[F31-340i]

....just checked mine. As per door jam they should be 2.6 front, 3.0 rear (19" 225M on an E91).

I'd not checked them for quite a while - what was interesting was that both right hand side tyres were spot on the pressures with no loss whatsoever.

Both left tyres (that have crash over a fair number of defects/potholes on the road verge during normal driving - I avoid most but obviously not all) had both lost a fair amount of pressure, down to 2.2 and 2.4. The tyre pressure monitor hadn't yet triggered - it seems its pretty useless on 19" RFTyres. I'm pretty sure the wheels are still not cracked.

Speculating, but I'm beginning to suspect these wheels/tyres are prone to loosing pressure during normal driving on rough road surfaces. Further speculation is that prolonged driving on the resulting underinflated tyres will lead to cracking due to excess weight being carried on the inside wheel rim.

So - if you're on 19"s - keep checking the pressures!

[HighlandPete]

^^^

+1

Check tyres regularly and reset the TPMS each time, to recalibrate the system.

HighlandPete

[toxicnerve]

Yeah,

I just got my E92 weekend just gone and have invested in a little (crappy/cheapo) 12V compressor and a Michelin pressure gauge. Going to be keeping a close eye on the pressures. Want to get decent life out of my tyres more than anything.

[NFS]

Originally Posted by ///ajd

The tyre pressure monitor hadn't yet triggered - it seems its pretty useless on 19" RFTyres. I'm pretty sure the wheels are still not cracked.

TPMS will ONLY trigger with a sudden rapid pressure loss. It will not tell you that the tyres are low.

Regular checking is very wise on runflats if you want to avoid excessive wear on the edges.

[F31-340i]

Originally Posted by NFS

TPMS will ONLY trigger with a sudden rapid pressure loss. It will not tell you that the tyres are low.

Regular checking is very wise on runflats if you want to avoid excessive wear on the edges.

The same TPMS system did work on my Mini Cooper S on 17" RFTs when they deflated slowly over a reasonably long period - as the 17" sidewall was much bigger it was still able to pick up the deformation of what turned out to be a very slow puncture - the pressure did have to drop a fair bit, but it still triggered a warning long before it was totally flat, but was just visibly starting to look a bit soft (say sidewall 15-20% compressed).

Even when the 19" have under 2.0bar in them you can't see any chuffing deformation in the sidewalls - they are so tiny/firm! I'm not going to experiment but I suspect letting 1 tyre down to 1.5 bar and running it wouldn't trigger a warning! The rolling diameter just doesn't change enough.

[YvesD]

Originally Posted by toxicnerve

Want to get decent life out of my tyres more than anything.

No chance with that nuclear reactor under the bonnet

Should have bought a 118d........

[toxicnerve]

Originally Posted by YvesD

No chance with that nuclear reactor under the bonnet

Should have bought a 118d........

So true. I'm a pretty laid back driver though especially in comparison to some (maybe most) of the other guys here.

[YvesD]

Originally Posted by toxicnerve

So true. I'm a pretty laid back driver though especially in comparison to some (maybe most) of the other guys here.

Respekt.

[HighlandPete]

Originally Posted by ///ajd

.... I'm not going to experiment but I suspect letting 1 tyre down to 1.5 bar and running it wouldn't trigger a warning! The rolling diameter just doesn't change enough.

There's the rub... indirect TPMS is not really what it is viewed to be. We must check tyres regularly, tyres can go well below setting pressures without any indication. Many users unwittingly believe they have a monitoring system that will tell them when the tyres need adjusting.

HighlandPete

[F31-340i]

...update. Just checked again.

Both left tyres lost 0.1 bar (front) and 0.2 bar (rear) - no change in the right tyres at all. All wheels not confirmed cracked - just checked by Main Dealer when it was in for the free goodwill headlamp washer jet replacement today.

Be vigilant!

J

[doughboy]

Originally Posted by NFS

TPMS will ONLY trigger with a sudden rapid pressure loss. It will not tell you that the tyres are low.

It does go off for slow pressure losses. The slow puncture I had in my old E90 would set it off every week or so when it lost about 7-10psi.

On the 335i last summer I set the pressures cold before we left for Cornwall on Holiday and reset the TPMS.

Then after 20 miles (car seriously fully loaded) the alarm went off, due the the rear tyre pressure GOING UP with heat from 40 to 47 psi and the fronts were unchanged it 'calculated' we had a puncture somewhere.


Of course, we all check our pressures every week as reccommended.....