[HighlandPete]

Certainly recommended to reset the system everytime we adjust pressures. The 'drive on' part, re-calibrates the TPWS. BMW have dropped the 'monitoring' reference and use 'W' (warning) these days.

The problem with not doing so and regularly checking pressures, is more than one wheel can decrease in pressure and take away the sensitivity of the indirect system we use on ABS wheel speed sensors.

The direct TPMS with internal wheel pressure sensors is much more accurate. And one/two wheel deflation doesn't lessen the trigger sensitivity.

Still don't know how you can get down to 8psi without a trigger, in normal conditions of use.

HighlandPete

[HighlandPete]

Originally Posted by Jeff123

...Problem with the RFT's is that you can't see when a tyre is low in pressure. The wifes Corsa gets checked only every couple of months on "normal" tyres, but with RFT's I reckon it's a more frequent job.

A friend of mine with a garage has seen cars come in for various jobs - some have RFT's that have only a few pounds of pressure in them - and the owners are driving around not knowing this!
Jeff

Definitely need checking more often. Many folks think they don't need to bother checking ERFTs, the car will tell them when to do so.

You identify a major reason why there are so many wear issues and also some failures, where folks are believing the RFT 'saved them'. Where the truth is possibly very different, the tyre failed due to it being a neglected RFT.

Also why BMW and the tyre makers are blaming users for wear being caused by low pressures. Users have given them genuine cause to say so.

HighlandPete

[SteveF1]

Its funny this topic should rear its head today as I've had trouble this morning with the opposite problem, an overactive tyre pressure monitor.

Last week the car was at Bowker BMW for a smart repair on the back drivers side alloy wheel and when I picked the car up and left the yard the tyre pressure light lit up on the dash. I spun the car round and took it back in and they took it back in the garage for a checkup. Ten minutes later the mechanic handed the keys back and said the wheels/tyres were checked and all pressures were fine and the system had been reset. I drove off and that was that.

This morning on the way to work the pressure monitor lit up again so I pulled into the nearest layby. I got out to see if there was anything noticeable and got back in and started her up again. This time the warning light disappeared so I carried on to work at a reduced speed. At work I checked the tyre pressures and they were all reading the same and all as per the doorframe rates.

I rang BMW up and they said they'd need to have the car in to check whether the sensors have failed or been disturbed when the wheel came off to be resprayed last week. I know for sure that although the wheel was removed from the car when the wheel was resprayed the tyre stayed on as there is overspray on the tyre itself. Not a problem with the beading or valve being disturbed although to be fair it could be any of the wheels as the stupid sensor doesn't even tell you that.

What the technician I spoke to said was that the pressure sensor only registers sudden losses of pressure greater than a third of a bar, anything less will not cause a dash warning light, nor will slow punctures.

Technology eh.....

[chris330D]

I got a nail in my drivers side rear last year and the warning went off in the dash. Trouble is can't say when I drove over the nail but the system worked. You do have to reset the system every time you change the tyre pressures. Sounds anal I know but you should check the tyre pressures weekly, sadly I do

[RichJ]

is a rft actually any safer in a blowout or sudden loss of pressure situation?

[HighlandPete]

Originally Posted by Rich Jones

is a rft actually any safer in a blowout or sudden loss of pressure situation?

I believe it should be, but I'm no longer convinced, as the condition of a run-flat is not necessarily known when it blows out. I know the tyre companies show good tyres being deflated at speed and the driver retains control. But... that is with a good tyre. What if the tyre has already gone soft, without the warning, perhaps been driven a good distance before the blowout/failure and is disintegrating inside, what then?

As some have only got a few miles before a RFT shreads, after the warning sounds, I'm not sure the concept is as good in the real world as the 'image' suggests.

The user still has to give the tyre a lot of attention. The common cause of many blowouts is said to be lack of pressure and tyre checks. So are we really any further forward, when the run-flat is giving a false sense of security to many users?

HighlandPete

[ss134]

Originally Posted by Rich Jones

is a rft actually any safer in a blowout or sudden loss of pressure situation?

Definately. Loss of control occurs when the sidewall of the tyre, which is usually kept secure against the rim by the internal air pressure, becomes separated from the rim flange and drops into the well of the wheel.

As soon as the beads are disconnected from the rim flange, loss of steering control will occur.

Run-flat tyres are designed to keep the tyre beads securely anchored to the rim flange area of the wheel even when operating at zero pressure.

[BIGTIME]

Is running higher pressure going to increase the chance of cracking my 225 alloys?

[BGM]

Originally Posted by BIGTIME

Is running higher pressure going to increase the chance of cracking my 225 alloys?

i really wouldn't of thought so...

even if you managed to put enough pressure in there to crack the alloy, the tyre will have long since popped

[HighlandPete]

Originally Posted by BIGTIME

Is running higher pressure going to increase the chance of cracking my 225 alloys?

As I understand it, the increased pressure 'should' help spread the forces from impact loadings, rather than a lower pressure contributing to more localised shock loadings. (The crown of the tyre is more involved with higher pressure). It's to do with the nature of the stiff sidewall, rather than the more balloon type conventional tyre, with a softer and yielding construction.

HighlandPete

[SteveF1]

Anyone know what tyre pressures I should be using on my car....as I doubt the door frame figures are right.

I drive the car alone most of the time, I have a staggered setup and run 17" M
Sport wheels. 225/45 front, 255/40 at the back.

Rough estimates.......

[HighlandPete]

Originally Posted by SteveF1

Anyone know what tyre pressures I should be using on my car....as I doubt the door frame figures are right.

I drive the car alone most of the time, I have a staggered setup and run 17" M
Sport wheels. 225/45 front, 255/40 at the back.

Rough estimates.......

Why are you doubting the placard recommendation? I'd be running about 0.2 bar above the lower setting pressure.

HighlandPete

[SteveF1]

Cause BMW have lowered the pressures after I complained that the ride was getting overly harsh and seemed to 'crash' over poor roads. After the car went in and was collected the pressures were down a few PSI to what they were before and the ride felt a bit better in general than what I was running them at previously (the door frame rates).

Some say run what the doorframe card says, some say harder and BMW have gone lower.....

[Jeff123]

Originally Posted by SteveF1

Cause BMW have lowered the pressures after I complained that the ride was getting overly harsh and seemed to 'crash' over poor roads. After the car went in and was collected the pressures were down a few PSI to what they were before and the ride felt a bit better in general than what I was running them at previously (the door frame rates).

Some say run what the doorframe card says, some say harder and BMW have gone lower.....

Hi

Mines the same type of car as yours and on non-RFT Falken's I run 2.1 and 2.3 (around 30 and 33). Most of the time it's just me or plus one passenger. Never much in the boot. This seems OK to me, however, I don't know as yet what the long-term tyre wear will be like.

Jeff

[YvesD]

Originally Posted by Jeff123

Hi

Mines the same type of car as yours and on non-RFT Falken's I run 2.1 and 2.3 (around 30 and 33). Most of the time it's just me or plus one passenger. Never much in the boot. This seems OK to me, however, I don't know as yet what the long-term tyre wear will be like.

Jeff

Did Falken recommend those pressures to you, they seem very low to me

Interestingly, correct pressures for my Vreds as advised directly by them for my very car....

45psi front, 47psi rear.....

They are still more compliant than the Flintstones, even at those pressures

[Rochdale Pioneers]

Thanks for the tip. I'm in non-Idrive and have been checking them every week or so as I used to do on non-RFT tyres on every other car I have ever had. The way I see it is this - run flat is there to be drivable if they get damaged. Like any other tyre they still need checking.

[Jeff123]

Originally Posted by YvesD

Did Falken recommend those pressures to you, they seem very low to me

Interestingly, correct pressures for my Vreds as advised directly by them for my very car....

45psi front, 47psi rear.....

They are still more compliant than the Flintstones, even at those pressures

No, mine is only a 320d M-Sport. The pressures on my 17" wheels are much less than yours. I simply took the lowest pressures off the door pillar. At this stage it seems ok. I ran the rft's at a broadly similar pressure and they were ok (for runflats).

Jeff

[ss134]

Originally Posted by SteveF1

Cause BMW have lowered the pressures after I complained that the ride was getting overly harsh and seemed to 'crash' over poor roads. After the car went in and was collected the pressures were down a few PSI to what they were before and the ride felt a bit better in general than what I was running them at previously (the door frame rates).

Some say run what the doorframe card says, some say harder and BMW have gone lower.....

Had the same problems as you regarding tyre pressure - my car used to 'bounce on the road and feel 'floaty' and unstable at autobahn speeds when i was running the recommended pressures.
I now run 2.2 F and 2.4 R and the car is much better in all aspects -the tyres have now covered 10000 miles and the wear is even.

Try these pressures and see how you get on - my mate has the 17s and he runs the same as me and has also noticed a huge improvement in handling.