How often to top up tyre pressure?

[denarii]

I bought a 2006 3 series with msport tyres in early June and just topped up the tyre pressure for the first time. The pressure was really low , like 1.5 bars when they are supposed to be about 2.8. I havent used it much for 3 or so weeks due to a holiday, but before that if the tyre pressure was a but low would it have damaged the run flats?

Thanks

[mmm-five]

I check mine every week and/or before a long trip.

If you've driven around for a while on heavily under-inflated run-flats, then you probably have damaged the sidewall, but you probably won't notice, and they don't show as much evidence of damage as normal tyres do, due to the stiffer/thicker sidewalls.

[DennisCooper]

Remember when you passed your test? well at least I hope you took one! but part of the things to learn were checking your vehicle and doing basic checks. Part of that was to ensure you monitor your tyre pressures every week and keep them at the correct levels. Under inflated tyres, the most common, increase wear and fuel consumption and not checking for as long a time frame as you've let lapse is definitely not recommended. That's why for a number of years, TPMS systems in other countries have been mandatory to alert the lazy drivers out there the pressure has lowered and for them to go top up. The UK of course is always late to the game and it's yet not mandatory (on new cars) but you can buy TPMS devices which will alert you. I suggest you get one of those fitted, over the course of the time you've not topped up with air, the increased fuel consumption probably would've paid for a system anyway !

Cheers, Dennis!

[edc]

To lose that much pressure in a relatively short period of time suggests potentially a bigger problem. The runflats on my e90 hold pressure forever.