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      11-18-2012, 01:50 AM   #1
totobmw
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NRFTs better performance?? Not to sure about that!

Ok, so only being new to the whole run flat saga, I read as much as I could on ditching the Rft's on my 135i with the idea I would also go get some 19in VMR 718s with Michellin PSS (225/35/19_255/30/19) as all I could read was how terrible the RFT's were and how better the feel and ride was with Non Rft's.

Though after having the new set up on the car for a week, I feel that, yes, it is quieter, however performance has been altered massively, to the point where I am careful on how I drive the car.

The car feels floaty and unstable. From what I have read, this is the normal for most first impressions for the reasoning of a weaker sidewall.

Though I am now at the point where I may rid of the PSS and get some 19in RFts to gain back the performance.

BMW remark 'all of our vehicles that use Run-flat technology have their suspension and braking components set up to accommodate Run-flat tyres. Should you decide to change to non Run-flats, it may alter the driving and handling characteristics of your vehicle. It is for this reason that this modification is not recommended by BMW as a manufacturer.' and may I add this is the same for most tire expert websites.

I run the tire pressures of 160KPA (40PSi) all round and though I am running 19's the rolling diameter difference is very minimal (1%) to the OEM RFTS which were running on the 261 Msport rims.
Additional to this the car is stock with the stock msport suspension.

How can I get back performance, will different pressures or springs or whatever help?
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Last edited by totobmw; 11-18-2012 at 06:58 AM.
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      11-18-2012, 03:32 AM   #2
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get a smaller width tyre to reduce sidewall softness
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      11-18-2012, 06:52 AM   #3
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That is an extremely tall rear tire... Can't be within 1% of the OEM tire.

I just did the calculation and a 255/40/19 is over 8% different than the OEM 245/35/18.

There is your float.
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      11-18-2012, 06:57 AM   #4
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Quote:
Originally Posted by b1aze View Post
That is an extremely tall rear tire... Can't be within 1% of the OEM tire.

I just did the calculation and a 255/40/19 is over 8% different than the OEM 245/35/18.

There is your float.
geez, error, have readjusted, is F 35_ R 30
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      11-18-2012, 07:03 AM   #5
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When I had my PSS on my STI (275/35/18 all around) I found 40 to be too high of a pressure. I was getting excessive wear on the middle of the tread patch. Try a bit lower?

When you say floaty, does it feel like suspension? Does it feel extra bouncy over bumps? Too high of a pressure might make it too firm.

Did you have an alignment done lately?
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      11-18-2012, 07:20 AM   #6
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Quote:
Originally Posted by b1aze View Post
When I had my PSS on my STI (275/35/18 all around) I found 40 to be too high of a pressure. I was getting excessive wear on the middle of the tread patch. Try a bit lower?

When you say floaty, does it feel like suspension? Does it feel extra bouncy over bumps? Too high of a pressure might make it too firm.

Did you have an alignment done lately?
Car is only new, so no alignment done, there is more under steer and additional body roll. Not sure if it is a suspension problem, though with the new rims and tyres maybe suspension may need to be altered?
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      11-18-2012, 08:00 AM   #7
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Your suspension bushings are set up for run-flats, replace them with stiffer bushings and your problem will disappear. That is the only issue. And honestly, when i changed over, i didn't notice a real difference other than I now had more straight line traction.
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      11-18-2012, 11:56 AM   #8
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Plenty of cars come off the truck with bogus alignments. At least with some of the Japanese cars.

Also, the alignment specs are pretty wide with toe angle, +\- .25 if I read the spec sheet correctly.
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      11-18-2012, 04:15 PM   #9
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Quote:
Originally Posted by Stohlen View Post
Your suspension bushings are set up for run-flats, replace them with stiffer bushings and your problem will disappear. That is the only issue. And honestly, when i changed over, i didn't notice a real difference other than I now had more straight line traction.
Have you attempted to do this? Or is this the norm.
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      11-18-2012, 04:34 PM   #10
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I have not done it yet, but it is pretty normal. Most people upgrade to the M3 links and bushings because of this.
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      11-18-2012, 08:06 PM   #11
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Not sure this helps but for "normal street driving" i have found that adding the M3 FSB and running Yokohama ADO8's on my car with VMR 19" rims it has improved handling and ride..225F/255R..The GREAT grip of the ADO8 ans very stiff sidewall has improved turn in as well,,,also they have worn very well for me..have them on the car now a year and a half...I have Michelins on my DD and indeed they do have sidewalls that are a tad soft,
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