Run Flat Tyres, Punctures and Tyre Pressures- Help!

[plastics]

Hi All - hope someone can help with my tyre issues - I have a 2.5i Z4, 17in runflats....I seem to be unlucky and get a puncture virtually every year and have had to replace a lot of tyres at the cost of nearly £200 each time. I am a complete novice when it comes to cars, and so apologies if the questions seem very naive!

Anyway, I had a whole set of new tyres replaced at the last servicing in November 2010 and last week I got the dreaded 'run-flat indicator' warning light. This time I measured the pressures - 130kPA in the passenger rear tyre (normal 230kPA), 220kPA in driver rear, 205kPA in the passenger front (normal 210kPA), and 210kPA in the driver front.
So, I thought obviously the passenger rear tyre may have had a puncture (nothing I can see) but needed to make a journey and was unable to organise a time to take in for a tyre change. I inflated all the tyres to the recommended pressures - front 210kPA and rear 230kPA, reset the tyre pressure monitor and just drove.

It then sat on my drive for 4 or 5 days, I checked my tyre pressures again, and all were normal apart from the passenger rear again which had gone down to 190kPA (the runflat tyre monitor warning had not come on). Again, I needed to make another journey - re-inflated this tyre to 230kPA and drove yesterday. Today, I checked the air pressure and it was still 225kPA so it seems to have held its air??

My questions are:
1. How do I know there is definitely a puncture, surely if I inflate it up, the pressure should go down very quickly and very low after a long journey?
2. I want to avoid spending another £200 to get another new tyre - is it safe to just inflate up to normal pressures and continue driving?
3. Is the runflat tyre monitor actually accurate in detecting a puncture, or does it sometimes just detect changes in air pressures - i.e. can it give false alarms, or is it accepted that if it does come on, you definitely have a puncture?
3. Does anyone have recommended tyre places that will be accurate, check whether I actually do have a puncture and potentially repair if possible, without ripping me off??? I was going to get a company to come and replace at home, but it means I have to be sure which is the punctured tyre...

Any advice would be most welcome....

 

[Half Colin]

The Tyre indicator system for European cars operates via the ABS system and monitors the relative rotation of wheels on the same axle. A lower pressure in one tyre reduces the rolling radius of that wheel tyre such that the wheels rotate at different rates. So it is not a true puncture indicator but an indication of a difference in pressure between the wheels on the same axle. It only works when the car is moving also. The US cars have a different system that actually monitors the pressure.

If I were you I would pump the tyres up correctly and drive the car for a few days. If it still loses pressure get it checked. It could also be a faulty valve.

 

[riche]

A couple of suggestions:

As already said. Get the valve changed first, little cost, come across the odd failure so rule this out.

Take wheel off and submerge to hunt for leaks, if it is still going down.
Check carefully around rims for damage, may not leak all the time but under sideways stress you may be triggering a small air leak at a damage point.

 

[jabber]

i have had punctures repaired on my runflats, apparentley as long as the pressure hasnt gone below around 14psi
and there is no damage to the sidewall
slightly of topic i have just had a puncture in the sidewall of a week old contisport tyre repaired by a specialist company via protyre cost me £27!

 

[plastics]

thanks for the advice guys

 

[Ragman]

runflats are the pits.....I changed to regular tyres and carry a footpump and tyre weld kit