How do double adjustable shocks work?
03-07-2011, 01:07 PM
#1
Racer
Thread Starter
How do double adjustable shocks work?
Can someone direct me to a good explanation of how double adjustable shocks work? It sure seems like no one knows. I have JRZ double adjustable RS shocks on a SPEC 996 use them for track only. I know when the car feels good, but sure don’t understand why… I am one of those people that just can’t stand something until I understand how and why something works!
So, what I think I know:
1. Compression: How fast or slow the shock compresses when you hit a bump or turn into a corner. The higher (or more “+”) you turn it up the stiffer or slower the shock compresses. On the JRZ’s this is the setting on the bottom of the shock.
2. Bump or Rebound: How fast or slow rebounds (or goes back down) after being compressed. The higher (or more “+”) you turn it up the slower the shock returns to the pavement (I think?). On the JRZ’s this is the setting on the top of the shock.
I have been told so many things (all different and opposite) from a lot of people, that leads me to believe that few really know how they work and how to set them when…
Can someone help me understand how these things work?
So, what I think I know:
1. Compression: How fast or slow the shock compresses when you hit a bump or turn into a corner. The higher (or more “+”) you turn it up the stiffer or slower the shock compresses. On the JRZ’s this is the setting on the bottom of the shock.
2. Bump or Rebound: How fast or slow rebounds (or goes back down) after being compressed. The higher (or more “+”) you turn it up the slower the shock returns to the pavement (I think?). On the JRZ’s this is the setting on the top of the shock.
I have been told so many things (all different and opposite) from a lot of people, that leads me to believe that few really know how they work and how to set them when…
Can someone help me understand how these things work?
03-07-2011, 01:09 PM
#2
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I will email you some stuff that may make this clearer...
03-07-2011, 03:15 PM
#4
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Magic. Pure Magic.
Or it starts with the piston and shim stack. The piston is a disk with holes in it and the shim stack rest over the holes. When the shock moves, the fluid goes through the holes and pushes on the shim stack, forcing it's way through the hole.
Now, when there isn't enough pressure (either small or slow movements) the fluid doesn't have enough force to move the shimstack. In those cases, it goes through a bleed circuit where there is a needle valve (that you get to adjust) to determine how much fluid goes through it. This is low speed dampening adjustments.
The external resorvoir holds the fluid that the shaft dispalces when it moves. This fluid that gets displaced by the shaft is done at a high speed and goes through another valve on it's way to the external reservoir. That valve on the reservoir is the high speed adjustment.
Or it starts with the piston and shim stack. The piston is a disk with holes in it and the shim stack rest over the holes. When the shock moves, the fluid goes through the holes and pushes on the shim stack, forcing it's way through the hole.
Now, when there isn't enough pressure (either small or slow movements) the fluid doesn't have enough force to move the shimstack. In those cases, it goes through a bleed circuit where there is a needle valve (that you get to adjust) to determine how much fluid goes through it. This is low speed dampening adjustments.
The external resorvoir holds the fluid that the shaft dispalces when it moves. This fluid that gets displaced by the shaft is done at a high speed and goes through another valve on it's way to the external reservoir. That valve on the reservoir is the high speed adjustment.
03-07-2011, 03:49 PM
#5
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Actually, if somebody could lead me to a primer (intermediate) on damper/spring relationships and functions - maybe even 964 specific, I'd be more than grateful (i.e. worth a pound of home cured bacon perhaps...).
03-07-2011, 04:13 PM
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03-07-2011, 04:28 PM
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I'm by no means a shock expert. Once you start trying to make shock dyno graphs tell me something about the car, I consider it magic. Especially double knee graphs like Stimola (RIP) used to make.
03-07-2011, 05:40 PM
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Get Jan Zuijdijk's book. It has very detailed description of how shocks work and how to dial them in.
The book is quite a difficult read (between the complicated subject and the presentation), but I still think it is the best book at explaining the why's and how's behind modern high-end dampers.
The book is quite a difficult read (between the complicated subject and the presentation), but I still think it is the best book at explaining the why's and how's behind modern high-end dampers.
03-07-2011, 06:36 PM
#11
Rennlist Member
two one way valves. both work against or with the spring.
compression (AKA: Bump) meters how fast the oil or gas can be pushed out of one chamber to another. more bump or compression, the harder the fluid has to be moved. it can make you feel ever bump in the road. however, very slow movement the springs will compress and the fluid transfers.
rebound: meters how fast the fluid is returned to the original reservior. how fast the tire can go to the direction of full or partial droop. too much rebound, and the wheel doesnt go back down after the compression cycle. If it cant go back down, and then you hit another bump, the car "jacks down" this is not good, because repeated bumps, with too much rebound, will have the car on its bump stops before you know it.
generally, you want to set the car up so its not too bumpy for a given track, and the car doesnt jack down anywhere. after that, its fine tuning all 4 corners, and all 8 control settings. add high speed and low speed to the equation, and thats 16 settings you can play with at the track. Not to mention the mix of spring rate, swaybars and aligment. makes my head spin!
compression (AKA: Bump) meters how fast the oil or gas can be pushed out of one chamber to another. more bump or compression, the harder the fluid has to be moved. it can make you feel ever bump in the road. however, very slow movement the springs will compress and the fluid transfers.
rebound: meters how fast the fluid is returned to the original reservior. how fast the tire can go to the direction of full or partial droop. too much rebound, and the wheel doesnt go back down after the compression cycle. If it cant go back down, and then you hit another bump, the car "jacks down" this is not good, because repeated bumps, with too much rebound, will have the car on its bump stops before you know it.
generally, you want to set the car up so its not too bumpy for a given track, and the car doesnt jack down anywhere. after that, its fine tuning all 4 corners, and all 8 control settings. add high speed and low speed to the equation, and thats 16 settings you can play with at the track. Not to mention the mix of spring rate, swaybars and aligment. makes my head spin!
Can someone direct me to a good explanation of how double adjustable shocks work? It sure seems like no one knows. I have JRZ double adjustable RS shocks on a SPEC 996 use them for track only. I know when the car feels good, but sure don’t understand why… I am one of those people that just can’t stand something until I understand how and why something works!
So, what I think I know:
1. Compression: How fast or slow the shock compresses when you hit a bump or turn into a corner. The higher (or more “+”) you turn it up the stiffer or slower the shock compresses. On the JRZ’s this is the setting on the bottom of the shock.
2. Bump or Rebound: How fast or slow rebounds (or goes back down) after being compressed. The higher (or more “+”) you turn it up the slower the shock returns to the pavement (I think?). On the JRZ’s this is the setting on the top of the shock.
I have been told so many things (all different and opposite) from a lot of people, that leads me to believe that few really know how they work and how to set them when…
Can someone help me understand how these things work?
So, what I think I know:
1. Compression: How fast or slow the shock compresses when you hit a bump or turn into a corner. The higher (or more “+”) you turn it up the stiffer or slower the shock compresses. On the JRZ’s this is the setting on the bottom of the shock.
2. Bump or Rebound: How fast or slow rebounds (or goes back down) after being compressed. The higher (or more “+”) you turn it up the slower the shock returns to the pavement (I think?). On the JRZ’s this is the setting on the top of the shock.
I have been told so many things (all different and opposite) from a lot of people, that leads me to believe that few really know how they work and how to set them when…
Can someone help me understand how these things work?
03-08-2011, 01:29 AM
#12
Rennlist Member
I'd be weary of that, what often feels better maybe not be faster.
At MSR last weekend I was helping setup that black e46 m3. I had the owner feel what the car felt with some understeer and what it felt like pretty loose. He said the understeering car felt better, he actually went slower.
At MSR last weekend I was helping setup that black e46 m3. I had the owner feel what the car felt with some understeer and what it felt like pretty loose. He said the understeering car felt better, he actually went slower.
03-08-2011, 08:55 AM
#13
Rennlist Member
I'd be weary of that, what often feels better maybe not be faster.
At MSR last weekend I was helping setup that black e46 m3. I had the owner feel what the car felt with some understeer and what it felt like pretty loose. He said the understeering car felt better, he actually went slower.
At MSR last weekend I was helping setup that black e46 m3. I had the owner feel what the car felt with some understeer and what it felt like pretty loose. He said the understeering car felt better, he actually went slower.
+1
03-08-2011, 09:53 AM
#14
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+2. Most drivers don't realize when their car is over-damped. Though the car feels locked down, overall grip will suffer and produce slower lap times.
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Larry Herman
2016 Ford Transit Connect Titanium LWB
2018 Tesla Model 3 - Electricity can be fun!
Retired Club Racer & National PCA Instructor
Past Flames:
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2004 GT3 Track Car
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1974 914/4 2.0 Track Car
CLICK HERE to see some of my ancient racing videos.
Larry Herman
2016 Ford Transit Connect Titanium LWB
2018 Tesla Model 3 - Electricity can be fun!
Retired Club Racer & National PCA Instructor
Past Flames:
1994 RS America Club Racer
2004 GT3 Track Car
1984 911 Carrera Club Racer
1974 914/4 2.0 Track Car
CLICK HERE to see some of my ancient racing videos.
03-08-2011, 10:41 AM
#15
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+2. Most drivers don't realize when their car is over-damped. Though the car feels locked down, overall grip will suffer and produce slower lap times.
Larry, I haven't yet read the suggestions above...please expand on your comment here if you would.
Larry, I haven't yet read the suggestions above...please expand on your comment here if you would.