BMW M Performance LSD for M235i, 335i, 435i Arrives. Pricing and technical FAQ inside |
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05-09-2014, 11:09 AM | #67 | |
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A well spec'd LSD should give you greater traction under acceleration, which helps getting out of corners. It should not impact turn-in on corner entry. What's important to note about lockup is that more lockup means the car wants to go straight. Not sure if you have any friends with an ATV, but they're a great way to understand the steering impact of a locked up rear axle. Turning an ATV at low speed is very hard. Especially if they're 2WD. A locked rear axle means the traction of the rear tires keeps the car going straight. That results in low speed understeer. Fortunately, LSD technology allows us greater flexibility. In this case, 30% under acceleration, and 9% under deceleration. This makes sense when you think about it. You're normally decelerating in to a corner, which is when you want the car to rotate easily based on steering input. The lower resistance helps keep the car rotating easily. When you get on the gas, the LSD goes to 30% lockup, and you get maximum traction on exit. You can dial in additional oversteer by applying more throttle. I really do recommend trying to get a ride on an ATV. Try turning it at low speed. For great fun, try pushing the ATV while it's off, then have someone turn the wheel. You'll get a real appreciation for why we don't all drive around on a spool (welded diff). It helps to have a working understanding of how a differential works too. This video is really old, but I think it's one of the best illustrations of how they work. You should check it out.
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05-09-2014, 11:54 AM | #68 | |
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05-09-2014, 01:19 PM | #69 |
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$3k MSRP for a full bolt in diff installed in a new pumpkin is not that bad. Price out a quality quiafe or OS rear diff, gear install and removal/install and you are not far off. For what you get in a full bolt in/ swap in assembly its a decent value.
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05-09-2014, 01:20 PM | #70 |
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Price is ok, but somewhat disappointing that it's not a factory option install (yet).
A Cadillac ATS has a mechanical diff right from factory. |
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05-09-2014, 02:20 PM | #71 | |
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Some diffs require you transfer the ring gear (and sometimes more) from the old diff to the new. Those bolts have to be properly torqued and the appropriate thread lock applied. If the tech who does the work doesn't do a good job cleaning up and re-applying the thread lock, you can end up with loose hardware in your rear-end in a surprisingly short period. That's, uh... not good for long term operation It's not rocket science. Any competent shop can do the job, and you should never have a problem. It's surprising how difficult it is to assess competency though. It's worth a little extra coin, IMO, to get a factory assembled unit with a warranty. Then again, I'm sure someone will be along shortly to point out some place where I can get a fully assembled, warrantied diff for $1,000 less. That's the aftermarket for you
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05-09-2014, 03:52 PM | #72 |
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As someone said above, this is actually a really good price concidering it's a factory BMW product. If I understand correctly, this diff comes as a whole (pumpkin, LSD unit, Ring & Pinion, etc) all in one. So it's just a straight swap. Not bad at all. Most LSD's will cost north of $4000 to do properly (a good one that is).
30% is fine for the street.
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05-09-2014, 04:19 PM | #73 | ||
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So if a drifter (or wannabe drifter) can drift easier by apply the right amount of throttle to create oversteer and control it with countersteer...am I right??
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05-09-2014, 04:51 PM | #74 | |
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http://image.4wdandsportutility.com/...easurement.jpg Drifters usually run spools, which introduces another effect that actually makes the rear end very loose. As you increase the amount of lock, you can also end up with something called scrub. People call it different things, but scrub is when your tires skid during turns because the amount of differential resistance exceeds tire grip. This only happens with certain types of LSDs though, and you don't usually see them in use on street cars (more often off-road). The one from BMW isn't going to scrub at all. In a race car, you really don't want scrub, because it reduces rear-end grip in tight corners. A tire loses grip very quickly once it starts to skid, so the scrub that occurs with a spool will actually cause the rear end to be more lose than if you had an open diff. Drifters love this side effect though, because it makes it easier to get the rear to step out. The other place you see spools and unsophisticated LSDs that scrub are in off-road vehicles. My dad has an old beater Suzuki Samurai with a spooled rear end. It's a beater truck for out at the ranch (in Central Florida). It is amazing how much more you can drive through (mud, sand, etc) with a spooled rear end, but when it comes to turning around, it's a nightmare. The front tires just want to slide. When you're driving on dirt roads, you have to be careful too, because it will snap oversteer on you at medium speeds. Sure is fun though
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05-09-2014, 06:01 PM | #75 | |
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05-09-2014, 08:04 PM | #76 | ||
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05-10-2014, 11:33 AM | #77 |
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That's some serious money, how many tenths of a second does it shave on those 5 track days per year?
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05-11-2014, 06:46 AM | #78 |
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The other option to consider is simply having www.diffsonline.com build you a customer LSD for the specific use you have planned. You can choose something like a 3-disc setup with ramp angles to give you the aggressiveness or lack thereof on acceleration and deceleration. You could also choose to go with a wavetrac, quaife, os giken LSD designs if desired. Don't underestimate the resale value of the diff when you're done with it also. If it's in good shape in 2-3 years, you can probably get about 60-70% of your money back selling it while in the meantime enjoying exactly what you'd like to have.
disclaimer: I have no connection with diffsonline other than selling them an E39 M5 diff years ago (my M5 LSD discs gave it up by 50k miles, so I bought a new one from BMW which I got an incredible discount on at the time) where I found Dan excellent to do business with, so I'd use them again in the future. To answer that question about the E9x M3 and E6x M5/6 LSDs -- those are viscous action LSDs with lockup varying from 0-100% based on load and slip. On corner entry (deceleration) they are open, 0%, so no corner entry to apex pushing. The "issue" some have with these is that they require slip to have started to begin to function, but I will say that it works right away and is very progressive with load (power). My jury is still out on my overall opinion of it, but I think you'll find no racer would care for the design -- they would much prefer an "old" Salisbury LSD with proper ramp angles for load/unload they want and the static lock they desire in order to give a more predictive and functional solution on track. I can say that comparing the E90 M3 LSD and the one in my E39 M5 (which btw is stock, 25% Salisbury LSD from BMW like the one being discussed in this thread), is that for serious driving on R-comps, the M5 diff is too weak. It needs much more locking on acceleration as the torque of the S62 can still spin the inside tire too much on corner exit on something like NT-01s or Hoosier A6s (hence the reason I wore out the discs in my unit by the time I had 50k miles on the car ). When I back-to-back these cars, I can tell right away how the M5 diff is allowing too much inside tire slip when powering out of a 2nd gear corner for example. The M3 feels more connected and can really put the power down on corner exit. Regards, Chuck
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05-11-2014, 03:32 PM | #79 | |
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Great info in your post
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05-11-2014, 09:06 PM | #80 | |
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Cheers, Chuck
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05-15-2014, 12:16 PM | #81 | |
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05-22-2014, 10:07 AM | #82 |
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Surprised they now went for a "1.5" way diff instead of a "2" way like the old units were (same ramp angle on accell and decel). Those these were 25% lock.
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05-24-2014, 04:41 AM | #83 |
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Jason,
Hi. I didn't see the F36 listed. At first I hoped it was because the F36 wasn't on sale yet...but that might be wishful thinking? Does the M Performance LSD not fit in the F36? And if not, will there be a version in the future? Thanks! |
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08-31-2015, 11:51 AM | #86 |
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I'm looking for the same information. BMW's site lists it as xDrive compatible but the local dealership told me it is not.
Calling BMW customer relations just referred me to the dealer. Is there a definite source? People on this site seem very knowledgeable so my apologies if this may seem obvious... |
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08-31-2015, 01:40 PM | #87 | |
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