[Red_Baron]

This is quite a colorful discussion with some good and other parts not so good. A fresh perspective may help.

Since I recently had an M-Performance differential installed, I though that I would chime in with some initial impressions. My car also has Dinan springs/bump stops/adaptive damper tuning. I think that this collectively tuned solution is close enough to coil-overs for discussion purposes here.

My car also was ordered with the track and handling package. The stock suspension is the weakest point of the car. I found it to be simultaneously under-sprung and under-damped. Comfort mode was the most egregious. Excessive dive/squat under braking/acceleration as well as body roll during cornering were evident. The excessive softness also degraded perceived predictability. I could feel the car load and unload wheels in spirited driving, loosing mechanical grip. I suspect that the very progressive rate of the springs are the biggest issue here.

Another big gripe of mine is that the car does not put the power down effectively/efficiently. Very careful/timid throttle application on the street was how I dealt with this. The large torque of the B58 is both a blessing and curse here.

Shockware came first. This is a +15% damping rate increase in each mode roughly. Secondary motions were removed. (overshoot and ringing after a bump) A slight improvement in the faults above was observed. A band-aid really.

Matched springs and bump stops came next. This was truly transformative. All controls from driver inputs became much more linear/predictable. Mechanical grip was noticeably better as the tires' available grip was actually used since the tires followed the road much better. Moreover, the car put power down better accelerating. The ride is still very comfortable. Passengers do not know that the suspension is not stock.

Finally, the M-Performance LSD came last. It really helps put the power down predictably. This is most noticeable in tight corners. No surprise here. What is left out of the everyday usefulness is that every single right/left turn to merge into traffic is clearly improved in both dry and wet. Those that say an LSD is wasted outside of a track event is not something I agree with. The net effect is improve linearity in the car behavior and higher driver confidence. I smile much more driving the car now. It was worth the $2600. Traction control still cuts power, but the intervention point is much higher and forward momentum is maintained. All chirping of the inside (right usually) wheel is gone. The throttle is now a much more predictable tool. Now I finally understand why RWD cars are revered for their driving dynamics.

After all that background, the suspension change was definitely more transformative. My vote is to do that first. Without the suspension improvements, my car would have been sold and replaced with something else. In retrospect, I should have just gotten and M3 instead since all the issues that I fixed are addressed stock there. My 340i is everything I hoped for now without an F80 M3's burden of way too much power for the street. (my opinion of course)

[dr.roro]

Appreciate all the insightful discussion.

Just to update my thoughts:
I agree with most of you on many points. I don't want an aggressive drop, and probably going just 0.5" lower than the stock RWD M Sport suspension would be perfect in my eyes, both aesthetically and functionally (remember, this is my daily driver). While I do not disagree that Ohlin's may be the best (or one of the best) coilovers for the platform, I also do not need the very best as I am neither a professional driver nor track-every-weekend kind of guy, nor do I consider spending several 100s of dollars to be worth the incremental value. I would be happy with just a minimal drop, improved handling, while maintaining every day comfort on public roads and highways. KW Street Comfort was a deliberate choice because these seemed to hit all those points.

I'm not sure where the blanket bashing of established brands like KW, Bilstein, etc. is coming from, but in all my research and browsing, I don't think I came across a single negative review of the KW Street Comfort (or V1/V2/V3 for that matter). Also, I believe some of the numbers you quoted for drops are off, or at least you selectively decided to quote the max drops for certain brands. For example, KW specifies their lowering height as 10-40mm -- right in range for both my own preference and maintaining "optimal geometry" like Ohlin's and BMW M Performance.

Also, while the main benefit of an LSD would be for cornering, wouldn't another major benefit be to prevent slipping in both wet and winter conditions? This would be highly useful for me having a RWD car in a region that gets its fair share of rain and snow (on top of already using winter tires).

Anyway, I am still contemplating which to do first (probably won't be until next summer at this point). I actually do enjoy the stock M Sport / Adaptive suspension 95% of the time so I'm not in any rush (as well as maintaining factory warranty for now). In the end, I think I am still leaning slightly towards the LSD first.... but probably after switching to some proper non-RFT tires first (i.e. MPS4S).

[Polo08816]

Originally Posted by kern417

so we agree on something. but there are plenty of people that got the ceramic brakes because it's the best, and why wouldn't you get the best if you're going to upgrade? so when someone asks if it's worth it, you have to consider other factors besides what's best performance-wise.

for example this go around on my 2018, i'm doing coilovers and axle back first. even though it doesn't make the car significantly faster, that's what made my previous cars the most fun and made the biggest difference in feel. my car already came with summer tires, and not interested in piggy back tunes currently, so i'm good in those areas. other mods will round it out down the road but an LSD wasn't the first thing i felt that i missed. i still can corner fast enough that my wife gets pissed at the lack of an o-shit handle.

My philosophy/approach has always been to replace when wear/tear and/or skill level requires it. But I wouldn't replace something that the producer hasn't thoroughly tested - and afterwards, presents a good value.

Originally Posted by Red_Baron

This is quite a colorful discussion with some good and other parts not so good. A fresh perspective may help.

Since I recently had an M-Performance differential installed, I though that I would chime in with some initial impressions. My car also has Dinan springs/bump stops/adaptive damper tuning. I think that this collectively tuned solution is close enough to coil-overs for discussion purposes here.

My car also was ordered with the track and handling package. The stock suspension is the weakest point of the car. I found it to be simultaneously under-sprung and under-damped. Comfort mode was the most egregious. Excessive dive/squat under braking/acceleration as well as body roll during cornering were evident. The excessive softness also degraded perceived predictability. I could feel the car load and unload wheels in spirited driving, loosing mechanical grip. I suspect that the very progressive rate of the springs are the biggest issue here.

Another big gripe of mine is that the car does not put the power down effectively/efficiently. Very careful/timid throttle application on the street was how I dealt with this. The large torque of the B58 is both a blessing and curse here.

Shockware came first. This is a +15% damping rate increase in each mode roughly. Secondary motions were removed. (overshoot and ringing after a bump) A slight improvement in the faults above was observed. A band-aid really.

Matched springs and bump stops came next. This was truly transformative. All controls from driver inputs became much more linear/predictable. Mechanical grip was noticeably better as the tires' available grip was actually used since the tires followed the road much better. Moreover, the car put power down better accelerating. The ride is still very comfortable. Passengers do not know that the suspension is not stock.

Finally, the M-Performance LSD came last. It really helps put the power down predictably. This is most noticeable in tight corners. No surprise here. What is left out of the everyday usefulness is that every single right/left turn to merge into traffic is clearly improved in both dry and wet. Those that say an LSD is wasted outside of a track event is not something I agree with. The net effect is improve linearity in the car behavior and higher driver confidence. I smile much more driving the car now. It was worth the $2600. Traction control still cuts power, but the intervention point is much higher and forward momentum is maintained. All chirping of the inside (right usually) wheel is gone. The throttle is now a much more predictable tool. Now I finally understand why RWD cars are revered for their driving dynamics.

After all that background, the suspension change was definitely more transformative. My vote is to do that first. Without the suspension improvements, my car would have been sold and replaced with something else. In retrospect, I should have just gotten and M3 instead since all the issues that I fixed are addressed stock there. My 340i is everything I hoped for now without an F80 M3's burden of way too much power for the street. (my opinion of course)

I'd only replace a wear item at the end of its life or if it simply can't handle a HPDE/track event (the thing that comes to mind for this stock M Sport Brake Option pads).

Originally Posted by dr.roro

Appreciate all the insightful discussion.

Just to update my thoughts:
I agree with most of you on many points. I don't want an aggressive drop, and probably going just 0.5" lower than the stock RWD M Sport suspension would be perfect in my eyes, both aesthetically and functionally (remember, this is my daily driver). While I do not disagree that Ohlin's may be the best (or one of the best) coilovers for the platform, I also do not need the very best as I am neither a professional driver nor track-every-weekend kind of guy, nor do I consider spending several 100s of dollars to be worth the incremental value. I would be happy with just a minimal drop, improved handling, while maintaining every day comfort on public roads and highways. KW Street Comfort was a deliberate choice because these seemed to hit all those points.

I'm not sure where the blanket bashing of established brands like KW, Bilstein, etc. is coming from, but in all my research and browsing, I don't think I came across a single negative review of the KW Street Comfort (or V1/V2/V3 for that matter). Also, I believe some of the numbers you quoted for drops are off, or at least you selectively decided to quote the max drops for certain brands. For example, KW specifies their lowering height as 10-40mm -- right in range for both my own preference and maintaining "optimal geometry" like Ohlin's and BMW M Performance.

Also, while the main benefit of an LSD would be for cornering, wouldn't another major benefit be to prevent slipping in both wet and winter conditions? This would be highly useful for me having a RWD car in a region that gets its fair share of rain and snow (on top of already using winter tires).

Anyway, I am still contemplating which to do first (probably won't be until next summer at this point). I actually do enjoy the stock M Sport / Adaptive suspension 95% of the time so I'm not in any rush (as well as maintaining factory warranty for now). In the end, I think I am still leaning slightly towards the LSD first.... but probably after switching to some proper non-RFT tires first (i.e. MPS4S).

Yes. I reside in Maryland as well and this is one of the reasons why I replaced my LSD.

The reason I'm an advocate for Ohlins is that they're not significantly more expensive than most of the other coilover solutions anymore. There was a time when they would cost you about $3000 but there's been a $700 price drop in the past year or so.

[kern417]

Originally Posted by dr.roro

.... but probably after switching to some proper non-RFT tires first (i.e. MPS4S).

i think everyone can agree that this should come first regardless of your opinion of other mods.

[kern417]

Originally Posted by Polo08816

My philosophy/approach has always been to replace when wear/tear and/or skill level requires it. But I wouldn't replace something that the producer hasn't thoroughly tested - and afterwards, presents a good value.

well originally you only said wear and tear, which makes no sense. i have a box of parts that i removed from my car and can replace in a pinch if anything fails including rotors, pads, clutch, diff, etc. the sole purpose is to replace broken aftermarket parts with stock so i can get around until aftermarket replacements can come in. if I don't go that route, i sell the stock parts and pocket the cash. so idk if you're goal is value or what, but no reason to wait for 50k+ life parts to fail before replacing them.

regarding skill level, meh. again, people aren't timing their drive to work. everyone that has commented with the mentioned mods only commented on feel. mods aren't all about track times. the guy is just trying to enjoy his car more without the sacrifices that OEM makes to (try to) please everybody and bridge comfort with performance. i'd rather drive a car that's more capable than my driving skills. how many people do you think picked the m3/m4 because their driving skills simple are beyond that of an f3x?

sorry, but you're just in the minority here.

[zinner]

I have driven VIR a few weekends on a stock chassis F30 N55. On the Msport suspension the only corner I have had issues with float/unbalance is T18 just before start finish. I usually can just stay mid/track and avoid that issue. However I have had plenty of times where I couldn't power out of a corner T3,T10 ,T12 because a single rear tire would slip and the car would start to oversteer.. So the LSD first rings true to me. A car with an LSD will just leave you in the dust cause they can add more power as they unwind and I can't add any power until you have strait front wheels.

I was just considering suspension as my next upgrade, but this has made me rethink it and maybe pick an LSD instead. Suspension upgrades are something that can be very susceptible to a company that sells a kit that "fits" a chassis versus a kit that improves the handling and has been tested and proved true. I am not at the point where I could make such a judgement on my own. So I tend to ask for advice from my HPDE instructors on what they use.

[Polo08816]

Originally Posted by zinner

I have driven VIR a few weekends on a stock chassis F30 N55. On the Msport suspension the only corner I have had issues with float/unbalance is T18 just before start finish. I usually can just stay mid/track and avoid that issue. However I have had plenty of times where I couldn't power out of a corner T3,T10 ,T12 because a single rear tire would slip and the car would start to oversteer.. So the LSD first rings true to me. A car with an LSD will just leave you in the dust cause they can add more power as they unwind and I can't add any power until you have strait front wheels.

I was just considering suspension as my next upgrade, but this has made me rethink it and maybe pick an LSD instead. Suspension upgrades are something that can be very susceptible to a company that sells a kit that "fits" a chassis versus a kit that improves the handling and has been tested and proved true. I am not at the point where I could make such a judgement on my own. So I tend to ask for advice from my HPDE instructors on what they use.

That issue of not being able to keep up with an LSD equipped car is even more pronounced on a tighter more technical track.

I agree completely with your thoughts on most suspension kits. For a RWD car, the only spring/strut combination that is proven true is the BMW M Performance Suspension Kit. Most other spring/strut combinations is a driveway mechanic piecing things together.

[kern417]

OP isn't on a track. And some suspension companies publish their dampening dynos and spring specs. i know H&R and KW do. and companies like bc racing that do build from the parts bin also can be swapped with swift springs at whatever rate you choose, and they'll revalve the shocks. at the end of the day. it's not about the perfect car setup. it's about your driving style and making your car match it.

[Polo08816]

Originally Posted by kern417

OP isn't on a track. And some suspension companies publish their dampening dynos and spring specs. i know H&R and KW do. and companies like bc racing that do build from the parts bin also can be swapped with swift springs at whatever rate you choose, and they'll revalve the shocks. at the end of the day. it's not about the perfect car setup. it's about your driving style and making your car match it.

No, he isn't. But he lives in Maryland where it can be hilly and snows.

Anyways, looks like he has already decided... see below.

Originally Posted by dr.roro

Appreciate all the insightful discussion.

Just to update my thoughts:
I agree with most of you on many points. I don't want an aggressive drop, and probably going just 0.5" lower than the stock RWD M Sport suspension would be perfect in my eyes, both aesthetically and functionally (remember, this is my daily driver). While I do not disagree that Ohlin's may be the best (or one of the best) coilovers for the platform, I also do not need the very best as I am neither a professional driver nor track-every-weekend kind of guy, nor do I consider spending several 100s of dollars to be worth the incremental value. I would be happy with just a minimal drop, improved handling, while maintaining every day comfort on public roads and highways. KW Street Comfort was a deliberate choice because these seemed to hit all those points.

I'm not sure where the blanket bashing of established brands like KW, Bilstein, etc. is coming from, but in all my research and browsing, I don't think I came across a single negative review of the KW Street Comfort (or V1/V2/V3 for that matter). Also, I believe some of the numbers you quoted for drops are off, or at least you selectively decided to quote the max drops for certain brands. For example, KW specifies their lowering height as 10-40mm -- right in range for both my own preference and maintaining "optimal geometry" like Ohlin's and BMW M Performance.

Also, while the main benefit of an LSD would be for cornering, wouldn't another major benefit be to prevent slipping in both wet and winter conditions? This would be highly useful for me having a RWD car in a region that gets its fair share of rain and snow (on top of already using winter tires).

Anyway, I am still contemplating which to do first (probably won't be until next summer at this point). I actually do enjoy the stock M Sport / Adaptive suspension 95% of the time so I'm not in any rush (as well as maintaining factory warranty for now). In the end, I think I am still leaning slightly towards the LSD first.... but probably after switching to some proper non-RFT tires first (i.e. MPS4S).

[XutvJet]

It's been my experience that most aftermarket suspension solutions can actually make a performance car handle worse, especially those that offer excessive drops. Many times people perceive reduced roll, dive, and chassis movement and a stiff suspension as improved handling and limits. That's often not the case and in some cases, the handling and limits could actually be worse.

Over the years, I've learned that if there's a performance upgrade from the factory, then chances are that's what you should go with assuming this is a mostly street car that may see some track time. The parts are built to OEM specs, longevity goals, NVH concerns, and will fit perfectly. The same can't be said of many aftermarket parts. I've also learned that race car parts rarely do well on the street where there pavement cuts, pothole, ruts, ice, snow, etc.

The bang for the buck here is the M Performance suspension and then the M Performance LSD. I wish I could put the M Performance suspension springs on my M235 because I'd love to have higher rate springs (apparently the springs won't work because I have the Adaptive suspension). The minor 10mm drop would be fine as well, but I don't really care about dropping the car. I want the better and much needed spring rates. I'd go with the Dinan spring setup but the drop is just too much. I want the wheel travel for the street.

[dr.roro]

^You make a good case for the M Performance suspension. Unfortunately, I have the Adaptive M suspension. Can I code out the EDC and get the M Performance suspension (or any coilovers) to work without error/warning lights? Or can I use the KW EDC Delete unit with the M Performance (or Ohlins) suspension?

[Dylan86]

Originally Posted by dr.roro

^You make a good case for the M Performance suspension. Unfortunately, I have the Adaptive M suspension. Can I code out the EDC and get the M Performance suspension (or any coilovers) to work without error/warning lights? Or can I use the KW EDC Delete unit with the M Performance (or Ohlins) suspension?

You can code out EDC or buy the EDC cancellation kit, from KW. I have the KW kit to coincide with my KW Clubsports. I could have saved the $$ and had the coding done, but whatevs.. It will probably be easier to sell everything as a whole (incl. the EDC kit) down the road once I'm ready for something new.

[butch_]

Originally Posted by Polo08816

APEX ARC-8 18x8.5 ET38, no spacers.

Originally Posted by drive

Pics?

+1
don't keep us in the dark / hyper black / anthracite

[Polo08816]

Originally Posted by butch_

+1
don't keep us in the dark / hyper black / anthracite

Anthracite. This is on the stock passive 704 Sport Suspension. Not on the BMW M Performance Suspension which would be about 10mm lower.

[Tchao]

Dr. Roro,

If you value daily driver with sporty characteristics, not a track toy, why not get Dinan springs and their shockware for your adaptive suspension. The adaptive suspension is such a great thing once you understand it. I personally do not want to loose it.
Granted it's not as adaptive as the M models, but the diluted one we have is still very good.

Going Dinan route, you have BMW approved R&D, so the things that the Mperf. suspension you value is not lost, like longevity, fitment, warranty, etc. Plus you can keep the adaptive intelligence aspect.

[dr.roro]

Originally Posted by Tchao

Dr. Roro,

If you value daily driver with sporty characteristics, not a track toy, why not get Dinan springs and their shockware for your adaptive suspension. The adaptive suspension is such a great thing once you understand it. I personally do not want to loose it.
Granted it's not as adaptive as the M models, but the diluted one we have is still very good.

Going Dinan route, you have BMW approved R&D, so the things that the Mperf. suspension you value is not lost, like longevity, fitment, warranty, etc. Plus you can keep the adaptive intelligence aspect.

I thought about that route, but I've read some mixed reviews on the Dinan springs. Also, I've read that they tend to sag and bottom out after a year or two.

[DOCTOR.Y]

I do not have KW suspension, but I have MP lsd, very good!

[Polo08816]

Originally Posted by XutvJet

It's been my experience that most aftermarket suspension solutions can actually make a performance car handle worse, especially those that offer excessive drops. Many times people perceive reduced roll, dive, and chassis movement and a stiff suspension as improved handling and limits. That's often not the case and in some cases, the handling and limits could actually be worse.

Over the years, I've learned that if there's a performance upgrade from the factory, then chances are that's what you should go with assuming this is a mostly street car that may see some track time. The parts are built to OEM specs, longevity goals, NVH concerns, and will fit perfectly. The same can't be said of many aftermarket parts. I've also learned that race car parts rarely do well on the street where there pavement cuts, pothole, ruts, ice, snow, etc.

The bang for the buck here is the M Performance suspension and then the M Performance LSD. I wish I could put the M Performance suspension springs on my M235 because I'd love to have higher rate springs (apparently the springs won't work because I have the Adaptive suspension). The minor 10mm drop would be fine as well, but I don't really care about dropping the car. I want the better and much needed spring rates. I'd go with the Dinan spring setup but the drop is just too much. I want the wheel travel for the street.

Originally Posted by dr.roro

^You make a good case for the M Performance suspension. Unfortunately, I have the Adaptive M suspension. Can I code out the EDC and get the M Performance suspension (or any coilovers) to work without error/warning lights? Or can I use the KW EDC Delete unit with the M Performance (or Ohlins) suspension?

Originally Posted by kern417

well originally you only said wear and tear, which makes no sense. i have a box of parts that i removed from my car and can replace in a pinch if anything fails including rotors, pads, clutch, diff, etc. the sole purpose is to replace broken aftermarket parts with stock so i can get around until aftermarket replacements can come in. if I don't go that route, i sell the stock parts and pocket the cash. so idk if you're goal is value or what, but no reason to wait for 50k+ life parts to fail before replacing them.

regarding skill level, meh. again, people aren't timing their drive to work. everyone that has commented with the mentioned mods only commented on feel. mods aren't all about track times. the guy is just trying to enjoy his car more without the sacrifices that OEM makes to (try to) please everybody and bridge comfort with performance. i'd rather drive a car that's more capable than my driving skills. how many people do you think picked the m3/m4 because their driving skills simple are beyond that of an f3x?

sorry, but you're just in the minority here.

Another thing to keep in mind about coilovers is that while they are great for the track, they are really designed for the advanced skill level driver who can manage weight transfer at the limit with consistency.

You may not realize the full benefits of a coilover setup on the street while you're cruising on the highway. The issue becomes when you suddenly find the car at the limits of adhesion. Everything happens a LOT faster and sooner than you expect in a car with coilovers as opposed to an OEM suspension. It's entirely conceivable that to the novice/intermediate level driver, a coilover setup could be a handful to drive at the limit.

[kern417]

Originally Posted by Polo08816

Another thing to keep in mind about coilovers is that while they are great for the track, they are really designed for the advanced skill level driver who can manage weight transfer at the limit with consistency.

You may not realize the full benefits of a coilover setup on the street while you're cruising on the highway. The issue becomes when you suddenly find the car at the limits of adhesion. Everything happens a LOT faster and sooner than you expect in a car with coilovers as opposed to an OEM suspension. It's entirely conceivable that to the novice/intermediate level driver, a coilover setup could be a handful to drive at the limit.

that exact same thing is true for an lsd. where the car could easily pull you in before, you'll find yourself spinning both tires at the limit now.

for me the benefit on coilovers was the ride and alignment. more camber + corner balance = more tire + more grip. the only 2 things that really wow'd me at the car's increased performance were 1. summer tires and 2. a performance alignment. when i dialed in the front end, it became a completely different car.

[Polo08816]

Originally Posted by kern417

that exact same thing is true for an lsd. where the car could easily pull you in before, you'll find yourself spinning both tires at the limit now.

for me the benefit on coilovers was the ride and alignment. more camber + corner balance = more tire + more grip. the only 2 things that really wow'd me at the car's increased performance were 1. summer tires and 2. a performance alignment. when i dialed in the front end, it became a completely different car.

Would you care to explain that?

[kern417]

Originally Posted by Polo08816

Would you care to explain that?

with an open diff, you spin one tire when you hit the limit in a turn. the other tire still has grip and is ultimately why the car slows down when it can't handle the throttle. with an lsd, you don't hit the limit until both tires are spinning, which requires more control from the driver to reel it back in. same concept around why you install an lsd if you want to drift your car. it's a lot harder to bring the rear around with an open diff.

[Polo08816]

Originally Posted by kern417

with an open diff, you spin one tire when you hit the limit in a turn. the other tire still has grip and is ultimately why the car slows down when it can't handle the throttle. with an lsd, you don't hit the limit until both tires are spinning, which requires more control from the driver to reel it back in. same concept around why you install an lsd if you want to drift your car. it's a lot harder to bring the rear around with an open diff.

So in theory, I believe what you're saying is...

With an open differential, the transition from stability to instability is slower. If you lose rear traction due to throttle application, it's more likely you can recover the car just by lifting. You may experience a tank slapper, but you may be able to recover the car with immediate and deliberate counter steer. With a locking differential, you tend to lose traction on both wheels simultaneously. The car will transition rapidly to sliding/instability. This requires the driver to be aware and capable of making a recovery which involves staying on the throttle and counter-steering immediately and with appropriate steering wheel input. The instinct to keep the throttle down is not present in most novice drivers. If you lift when both wheels are spinning, you definitely will spin the car. On braking, a locking differential will provide a bit more stability at the expensive of the ability to turn-in quickly.

However, I think we need to frame this around the fact that the MP LSD is an OEM stock 1.5 way unit and not an aftermarket 2 way LSD for race applications.

For regular street driving with DSC fully on, it will still intervene despite the car having an LSD and save the driver from him/herself.