[RoyB]

I have an M340 and have about 1300 miles on my M550. Love everything about the M550, but coming from the M340 there are 2 things the M340 accel at.

1- Handling. The m550 feels like it under-steers badly. I realize I have more weight over the front axles, but when I drive them back to back, it's pretty noticeable.

2- Throttle response is significantly better on the M340.

I have the 19" Summer Runflats (Pilot Sport 4 ZP) on the M550, 275/245. I have Pilot Sport 4S non runflats on the M340, 235 square (19s) for comparison.

Would going to a wider front tire help under-steer? Stiffer sway bar? Programming? Almost wishing I had sprung for the rear steering now. The M340 is so twitchy in comparison.

[ashmostro]

Wider tires up front will definitely help. I'm about to install the F90 non-comp sway bars on my lowered (Eibach) M550i and I'd be happy to report in when done.

But yeah, a square setup with 275's up front would make a pretty big difference.

Do you have the 19" or 20" wheels? Some of the understeery feeling is also from tire fold-over, which the 19's do a lot more than the 20's in our spec.

[RoyB]

Originally Posted by ashmostro

Wider tires up front will definitely help. I'm about to install the F90 non-comp sway bars on my lowered (Eibach) M550i and I'd be happy to report in when done.

But yeah, a square setup with 275's up front would make a pretty big difference.

Do you have the 19" or 20" wheels? Some of the understeery feeling is also from tire fold-over, which the 19's do a lot more than the 20's in our spec.

I have the 19s, summer RFT. I also checked the tire pressure and the rears were set higher than the fronts and the fronts were underinflated a couple PSI. Factory calls for higher in the front so I am going to get them where they need to be and see how that helps. Great job PCD setting the incorrect tire pressures.

[ashmostro]

Yeah, I've never met a dealer, mechanic, or tire installer that really cares about setting pressures correctly. Good on you for checking.

[23109VC]

Ashmoto-

I’d be very interested to hear how you like the springs on your M550? And report back when you get the sways in. I have a stock 2018 M550…love everything about it except the handling. I recently test drove a new M4 comp convertible - they weight EXACTLY what an M550 weighs..a bout 4300 lbs..and that thing handles like it’s on RAILS compared to our cars… similar sized wheel/tires..it’s all suspension tuning…

So an M550 could handle really well… relatively speaking …. It’s not gonna handle like a 911…but it will handle well..but you’d need to make a lot fo changes…. I dont know if just springs and sways would do it..but it sure woudl probably help. I would think a full spring setup installed and new sways from a base M5 woudl be maybe $2000 parts/labor tops.

How much did the springs help handling?

My only fear with hte lowering springs on our stock adaptive dampers is that you’re going to strain them more and they wil wear out prematurely. And I’m sure a new set of adaptive dampers on our cars - installed - is a pretty expensive ordeal. I actually googled the price of the parts.. they are $1000 EACH. So all four, plus labor..you’re talking about a $5000 job… ouch.

What is the lifespan of hte adaptive dampers?


Anyway - please tell more about your setup! And how it handles vs stock!! Thanks.

[ashmostro]

I actually really like how my car handles now. The eibach are totally fine with the stock shocks. BMW adaptive shocks are pretty stout; I wouldn't worry about them.

That all said if I were to do it again I would get MSS springs so I could bring the fronts up a little bit. The eibach setup is a single part number for both the 550 and 540 and I think it was optimized for the 540, as the fronts are a touch too low visually. No ill effect on handling though.

The sways were transformative too. I would urge you to do both mods as the springs alone didn't give me the flat cornering and responsiveness I wanted. I would even go for the Comp sway bars if you are really focused on handling over ride comfort. I could have gone with these stiffer bars (I might still do).

Finally, the M4 rides the way it does not only for its suspension but the wide tires particularly in the front end. Wider wheels and tires will make a bigger difference if you want to maximize the cars grip.

[claykin]

Sounds like OP would have benefit from the DHP option for his M550

[ashmostro]

That's a moot point though isn't it

[Boosted_8]

I got mine moving well with the following minor changes: ditching the run flats, adding some camber to the front wheels, fitting M5 sway bars.

If I was keeping the car long term I would looks at HAS kits. I figure by this point you would be better off just having an M5 however.

[23109VC]

How much would handling change by getting rid of run flats?

Since the suspension was tuned for runflats, if I switched to regular summer tires - woudl the car then feel “spongy” or “squishy”….

[G30M]

Originally Posted by 23109VC

How much would handling change by getting rid of run flats?

Since the suspension was tuned for runflats, if I switched to regular summer tires - woudl the car then feel “spongy” or “squishy”….

run flats are in theory more direct and quicker to respond to inputs as the walls are stiff, how much will it change, i don't know

[G30M]

Originally Posted by RoyB

I have an M340 and have about 1300 miles on my M550. Love everything about the M550, but coming from the M340 there are 2 things the M340 accel at.

1- Handling. The m550 feels like it under-steers badly. I realize I have more weight over the front axles, but when I drive them back to back, it's pretty noticeable.

2- Throttle response is significantly better on the M340.

I have the 19" Summer Runflats (Pilot Sport 4 ZP) on the M550, 275/245. I have Pilot Sport 4S non runflats on the M340, 235 square (19s) for comparison.

Would going to a wider front tire help under-steer? Stiffer sway bar? Programming? Almost wishing I had sprung for the rear steering now. The M340 is so twitchy in comparison.

the engineers have mounted 245 on 8" and 275 on 9" rims, these tires have a very narrow tread in reality

get a 275 square set up on 10.5" rims (check the tread width on tirerack before choosing - if you don't want to check get michelin pilot sport 4/5/4s they have wide tread)

[23109VC]

I want my M550 to handle like a 911….no hope… I think I’m screwed

At the end of the day I really want a Porsche 911. I need to stop teasing myself and just sell my fucking car and buy a Porsche.

[G30M]

Originally Posted by 23109VC

I want my M550 to handle like a 911….no hope… I think I’m screwed

At the end of the day I really want a Porsche 911. I need to stop teasing myself and just sell my fucking car and buy a Porsche.

you can't make the 550 handle like a Porsche

2000kg with 60% weight in the front
vs
1500kg with 60% weight in the rear

but i have no need for it to handle like a Porsche coz i don't have access to a track

[G30M]

Originally Posted by RoyB

2- Throttle response is significantly better on the M340.

try performing a throttle body adaptation reset

[jsf721]

I have done many track days and have owned many performance cars.

You will be hard pressed to overcome the mass and weight of the 550 or approximate the feel of the 340.

I was dying to drive the M5C on the track and I did. What a handful that car was at speed. Literally exhausting to drive at the limit on a track. After that I took the M2C on the same stretch and it was a marked improvement in how I felt driving it. Less weight to manage and easier set up and suspension load. Less brake drama at the stabbing point. I was not timed but it felt like I could drive it faster around the track.

I am not a professional driver. Not even close. And when we switched seats with the instructor that is clear as day but I did win the timed auto cross M240 so I was the self proclaimed king of the hacks. Went home with some luggage as a prize.

[Rocket455]

Originally Posted by RoyB

1- Handling. The m550 feels like it under-steers badly. I realize I have more weight over the front axles, but when I drive them back to back, it's pretty noticeable.

2- Throttle response is significantly better on the M340.

OP: after the lease on my '20 M340i ended, I went for an M550i (non-DHP), and my experience is the same. I just ended up having to adapt and avoided slinging the 5er around corners like I did the 3er.

[matadore]

I can only vouch for upgrading the sway bars to at least M5s. I did it on my 540, and it's great in the cornering without touching the suspension, so still sort of comfy in potholes. Keep in mind it bounces much more than the standard sways, especially in the back without the weight balancers.

[Junebug85]

Originally Posted by matadore

I can only vouch for upgrading the sway bars to at least M5s. I did it on my 540, and it's great in the cornering without touching the suspension, so still sort of comfy in potholes. Keep in mind it bounces much more than the standard sways, especially in the back without the weight balancers.

I'm looking to fit the M5 sway bars to my 540i, along with the F90 rear cross member and x brace. My car is currently lowered on MSS.

When you say weight balancers, do you mean the vibration dampeners that can't be fitted to the M5 bars, or do you mean something else?

The bounce you mention, are you experiencing that while driving down the road or when your go over speed bumps? Have you considered upgrading your spring setup? Just thinking maybe the stock suspension is travelling alot hence the bounce where as on a lowered spring setup, it would travel less. I take it you have a M Sport model?

[JCtx]

I'm making the DHP a deal-breaker option if I can find a fully optioned M550i. Otherwise, I'd get an M850i, which has it standard. I considered a 911 base, since it's the only one that rides decently (the S and above are too stiff for my wife), but it's ultra noisy on broken pavement. And configured at $135K, I'd barely avoid calling it a stripper. That includes the mandatory performance options, like 20" wheels (with wider tires), sport exhaust, and sport chrono, and just Bose (which is crap), leather package (to avoid vinyl seats), and that's about it. ZERO driver/safety aids, which is crazy. To equip it like an M550 or M850, it'd easily get to 150 grand. And yes, it'd definitely handle better than both the M550 and M850, but probably not by much. And it'd be a torture on a trip. I don't want that anymore, so MUCH prefer an M850 loaded to the gills for about $118K.

[Boosted_8]

Originally Posted by Junebug85

I'm looking to fit the M5 sway bars to my 540i, along with the F90 rear cross member and x brace. My car is currently lowered on MSS.

When you say weight balancers, do you mean the vibration dampeners that can't be fitted to the M5 bars, or do you mean something else?

The bounce you mention, are you experiencing that while driving down the road or when your go over speed bumps? Have you considered upgrading your spring setup? Just thinking maybe the stock suspension is travelling alot hence the bounce where as on a lowered spring setup, it would travel less. I take it you have a M Sport model?

This sounds like the sway bars were set up with preload while the car was up in the air? Generally you don't want that on a road car.

[JCtx]

Can the DHP option be retrofitted to an M550 not equipped with it? Guess all 550s would have to be pre-wired for that to work, but it'd probably be the best option to improve handling, no? Unless it's not very effective. DHP is deal-breaker option if I end up with an M550 (vs an M850), but wonder how effective that option really is. The nice thing about sway bar actuators is no ride penalty in comfort.