[bradenc27]

Don’t know too much about suspension but have been trying to figure out what to do.

Problem: Car seems to be a little wobly/unstable at higher speeds. I know some of that is due to short wheelbase, but I am looking to make it more stable at higher speeds, specifically the rear. Not sure if I should upgrade the sway bars, toe links, maybe coil overs or what.

Any suggestions would be appreciated, I’m on stock suspension.

[Drop the hammer]

You need a wheel alignment. Car should be planted stable all the way up in speed. I’ve had many wheel alignments and the most stable is stock alignment and it does need to be done periodically. I’ve had a street alignment (zero front toe) and cut down significantly on tire wear but is not near as stable. Went back to more toe-in and it’s solid now. Rear should also have some slight toe in.

I’m pretty sure this is your issue. Also if you run fatter tires and/or spacers handling is affected.

[bradenc27]

I had an alignment less than a month ago and I’m running 265/35/19 in front and 285/35/19 in rear. It’s usually 110-140 that it starts to feel unstable.

[bradenc27]

Here’s the sheet from BMW

[D.Yooras]

Without changing anything other than alignment, you need more rear camber. -1.8 to -2.0 if you're going to be going that fast.

If you're looking to change parts, you'll want to do coilovers first, something with good wheel control like Bilstein PSS or Ohlins. But you'll want to go minimum lowering no matter what you get because you're going to need the wheel travel.

Unfortunately, these cars do not have enough spring stiffness from the factory for how hard they can corner so BMW tried to overcome that by adding a lot of damping. This makes the car feel great until you start throwing it's weight around at which point the dampers start to lose precision control of the body.

Lastly, be careful where you're going that fast, crashes at 120-140 tend to be pretty nasty even in the best case scenario.

[Carrera2RS]

I'd check tyre pressures as well,

If you Lower the car and improve the damping on rebound (Coilovers) that helps a lot

PS You're not running a font splitter and no additional rear spoiler are you ?

[bradenc27]

I have a front splitter and a rear lip along with the winglets

[bradenc27]

Originally Posted by D.Yooras

Without changing anything other than alignment, you need more rear camber. -1.8 to -2.0 if you're going to be going that fast.

If you're looking to change parts, you'll want to do coilovers first, something with good wheel control like Bilstein PSS or Ohlins. But you'll want to go minimum lowering no matter what you get because you're going to need the wheel travel.

Unfortunately, these cars do not have enough spring stiffness from the factory for how hard they can corner so BMW tried to overcome that by adding a lot of damping. This makes the car feel great until you start throwing it's weight around at which point the dampers start to lose precision control of the body.

Lastly, be careful where you're going that fast, crashes at 120-140 tend to be pretty nasty even in the best case scenario.

Think I’m going to go with the bilstein PSS, thanks for the input

[Carrera2RS]

Swapping from stock suspension to something like the PSS will transform the feel, I live my AST kit, which was developed between Litchfield and AST. It feels very planted at all speeds.

If you have a 3-way kit I did find increasing the damping on the rebound can help with the 'planted' feel as this reduces the lift over crests and if you have an undulation limits the feeling of oscillation

[Carrera2RS]

PS If you can budget the cost in replacing your hubs with BMW -ve camber hubs is terrific I get a near perfect 2.15 degree -ve camber at 600F ride height and it was around £600 for the two parts, fitment cost more but nt crazy. I hated the NVH and harshness of comer plates

[///MPhatic]

Originally Posted by Carrera2RS

I'd check tyre pressures as well...

This is overlooked by so many people, yet it's the first thing that should be checked, and largely responsible for the unstable feeling at speed.

Tire pressure - proper alignment (for the situation) - modify per your needs

[OG Shark]

bradenc27 the bit of rear instability/twitchiness is inherent in the F87 like you said. Bit of a double edged sword in that it makes for a fun car to push but can be a bit too much in the high speed stuff. Definitely something we focus on for the track but certainly applies to the street as well. You mentioned suspension and like others said a good coilover kit helps here. Much improved weight transfer and dampening help tame the instability. A good kit can also do this while improving ride quality/characteristics. As this is felt 100% of the time you are driving the car I feel a good coilover kit is the best bang for the buck improvement you can do on this platform over any other. I prefer things like sway bars to be incorporated afterwards to help fine tune the car if needed - but really a good coilover can take this car very, very far (more on this later). Sways are friendlier on the budget for sure and can help control the weight transfer but feel like they are more of a bandaid to try to cover the stock's weaknesses. Also with a good kit you have the added benefit of dialing in more camber if desired. Not all camber plates add NVH - some certainly do but definitely not all of them (Nitron's do not).

I'm not a big fan of the aesthetics of adding a wing to a street car - but on the F87 it can really help out in the high speed stuff. Do not need much - something like the M2 CS Racing or M235/240 iR wings are not as overpowering visually or performance wise but do help to calm the rear down at speed. Wasn't my first choice to run one but at the tracks I frequent where I get my high speed runs in it made a noticeable improvement on the rear.

The alignment doesn't look awful. Toe in at the rear like you have helps promote stability at speed. I'm not a fan of toe in at the front like that but it shouldn't be doing anything to destabilize the car. I prefer at minimum neutral up front trending towards out if you do not mind a little added tire wear.

The first part of my M2 build we did a straightforward bolt on approach to see how far it would take us. The only suspension upgrade was with our custom spec single dial adjustment Nitron R1 coilovers. Power was increased with a tune and tmic while adding flex fuel capability. Brakes were upgraded as well. Also ran the m240iR wing. Car was full weight and very much daily driver comfortable (better than oem imo). With this combination the car could produce lat g's in excess of the S55 recommended level for the oil and also cause fuel starvation in the high speed stuff. Not that that stuff is great but the point being we were able to overcome the rear instability and have some serious grip. Even with the threshold being higher than stock it is still friendlier at the edge. The dampers do the vast majority of the work here but I also ran the wing as we were pushing for the fastest F8x lap at COTA with this configuration. Achieved this with room to spare in a full weight, fully comfortable street car - the main reason I love the M2. Speeds up to 160 in this trim - completely stable.

Pic with a wing if you are curious

[///MPhatic]

Buy yourself a used OE trunk before you buy a wing.

[OG Shark]

Originally Posted by ///MPhatic

Buy yourself a used OE trunk before you buy a wing.

Other option if you run either the M235iR or M2 CS R is to get the corresponding motorsport trunk for it. Reinforced and predrilled holes make the install easy. Otherwise yeah not a bad idea to pick up a used one.

[bradenc27]

Originally Posted by OG Shark

bradenc27 the bit of rear instability/twitchiness is inherent in the F87 like you said. Bit of a double edged sword in that it makes for a fun car to push but can be a bit too much in the high speed stuff. Definitely something we focus on for the track but certainly applies to the street as well. You mentioned suspension and like others said a good coilover kit helps here. Much improved weight transfer and dampening help tame the instability. A good kit can also do this while improving ride quality/characteristics. As this is felt 100% of the time you are driving the car I feel a good coilover kit is the best bang for the buck improvement you can do on this platform over any other. I prefer things like sway bars to be incorporated afterwards to help fine tune the car if needed - but really a good coilover can take this car very, very far (more on this later). Sways are friendlier on the budget for sure and can help control the weight transfer but feel like they are more of a bandaid to try to cover the stock's weaknesses. Also with a good kit you have the added benefit of dialing in more camber if desired. Not all camber plates add NVH - some certainly do but definitely not all of them (Nitron's do not).

I'm not a big fan of the aesthetics of adding a wing to a street car - but on the F87 it can really help out in the high speed stuff. Do not need much - something like the M2 CS Racing or M235/240 iR wings are not as overpowering visually or performance wise but do help to calm the rear down at speed. Wasn't my first choice to run [...]

OG Shark

Great write up, I did end up going with the bilstein b16. Definitely agree with sway bars and how they help but more of a bandaid. Everything I have read online is that the dampners are the problem. I saw they had one bilstein kit left at tire rack and pulled the trigger. Arrived the next day. Super excited to get it installed and feel the difference as it is starting to get warmer over here.

[Track/S]

Originally Posted by Carrera2RS

Swapping from stock suspension to something like the PSS will transform the feel, I live my AST kit, which was developed between Litchfield and AST. It feels very planted at all speeds.

If you have a 3-way kit I did find increasing the damping on the rebound can help with the 'planted' feel as this reduces the lift over crests and if you have an undulation limits the feeling of oscillation

I never had floating on rear with stock suspensions, now with thicker stabs, 3way coilovers, camber plates, uniball all around I have amazing flotation on back, I have to try increasing the rebound.