I heard you knotan and will record sights and sounds next time
I have reached a point where I have to tackle the suspension - something I have not done before and which I approached with much respect
And if anybody discovers fundamental mistakes I am making in the following, please let me know
To choose the correct type and length shocks was a first step, but now it's time to find the right springs to finally put the car on its wheels. Armed with some dry theory I knew the first thing to do was to find out the motion ratios and sprung mass to eventually calculate the spring rates. Here you see my high-tech wheel motion measuring device. This way I could pretty accurately put wheel and shock movement into relation. Surprisingly this motion ratio came out the same in front and the rear at 1.6 - i.e., for each unit the shocks move, the wheels move 1.6 units. This will be important for all following calculations:
Then we put the wheels on the car and set it down on two scales - placed between the wheels in the front and rear - so that the wheels touched the ground. This way, we would only measure the sprung mass, without the weight of the wheels, uprights, brakes and parts of the suspension. We would measure this with myself in the seat, half-full tanks, and added the weight of the body parts which are now in the paint shop. This came out at 424 kg in the rear and 224 in the front.
I had also noted extended and compressed lenghts of the shocks, and most importantly, length at assumed ride height. With that I set about some calculations based on the simple formula of: Wheel Rate = Spring Rate / Motion Ratio ^2, and: Spring Rate = Wheel Rate x Motion Ratio ^2. These calculations resulted in certain spring rates and sizes I need and I have put in an order for these springs. An apology here - I will only provide detailed information on how I did the calculations if they really work out as I had planned. Because, otherwise, I know I made mistakes and don't want anybody to repeat these and hold it against me
And, as quick and dirty as this sounds, with my limited knowledge of this, it took me hours boiling over the various sources I have on suspension theory (among them the Caroll Smith books) to understand what's going on and what I should do
Here's a back view with the big wheels and the chassis at ride height. The wheels I am using here are "replica" three piece wheels from Fox Racing Developments. But I would still be interested in a set of good one-piece magnesium wheels, all 15" diameter and 4.5" backspacing, the fronts 9" wide, the rears around 14" wide.