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Discussion Starter · #1 ·
I have a BMW 645Ci with Sport Package. I need some professional advice on switching from OEM Run-Flat tires to regular "high performance" radials.
I have always run the OEM Potenza RE050A RFT Tires:
•Front: 245/40R19 W94
•Rear: 275/35R19 W94
They are truly underperformers. I live in Greenville SC and I push the car hard having fun on back roads of NC. The OEM RFT tires break traction routinely; (in addition to other poor performance characteristics).

I made a spreadsheet on all the top performance summer tires and there are many that rate higher in traction, cornering stability, ride / noise comfort.
So I want to switch.

Question 1:
The car was designed for RFT tires (stiffer, thicker sidewalls, etc.) and though other tires rate better, will the 645Ci perform as well on regular radials?
I am considering the following five tires. All rate better in the above areas than the OEM RFT: 1) Michelin Pilot Sport PS2; 2) Pilot Sport; 3) Pilot Sport A/S Plus; 4) Potenza S-04 Pole Position; and 5) Toyo Proxes T1R.
Not looking for a tire recommendation per se - but if you have any experience, I would be interested. What I AM LOOKING FOR - is advice on whether or not the car will perform as well on regular non-RFT radials because it was designed for the stiffer/thicker RFT tires that have basically different characteristics.
Is there any reason (from a performance standpoint) that I cannot put on regular radials?

Question 2:
I am considering "upsizing 0"; (means keep the same 19" wheel but use a "255" on the front and "285" on the back. There are several tires that will be within 2% of the key diameter and rev/mile characteristics of the OEM (no speedo change); but will give me more tire on the pavement.
Is there any reason I cannot or should not do this?

Thanks,

Scott
 

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The M6 runs non-runflats in 255/40R19 and 285/35R19 so you will have no problems doing a plus zero.

I would just buy an M-mobility kit and throw it in the trunk, there is a spot for it in the wheel well. It consists of a 12V air pump and a can of sealant.

The RE050A RFT have poor grip in the wet and dry but they turn in very well due to the stiff sidewalls. They are actually the best street tire I've tried on the track due to the stiff sidewalls.

Answer 1
Based on my experience with non-RF vs RF tires, something like a PS2 will give way better wet and dry grip, be very quiet and are in a different league when it comes to comfort over bumps compared to the RE050A. Turn in will be a little less sharp due to sidewall flex.

Answer 2
Go for it. You will have no issues.
 

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SVSCME
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:stupid: The PS2's is what's on my 6er and I totally agree with statement 1.
 

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I have experience on my C6 going from a RFT to a Non RFT. I have used both the Michelin Pilot Sport PS2 and the Toyo Proxes T1R, For the money I really liked the Toyos they were hands down just as good ride, and performance wise I could not tell a difference between the two. Also the Toyo's lasted much longer. Both Tires were a much improved ride in my C6 aLso much more quiet than the RFTs Grip also improved. I will be going with TOYO Proxes T1Rs in the near future.:thumbup:
 

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I've run Hankook Ventus V12s all around, for several thousand miles now, and they're great. Quiet, great grip, less expensive.
 

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06 BMW 650i Sprt/Prem Pkg
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255/35ZR21 FRONT
295/30ZR21 REAR
Pzero's (Non RFT)

I have a led foot and love a tight curve and have no problems with these. Great performance with and excellent speed rating...
 

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Yorgi where can you get that mobility kit? How much?

Sent from my PC36100 using Bimmer App
 

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Michael
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Yorgi where can you get that mobility kit? How much?

Sent from my PC36100 using Bimmer App
BMW sell them but not cheap!! or buy a small powerful pump and a can of tyre weld, a get you home option from any car parts company.
I for my part have put a permanent tyre solution into my tyres which should they ever get a any nail/screw incursion automatically reseal. The only downside to the use of this product is the tendency for the wheels to be slightly unbalanced for a couple of miles if you have left the car standing for any period, for me this is a small price for peace of mind when using non-runflats.
 

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