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M240i with harsh ride -- would changing tires help?

Discussion in 'BMW' started by DMdoc, Sep 23, 2017.

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    DMdoc

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    I bought a 2017 M240i convertible with about 4000 miles (it had been a dealer loaner car before I bought it). The ride is harsh. The dealer's head service guy says it's normal; they checked tire pressures, and no shipping block problem. Present tires are runflat Pirelli Cinturato P7 225/40 R18. Would switching to non-runflats and/or another size improve the ride? Any drawbacks except $ and lack of a spare tire?
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    steven s

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    Low profile 18" tires, stiff suspension. I guess you might feel like it's a harsh ride.
    I would also say it's normal.

    Perhaps tires with not as low of a profile may help. That and replacing your springs with something softer.
    Then it's no longer an M240i
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    MGarrison

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    Normal tires should help a bit. Even better would be downsized wheels and normal tires with a higher aspect ratio (more sidewall). Otherwise, different shocks, although I wouldn't know if the non-M-pkg. 2'er 'vert shocks would be the same fit or appropriately tuned/valved. A oe shock swap would get into comparing curb weights between models, although spring height might also be an issue - you wouldn't want stock shocks being destroyed by bottoming out on sport springs, for instance. If, say, a 230 'vert weighs the same as yours, or reasonably close, then the 230 shocks might be just fine as far as valving/tuning, at least - bottoming is another issue . If you have adaptive suspension, that might make such a swap impractical or harder to figure out if it would work, although presumably if yours had that, a softer suspension setting might be working better for you. See if Koni has FSD shocks for your car, that might be a route to consider.

    If you were to go the smaller dia. wheel route, consider a square setup running the same size rims & tires all 4 corners. A plus of a square setup is you can rotate the tires front to rear, which helps even out the wear. Usually on BMW's the neg. camber in the rear wears out the inside edge of the rear tires, but the fronts usually are zero camber, so the wear is more even across the tread. Being able to swap tires around, you can even out those wear factors. Otherwise, all you can do is have the tires flipped on the rims, but that's only good if the tread design is symmetric.

    I have Apex wheels on my E92, no complaints - I think you'd have to call them to discuss the best fitment for your car & preferences. Tire rack shows a lot of rims but it's kind of hard to search outside-the-box, as it were. Selecting the staggered setup, TR shows 19x9 wheels for the rear with an offset ranging 44-48mm, but to see if there were 17x9's in the right offset range and bolt pattern, you have to look at the wheel specs individually, and you still can't see if the hub bore dia. is right for the car. But, the rears aren't the whole picture, if you wanted to run as square setup, the offset range has to be within what will work on the front. Point being, a conversation with TR might be needed to see what they can tell you. Apex has a lot of BMW-specific fitment experience, however. I'm running 17x8.5 Arc 8's w/ 255/40's on my E92, but 2er, different car so different fit. Always best to get the lightest wheels possible - however, the lighter they get, the more expensive they get. I shoot for the lightest weight that's reasonably priced, from sellers I trust to be selling a quality wheel.

    You might prefer the performance of the extra-sticky but also-short-lived high perf. summer range of tires, but if you need minor winter capability &/or are willing to trade off some of that grip & stopping distance for tire life, then maybe the max perf. all-season route - non-rft: if 255/40-17, couple choices there, Conti DWS-06 or Michelin Pilot Sport A/S 3+; same for 245/40-17; you get a little more sidewall with the 255. With BMW speedo usually showing about 5mph faster than actual speed, I'm rarely concerned about exact duplication of stock rolling diameter, since the speedo's not dead-on actual speed anyway.

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