BMW offered two shock/spring options on the E46 and most other models: sport and non-sport. Each has a different spring rate (the stiffness), ride height, and shock absorber stiffness. Obviously "sport" is lower and stiffer than "non sport". A general rule is the stiffer the spring/shock, the better the car handles. But there is much more to a good set-up than just "stiffness" so you must choose a set-up that best suits your driving style.
Here are some tips for choosing the right suspension:
- Prioritize your needs. Do you like canyon carving or comfortable commuting? Can you handle bumps and humps? How low do you want your car? What is your budget? What are the roads like where you live? Does it snow/ice? How often can you afford to replace tires, shocks, etc? Make a list and be realistic, lots of guys buy the super hard "corner carver" kits only to regret it after the initial giddy feeling wears off. And at $700-$2500, it ain't a cheap mistake to make!
- Once you have your list of things you want, take some time and do your research. Talk to the guys at Turner Motorsport, Bimmerworld, and other shops that race what they sell. They can tell you what works on the track and what works on the street. Most are more than willing to tell you their experience if you just ask. Also check the online forums (caution:the public is ultimately one sided and few people have the ability to be objective with their views so keep that in mind when they tell you XYZ kit is the only way to go).
- Keep in mind the "collateral damage" you might cause to your car. Damage? What damage? So glad you asked. Things like tire wear, shock life, and body damage from scraping can all be things you have to deal with. Personally I deal with a severe inner tire wear problem from being lowered, great for tearing up the twisties, not so great when I am always buying tires. And I can't tell you how many times I have scraped my bumper by pulling to far forward in a parking space. Also, the lower and stiffer you go, the sooner shocks tend to need replacement (especially in pot hole riddled parts of the world).
- Buy the best kit you can afford. Just as the engine is the heart of your drivetrain, the shocks and struts are the heart of your suspension. Going with a more expensive but tried and true brand can save you hassle and time down the road.
Next installment we discuss sway bars! Don't miss it!