[Adcampo]

I've had my car a few months. It's got port installed HAS. It seems they set up it at full drop at port.

I've noticed it's pretty stiff. The stance looks good and the rear sits pretty low. How much impact to ride quality would it be if I raised the rear 2-5mm?

[forcefed]

Originally Posted by Adcampo

How much impact to ride quality would it be if I raised the rear 2-5mm?

None, its the spring that's causing the stiffer ride not the height.

[Adcampo]

Originally Posted by forcefed

None, its the spring that's causing the stiffer ride not the height.

Gotcha. Thx.

[M3SQRD]

If your car is maxed out on the amount it can be lowered then you’re probably running on the bump stops. BMW uses the bump stops to limit travel at the stock ride height. Lowering the car on the stock suspension means you’re running on the bump stops more often. Raising the ride height to BMW’s recommended ride heights (I can’t recall if it’s a 10 mm or 15 mm drop?) will reduce the use of the bump stops and improve ride quality. The MP HAS spring rates are only around ~10-15% stiffer than stock. It’s not a huge difference in rate so stock cars still have a stiff ride.

[Adcampo]

Originally Posted by M3SQRD

If your car is maxed out on the amount it can be lowered then you’re probably running on the bump stops. BMW uses the bump stops to limit travel at the stock ride height. Lowering the car on the stock suspension means you’re running on the bump stops more often. Raising the ride height to BMW’s recommended ride heights (I can’t recall if it’s a 10 mm or 15 mm drop?) will reduce the use of the bump stops and improve ride quality. The MP HAS spring rates are only around ~10-15% stiffer than stock. It’s not a huge difference in rate so stock cars still have a stiff ride.

Yeah, I had read that port installed HAS is set at 10mm drop. I was surprised to see it was full max down.

I notice the stiffness is on small bumps and small dips in the road. Doesn’t feel like it’s hitting the bump stops. I’ll take a look and see about raising it some.

[M3SQRD]

Originally Posted by Adcampo

Yeah, I had read that port installed HAS is set at 10mm drop. I was surprised to see it was full max down.

I notice the stiffness is on small bumps and small dips in the road. Doesn’t feel like it’s hitting the bump stops. I’ll take a look and see about raising it some.

BMW bump stops have a nice progressive stiffness curve so when they’re first engaged they add a small amount to the overall effective front spring stiffness and then continues to ramp up with further compression. This means you shouldn’t feel whether the bump stops are being used. Riding the bump stops is not necessarily a bad thing if the suspension tuning is done correctly. It’s when a bump stop that has a huge initial stiffness is used and the suspension crashes into it is when you’ll feel the bump stops because there’s a massive instantaneous increase in effective front spring stiffness. Ride quality and grip suffer in this case. If you can, push the bump stop down until it touches the top cap of the strut body and then drive your car. The bump stop will end up at the top of the strut piston rod (i.e., at the upper strut mount) if you’re engaging the bump stops.