Cars have springs and dampers that help them go along their way.
If you are still fuzzy on the hows of springs and dampers,
http://www.howstuffworks.com/car-suspension.htm is a good place to start.
The reason I made my comments at the beginning is that none of this should be of any real mystery if one understands the responsibility of springs and dampers in a car.
It is the same as reading a baking recipe that asks for 10 grams of salt for every 100 grams of flour, and then asking how much salt you need if you’re using 200 grams of flour.. the question becomes not one of recipe but of basic math.
But I digress.
A few point notes for assimilation:
- A spring has a rate, this rate determines the speed at which weight transfer occurs, the stiffer the spring, the faster the weight transfer.
- Linear spring rates are a nice thing, they make life predictable.
- Many things can act as a spring… or an energy absorbing device, if you will
Moving on.. all damper/strut systems have some form of bumpstop to prevent the shaft of the damper from punching through the bottom, it would be dangerous to design a mass product without such a consideration (although I’m sure F1 doesn’t have these limits.. but who knows).
The question becomes what to do with that bump stop.
“coilovers” (as we know them), typically have higher spring rates that are linear. If chosen CORRECTLY for the application, then the damper should never bottom out, the springs should never coil-bind, and the bumpstops serves its intended role as a last resort safety mechanism to preserve the damper in the event of an unforeseen shock to the system.. such as hitting a raised curb or running over debris.
The term “being on the bumpstops” is meant to describe those situations where you’ve run out of suspension travel. Your springs were too soft, your damper travel was limited, or both. You are now resting on the bumpstop, and your car is no longer suspended. Any subsequent attempt at absorbing a bump is left with the chassis doing the work and eventual failure of components that overwise would have lasted a long time.
However, on an OEM car, the term need not be understood as it is the racing world. This is because, as demonstrated most often in a macstrut car, the bumpstop also acts a secondary spring with a progressive rate approaching infinity.
This accomplishes a number of things:
1. For minor two and single wheel bumps and dips in the road, your car is utilizing only its springs, this is essentially “the softest setting”
2. when you attack a turn, you engage your bumpstops which increases the effective spring rate, this helps you “set the car” faster and helps fight body roll (not the same as reducing it.. but that’s another topic)
*because they are progressive and soft, you do not feel them engage and there is no jarring "bang" (when you bang that means you've run out of ALL travel.. the bump was too much for your entire spring "system).
3. functions as a safety mechanism for the damper once it is compressed to a maximum point
so as you should see, it is a solution to the everyday problem of mass produced cars and how to make a sports car comfortable during the daily drive.
Now the problem with “lowering” springs is that they “lower” the car on to the bumpstops, which now become engaged ALL the time. So you no longer have a soft spring setting for daily driving, you are now permanently set to a high spring rate mode.
“lowering” the car 2 inches or whatever is downright ludicrous for street driving because you’ve eliminated any real suspension travel and your rates are approaching infinity at this point, so unless you’re driving on glass roads this is a joke.
You can “cut” a hard portion of the bumpstop to give yourself more room to travel, but you haven’t solved the problem of utility, you may have made the car bearable in a straight line on city streets, but you’re not stiff enough to avoid resting on the bumpstops during cornering… so whenever you corner hard, you’re relying purely on the grip of your tires and the strength of your shock towers to hold you in place. This is not efficient.
So, that’s that.