Quote Originally Posted by chargeR View Post
I also don't understand. If you adjust the ride height on a coilover that has both spring perches and a lower perch like in this picture:



Then if you adjust the ride height using the lower collar then droop travel should be nearly unchanged (neglecting small changes in motion ratio and stuff). How is it that you could reduce droop travel using this method? The only way to eat up droop travel in such an arrangement would be to wind up the two spring perches thus compressing the spring.

The total length of the shock absorber determines how far the wheel drops when the chassis is lifted, say over a bump or even on a jack. Most Japanese coil over kits have very high spring rates for what are pretty light cars so they don’t compress the springs much. Cheap coil over kits don’t have helper/ keeper springs on the front or rear, even more expensive kits only have them on the rear. With high springs rates not being compressed much the only answer is to limit the travel of the shock to keep the springs captive. This is further exacerbated when they use short body shocks as they also have to use short shock shafts, which further limits the amount of droop available.

This triple combination (short shock, high spring rate, no helper/tender spring) means you don’t need much of a bump to lift the wheels off the ground. Using a larger swaybar helps when it’s roll that causes the wheel to unload, but has no effect when both wheels are affected by the bump.

As a comparison jack up a standard car, front or rear, and see how much the wheels droop, Car manufacturers aren’t stupid, they design in this amount of droop for a good reason, to keep the wheels on the ground. Which after all is pretty important, it really hard to control a car when its wheels are off the ground.

An example perhaps, most people last year heard about the Skyline that flew of the road, hit a tree and killed the 2 occupants. That accident was put down as being caused by speed, but the fact is that wasn’t the route cause. The car had almost zero suspension droop, so when it went over a hump around a slight bend in the road all 4 wheels came off the ground. When the driver turned the steering wheel to negotiate the corner and applied the brakes to slow down, nothing happened as the wheels were off the ground. It carried on in a straight line into a tree.

The need for droop translates to racing, whether bouncing a car of the ripple strips or lifting the rear wheels over the hump in Conrod Straight. Take a look at how much the suspension droops in a V8Supercar when it’s up on the jacks. A pit stop is a good time. As a rule of thumb we run 2/3rd of the suspension travel for compression and 1/3rd for droop. For use on race track which in general is much smoother than the average road.


BTW I noticed in that picture the tie rod end is still connected below the steering arm, not a good idea when the car is lowered more than 25 mm. It really should be swapped for a steering arm with the ball joint taper on the top, which helps correct the bump steer. I find it hard to believe that a coil over supplier that sells kits for drastic lowering ignores the need for such essential correction. Whatever kit they are I would suggest not buying them if you intend to lower the car more than 25 mm. If you already have them then you need to do something about the incorrect steering arm


Cheers
Gary