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[jkoral]

Originally Posted by mosx

I have a 235/255 setup on the BMW Performance Suspension, no rubbing anywhere. Even with 4 200lb+ guys in the car.

I am also running a 235/255 setup (seems much less common) on the stock OE wheels with the BMW Performance Suspension.

I'm not aware of any rubbing. The only time I worried was when I had 5 adult men in the car (3 squeezed in the back).

I plan on taking my wheels off this weekend and I'll get a good look at the wheel well.

[M34lnch]

Originally Posted by GotM

The increase in height should be due to the change in tire size, not RFT to non-RFT. Assuming that the same aspect ratio is used for stock to larger tire.

Using info I found on Tire Rack (Pirelli P Zero specs)

Stock rear tire size
245-35-18 => 24.5" overall height

Using the larger 255, same 35 aspect ratio
255-35-18 => 25.2" overall height

This is great info. Is there any downside to the height changes? I'm guessing the speedometer would be off slightly? Anything else?

[GotM]

Originally Posted by M34lnch

This is great info. Is there any downside to the height changes? I'm guessing the speedometer would be off slightly? Anything else?

On my M Roadster the increased height improved the speedo accuracy.

I believe my 1ers speed is slightly off now, and I think it will be more accurate when I go to the larger 255 tires. I should be placing my order today .

If your speedo is currently accurate, then you may notice a slight change. The dimensions I listed above would account for about a 2.9% speedo change.

[M34lnch]

Originally Posted by Dackelone

Yes, I am very happy with my non-RFT Michelin's. I gave up a tad bit of steering response for a MUCH better ride quality. And the dry and wet grip is way better now than with my OE Dunlap RFT's. What you will notice most is the car doesn't hop & skip around (over bumps) as much as it did with the RFT's. Even going over little dips on a flat road with RFT the car's tires would hop or feel like they would hang up in the air... now the car's suspension feels like it is working more in harmony - togther.

I would not go back to RFT's.

Dackel

I know exactly what you're talking about with the hopping and skipping over bumps... if non-RFTs help get rid of that, I will be thrilled.

However, I do a lot of high speed driving on the freeway and I do not want any loss of confidence that I current enjoy in my 135i with the RFTs. When you drive fast on the freeway do you still feel like you have the precision to manuever around without feeling insecure? I am considering the Michelin PSS 225/40/18 and 255/35/18 on stock suspension and wheels. Can anyone speak to this?

[Dackelone]

Originally Posted by M34lnch

I know exactly what you're talking about with the hopping and skipping over bumps... if non-RFTs help get rid of that, I will be thrilled.

However, I do a lot of high speed driving on the freeway and I do not want any loss of confidence that I current enjoy in my 135i with the RFTs. When you drive fast on the freeway do you still feel like you have the precision to manuever around without feeling insecure? I am considering the Michelin PSS 225/40/18 and 255/35/18 on stock suspension and wheels. Can anyone speak to this?

I think IF you go with the Michelin's... they are top ultra performance tires - and you will be happy with them. I am.

While I do think switching from RFT to non RFT - you do loose a touch of turn-in response... in all other areas you just gain so much in ride comfort, grip, and a lot less of a bumpy/jumpy ride. I am happy with my PS3's. Btw... I have driven to about 180 mph with the PS3's and I feel totally comfortable with them at speed.

[ItsHectic]

After reading this thread I have had second thoughts on getting rid of runflats.
I dont care about bumpiness of the ride, but I dont want to lose steering response.

The reason I was considering non RFTs is because I heard they will improve steering wheel feedback, is this true?

[M34lnch]

JustMe, I think you should get your new ride first and drive it with the run flats. Then you'll have an idea as to what we're talking about in terms of the bumping and hopping around that this car does.