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Hello all! I hope this is the right forum for this question. I'm hoping to get your thought on what could potentially be wrong with my M235i RWD. I acquired this vehicle about a month ago from a relative who passed away. He purchased it brand new in 2016 and only put 17k miles on it. I drove it from Tampa FL to Boston, straight shot. I was thinking to myself how fun of a vehicle it is. I own a 2018 M3 ZCP with 3k miles on it, and I noticed some similarities in the behavior of its little baby cousin the M235i. The day after I get home I walk outside and notice it has a flat time. I check under the car to see if maybe there was a nail or something and I see the insides of both tires were worn down to the metal! First of all i'm super lucky they didn't give out while doing 120mph on my way home, but then I thought that it was also odd for a car with 17k miles, driven by an 80 year old man would need tires. I also found it odd that only the inside edge of the tires were so warn down vs them wearing evenly.
I'm not sure if i'm going to keep the M235i or not. Partially because I live in New England and this not exactly rear wheel drive convertible territory, AND I already own an F80, and 2 F30s. So I picked up 2 cheap tires (nexus or some brand like that). I had them installed and I put the wheels back on the vehicle. I immediately notice that the vehicle feels different. It's hard to describe but it feels like the rear end is swaying side to side when I try and change lanes at highway speeds. Almost like the rear tires are only at 20lbs pressure. I email the company I ordered the tires from and they agreed to take them back. I had to send them a video of me taking an easy on ramp at 40mph and my traction control light flashing at me.
I purchased 2 michelin sport AS3 tires for the rear and while the problem was greatly reduced, I can still feel that swaying/unstable sensation. The vehicle originally came with super sports, and I'm at the point where I don't know if putting super sports on it will solve the issue or if there is something else going on.
It was a clear night and day difference from what it felt like on the 1200 mile trip from Florida to the time I got the new nexus tires installed.
Can this issue be because I'm not using super sport tires? I've read other posts where people have installed sport AS3's and not ever mentioned that the vehicle didn't handle correctly afterwards. I'm really hoping someone here can help me out. I'm ready to purchase the super sports but i'd be basically throwing money away again if that's not what the issue is.
Thanks!
 

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Middle wear is a sign of over-inflation. Misalignment can make the car feel twitchy. Brand new tire don't have all their grip in the first few hundred miles, because of lubricant used to keep them sticking from the mold during the manufacturing process. Tires of a lower load rating will feel "swervy."

Tires are the only thing that connects the car to the road, and isn't a place to save money with a performance car.
 

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Discussion Starter · #4 ·
Middle wear is a sign of over-inflation. Misalignment can make the car feel twitchy. Brand new tire don't have all their grip in the first few hundred miles, because of lubricant used to keep them sticking from the mold during the manufacturing process. Tires of a lower load rating will feel "swervy."

Tires are the only thing that connects the car to the road, and isn't a place to save money with a performance car.
Thanks so much for this! I just went out and checked on the load rating because it's definitely a "swervy" feeling. The fronts (which are still the stock Michelin Super Sports) are 88Y. The rear are the new Sport AS3 and they are 92Y. Could that be the reason i'm getting that swervy feeling when changing lanes? It's also causing the traction control light to come on during on/off ramps with very little acceleration.
 

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It's probably the (lack of) quality of the new tires. The PSS's are a good as it gets. Nexens***8230; not so much. Even mixing old and new good tires can cause problem. I had an M3 that when through three sets of rear tires and two sets of front tire. When I had two tires on one end and old tires on the other end, I had massive oversteer or understeer.
 

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Years ago I had a Porsche 356 that was very sensitive to tire inflation pressures. An inexpensive experiment would be to over-inflate the rear tires by 4 psi above placard values. That decreases over-steer, which may be your swaying feeling. If that works, the explanation is that the front Michelins are stiffer, with what is called a low slip angle. Putting more flexible tires on the rear as you did means that the rear is loose, or swinging wide in the corners. Increased inflation will stiffen the tires. Don't underinflate the front tires--that can lead to excessive heat build-up and blow-outs. If higher pressure in the rear solves the problem, putting matched tires front and back will also solve it--or you may want to save the front tire money and invest in 4 snow tires for our New England winters.
 

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I know this is a late bump - but...

I just bought a 2016 M235i (50k miles) and after reading all the raves about the handling and steering - I feel the same experience when changing lanes at high speed, something I've never felt in any of the BMWs I've ever owned, an e30 325i cab, E34 328i Saloon, a Z3, or the 2020 M4 cabrio comp package I also currently own. At higher speeds, even in a straight line, it feels like the back end wants to follow a different track than the front end, occasionally. It is very composed and really has tighter steering than the M4 at lower speed - but during hard acceleration at higher speeds, lane changes sometimes feel very unstable and even going in a straight line I feel like the rear end shimmies or sways from side to side. Again - it is like the rear of the car is tracking different than the front. It almost feels like trailer sway... a tail wagging the dog sensation - or driving a live rear axle car like an older Mustang.

My E30 would top out at 137 and despite those having a skittish rear end - it felt more planted and confident than the M235i. They're both cabrios and of very similar dimensions so I don't think it is related to body flex. The dealer did swap out two tires according to the carfax during prep (same make and manufacturer, Pirellis).
 
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