How does one go about choosing a shock and spring when changing to a completely different suspension design than what a car originally came with?
I'm considering removing the IRS from my car and putting in a solid axle Ford 8.8 to avoid broken rear diffs and CV axles. Going to build a torque arm due to packaging constraints on the chassis, and would be attaching the shock/spring ahead of the axle, on the lower link arm. Separate spring/shock combo or coilovers could work. What's a Grassroots solution when starting from scratch?
I don't have any personal experience, but I know there should be plenty of people here on the forum that could offer guidance. Best of luck to you.
P.S. I wouldn't be doing my job if I didn't drop a few articles that might be helpful:
Spring rate you can probably get in the ballpark using effective wheel rates to figure out what spring you need, if you like the setup you have now or if there's an established "good" spring rate from the enthusiast community.
Shocks are more complicated, if they're off the shelf you will want something from a similar weight vehicle with similar spring rates and a similar shock mounting configuration. Reason being that most independent suspension shocks aren't a 1:1 wheel rate like solid axles usually are, solid axle shocks are often mounted at an angle which also takes away from their effective rate (trig can help calculate for similar wheel rate) and solid axles have a lot of unsprung weight that tends to change how the damping is set up. A heavier vehicle will also tend to have stiffer shocks for body motion control, and stiffer spring rates will tend to mean more rebound damping, so there's just a lot of variables to play with, but you may be able to look at these things to find some OEM application that gets you close.
Aftermarket solutions exist that are rebuildable, allowing you to tune shim stacks to dial in damping. external clicker adjustments may or may not be enough. You just have to decide how nuts you want to go with it. Also depending on the vehicle, motorcycle rear shocks can be an option since they offer a lot of external adjustment, plus are rebuildable, for a good price. But they will definitely need a revalve to work in an automotive application.
Colin Wood said:
I don't have any personal experience, but I know there should be plenty of people here on the forum that could offer guidance. Best of luck to you.
P.S. I wouldn't be doing my job if I didn't drop a few articles that might be helpful:
And I wouldn't be doing mine if I didn't drop links to GRM stories I was involved in on this topic 
https://grassrootsmotorsports.com/project-cars/LS-Swapped-2003-Nissan-350z/how-prepare-car-test-day-project-ls-swapped-350z/
https://grassrootsmotorsports.com/project-cars/2019-nd-mx-5/how-fast-can-custom-built-coil-overs-at-off-the-sh/
