[Edslittleworld]

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?

[Outlaw 06]

Originally Posted by Edslittleworld

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?

Yes. I have a 2021 M240i with 6-speed manual and I felt the same unacceptable "yaw" under hard acceleration. I always drive in Sport+ (unless I deactivate DSC), so that's the mode where I noticed it. I asked a racing buddy of mine to test drive the car and he felt it too. I installed the M Performance LSD, and that seems to have solved the issue, but I won't know for sure until I take the winter wheels/tires off and reinstall the high performance summer tires/wheels in the beginning of Spring. At this (mid-Winter) point, I think the winter tires are the cause of any remaining instability in my M240i.

[Moflow]

Originally Posted by Edslittleworld

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?

LSDs are awesome, especially for accelerating out of a corner. I'm sure it would help your squirrely rear end.

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.

[RvR]

Originally Posted by Edslittleworld

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?

The M Performance LSD greatly improved the stability of my car, under hard or even modest acceleration. I expected the former, but the latter surprised me. I could tell the difference driving away from the dealership, at only modest speed. My only regret, I should have done it sooner.

[dradernh]

Originally Posted by Edslittleworld

...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?

I don't have a link, but if you've missed it there was another thread on this subject that appeared here during, I think, the last 6-9 months. It may offer some useful input if you can find it. (Maybe try the Suspension | Chassis | Brakes sub-forum?)

[Outlaw 06]

Originally Posted by Edslittleworld

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?

Please see my new post at https://www.2addicts.com/forums/show...9#post27390409

[freakystyly]

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.

[Michael Avedis]

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

[Pray for Mojo]

The back and forth is the ediff shifting the power between wheels, LSD solves it completely.

[XutvJet]

Originally Posted by Pray for Mojo

The back and forth is the ediff shifting the power between wheels, LSD solves it completely.

^Yep.

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.

[Nickies]

Originally Posted by Outlaw 06

Yes. I have a 2021 M240i with 6-speed manual and I felt the same unacceptable "yaw" under hard acceleration. I always drive in Sport+ (unless I deactivate DSC), so that's the mode where I noticed it. I asked a racing buddy of mine to test drive the car and he felt it too. I installed the M Performance LSD, and that seems to have solved the issue, but I won't know for sure until I take the winter wheels/tires off and reinstall the high performance summer tires/wheels in the beginning of Spring. At this (mid-Winter) point, I think the winter tires are the cause of any remaining instability in my M240i.

I also agree on this as well as other posters. This is the only negative point I have about my M240i RWD. I am a very conservative driver that never push the car hard but we are in the mountains here on the Olympic Peninsula and its better to be careful than sorry.

[GZed]

I recently sold our F23 230i and purchased an F23 M240i. It immediately shocked me how much the rear yaws under heavy acceleration, and the way that the car deals with the yaw is very unpleasant. I'm getting quotes on the M Performance LSD, but in the meantime I checked the rear pressures and they were 40psi cold. I dropped them to 36psi and tested again. It is significantly better with the lower pressures. Its actually now good enough for everyday driving in the dry, but I still think I'll get the LSD installed to maximise rear grip. Especially for low grip situations.

[XutvJet]

Originally Posted by GZed

I recently sold our F23 230i and purchased an F23 M240i. It immediately shocked me how much the rear yaws under heavy acceleration, and the way that the car deals with the yaw is very unpleasant. I'm getting quotes on the M Performance LSD, but in the meantime I checked the rear pressures and they were 40psi cold. I dropped them to 36psi and tested again. It is significantly better with the lower pressures. Its actually now good enough for everyday driving in the dry, but I still think I'll get the LSD installed to maximise rear grip. Especially for low grip situations.

Yeah, the LSD will help immensely. I always felt that the front and rear axles with the M235/M240 were at odds with itself. The LSD, Eibach lowering springs (30% stiffer than stock, 1/2" drop, levels the car), and a set of Bilstein Damptronic shocks fixes much of the rear axle sway and looseness. On the front, getting a 245 width tire up there makes a huge difference. I felt like the only other thing missing from my M235 was F/R sway bars as the sway bars on the car are puny. I never got around to adding them before I sold my M235 and got an M2.

[F22Cam]

I’ve got a rwd stage 2 m235 no suspension mods.

I can attest the lack of rear end stability under heavy acceleration is surprising.

It’s fun to slide around at low speeds, but at high speeds the car does not give the same confidence.

This is one of the things that made me realize I need a true M car next

[XutvJet]

Originally Posted by F22Cam

I’ve got a rwd stage 2 m235 no suspension mods.

I can attest the lack of rear end stability under heavy acceleration is surprising.

It’s fun to slide around at low speeds, but at high speeds the car does not give the same confidence.

This is one of the things that made me realize I need a true M car next

Agreed, my biggest gripe about the M235 was the chassis/suspension dynamics and front tire width. Power was fine with a quality catted downpipe and a basic tune. The chassis wasn't horrible by any means, but it really needed a lot of help and at quite a bit of expense to get it to be fairly decent.

I absolutely love the 1st gen 2 series chassis and N55, so going with an M2 was as easy choice. The suspension and overall dynamics is a huge step forward. Also, the N55 teamed with the DCT is a game changer. This car in stock form feels as fast/quick as my Stage 2 M235 6MT to 110mph. All that extra gearing and no boost loss of shifts makes a big difference. As the years went by, I became pretty convinced that turbo BMWs perform quite a bit better with a well sorted automatic. The 6MTs are fun, but even those require lots of little mods to make them acceptable and I think BMW has little interest in making for a good 6MT driving experience, IMO.

[TrboMike]

Before the expense of an LSD it might be wise to throw it on an alignment rack and make sure your alignment is not off causing some of your problems. Might be even wiser to go to an alignment shop that is autocross/race friendly and tell them your issue and they can dial in the rears to be more stable in squat (hard accel).