The issue with the M4 is that BMW have attempted to use the springs to control the ride and the dampers to control the roll, this is pretty typical for manufacturers as they have to create a car to appeal to the widest set of driver types. However, this creates the issue that the car is too soft in its softest setting and lacks grip in the Sport+ setting and with its comedy ride height looks a bit crap too.
On the standard car most owners adopt comfort on the damper setting when bimbling along which offers a good amount of grip and a comfortable ride, its no McLaren but its a good set up and nice and comfy, the issue is that the M4 is a sports car so when owners want to push on then press Sport or Sport+ in the hope that that the stiffer damping makes it all bit more sporty.
The issue is that the springs are too soft to really be able to control the aspect movement of the chassis, so BMW have used the damping to do that with the stiffer damping being used to control body roll and make the car feel a bit flatter, the downside of this of course is a stiffer damper (compression and rebound) generally means less grip so owners hit the Sport or Sport+ setting and immediately complain of lack of grip as the traction control kicks in. What you want is the grip of comfort setting on the dampers but less roll and body movement in cornering.
By fitting a lower and stiffer set of springs you achieve everything you need – less body roll in the corners, a better stance and less change in pitch and yaw in braking but you can still run a softer damper setting to maximise grip. Now to get the best handling from the car you can use comfort setting (in the wet) or Sport mode and leave Sport+ for billiard smooth roads and on track. It really is a massive transformation.
We spent a lot of time testing the various different lowering spring kits available and these are the best, by far.
Of course it also hugely improves the look for the car, before and after in these shots is obvious but its not so low as to hit speed humps or make you look like a muppet.
We obviously recommend that we fit these springs, whilst there is limited adjustment on the M4 (front camber is fixed for example) there are some changes we can make to improve the geometry.