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      05-03-2015, 09:48 PM   #1
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Differential Review

My track weekend is over and I have been able to (at least a little) assess the difference that an LSD makes in an M235i on the track compared to stock.

In a word -- huge.

(Just a reminder, the differential is custom with 35/60 ramps, about 90(ish) pounds of preload, and a 3.46 ratio.)

It's honestly like driving a different car, for the better. Every corner is confidence inspiring (unless you blow the turn). You're never really afraid of losing your tail. It's very hard to upset the car with the differential in. In some limited circumstances (when you blow a turn and try to correct), you feel the back step out a little, but it is so progressive and predictable that it feels like the chassis is feeding the movement into your brain telepathically. You just kind of go "oh . . . . back's going out . . . okay, fixed" and you're good to go.

I've never driven an "M" car, but I suspect that this is what some people refer to when they mean that the car feels more "connected" to the road. At all times this weekend I felt 1. stable and 2. confident. It's really pretty amazing.

Comparing this weekend to the previous dozen or so days I've had on track with an open differential, I understand what all the fuss is about (at least for track applications). It's just a totally different experience.

As far as handling characteristics, I cant really tell if my car is tight or loose right now. Sometimes it feels tight, but I keep turning the wheel and the car keeps turning in, so I'm not plowing in too hard. On the other hand, I've had a few minor situations when my tail got loose, but they were extremely controllable and not frightening. I suppose my car is just about neutral? I think I need some more seat time to figure it out.

As far as the street . . . I'm not convinced it's worth the several thousand dollar (at least 2.5k for the M Performance diff) premium. Yeah, you do feel it, but if you're driving like a sane human being, it's kind of rare. I suppose it makes you feel more like this is a true performance car with the limited slip carrier, but you honestly don't need it. It's just nice to have. On the track however, if you plan to do it often, this is a very important upgrade.

Also, the shortened ratio (3.46) is pretty cool. That extra torque is crazy -- very useful and fun on both the track and the street. I think it fits the car's personality a little better than the 3.08 (revs faster), but I can understand why BMW went with the 3.08 (fuel econ and all). It's really a personal preference thing, but holy shit does this car launch now.

I'll post the video after I am done editing. I was running in the low 2:20's pretty consistently driving at about 7/10ths (around 2:22). I'd never been to this track before, so it was a learning weekend. Tons of fun though, especially turn 13 -- heavily banked, so you can pull some serious g's going through it. Would recommend going to this track (if you're West Coast).

EDIT: No video this time. Camera is shaking too much (for some odd reason) and the audio is terrible (tried a different setup this time -- too much wind noise).

Last edited by Liquidpaper; 05-04-2015 at 05:31 PM.. Reason: Video sucks.
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      05-03-2015, 10:39 PM   #2
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What tires are you using pre/post LSD upgrade? Just curious if you've used some good high performance tires (not PSS) prior to the upgrade. I'd love to bite the bullet on it, but until it becomes legal for F-Street class in autox I sadly will remain in the open diff world.
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      05-03-2015, 10:40 PM   #3
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Sounds like a heck of a good time, glad I got the LSD as well Now for a proper track weekend, harder to find up here though.
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      05-03-2015, 10:40 PM   #4
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Using Direzza IIs pre and post.
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      05-03-2015, 10:45 PM   #5
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Using Direzza IIs pre and post.
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      05-03-2015, 11:49 PM   #6
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How did you the custom diff? Directly from factory?
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      05-04-2015, 12:09 AM   #7
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I believe it's custom from DiffsOnline (http://diffsonline.com/). I could be incorrect, but that's what I'm remembering.


What track were you at?
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      05-04-2015, 12:29 PM   #8
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Originally Posted by dharo1 View Post
How did you the custom diff? Directly from factory?
I did get the diff from Diffsonline.com

Quote:
Originally Posted by inktomi View Post
I believe it's custom from DiffsOnline (http://diffsonline.com/). I could be incorrect, but that's what I'm remembering.


What track were you at?
I was at Chuckwalla Valley Raceway in sunny Desert Center, California.
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      05-04-2015, 01:38 PM   #9
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Quote:
Originally Posted by Liquidpaper
Quote:
Originally Posted by dharo1 View Post
How did you the custom diff? Directly from factory?
I did get the diff from Diffsonline.com

Quote:
Originally Posted by inktomi View Post
I believe it's custom from DiffsOnline (http://diffsonline.com/). I could be incorrect, but that's what I'm remembering.


What track were you at?
I was at Chuckwalla Valley Raceway in sunny Desert Center, California.
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      10-17-2016, 05:24 PM   #10
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Liquidpaper curious how the diff did on subsequent track days and if you would have done anything different if you did it again? Considering getting a similar setup for my e92 m3. Also, this car is still my DD so any thoughts with that in mind?
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      10-17-2016, 05:34 PM   #11
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Originally Posted by ///Mobbin View Post
Liquidpaper curious how the diff did on subsequent track days and if you would have done anything different if you did it again? Considering getting a similar setup for my e92 m3. Also, this car is still my DD so any thoughts with that in mind?
Diff has been working great. Amazingly it makes little to no noise on the street. I attribute that to either 1. the high build quality, 2. the sound deadening in the 2 series or 3. both.

Looking back, my only regret is that I think it was a bit overkill to do the custom ramp/clutch carrier. I think for a more experienced driver it would have been great, but for me, all I needed was some limited slip capability -- the one I got was overkill. I could have gone with the wavetrac core (or quaife for that matter) and have been fine and saved some money (like $1,200).

That being said, I do not regret my decision, but I think I could have been smarter about where my money went. I would definitely do it again (but maybe with a torsen core rather than the custom clutch job).

Dan does a great job with these differentials and are totally appropriate for street driving. Only recommendation is just stay current with your oil changes -- I get my diff oil changed with the recommended redline oil every third engine oil change (I do my engine oil changes about every 5,000 miles, so the diff is every 15,000 miles).

I will say that after a year and a half of having the differential, it was the most transformative modification -- I think it was what the m235i was "missing" in my opinion (additional camber to the front tires not withstanding).
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      10-17-2016, 09:31 PM   #12
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Quote:
Originally Posted by Liquidpaper View Post
Diff has been working great. Amazingly it makes little to no noise on the street. I attribute that to either 1. the high build quality, 2. the sound deadening in the 2 series or 3. both.

Looking back, my only regret is that I think it was a bit overkill to do the custom ramp/clutch carrier. I think for a more experienced driver it would have been great, but for me, all I needed was some limited slip capability -- the one I got was overkill. I could have gone with the wavetrac core (or quaife for that matter) and have been fine and saved some money (like $1,200).

That being said, I do not regret my decision, but I think I could have been smarter about where my money went. I would definitely do it again (but maybe with a torsen core rather than the custom clutch job).

Dan does a great job with these differentials and are totally appropriate for street driving. Only recommendation is just stay current with your oil changes -- I get my diff oil changed with the recommended redline oil every third engine oil change (I do my engine oil changes about every 5,000 miles, so the diff is every 15,000 miles).

I will say that after a year and a half of having the differential, it was the most transformative modification -- I think it was what the m235i was "missing" in my opinion (additional camber to the front tires not withstanding).
Appreciate your thoughts and advice, thank you! I've also considered a TBD like the Quaife or Wavetrac, which both have great reviews but since I already have the factory M VLSD I'm afraid it may not be enough of an upgrade for me. I do about 8-10 track days per year now and consider myself intermediate+, you think I might be a good candidate for a clutch pack unit or should I study/consider the Wavetrac further first? One thing I've read about the clutch pack units is that they also provide increased stability when braking, which I would appreciate, not sure if the TBD's do that. These units are pricey, no doubt so sage advice either way and thanks again for sharing!
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      10-19-2016, 05:55 PM   #13
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Quote:
Originally Posted by ///Mobbin View Post
Appreciate your thoughts and advice, thank you! I've also considered a TBD like the Quaife or Wavetrac, which both have great reviews but since I already have the factory M VLSD I'm afraid it may not be enough of an upgrade for me. I do about 8-10 track days per year now and consider myself intermediate+, you think I might be a good candidate for a clutch pack unit or should I study/consider the Wavetrac further first? One thing I've read about the clutch pack units is that they also provide increased stability when braking, which I would appreciate, not sure if the TBD's do that. These units are pricey, no doubt so sage advice either way and thanks again for sharing!
ATB differentials do not provide "lock up" upon deceleration, only acceleration. So a Quaife or Wavetrac would not provide any increased stability on breaking, only on acceleration. So, less prone to understeer at the limit on corner entry, but less stability under breaking. The differential I got is a 35/60 ramp, so I get a fair amount of lockup under breaking. When you have to haul the car down really quickly, its a nice feature.

If you are an intermediate driver, you would probably appreciate the advantages of a clutch type differential with custom ramps. That being said, how much is it worth to you?

Also, since you are running an e92 M3, you might be interested in changing the final drive ratio for some more torque. I had mine changed from a 3.08 to the 3.46, same ratio as in the M2. It makes a significant difference, seeing as the gear ratios are the same in both cars (for the 6 speed).
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      10-20-2016, 08:14 AM   #14
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Quote:
Originally Posted by Liquidpaper
Quote:
Originally Posted by ///Mobbin View Post
Appreciate your thoughts and advice, thank you! I've also considered a TBD like the Quaife or Wavetrac, which both have great reviews but since I already have the factory M VLSD I'm afraid it may not be enough of an upgrade for me. I do about 8-10 track days per year now and consider myself intermediate+, you think I might be a good candidate for a clutch pack unit or should I study/consider the Wavetrac further first? One thing I've read about the clutch pack units is that they also provide increased stability when braking, which I would appreciate, not sure if the TBD's do that. These units are pricey, no doubt so sage advice either way and thanks again for sharing!
ATB differentials do not provide "lock up" upon deceleration, only acceleration. So a Quaife or Wavetrac would not provide any increased stability on breaking, only on acceleration. So, less prone to understeer at the limit on corner entry, but less stability under breaking. The differential I got is a 35/60 ramp, so I get a fair amount of lockup under breaking. When you have to haul the car down really quickly, its a nice feature.

If you are an intermediate driver, you would probably appreciate the advantages of a clutch type differential with custom ramps. That being said, how much is it worth to you?

Also, since you are running an e92 M3, you might be interested in changing the final drive ratio for some more torque. I had mine changed from a 3.08 to the 3.46, same ratio as in the M2. It makes a significant difference, seeing as the gear ratios are the same in both cars (for the 6 speed).
I appreciate the write-up and insight, thanks! For the price I think I should make certain I'm keeping this car for awhile before I make the call. I should also consider what other mods I could do for the same (though my car is well along already). One thought I had was to buy a second used diff to sell with the car so I can sell whatever custom setup I have separately w/o being under time constraints.

Then I hear you on the final drive ratio. My DCT car started out with a 3.15 ratio and was upgraded by the previous owner to a Dinan (BMW Motorsports) 3.45, which is the max recommended for a DCT e92 m3 w/o some remapping of the engine/transmission software and I've only heard of folks in Germany doing this, no one in the US has this knowledge that I'm aware of.

Enjoying the 3.45 so far!
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      03-21-2017, 01:18 PM   #15
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Fantastic. Thank you for providing us with your insight.
A have a few questions prior to purchasing the M Diff, especially for track duty.
With your custom diff. do you notice a difference with a reduction in the cars nature to understeer? Easier to power oversteer? Do you run the car with traction and slip control disabled? What tyre pressures do you run?
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      03-21-2017, 01:23 PM   #16
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Fantastic. Thank you for providing us with your insight.
A have a few questions prior to purchasing the M Diff, especially for track duty.
With your custom diff. do you notice a difference with a reduction in the cars nature to understeer? Easier to power oversteer? Do you run the car with traction and slip control disabled? What tyre pressures do you run?
No, the car will actually understeer "more" because of the Diff because the back has so much more traction (2 wheels v 1). What removes understeer is extra camber/rubber in the front.

The car is easier to power oversteer as it is more predictable. Without the diff, once you lose the back end, it is very hard to predict where it will go. With the diff, the back steps out very progressively and is easy to correct. I usually run the car with everything disabled when on track. I try to run 36 psi front and rear while hot. Keep in mind I am running -2.3 camber front and -2.25 camber rear though, so I don't have any sidewall rollover. Also I am running Hankook RS3 tires.
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      03-21-2017, 01:24 PM   #17
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I have the M Performance LSD in mine and the upside is that its great all around.....it doesnt make any noise and is very "driveable" every day

The downside is that its only a 30% lockup iirc and there have been times when accellerating in a more spirited manner I can feel one wheel spin and the other get SOME power.....and I find myself wondering if I would have been better off (happier) with something more agressive
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      03-21-2017, 01:26 PM   #18
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I have the M Performance LSD in mine and the upside is that its great all around.....it doesnt make any noise and is very "driveable" every day

The downside is that its only a 30% lockup iirc and there have been times when accellerating in a more spirited manner I can feel one wheel spin and the other get SOME power.....and I find myself wondering if I would have been better off (happier) with something more agressive
I'll be honest -- my diff makes no noise whatsover. However, it was custom built and very expensive.

If I could do it all over again, I would probably have gotten a torsen diff or the MP LSD. I love my diff, but it was really expensive, and considering I am a rank amateur, I probably wouldn't know the difference.

However, moving the ratio up to 3.46 from 3.08 was the best thing I've done to the car.
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      03-21-2017, 01:31 PM   #19
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Quote:
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I'll be honest -- my diff makes no noise whatsover. However, it was custom built and very expensive.

If I could do it all over again, I would probably have gotten a torsen diff or the MP LSD. I love my diff, but it was really expensive, and considering I am a rank amateur, I probably wouldn't know the difference.

However, moving the ratio up to 3.46 from 3.08 was the best thing I've done to the car.
Yep.

I wonder if I would notice it ENOUGH to make a difference......I probably wont track the car more than 1-2x/year and thats only for recreational purposes.......I'm no wanna be racer (yet?)

I do however want to upgrade to a dinan stage 1/2 option and add an exhaust to it and felt that SOME sort of upgrade over the open differential was a prerequisite for any of this,.....

I can always upgrade to a qualife (sp) or something else more agressive down the road if the want/need is there I suppose
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      03-21-2017, 01:37 PM   #20
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Yep.

I wonder if I would notice it ENOUGH to make a difference......I probably wont track the car more than 1-2x/year and thats only for recreational purposes.......I'm no wanna be racer (yet?)

I do however want to upgrade to a dinan stage 1/2 option and add an exhaust to it and felt that SOME sort of upgrade over the open differential was a prerequisite for any of this,.....

I can always upgrade to a qualife (sp) or something else more agressive down the road if the want/need is there I suppose
I think if you are going to do a power upgrade, a differential would be a very important supporting mod. Nothing more embarrassing than a one-tire burnout.

Honestly, the car should have come from the factor with some sort of LSD (maybe not the crazy M division trick LSD, but something). However, I wouldn't recommend going my route necessarily due to cost. If I could do it again, I would still use diffsonline and get he 3.46 gears, but with a Wavetrac carrier probably. Would save a lot of money.
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      03-21-2017, 01:43 PM   #21
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Quote:
Originally Posted by Liquidpaper View Post
I think if you are going to do a power upgrade, a differential would be a very important supporting mod. Nothing more embarrassing than a one-tire burnout.

Honestly, the car should have come from the factor with some sort of LSD (maybe not the crazy M division trick LSD, but something). However, I wouldn't recommend going my route necessarily due to cost. If I could do it again, I would still use diffsonline and get he 3.46 gears, but with a Wavetrac carrier probably. Would save a lot of money.
Part of me really wants the M2 and the trick rear end, double clutch and suspension bits....

But the 2 series is soooooo driveable all the time with the adjustable suspension

And the B58 has soooo much potential for making power.......

I cant complain at all about the gearing in my 240 and am wondering what issue you encountered that pushed you from 3.46 from 3.08?

Obviously you have more torque now.......
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      03-21-2017, 01:48 PM   #22
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Part of me really wants the M2 and the trick rear end, double clutch and suspension bits....

But the 2 series is soooooo driveable all the time with the adjustable suspension

And the B58 has soooo much potential for making power.......

I cant complain at all about the gearing in my 240 and am wondering what issue you encountered that pushed you from 3.46 from 3.08?

Obviously you have more torque now.......
Not really an issue. I was getting the rear end built and the builder asked if I wanted the ratio upgrade -- he recommended it as a lot of the 1 series guys did it. That and the gearing was just too long for my taste. On track, third gear put you at about 110 mph. That is too long for a 7000 RPM redline.

Here is the thing, is the M2 better? Yeah. Is it different enough to warrant getting rid of a perfectly good M240i (in your case) and getting that car? I don't really think so, but your mileage may vary.
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