Changing Spring Rate on C36 Update 2

Following is quoted from a forum discussion on benzworld.org:

Springs differ in two main areas... spring rate and spring length. Changing the length does affect the rate, but let's talk about springs in their static state.

Mercedes makes a whole series of different springs. They have different rates and lengths. These different springs are spec'd for different cars. Higher spring rates are generally for use in a heavier car. Spring rates can also be increased to vary the "sporty" driving nature of the car. Different spring lengths are used to vary the ride height of a specific car. The different thickness spring shims (often referred to as "pads" on the forums) are used to vary the space between spring perches, effectively changing the length of the spring.

For a given car, using the weight based on the number of options installed, the desired ride height based on the car market, and the intended ride quality, the intended spring and shim can be calculated.

Because Mercedes wanted a more "sporty" driving quality with the AMG models, a higher spring rate was in order. Depending on whether the AMG car is intended for US or Euro markets, a different spring length is chosen to provide different ride heights. Since Mercedes has a huge catalog of different springs from which to choose, the logical course would be for AMG to specify what the desired characteristics are, then choose the off-the-shelf spring that matches these characteristics. The W210 E-class springs are higher spring rates to handle the slightly increased weight of the car, so these were used. That's why the AMG cars come from the factory with springs that look like regular Mercedes springs and have regular Mercedes part numbers.

Changing Spring Rate on C36 Update 1

This is a quote from a website http://www.spdusa.com/change.htm:

the Mercedes C280 sedan is changed into the Mercedes C280 Sport with very small changes. It has stiffer sway bars, the shocks are calibrated stiffer and like the Honda, they change the upper link in the front suspension. The spring rates are not changed!. The car is much more controllable at high speeds and high rates of yaw (turning quickly). The Mercedes C36 (now C43) has slightly stiffer springs for Europe, but not America.

Out of curiosity I have ordered a new spring kit for the C36. It was the H&R Sports Spring Kit Part Number 29377, designed for C36, C43, CLK430 and CLK55. They will lover the vehicle by 25mm, as claimed by their website and specification. Again I have ordered the spring kit with a reasonable discount via Pak Lok, my favorite garage for Mercedes. I chose H&R because of its reputation in ride quality and its German origin.

There is another H&R Sport Spring Kit Part Number 29277 for are designed for the rest of the W202 model range (for the lesser models like C280, C180 and anything in between). It says it will lower the height by as much as 40mm, which is scary to me. 

We needed to find the W210 spring pads to fit the top section of the H&R springs as they were not flat at the top as the factory springs. Judging from the difference in heights I selected the thickest spring pads front and rear. However when we dropped the car to the ground I was hugely disappointed. The car simply sat too low and it just looked plainly stupid. I was sure that was not the 25mm I had been expecting. I don't mind firmer spring rate but I seriously challenge the usefulness of lowered suspension.

Besides the ground clearance concern I had also issues with the reduced spring travel. It is bad for handling in my knowledge as we are dealing with street condition.

My drives in the next few days turn out fine. The springs were obviously carefully engineered not to be offensive. The ride was actually acceptable 85% of the time. Handling and traction have improved a lot, 40% plus in my subjective valuation. Steering responsive and diving while braking are also vastly improved. Still I could feel 15% of the time the whole car was under-damped, as I kept the very expensive factory Bilstein-AMG shock absorbers which was merely one year old. My wife actually prefers the new found handling finesse and gained traction. She does not mind the added hardness.

For me personally I prefer the softer and more floaty ride over sharpened handling and added traction. Anyway I don't really needed them to help me to drive fast and to meet occasional challenges on the streets. And I don't need to take the C36 to a morning drive. And I have planned to revert to the factory springs whenever I can find time to do so. I would like a new set of factory springs which I hope will be softer than my original springs that came with the C36, as well as the H&R spring kit.

Here are two web links to the H&R site (one from US and one from Germany):

http://www.hrsprings.com/site/index.html

http://www.h-r.com/