12:05 Garage- ’70 Duster build
I think I upset the applecart enough on my post in the suspension section regarding my geometry improvements to my HDK setup, so lets move to something less conflicting, leaf springs.
Hotchkis advertised their leaf springs as "geometry correcting". The leaf is bent in a manner that it lands in approximately the center of the front spring eye. I think their front hanger hole is in a different location from stock also. Someone will have to educate me on this because I've never run a stock hanger and its been decades since I've even seen one. Mounting location and the arch of the spring is what lowers the car enough that some don't like them. I started reading about rear roll center on leaf spring cars and found this:
This made me start thinking about my change to sliders. While I don't think the roll center height will change in relation to the ground because the arc of the spring and the wheel are the same, what changes is the distance from the roll center to the center of gravity. So this got me thinking that perhaps my change to sliders made my leaf springs have incorrect geometry as compared to what Hotchkis had in mind when they designed them. The rear leaf spring eye is now approximately 1-1.5" closer the frame rail now. (I didn't measure the height different between slider and shackle.) In my mind, now the front eye needed to be raised to get correct geometry back. Lucky for me when I modified my front hangers I incorporated some options, as seen previously in this thread. The middle hole is the Hotchkis location and that's where I had the springs for a while. The top hole is 1" higher.
I figured why not see what happens if I moved to the top hole. I did some geometry calculations and determined it would drop the car about 3/8". My calculations were correct and here are the results. As a side benefit, it looks much better! I have to imagine the rear roll center being closer to the rear center of gravity will help. Who knows? At this point, all the keyboard commandos think a CoC car can't handle and will fall apart from chassis instability anyway, so whatever I say is irrelevant. I'll be over here making constant improvements to my suspension education and my car while all those guys walk past their junk on jackstands everyday.
I think I upset the applecart enough on my post in the suspension section regarding my geometry improvements to my HDK setup, so lets move to something less conflicting, leaf springs.
Hotchkis advertised their leaf springs as "geometry correcting". The leaf is bent in a manner that it lands in approximately the center of the front spring eye. I think their front hanger hole is in a different location from stock also. Someone will have to educate me on this because I've never run a stock hanger and its been decades since I've even seen one. Mounting location and the arch of the spring is what lowers the car enough that some don't like them. I started reading about rear roll center on leaf spring cars and found this:
This made me start thinking about my change to sliders. While I don't think the roll center height will change in relation to the ground because the arc of the spring and the wheel are the same, what changes is the distance from the roll center to the center of gravity. So this got me thinking that perhaps my change to sliders made my leaf springs have incorrect geometry as compared to what Hotchkis had in mind when they designed them. The rear leaf spring eye is now approximately 1-1.5" closer the frame rail now. (I didn't measure the height different between slider and shackle.) In my mind, now the front eye needed to be raised to get correct geometry back. Lucky for me when I modified my front hangers I incorporated some options, as seen previously in this thread. The middle hole is the Hotchkis location and that's where I had the springs for a while. The top hole is 1" higher.
I figured why not see what happens if I moved to the top hole. I did some geometry calculations and determined it would drop the car about 3/8". My calculations were correct and here are the results. As a side benefit, it looks much better! I have to imagine the rear roll center being closer to the rear center of gravity will help. Who knows? At this point, all the keyboard commandos think a CoC car can't handle and will fall apart from chassis instability anyway, so whatever I say is irrelevant. I'll be over here making constant improvements to my suspension education and my car while all those guys walk past their junk on jackstands everyday.
