...Front RHS is 21.....Front LHS is 30

Looks like just need some puff in RHS then?

That will probably reset the TPMS, the question now is why such a loss of pressure? Anyhting obvious? If not see if it happens again.

OT, a lot of users seem to think that the TPMS obviates them from regular tyre pressure checks but often the gradual presure loss in RFTs is signiicant and, of course, if the pressure across an axle falls roughly in line, the TPMS doesn't recognise it.

I have seen examples of tyres down by 7 or 8 psi in pairs but the owner had no idea.

Surely a change of that magnitude across a pair is normal behaviour for cold to warm tyres in normal use.

No it isn't an increase of more than 3 or 4 psi maximum would be odd.

Anyway that's not what I meant. What I am saying is that if a pair of tyres, on the same axle, lose pressure at about the same rate, the TPMS will never pick up the loss, as it works on the ABS system, measuring rotational speeds which vary with rolling diameter.

Well, Michelin's website talks about a notional difference of 4-5 PSI from cold to hot.

[DSM2]

Roger645 said:

DSM2 said:

Roger645 said:

DSM2 said:

bigfish said:

Just have.....

so...Front RHS is 21.....Front LHS is 30

Looks like just need some puff in RHS then?

That will probably reset the TPMS, the question now is why such a loss of pressure? Anyhting obvious? If not see if it happens again.

OT, a lot of users seem to think that the TPMS obviates them from regular tyre pressure checks but often the gradual presure loss in RFTs is signiicant and, of course, if the pressure across an axle falls roughly in line, the TPMS doesn't recognise it.

I have seen examples of tyres down by 7 or 8 psi in pairs but the owner had no idea.

Surely a change of that magnitude across a pair is normal behaviour for cold to warm tyres in normal use.

No it isn't an increase of more than 3 or 4 psi maximum would be odd.

Anyway that's not what I meant. What I am saying is that if a pair of tyres, on the same axle, lose pressure at about the same rate, the TPMS will never pick up the loss, as it works on the ABS system, measuring rotational speeds which vary with rolling diameter.

Well, Michelin's website talks about a notional difference of 4-5 PSI from cold to hot.

Well, closer to 3/4 than to 7/8?

A real life example might be my 911, 355hp through the rear wheels and most of the car's weight over those wheels. Cold tyres 2.7 bar rise to 3.0 when hot. 4.4psi. I can't see most other cars being more than that under normal conditions.

Anyway,this is now way OT.

Edited by DSM2 on Sunday 20th September 14:02

[Roger645]

DSM2 said:

Roger645 said:

DSM2 said:

Roger645 said:

DSM2 said:

bigfish said:

Just have.....

so...Front RHS is 21.....Front LHS is 30

Looks like just need some puff in RHS then?

That will probably reset the TPMS, the question now is why such a loss of pressure? Anyhting obvious? If not see if it happens again.

OT, a lot of users seem to think that the TPMS obviates them from regular tyre pressure checks but often the gradual presure loss in RFTs is signiicant and, of course, if the pressure across an axle falls roughly in line, the TPMS doesn't recognise it.

I have seen examples of tyres down by 7 or 8 psi in pairs but the owner had no idea.

Surely a change of that magnitude across a pair is normal behaviour for cold to warm tyres in normal use.

No it isn't an increase of more than 3 or 4 psi maximum would be odd.

Anyway that's not what I meant. What I am saying is that if a pair of tyres, on the same axle, lose pressure at about the same rate, the TPMS will never pick up the loss, as it works on the ABS system, measuring rotational speeds which vary with rolling diameter.

Well, Michelin's website talks about a notional difference of 4-5 PSI from cold to hot.

Well, closer to 3/4 than to 7/8?

A real life example might be my 911, 355hp through the rear wheels and most of the car's weight over those wheels. Cold tyres 2.7 bar rise to 3.0 when hot. 4.4psi. I can't see most other cars being more than that under normal conditions.

Anyway,this is now way OT.

Edited by DSM2 on Sunday 20th September 14:02

Taking it back OT, I found this:

The Tyre Puncture Warning System regularly monitors the tyre pressures of all four tyres by comparing their rotational speed when the vehicle is being driven. Whenever tyre pressure drops by approximately 30 per cent or more, the wheel's rolling radius changes significantly and rotates at a different speed from the other wheels. Via DSC's wheel-speed sensors, the Tyre Puncture Warning System recognises any such major deviation. Within one to three minutes, this system triggers a pressure-loss indication on the instrument panel, plus an audible warning. In a vehicle equipped with the iDrive interface, the warning appears on the Control Display.

That's why a 7psi sihft would not be picked up.

[bigfish]

Well....put some puff back in the tyre...and reset the puncture computer thingy

Drove for 2 hours (before hand back to wife) and seems ok

Will test pressure in tyre in a few days to check, but so far, all seems well

Thanks for comments/help

[PartsGuru]

Just been trying to read all the info given and it all got too technical for me lol!! I've had customers with the same problem and it has been a buckled wheel!!They've tended to be the bigger wheels that buckle on the inside edge and it appears our unkept roads are causing the problem.It's not always that obvious to the naked eye either.

Edited by PartsGuru on Wednesday 23 September 15:07