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2Addicts | BMW 2-Series forum Technical Topics B58 (M240i) Engine, Transmission, Exhaust, Tuning My experience with BMW’s M Performance Limited Slip Differential (LSD).

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      03-25-2021, 08:23 AM   #1
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My experience with BMW’s M Performance Limited Slip Differential (LSD).

Please note that my 2021 F22 M240i is equipped with a manual gearbox (and rear wheel drive). Additionally, the first thing I do after starting my M240i is toggle the Driving Dynamic Control switch to “Sport +” mode, so the intrusiveness of the car’s electronic nannies may vary if you’re routinely driving in different modes.

In January 2021, I had my local BMW dealer install an M Performance LSD in my M240i to replace the abysmal stock open diff in the car. During the winter, I drove my car on a square set-up of 17” Pirelli Winter Sottozero tires. The LSD provided an immediate and noticeable improvement in the performance of the car on the softer snow tires.

With the coming of spring, I put the stock, staggered, 18” Michelin Pilot Super Sport max performance summer tires back on the car. As expected, the LSD has also greatly improved the power delivery to the rear wheels on the stickier summer tires in wet and dry conditions. The car’s handling and traction with the LSD are now predictable and far superior to the way it was with the stock open diff. It’s literally a night and day difference during both acceleration and throttle lifts or braking (decelerating) for turn-in. The adverse yaw that was induced by the car’s stock open diff under hard acceleration has also been eliminated by the LSD. The car’s electronic nannies are also significantly less intrusive with the LSD (specifically, the computer-induced engine power reduction and intermittent braking action on the slipping wheels with the old open diff).

Regarding clutch-type verses helical-type LSDs. I have clutch-type, LSDs in my E46 M3, my Porsche 718 Spyder and my M240i now too. I have helical LSDs in my Honda Civic SI and my NB Spec Miata race car. I’m used to driving cars with LSDs, so I might have a better “feel” for the shortcomings of cars without LSDs compared to people who only drive open diff cars.

When both drive wheels are on the ground, I can’t perceive any difference between helical and clutch-type LSDs. However, whenever I find myself in a situation where one of the drive wheels momentarily lifts off the ground (perhaps when taking too much curbing on a track), the helical LSD’s power delivery/traction is less predictable and inferior to a clutch-type LSD. That’s the only (slight) performance “con” of helical LSDs in my experience. I’m mentioning this subtle performance difference just in case you’re considering installing a helical vs. clutch-type LSD for occasional track duty. Both types of LSDs provide impressive performance though.

There are a lot of posts about horsepower mods on this forum, and I understand that engine tunes are cheap, but it’s my experience that the stock open differential (lack of traction) is limiting the M240i’s overall performance the most, not the stock engine. Simply put, the stock open diff in these cars can’t adequately handle a stock B58’s rated horsepower and torque, so more horsepower alone won’t improve the car’s overall performance (and more horsepower will probably degrade the traction proportionally in cars equipped with the stock open diff).

Even though BMW hasn’t offered LSDs as factory options in non-M cars for over 25 years, it’s still very disappointing to me that performance cars like the M240i are only equipped with open diffs from the factory. It’s quite unsatisfactory that BMW only provides open diffs in “ultimate driving machines” like the M240i, especially when considering the fact that Honda offers enthusiasts helical LSDs as standard equipment on the $25k Honda Civic SI, while BMW doesn’t even offer an LSD as an option on a $50k M240i…

IMO, a LSD is a “must have” option in order to put down a B58’s significant power to the rear wheels properly and improve the M240i’s overall performance.

Fortunately for enthusiasts, there are several brands and types of LSD’s available to replace the M240i’s stock open diff (I HIGHLY recommend replacing the stock open diff with a LSD as soon as possible after you buy the car).

If you haven’t installed a LSD in your M240i yet, then you should seriously consider doing so, because it will transform your car’s performance.
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      03-25-2021, 08:53 AM   #2
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I have seriously been debating on getting one of these installed on my 2021 M240x. Are the RWD versions pushy/understeer-y as well? If so, did you notice a difference on how hard the car pushes around corners? You mention a noticeable difference in throttle lift (lift off oversteer?) so just curious for your thoughts.

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      03-25-2021, 09:32 AM   #3
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Quote:
Originally Posted by randmness View Post
I have seriously been debating on getting one of these installed on my 2021 M240x. Are the RWD versions pushy/understeer-y as well? If so, did you know a difference on hard the car pushes around corners? You mention a noticeable difference in throttle lift (lift off oversteer?) so just curious for your thoughts.
The M Performance LSD's (9%) lockup on deceleration noticeably helps my rear-wheel-drive M240i turn-in better upon throttle lift and trail braking, even at public road speeds. There's such a noticeable "seat of the pants" improvement in handling, that I don't think I'll need to mess around with the car's front suspension at this point (I've been considering installing front camber plates and a front sway bar to reduce understeer).
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      03-25-2021, 02:54 PM   #4
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An LSD and front camber adjustment were at the top of the list before I bought my car. If they hadn't been available, I would have purchased a different car.
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      03-25-2021, 04:25 PM   #5
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Its bonkers to me that the standard 2-series doesn't come with an LSD.

Any performance car with more than about 200 hp, that weighs 3000+ lbs should have an LSD IMHO. I get it, its a hard thing to explain to consumers and make them care about, but it really takes just one drive at 8/10ths or so to see just how beneficial they are.

My shitty lemons car with 105 hp has an open diff and even with that tiny ass power level and even though it's rear-wheel drive on extremely sticky track rubber, it spins its inside right rear tire in third gear when exiting corners. Super annoying.
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      03-25-2021, 05:25 PM   #6
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Quote:
Originally Posted by Outlaw 06 View Post
(I've been considering installing front camber plates and a front sway bar to reduce understeer).
I know it's a different platform but I messed with my front end with the E90 and noticed the biggest difference was width of tires. M3 arms helped turn in a bit but sway bar introduced under steer but it may have been oversized by a bit, do that last IMO.

This platform ... I'm still a noob.
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      03-25-2021, 06:35 PM   #7
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I couldn't agree more with your assessment.
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      03-27-2021, 07:26 AM   #8
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Quote:
Originally Posted by Moflow View Post
Its bonkers to me that the standard 2-series doesn't come with an LSD.

Any performance car with more than about 200 hp, that weighs 3000+ lbs should have an LSD IMHO. I get it, its a hard thing to explain to consumers and make them care about, but it really takes just one drive at 8/10ths or so to see just how beneficial they are.

My shitty lemons car with 105 hp has an open diff and even with that tiny ass power level and even though it's rear-wheel drive on extremely sticky track rubber, it spins its inside right rear tire in third gear when exiting corners. Super annoying.
Agreed. "Positraction" LSDs have been around in various forms for over 60 years, and it astounds me that BMW doesn't even offer it as a factory option these days in it's M Sport cars with engines producing well over 300 hp and 300 lb-ft of torque. It just indicates that BMW isn't really serious about the performance of these cars. ESPECIALLY when considering that Honda puts helical LSDs as standard equipment in $25k Civic SIs (as I previously mentioned).
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      04-03-2021, 04:17 PM   #9
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Quote:
Originally Posted by Outlaw 06 View Post
Agreed. "Positraction" LSDs have been around in various forms for over 60 years, and it astounds me that BMW doesn't even offer it as a factory option these days in it's M Sport cars with engines producing well over 300 hp and 300 lb-ft of torque. It just indicates that BMW isn't really serious about the performance of these cars. ESPECIALLY when considering that Honda puts helical LSDs as standard equipment in $25k Civic SIs (as I previously mentioned).
And, even Cadillac spec'd it as standard equipment on the "V-lite" ATS coupe I cross shopped when I bought my M240i in December 2016.
It is ridiculous that it is not even available as a factory option on the "M-lite" cars when BMW already has a part number for it.
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      04-10-2021, 06:53 PM   #10
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If the military discount was for your service. Thanks you. Thanks also for the knowledgeable write up.
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      04-10-2021, 07:44 PM   #11
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Quote:
Originally Posted by Moflow View Post
Its bonkers to me that the standard 2-series doesn't come with an LSD.
Why would BMW do that?

It would just cost the company more money, they couldn't charge more for the base car simply because it includes an LSD, and the average buyer won't notice the difference.

BMW is doing what it does best: sell cars buyers want at prices they're willing to pay. LSDs are irrelevant to that calculation unless the cars are M-cars, which ours are not.
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      04-10-2021, 07:53 PM   #12
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Quote:
Originally Posted by dradernh View Post
Why would BMW do that?

It would just cost the company more money, they couldn't charge more for the base car simply because it includes an LSD, and the average buyer won't notice the difference.

BMW is doing what it does best: sell cars buyers want at prices they're willing to pay. LSDs are irrelevant to that calculation unless the cars are M-cars, which ours are not.
You're right, they can get away with it, therefore they will do it. Especially with how good brake activated fake LSD's are these days.

So let me revise my statement: It's bonkers to me that the average entry level luxury car buyer doesn't demand an LSD on a relatively powerful, rear-wheel drive, sporty car such as the 230i/240i.
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      04-11-2021, 11:31 AM   #13
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The LSD ( helical in my case ) was the first performance mod I did to my car. I can't imagine driving the car without it and I can understand why BMW dropped the "ultimate driving machine" motto, they are only focused on profits now.

Thankfully we can fix this shortcoming and make this cars what they were supposed to be in the first place.
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      04-11-2021, 05:59 PM   #14
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Quote:
Originally Posted by Moflow View Post
You're right, they can get away with it, therefore they will do it. Especially with how good brake activated fake LSD's are these days.

So let me revise my statement: It's bonkers to me that the average entry level luxury car buyer doesn't demand an LSD on a relatively powerful, rear-wheel drive, sporty car such as the 230i/240i.
That's just it, though, isn't it: the average entry-level luxury car lessee has never heard of an LSD, but they do know that AWD and all-season tires are standard today and so they must be good.

BMW makes M-cars for enthusiasts who want a car that comes with an LSD already installed. If we don't want or don't want to pay for one of those cars, then BMW offers the few RWD owners their M Performance LSD for a competitive sum when compared to the aftermarket alternatives. Buying a BMW with no LSD gave me a choice of diff types that I was happy to take advantage of.
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      04-11-2021, 08:12 PM   #15
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Quote:
Originally Posted by dradernh View Post
Buying a BMW with no LSD gave me a choice of diff types that I was happy to take advantage of.
What are your thoughts on the value of putting an LSD in my new to me ‘16 m235i rwd manual with 28.5k mi...? It’s a big investment in a 5 year old car but it seems tempting from what I’m reading. I won’t be tracking the car but I imagine I’ll drive it in a more “sporting” manner than my wife when she takes it out.
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      04-12-2021, 10:11 AM   #16
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Quote:
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What are your thoughts on the value of putting an LSD in my new to me ‘16 m235i rwd manual with 28.5k mi...? It’s a big investment in a 5 year old car but it seems tempting from what I’m reading. I won’t be tracking the car but I imagine I’ll drive it in a more “sporting” manner than my wife when she takes it out.
If you like accelerating out of corners in a spirited manner, you'll be able to take advantage of an LSD. There are certainly plenty of roads in So. NH where having an LSD would make the car noticeably more fun to drive (more so West of the Everett Turnpike & I-93, maybe?). Having one would also make winter driving a more enjoyable experience.

I don't think it would add much to the value of your car when you sell it unless it was going to an enthusiast. You might do better keeping the old diff and re-installing it before selling the car; then you'd have an LSD to sell to another 2 Series owner. That was going to be too much trouble for me, but the Boston region has a lot of BMW enthusiasts and track rats, so it's entirely possible that someone local would buy it from you.
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      04-13-2021, 02:49 PM   #17
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Good points. I don’t plan to sell the car anytime soon so I’m not concerned with resale. Are you comfortable with the idea of having an LSD installed at a good independent shop or is that the type of job you’d stick with the dealer for?
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      04-13-2021, 05:43 PM   #18
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An indy is fine, it's not a complicated job.
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      04-13-2021, 06:49 PM   #19
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Quote:
Originally Posted by 60_Driver View Post
Good points. I don’t plan to sell the car anytime soon so I’m not concerned with resale. Are you comfortable with the idea of having an LSD installed at a good independent shop or is that the type of job you’d stick with the dealer for?
Any decent shop can do it. I'd look for one that specializes in BMWs.

If you haven't id'd one yet, I highly recommend Mike Morris' shop in Newbury, Mass: https://schnellerbmw.com/. VSR in Bedford, NH is another I've used that can do the job: http://www.vsr1.com/.

I suggest installing Turner Motorsport's rear subframe bushings at the same time; they'll enable you to get more out of the diff: https://www.turnermotorsport.com/p-3...ame-mount-kit/. Although Turner says there's "a minimal increase" in NVH, I haven't noticed it in my car. That may just be me, though.

If you end up getting a diff, be sure and let us know what you think of it!
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      04-13-2021, 08:33 PM   #20
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Good stuff, tyvm!

A friends husband runs a high end Indy shop. He recommended 3D Autoworks in Hudson, NH: https://3dautoworks.com their reviews look pretty good.
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      04-14-2021, 04:47 PM   #21
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Quote:
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Good stuff, tyvm!

A friends husband runs a high end Indy shop. He recommended 3D Autoworks in Hudson, NH: https://3dautoworks.com their reviews look pretty good.
You won't go wrong at 3D. Like Schneller & VSR, they're members of the independent BMW shop organization BIMRS.org: https://www.bimrs.org/.

3D's only a couple of miles east on 111 from Granite State Dyno & Tune, an excellent shop if you ever decide you'd like to know how much power you're putting down.
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Last edited by dradernh; 04-14-2021 at 04:57 PM..
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      05-09-2021, 03:21 AM   #22
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I want to add to my m240xi. Anyone provide part number for 2017 automatic xDrive? Seattle dealer told me they don’t work on xDrive and won’t install so any shop recos in WA would help too.
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