02-27-2021, 05:08 AM | #1 |
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M240i unstable under hard acceleration?
Two years ago, I bought a barely used CPO 2017 M240i with the 6-spd manual. It was (and still is in) in perfect condition. It has 17K miles on it. It drives well and tracks straight with good tires and the correct pressure. However, full straight-line acceleration seems to lighten up the rear end and it feels a bit unstable or "squirrely". I don't detect any wheel slippage either thru feel, sound or indicator lights. I partly blame this on the lack of a rear limited slip diff (LSD). Since I really like the car, I'm thinking of installing the M-diff for $3K. Would that help with the instability?
Last edited by Edslittleworld; 02-27-2021 at 05:41 AM.. |
02-27-2021, 06:30 AM | #2 | |
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Edslittleworld33.00 |
02-27-2021, 04:36 PM | #3 | |
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That said, the M240i is a pretty powerful car sending all that power through just the rear wheels, and it doesn't have the widest tires ever. You're probably still going to be near the limits of traction when you floor it in the lower gears. But it should be a lot more predictable and easy to control with an LSD. Without the LSD, the car is controlling the rear end by using the rear brakes one side or the other (whichever side begins to spin) which might contribute to the rear end wiggle, even though its keeping you from doing a big one wheel burnout. |
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bobkat09151.50 |
02-27-2021, 05:25 PM | #4 | |
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Yes, it would help significantly
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Edslittleworld33.00 |
02-27-2021, 06:16 PM | #5 | |
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2017 M240i: 23.8K, 28.9 mpg, MT, Sunroof Delete, 3,432#, EB, Leather, Driving Assistance Package, Heated Front Seats | Sold: E12 530i, E24 M635CSi, E39 520i, E30 325is, E36 M3 (2)
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Edslittleworld33.00 bobkat09151.50 |
03-25-2021, 08:26 AM | #6 | |
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03-25-2021, 09:12 AM | #7 |
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Agreed on squirrelyness and LSD is on the shopping list for the future. I've recently come from an N52 and I thought even that engine could benefit from an LSD, it's crazy to think these high torque turbo engines don't even get one.
Stickier tires / width of rubber would be a band aid, if you plan on replacing them anyways but the root of the problem is still there with a 1 tire fire. |
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03-25-2021, 09:19 AM | #8 |
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unstable rear
I have a 228 manual and experience a similar rear stability issue, but I am sure not to the extent of what you are experiencing .
My feeling is that it is the soft rear subframe bushings. Inserts would/ could solve this. I had a 335i convertible, with the added weight and power the rear would feel loose, installing the inserts solved the issue in that car. Much more planted. when I change springs I will be installing these on my car. have fun |
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03-25-2021, 01:35 PM | #10 | |
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Adding an LSD to these cars totally transforms them. The increase in rear axle traction and stability is immense. Run a 245/35R18 square summer tire setup and you massively increase front end grip as well. BMW spec-ing 225 width tires in the front really hampers them, kills tire shoulders as well.
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03-27-2021, 10:52 PM | #11 | |
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2019 M240i, Melbourne Red, Black Interior. 3M Tint, Premium Package, Harman Kardon, Adaptive LED Head Lights, M Performance Exhaust and Diffuser, Chrome Exhaust Tips, 719M Bi Color Wheels, Black Kidney Grille, Burger Tuning JB+.
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