BMW 3-Series E92 Coupe (2006 - ) - Replacement "normal" tyre pressures.

Honest John Back Room » Motoring discussion
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Sun 11 Jan 2009 11:24
Replacement "normal" tyre pressures. - Dude - {P}
Having just switched from RFT`s to conventional tyres, the tyre supplier was not 100% sure as to the correct tyre pressure, they have inflated to the same level as the run flats.

Could someone please confirm if this is correct or not ?

Incidentally, I know H.J. is an advocate of RFT`s, but the improvement to the ride, steering control and reduction in road noise has totally transformed the car for the better.
There is no question that in cold weather, RFT`s are positively dangerous with serious tramlining and bone shaking ride.

Edited by Pugugly on 11/01/2009 at 11:46

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Sun 11 Jan 2009 13:01
Replacement "normal" tyre pressures. - colinh
Was it ever resolved whether changing from run-flats counted as a modification requiring:

a) Notification to insurance company

b) Contravening the original type approval for the car and therefore the construction regulations?

Search and Google seem to bring up different views

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Sun 11 Jan 2009 13:40
Replacement "normal" tyre pressures. - Dude - {P}
The subject was raised with our insurance company and they said there was no problem from their prospective with no increase in premium required.

This changeover to conventional tyres is now happening on too wide a scale and as far as contravening the original type approval, BMW must recognise the dilemma as they have now produce a specific space saver spare wheel for the E90 series along with jack and wheel brace.

The cost of this kit for a used vehicle is nearly £200 from a BMW main dealer, but if ordered for a brand new car, is just over £60.
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Mon 12 Jan 2009 14:41
Replacement "normal" tyre pressures. - Dude - {P}

Can now confirm that the pressures for conventional tyres is the same as for RFT`s

we have gone for 2.3 bar fronts and 2.4 for the rears and am absolutely delighted with the switch - like driving a new car !!!!
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Wed 28 Jan 2009 22:34
Replacement "normal" tyre pressures. - fortygreen
Would be great if you could post on your impressions on any effect on fuel consumption. Do the extra stiff sidewalls of RFTs contribute to lower rolling resistance, which BMW quotes as part of Efficient Dynamics?
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Thu 29 Jan 2009 07:32
Replacement "normal" tyre pressures. - Collos25
Do you mean you have gone from low profile to normal profile tyres?.I had Michelin normal profile run flat tyres on my honda and are no different in usage to the tyres that have replaced them the actual difference in construction the run flat have much stiffer side walls and weigh considerable more.Low profile whether they are run flat or not will tram line and amplify any bumbs.
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Tue 3 Feb 2009 15:53
Replacement "normal" tyre pressures. - Dude - {P}
Would be great if you could post on your impressions on any effect on fuel
consumption. Do the extra stiff sidewalls of RFTs contribute to lower rolling resistance which BMW
quotes as part of Efficient Dynamics?

>>

In response to your question fortygreen, there has indeed been an improvement in fuel consumption by 1.5 mpg. over the 2k miles since fitting.

Whether this is due to the reduced weight of the conventional tyres over R.F.T`s but I believe it is more likely the result of less road drag by the conventional tyres, as road noise, which was quite high, has now almost disappeared.
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Sat 7 Feb 2009 22:28
Replacement "normal" tyre pressures. - fortygreen
I thought it would other way round if anything, because BMW say their tyres are part of the ED package with low rolling resistance. So what size wheels/tyres do you have and what make of new tyre have you gone for? I'm on the original Bridgestone Potenzas on 18" rims. No probs with road noise, it's the tramlining I find alarming on certain stretches of motorway. All in all you seem to make a convincing case Dude for ditching the run-flats.
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