What should this car feel like at speeds over 100 mph? Do I Need New Shocks/Springs?

[99' Mcoupe]

I wanted to get to know this car for a few months of driving before asking these questions. After getting comfortable with the car and driving at speeds up to 125 mph I'm wondering if I need shocks and/or springs.

It is a '99 with 50,000 miles and all service records from the day it was born. I had a full inspection done at a BMW dealer that included compression and leak down tests. The only items needing attention were the windshield wipers and tires. I put new Pirelli's on right after I bought it.

The shocks are orignal. The best way for me describe the car at these speeds is floaty. I believe the car should stick to the road better than it does. It still feels safe, but to me shocks don't last forever.

I'm looking for input from other drivers of this car. What does your car feel like at this speed? How do I positively confirm I need new shocks?

I'm considering Bilstiens with Eibach or H&R Springs. I don't want to spend the money to do this and not see improvement in ride quality. The car is low enough so I'm not interested in lowering, just better handling.

The car already has what I consider to be tasteful and useful mods. Cold air intake, Stage one Dinan Software and Tri-Flow Exhaust.

As an aside, I took a 2006 Z4 M Roadster for a spin yesterday and the exhaust was quieter than mine. I like mine better with it's throaty sound!

[dana r ideen]

I have a 97 z3 with 2.8 L engine and it was lowered and strut stiffener bars and a frame stiffener was added. It does the same thing that yours does at high speeds. It has a rear wing (spoiler) that came with the car and has not been added, but I think that I will have it placed on the car. Mine appears to have performance shocks and springs added when the lowering was done (currently at 75,000 miles) 10k ago. I bought it last Mar 06. I think that the problem is due to the lifting of the rear end due to airflow separation since the car has no lip or wing on the rear end like the new z4. Did you take the 06 z4 up to 120mph to see how it felt? By the way, I am having a ball with this car at lower speeds and am glad I bought it. It replaced a 911sc that I totalled in January. See ya.

[Schneller]

"Floaty" is a relative term that can be caused by a number of different factors. Unless the car has seen alot of bumpy roads, I'd be surprised if the stock suspension is worn out. However, worn tires, faulty chassis alignment, any play in the tie rods or control arm ball joints will make the car feel uncertain, especially at speed. The correct way to check control arm & tie rod end ball joints is to lift the car & then compress them using a set of "waterpump" (read large) pliers. If you can see the ball joint compress more than one millimeter I'd replace the component & realign the vehicle.

If the chassis checks out & you'd like something sportier, the trick set-up is Koni Sport shocks & struts combined w/ B&G or Koni springs. The H&R springs for the Z3,we have found, to be too low in the rear with too little spring travel. Since you're from the southwest and your car will probably not see any snow, either the Koni Coil over kits or Bilstein PSS coil over kits will also work well.

Have Fun!

Mike Morris
Schneller BMW Performance
Newbury, MA