Comfort vs sports

[boss2k]

At comfort suspension setting the car feels more bouncy and harsh than sports suspension setting, comfort is suppose to be softer

Am lowered on eibach springs

Any idea? Should I lower the tire pressure , keep them 33 cold

[AlterZgo]

Softer shocks does not always mean better ride quality. Why? Well, when you lower the car and keep stock shocks, they are not designed for the reduced suspension travel. This is exacerbated if the springs are relatively soft (as Eibachs are) because the lower ride height causes the car to bottom out on the suspension even faster. When the car bottoms out, you're basically reaching near infinite spring rate, i.e. you go from say 300 lb/in of travel to 1000 lbs/0 inches of travel. So the car feels like crap.

Not only that, but if you already have a fair number of miles on the car, then lower it, the stock shocks are already worn to a certain extent and adding springs, even with nominally higher spring rates, may overwhelm what damping is left of the stock shocks further contributing to the bouncy ride.

In summary, the harshness you are feeling may be caused by the suspension bottoming out and the bounciness is from the stock shocks not having sufficient rebound and compression damping to prevent the car from oscillating over and over again from the increased spring rate. Increasing shock setting from comfort to sport and sport+ can help some, but will introduce its own set of compromises and issues with respect to ride quality.

Also noted you keep tire pressure at 33. Drop it to 32 as per stock specs. That will help a bit. But, to solve the issue, you need to get either full coilovers or new aftermarket shocks with higher amounts of damping that can match the lowering spring's increased spring rates.

[boss2k]

Originally Posted by AlterZgo

Softer shocks does not always mean better ride quality. Why? Well, when you lower the car and keep stock shocks, they are not designed for the reduced suspension travel. This is exacerbated if the springs are relatively soft (as Eibachs are) because the lower ride height causes the car to bottom out on the suspension even faster. When the car bottoms out, you're basically reaching near infinite spring rate, i.e. you go from say 300 lb/in of travel to 1000 lbs/0 inches of travel. So the car feels like crap.

Not only that, but if you already have a fair number of miles on the car, then lower it, the stock shocks are already worn to a certain extent and adding springs, even with nominally higher spring rates, may overwhelm what damping is left of the stock shocks further contributing to the bouncy ride.

In summary, the harshness you are feeling may be caused by the suspension bottoming out and the bounciness is from the stock shocks not having sufficient rebound and compression damping to prevent the car from oscillating over and over again from the increased spring rate. Increasing shock setting from comfort to sport and sport+ can help some, but will introduce its own set of compromises and issues with respect to ride quality.

Also noted you keep tire pressure at 33. Drop it to 32 as per stock specs. That will help a bit. But, to solve the issue, you need to get either full coilovers or new aftermarket shocks with higher amounts of damping that can match the lowering spring's increased spring rates.

Thanks for the reply, i just have 5k miles on the car and have put appx 2k miles with new springs, do you still think stock shocks are wearing out that quick?

Also correct me if i am wrong there is not much spring rate difference between stock ZCP and Eibach and thats the reason i went with Eibach V2 lowering springs.

[FriedPiston]

ZCP strut dampers are stiffer than base, so it can handle lowering springs with a mild drop just fine. I'm on Eibach V1 (fronts only), and definitely do not feel a bouncy ride in Comfort Suspension mode with CS EDC coding.

Try lowering air pressure to 30 psi cold all the way around.

[AlterZgo]

Originally Posted by boss2k

Thanks for the reply, i just have 5k miles on the car and have put appx 2k miles with new springs, do you still think stock shocks are wearing out that quick?

I wouldn't say that 5K miles will wear out the stock shocks. But it's really a personal preference thing. Most people don't notice the shocks breaking in and getting softer after tens of thousands of miles. However, I personally always notice stock shocks getting softer even after a few thousand miles in every single car I've ever owned.

You may be more sensitive to it like me. Others may ride in your car and think it feels totally fine.

The point is, while turning the shocks to sport and sport+ may help prevent the car from bottoming out and prevent some of the bounciness, you will not be able to get back to stock ride quality without going to full coilovers or a set of shocks with shortened shock bodies that are designed to match the lowered ride height of lowering springs.

Suspensions on sporty cars like M3s and M4s do not have much suspension travel - maybe 3" of compression travel or so. When you reduce that suspension travel modestly by 1", you're basically taking away 1/3 of the available suspension travel. That will be felt no matter what you do with shock settings or tire pressures.

[Racer20]

Comfort mode is for cruising on the freeway or dealing with road surfaces with small imperfections. Even the owners manual states that for very rough roads, sport or sport + will be better. Large impacts and heavy suspension excitation requires more damping to properly prevent impacts from intruding into the cabin and settle the body down before bounce and pitch becomes excessive.