The JRZ 50 DA shaft has been making a big difference on track for many of our racing clients. We love shipping out more grip, and thought that we could help even more by explaining what it is and what it does.
The 50 DA shaft is a double adjustable part, which allows us to adjust rebound bleed and compression bleed past the main piston. Rebound bleed on the red knob is what many of you are used to, as this is the same basic adjustment type on all JRZ dampers outside of the 4 way. The little black kno is the compression bleed. This is where we start to make a big difference from what the standard JRZ does.
Let's compare the differences between a standard JRZ 3 way adjustment range (model 12 32) and a 50 DA compression adjustment range, with digressive valving.
Starting with the 12 32 high speed:
And the 12 32 low speed:
Now the 50 DA compression bleed, with a digressive valving:
Compression bleed on the shaft allows us to do a few different things, depending on how the piston valving is setup. Normally, a JRZ will have a soft linear piston valving, letting the canister do more of the work. We can do a digressive valving with the FA 3030 piston - as shown above - we can also do a linear valving with the FA 3030 or our standard (80 60, 80 40 etc) pistons.
A big distinction is how much more the compression force changes at lower velocities. This influences grip and feel significantly.
Another major difference, is how the damper responds through time, looking at a standard type of JRZ (blue) versus a 50 DA / FA3030 digressive (red) damper, we see similar overall forces and matching low speed slope, but big differences in the "zero point". Note where the lines touch the left side of the graph at zero velocity:
All of these things result in major differences in how the car feels and what we can achieve from a tuning perspective. While this is a brief synopsis of the topic, we hope it was informative.
The application can be much more involved than we can practically cover in an email. We're working on a video to go more in depth.
For more information, please feel free to call or email anytime. We're always on call.
-The Olsen Motorsports Team