Little spring pushes against big spring at full droop. @snuffnwhisky can splain it better.
Tender spring setup. I'll put this in basic terms, just examples. Lots of variables with shock angles, mounting locations, etc.
- You have a 2,000# machine, 500# at each wheel.
- You have a 10" stroke shock and want the ride height with 6" up travel and 4" down.
- You want a spring rate of 300# per in.
- You would need to put 1,200# on that spring to compress the shock 4" to get ride height but only have 500# on it.
- With no spring preload the spring will only compress 1.66" at ride height.
- If you back the preload rings off to get the correct ride height, your spring will be loose when the shock extends.
- Add a dual spring like a 200# over 300# and your new spring rate is 125# per in. (200 + 300 / 4)
- Now the 500# load compresses the springs 4" with no preload.
- With a dual spring setup, Get the correct length upper spring so it coil binds at ride height and now the rest of the up travel is at 300# per in.
- OPTIONAL, install a longer upper spring and crossover nuts to get a dual rate setup. You can move the crossover nuts down to where they touch the spring divider at ride height and it will preform just like a tender spring setup above.
- With the Dual rate setup, it allows you to move the crossover rings up higher so you can have that 125# per in spring rate past the 4" of compression at ride height and transition to the 300# rate farther in the travel.