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  • Here are the dyno results showing the compression forces for the two different shim stacks from pg 1.
  • When comparing shim stacks, we always ask ourselves "how does stack 1 compare with stack 2 ?"
    • We always put the changed stack first and the original stack second.
    • In this case, the mod stack (1027) will be Stack 1, and the stock stack (1024) will be stack 2.
  [1027] [1024]    
  mod stk    
  Stack 1 Stack 2 1-2 1/2
ips co (lbs) co (lbs) lb diff % diff
1
  25  
  25  
0 100 %
2
  42  
  42  
0 100 %
3
  61  
  61  
0 100 %
4
  80  
  80  
0 100 %
5
  97  
  97  
0 100 %
10
  165  
  175  
-10 94 %
20
  286  
  307  
-21 93 %
30
  397  
  425  
-28 93 %
40
  493  
  530  
-37 93 %
50
  584  
  627  
-43 93 %
60
  669  
  718  
-49 93 %
70
  748  
  803  
-55 93 %
  • Here is a description of the data table and what the numbers represent.
  • The ips column is the velocity the shock is stroked on the dyno.  This velocity is inches per second.
  • In this case, we made 12 consecutive runs on the dyno (one right after the other) so we have a range of velocities at which to compare compression force numbers.
    • (View the 'dyno run video' link on the left to see how the shock is tested).
         
         
ips        
1        
2        
3        
4        
5        
10        
20        
30        
40        
50        
60        
70        
  • Compression force numbers for Stack 1 (the mod stack).
  • The dyno strokes the shock at the given velocity, and a load cell reads the peak force from the shock.  Force is in pounds.
  • The force numbers are then recorded for each velocity.
  • In this case, the compression force for Stack 1 at 1ips = 25 lbs, 2ips = 42 lbs etc.
  • You will notice the force increases with the velocity.  The same thing happens when riding the bike.  When you hit small bumps at slower bike speeds, the velocity is low and the damping force is low.  As you start hitting larger bumps at faster bike speeds, the shaft velocities and damping forces increase.
  [1027]      
  mod      
  Stack 1      
ips co (lbs)      
1
  25  
     
2
  42  
     
3
  61  
     
4
  80  
     
5
  97  
     
10
  165  
     
20
  286  
     
30
  397  
     
40
  493  
     
50
  584  
     
60
  669  
     
70
  748  
     

 
  • Compression force numbers for Stack 2 (the stock stack).
  • We are comparing the force numbers from one stack against the other.  We put Stack 1 and Stack 2 side-by-side in the table.
  • You can easily see any differences in the compression force numbers.
  [1027] [1024]    
  mod stk    
  Stack 1 Stack 2    
ips co (lbs) co (lbs)    
1
  25  
  25  
   
2
  42  
  42  
   
3
  61  
  61  
   
4
  80  
  80  
   
5
  97  
  97  
   
10
  165  
  175  
   
20
  286  
  307  
   
30
  397  
  425  
   
40
  493  
  530  
   
50
  584  
  627  
   
60
  669  
  718  
   
70
  748  
  803  
   

 
  • Differences between the stacks.
  • We want to know exactly how much Stack 1 (mod) changed. 
  • In the last two columns, we calculate both the pound difference (lb diff) and the percent difference (% diff) between the two stacks.
  • In the lb diff column we can see:
    • At 5ips, the diff is 0 lbs.  Stack 1 and 2 are the same at this velocity. This indicates the shim changes did not influence the damping at these lower velocities.
    • At 50ips, the diff is -43.  Stack 1 lost 43 lbs damping force at this velocity.
  • In the % diff column, we see the percentage Stack 1 has changed over Stack 1.
    • At 5ips, the % diff is 100%.  The compression force for Stack 1 did not change.
      • 100% = 1.0   ( 97 x 1.0 = 97 )
    • At 50ips, the % diff is 93%. 
      • ( 627 x .93 = 584 )
  [1027] [1024]    
  mod stk    
  Stack 1 Stack 2 1-2 1/2
ips co (lbs) co (lbs) lb diff % diff
1
  25  
  25  
0 100 %
2
  42  
  42  
0 100 %
3
  61  
  61  
0 100 %
4
  80  
  80  
0 100 %
5
  97  
  97  
0 100 %
10
  165  
  175  
-10 94 %
20
  286  
  307  
-21 93 %
30
  397  
  425  
-28 93 %
40
  493  
  530  
-37 93 %
50
  584  
  627  
-43 93 %
60
  669  
  718  
-49 93 %
70
  748  
  803  
-55 93 %
 
   
 
 
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  valving info
valving 001
valving 002
valving 003
valving 004
valving 005
 
  complex stacks
complex shim stacks
 
  more valving info
valving 101
valving 102
valving 103
valving 104
valving 105
valving 106
valving 107
valving 108
valving 109