I'm building a 29 Model A Roadster and have a new 9" rear end. I have about 6" of clearance between the axle tube and the frame. Does anybody have any idea of what size spring and shock to use for a coil-over setup?
A lot of variables, and much depends on what you intend to do with the car. A longer shock arrangement can give a softer ride quality because you can use a softer spring. There are also progressive springs that can offer a softer ride then get stiffer as load increases. What you need to know is what the rear end weighs, and how long your shocks are. Without that info, it's just guesswork. Could be 100 lbs/in, could be 200. If I had to guess, I'd choose somewhere around 110 to 130. Springs themselves are fairly inexpensive, so if you miss, it's not a big deal. Edit: Also, where the springs are located has an effect. Shocks and springs in front of the housing requires slightly stiffer springs than behind the housing
If you're looking to use those ugly shock brackets in the pics, there's so much adjustability it's hard to understand the need for the question! Those brackets are more suited to a race car. If I've got that wrong you need to mock up mounts and measure the length between them at ride height. Armed with that info and an idea of the weight of the rear of the car you can talk to coilover suppliers. There's useful info on the Speedway site which should help. Chris
Most use a 14" extended and 10" collapsed shock. Many variables for spring choices. A lot depends on how your shock is mounted, angled or straight. I would suggest you go to Ridetech's coil over page and read the info and play with their spring calculator. To get it right, you will need wheel weights of the car as ready to run. If you know someone who has springs you could borrow, it would give you a starting point to begin with.
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