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I first noticed unpredictable handling on my Z4 around 3,500 miles. The problem was worse in town on streets that have bumps, seams and/or potholes. On smooth open roads at higher speeds the Z4 handles OK. But on rough city streets I need to maintain a vise-grip on the wheel so I don't hit the curb or another vehicle.

The dealer has had the car on the lift 5 times in 18 months, each time tweaking the alignment. After each visit, the steering felt a little better but in days it went back to it's old ways. The service techs maintained this sensitivity was normal, something I need to get used to. But I don't buy it. So for the past couple of months I got opinions from an independent garage, another BMW dealer plus a Firestone tire shop. All said the cause was probably the rigidity of the Run-Flat tires. The other BMW dealer even switched tires so we could test their theory. They were right--new tires made for much smoother, more effortless handling.

My Z4's "Tramlining"is more troublesome than steering that's simply "Twitchy" or "Sensitive". Numerous Z4 owners say they are plagued by Tramlining and have been as far back as 2005. From their comments, it's evident that BMW has known about this problem too. Why my dealer never mentioned tires as the possible culprit is a mystery.

I'm going to replace all 4 tires so I can enjoy driving again. It's either that or sell the car--and with Spring coming I'm not sure I want to do that!

So I need help: Should I replace the Run-Flats with non-Run-Flat tires? But if I do, don't I risk getting stuck if I get a flat out in the boonies? Or are there Run-Flats with less sidewall rigidity and a smoother ride than my current 225/45-R17 Bridgestone Potenzas?

I'm not looking for ultra-high performance from my tires--I don't take corners at 70 mph!!! I just want a safe, smooth ride with some level of performance so I can enjoy the car's capabilities. Does anyone have some good recommendations??? Help!
Generally speaking, the higher the performance level and dry grip of a tire, the more likely it is to tramline. Since you aren't looking for ultra high performance tires anyway, you can certainly get tires that should help reduce tramlining quite a bit. I would agree with rmorin49's recommendation of the Avid Envigor, along with the Dunlop SP Sport Signature as smoother, quieter riding tires with longer wear and reduced tramlining.

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