PSA: Think twice before lowering your car

[jet_dogg]

My first car ever was slammed with cut springs on stock shocks and my wheel never crashed through the fender, guess I got lucky!

[Tbonem3]

He's got very good points and it's mostly to do with performance, not comfort.

I would say a good rule of thumb is to increase spring rate in equal measure to the removal of travel. Lowering the car by losing travel, but not ramping up spring rate will have you on the bumps constantly and ruin handling.

But as I already said, you can lower the car a decent amount without sacrificing handling.

We can have our cake and eat it too, to a degree.

[Sharocks]

Yea I'm not un-modding my car to make it more comfortable.

Also exactly why I have multiple cars.

[Tbonem3]

stack height aka mounting point

[cobra]

Yeah I'm still gonna drop my shit.

And lol @ the scraping, don't ever drive any real sports cars guys.

I mean, to each his own. A lowered car definitely looks better I'm not arguing that 😄. Everyone has different priorities.

You can lower the car almost a full inch without reducing travel FYI

That does not make sense. There is physically only 2-3 inches of bump travel. If you remove an inch, you now have that much less travel (all else being equal).

[Tbonem3]

You can lower the car almost a full inch without reducing travel FYI

[jet_dogg]

Yeah I'm still gonna drop my shit.

And lol @ the scraping, don't ever drive any real sports cars guys.

[cobra]

My findings exactly. I added a 1/2” shim to my Dinan front springs above the spring hats to bring travel back to stock levels. My tired bump stops measured 1” of free travel before hitting the bump stops with the 1/2” spacers. New front bump stops are next up on the list as the tired ones are partially collapsed from the previous owner’s lowering spring install.

For the rears, I did this (also measuring 1” free travel on my Dinan springs and 5mm spring pads):

Fascinating. Did you change anything in the rear? What did you feel from shimming the front up?

The rear Dinan springs are pretty nice - linear rate 475lb/in, and barely lower it (only 3/8").
The fronts are too short and too soft. They are only 175lb/in and lower it anywhere from 5/8" to 7/8". They should be more in the 250-300 range, but.... then that wouldn't have worked from a packaging standpoint since they already have 0 preload, and the stock fixed spring perch would not accommodate a helper spring. Shortening their travel internally could have been a solution, but I am 99% sure the Dinan Konis are just regular off-the-shelf Konis.

[cobra]

Welcome to the world of bump stop tuning! The geometry/shape and material will affect the behavior of the bump stop when compressed.
Because of the McP strut is more-or-less (for better-or-worse) becoming the de facto front suspension, the OE's are putting soft front springs for ride, then tuning the bump stops to suit their needs.

Bump stops are not all the same. A good bump stop manufacturer will publish Force-Displacement info on their bump stops. I attached info from Koni and Penske.
If you are a believer in the Flat Ride concept, then the bump stop is critical to how your car will behave at the limits.

Absolutely! My personal opinion (coming from the motorcycle world) is the bump stop should be used as just that - a bump stop. Using it has an active suspension component generates rather progressive spring rates. Those progressive spring rates are not matched by progressive (position sensitive) damping. I think of that feeling when driving hard in a corner, and the car starts feeling 'bouncy' because the ride frequency just doubled and the damper can't control things. On an electronic-suspension this can be addressed to some degree.

Also my opinion, but I am not sold on the Flat Ride concept. It is based on 2 justifications: referencing OE vehicle parameters (which are compromised), and "fast settling" (which only applies in one very specific vehicle speed/damping situation). I have run a rear-bias stiffness and I'm not in love with the feeling or handling. It feels as though it pivots around the rear while I prefer something more balanced.

[Bry5on]

My findings exactly. I added a 1/2” shim to my Dinan front springs above the spring hats to bring travel back to stock levels. My tired bump stops measured 1” of free travel before hitting the bump stops with the 1/2” spacers. New front bump stops are next up on the list as the tired ones are partially collapsed from the previous owner’s lowering spring install.

For the rears, I did this (also measuring 1” free travel on my Dinan springs and 5mm spring pads):

[Casa de Mesa]

I lowered my car right about that conservative amount (not as low as others go) to balance performance and cosmetics. I simply dislike the looks of the stock fender gaps. I recognize this impedes the geometry(-ies) built around stock ride heights, and compromies elsewhere, but it's not a massive degradation in performance with a properly setup coilover.

Also, damper quality plays a big role here too. It's like hifi audio. Doesn't matter how many watts you have if that first watt is crap.

[maw1124]

I’ve always felt like this car is low enough, almost too low actually (judging by the extra effort this older guy has to exert getting in and out of it). Not to mention the abused front bumper I still haven’t gotten around to replacing. Since I have other cars and drive this one the least, I don’t worry so much about it. But I’m definitely not looking to lower it.

maw

[elbert]

They also use a different bump stop geometry.

Welcome to the world of bump stop tuning! The geometry/shape and material will affect the behavior of the bump stop when compressed.
Because of the McP strut is more-or-less (for better-or-worse) becoming the de facto front suspension, the OE's are putting soft front springs for ride, then tuning the bump stops to suit their needs.

Bump stops are not all the same. A good bump stop manufacturer will publish Force-Displacement info on their bump stops. I attached info from Koni and Penske.
If you are a believer in the Flat Ride concept, then the bump stop is critical to how your car will behave at the limits.

[///Mangler]

This is why when you look closely at a BMW chassis that is used for racing, they raise the pick up points of the suspension the amount they lower the car. Suspensions are designed and engineered at a certain static ride height and settings. ANYWHERE away from this degrades the response that we are looking for.

T

[Obioban]

Yeah, my car is pretty much stock height (+- corner balance). It's just better for everything-- comfort, handling, scraping, camber curve, roll centers, bump steer.