Multi rate Spring Set for the TRA 1/16 Shocks used on the Slash, and Revo.
Spring Steel Construction
PROGRESSIVE-Rate Springs, PROGRESSIVE-Rate (PRS) allow the optimum spring rate for each application. These multi-rate springs are soft at the beginning to soak up the small bumps, but transitions (crosses over) to the stiff part of the rate to resist bottoming on jumps and other big "hits. "
Two 1.1mm wire Purple PROGRESSIVE Rate Springs
Two 1.3mm wire Titanium PROGRESSIVE Rate Springs
Two 1.22mm wire Blue PROGRESSIVE Rate Springs
Blue
length: (25mm)
Inner diameter: (10.9mm)
Wire diameter: (1.22mm)
Titanium
length: 19mm
Inner diameter: 10.9mm
Wire diameter:1.20
Purple
length: 22mm
Inner diameter: 10.9mm
Wire diameter:1.28
Hot Racing progressive springs each coil is spaced differently and have a variable spring rate. When free, it is easy to compress progressive springs for first few mm. As you apply more forces, coil on a progressive spring come closer. After a certain point, coil at both end of progressive springs becomes inactive, and that makes the spring stiffer. Apply more forces to mid part of the progressive spring then it becomes stiffer because as the number of active coils in a spring decreases, the spring rate increases. So, progressive springs may both be sensitive to very small bumps on the road, while giving the stiffness you need during hard braking and turning.

description revised by: DB March 20, 2013