Runflats Binned....

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preppeller
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Post by preppeller » Sat Jan 20, 2007 8:25 pm

Ok, sorry to be spamming 3 posts in a row, but I wanted to get to the bottom of what you can get away with on the standard BMW M Sport 7.5x18 Front and 8x18 Rear rims.

using http://www.carbibles.com/tyre_bible.html which has lots of calculators on there, I have gotten to the following conclusion:

The best tyre sizes which are in stock in plenty at mytyres (with good brand names and not run flats, fit comfortably on the current rim sizes and only change the speedo by -0.7% (well within boundries ie 70mph on the speedo is actually 69.51mph) are.... *drumroll*

225/40x18 on the front and 245/35x18 on the rear.

:)
BMW 130i M Sport, Sapphire Black with Boston Black Leather, Xenons, HiFi

roofer
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Post by roofer » Sat Jan 20, 2007 8:35 pm

preppeller wrote:roofer, I notice you went for wider tires but with a profile which kept the rolling radius within 1%. Do the wider tyres fit on the standard bmw 18" rims? because mytyres have plenty of those sizes in stock.
I chose these sizes because i'm getting a set of Alpina Dynamics in 8"/8.5". You can fit a 255 from an 8" upwards rim :)

Tyre pressure monitor works fine, and i kept the M mobility system from my M5.

They're scrubbed in now, it sticks like a limpet 8)

BMWCAR magazine have fitted 225/40/18 all round, and report good things :)

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Post by megansdad » Sat Jan 20, 2007 8:44 pm

OK MY TUPPENCE WORTH.
I absolutely hate RUN FLATS ,i think they spoil the I Series. They do spoil the ride quality, especially on these roads here in N.Ireland.

I have just turned 7,000miles on mine and the front ones have about another 2,000 left if i am lucky.
Today i have just had my first flat,thanks to a nail. my Tyre center Repaired it although they did say they should,t but i brow beat them into doing it.(they plugged it).

I would replace the lot of them but my BMW Dealer states Replace them and lose your 3 YEAR Warranty, so i am dammed if i do and dammed if i don,t.Not much of a choice really.Looks like i am stuck with Run Flats.

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weasley
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Post by weasley » Sat Jan 20, 2007 9:35 pm

preppeller wrote:Also, does it bugger up the flat tyre indicator on the onboard computer?
Tyre pressure monitor works fine
I was under the impression that the tyre deflation detection didn't measure pressure but monitored the rotational speed of all four wheels. When a tyre deflates (even a RFT) the overall radius decreases, so the rotational speed increases - the ECU sees this and interprets it as a flat tyre. Hence the need to re-initialise the system every time you change tyres, or (strictly speaking) top up tyre pressures.

So, in summary, it should work perfectly well with a non-RFT (in fact maybe even better!).

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Ikki
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Post by Ikki » Sat Jan 20, 2007 10:29 pm

weasley,

It's not illegal to run without a spare or any way of fixing a puncture. It is illegal to have a spare that is defective or below minimum tread depth. :roll:
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Post by roofer » Sun Jan 21, 2007 12:48 am

So, in summary, it should work perfectly well with a non-RFT
That it does 8)

Had it round the lanes tonight....the car is transformed.

No rear skipping out mid bend ridges.
No nanny light blinking every two seconds, and you can feel the compliance in the tyres, which makes the information they give much more accurate 8)

Launching it off the line now just see's it accelerate, insead of having the DTC cut in......now i know why the M division won't specify them.

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Re: Runflats Binned....

Post by 130girl » Sun Jan 21, 2007 5:13 am

roofer wrote:...For P/Zero rosso, 255/35 rears, 225/40 fronts.

Ride quality is transformed, turn in is crisp.

I will never buy a Runflat shod car again :evil:
I'm jealous roofer- my RFT are too new to change but will certainly be considering this option later. Can you tell us whether you needed to modify your guards to make the new tires fit? Especially the rear- the OEM 225 is already pretty tight??? Any rub on big bumps with 255?

Any pics? The rear view must look awesome!

130girl

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Post by roofer » Sun Jan 21, 2007 1:06 pm

Any pics? The rear view must look awesome
Of course :)
Image

Clearance to shock

Image

Outer arch clearance, this pic shows the car 'loaded', as the other side is on the kerb
Image

I have about 60 kilos of work stuff in the boot as well, no rubbing/fouling issues at all, hth :)

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ghibbett
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Post by ghibbett » Sun Jan 21, 2007 4:36 pm

preppeller wrote:The best tyre sizes which are in stock in plenty at mytyres (with good brand names and not run flats, fit comfortably on the current rim sizes and only change the speedo by -0.7% (well within boundries ie 70mph on the speedo is actually 69.51mph) are.... *drumroll*

225/40x18 on the front and 245/35x18 on the rear.

:)
Hi Preppeller,

Have you found decent *matching* tyres over both sizes?

Cheers,
Current :-)
S50 M-Coupe, Estoril Blue
Black Leather, Heated Seats
Harman Kardon, Tracker

Gone :-(
130i M-Sport, Le Mans Blue
Xenons, Boston Leather
Prof CD, 6 CD Changer
Tracker, Darkline rear lamps

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preppeller
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Post by preppeller » Sun Jan 21, 2007 5:47 pm

looking at mytyres, they have Dunlop Sport Maxx and Pirelli P Zero Rosso in both sizes. My best experiences in the past have been with bridgestone potenzas, however they dont have matching ones of those in front/rear sizes.

I may be tempted to get 225/40 for all tyres when I ditch my runflats though because I would prefer my car to stay a little tail happy :)
BMW 130i M Sport, Sapphire Black with Boston Black Leather, Xenons, HiFi

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ghibbett
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Post by ghibbett » Sun Jan 21, 2007 7:29 pm

preppeller wrote:I may be tempted to get 225/40 for all tyres when I ditch my runflats though because I would prefer my car to stay a little tail happy :)
Been thinking along this route too.
How far-off are you from needing new tyres?

Cheers,
Current :-)
S50 M-Coupe, Estoril Blue
Black Leather, Heated Seats
Harman Kardon, Tracker

Gone :-(
130i M-Sport, Le Mans Blue
Xenons, Boston Leather
Prof CD, 6 CD Changer
Tracker, Darkline rear lamps

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preppeller
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Post by preppeller » Sun Jan 21, 2007 8:10 pm

Well, the fronts are still pretty good but the rears are 2/3rd done - I would say another few months until I just give up on the run flats and ditch them, whatever the state.
BMW 130i M Sport, Sapphire Black with Boston Black Leather, Xenons, HiFi

130girl
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Post by 130girl » Mon Jan 22, 2007 3:49 pm

roofer wrote:
Any pics? The rear view must look awesome
Of course :)

Outer arch clearance, this pic shows the car 'loaded', as the other side is on the kerb
Image

I have about 60 kilos of work stuff in the boot as well, no rubbing/fouling issues at all, hth :)
thanks roofer Image
the tyres fill the wheels right out to the sides now. looks much better!!!
130girl

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Post by roofer » Thu Feb 01, 2007 11:04 pm

Now got a 1000 miles on them.....the car is transformed, the steering is alive again 8)

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Iwant1
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Post by Iwant1 » Thu Feb 01, 2007 11:19 pm

roofer, thanks for the info. I was going to put 245/35 R18 non-RFT on the rears as I thought that was the biggest you can have, now 255 will be the go! awesome! :D
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