Penske 8900 series Technical Manual Download Page 24 | Manualshive

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24

Linear Piston

Each piston face has a dished surface, to preload the valve shims flat against the piston face. The standard dishing is 1° on

both the compression and rebound sides of the piston. By increasing the compression side dishing to 2°, the shims become

increasingly preloaded, causing a slight delay in opening during compression movement. The dishing causes the shims to

snap open, in return giving the car a snappier feel as opposed to a smooth roll, once again this modification is for driver feel.

If you have questions on piston dishing, call our technical staff for information and recommendations.

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Summary of Contents for 8900 series

Page 1: ... Preload Shim Spacers 21 Pistons Flow Rate Through Multiple Bleed Holes 22 Piston Selection 23 Linear Piston 24 Digressive Piston 25 Velocity Dependent Piston VDP 26 Damping Adjustments 28 Dyno Graph Overview 30 Notes 34 Table of Contents Page Technical Manual Motorcycle Shocks 8900 Series REV 3 27 01 7 Main Office Midwest West 150 Franklin St 12666 US 12 2499 S Stockton St P O Box 1056 P O Box 66...

Page 2: ... person should hold the front of the motorcycle straddling the front tire 3 Have the rider wearing all of their gear sit on the bike in a tuck position 4 The third person should then measure the distance between the axle center line and a convenient location on the rear subframe same locations used in Step 1 5 Record this measurement as B STEP 3 1 Subtract B from A This number is your sag The amou...

Page 3: ...3 Notes ...

Page 4: ...e rear ride height 2 Transfer weight from the rear wheel to the front wheel 3 Make the front turn in quicker 4 Reduce chain torque to the rear wheel Going SHORTER with rear shock length eye to eye will 1 Lower the rear ride height 2 Transfer more weight to the rear wheel 3 Make the front turn in slower 4 Increase chain torque to the rear wheel CAUTION DO NOT EXCEED THIS LENGTH Ride Height Adjustme...

Page 5: ...ompression can bring about a harsh feeling by allowing too much shock travel Excessive wheel spin exiting corners 1 Repeat above steps 2 Rebound can be too fast allowing the rear to unload and spin the tire Use caution when changing rebound Wallowing exiting corner 1 Stiffen low speed compression clockwise 2 Stiffen high speed compression 1 to 2 clicks at a time 3 Decrease rear spring sag 4 Slow d...

Page 6: ...levis 41 SR 89225 Spring Retainer 8900 2 25 55mm 42 RR 06 Wire Ring 0625 Wire Diameter x 1 900 Incomplete Part Number PART NO 1 BD 81__ Body Aluminum Coil over 10 0 24 0 2 RH 89225 Ride Height Adjuster 8900 2 25 3 OR 2221 B O Ring 2 221 Buna 70 4 HO 87__ Hose 4 36 in 1 increments 5 FT __ Fitting 45o or 90o 1 8 NPT 6 BC 81__ Body Cap 8100 0o 45o 90o 135o BC 89CL Body Cap 8900 Clearance 7 MO 8T Mono...

Page 7: ...ortest Stroke Body Length 0 o 315 o 270 o 225 o 180 o 45 o 90 o 135 o 0 o 315 o 270 o 225 o 180 o 45 o 90 o 135 o Reservoir Clocking â â â â â â __ 90o Fitting __ 45o Fitting __ None Type of Adjuster ________________ Eyelet Bushing Total Width ________ Bolt Diameter ________ Body Cap Bushing Total Width ________ Bolt Diameter ________ ...

Page 8: ...1 Drum CD 8100 24 OR 2013 B O Ring 2 013 Buna 70 Incomplete Part Number PART NO 1 IU 22 S Air Valve Port O Ring Steel IU 04 Valve Core 2000 psi IU 06 Valve Cap High Temperature OR 2010 O Ring 2 010 Buna 70 2 RR 06 Wire Ring 0625 Wire Diameter x 1 900 3 CP 81R Cap 8100 Reservoir 4 OR 2221 B O Ring 2 221 Buna 70 5 PB 55 Piston Band 55mm 6 PI 81R Piston Reservoir 1 72 Diameter 7 OR 2323 M O Ring 2 32...

Page 9: ...ter is the CD drum The CD drum has 6 settings numbered 1 6 with number one setting the largest hole being full soft and number six the smallest hole being full firm As fluid is forced through the CD drum Figure 1 it is metered through one of the preassigned orifices in the drum it then enters the reservoir body moving the floating piston The floating piston is designed to separate the fluid and ni...

Page 10: ... 34 IU 20 A Air Valve Port O Ring Aluminum IU 04 Valve Core 2000 psi IU 06 Valve Cap High Temperature Incomplete Part Number PART NO 1 RR 12 Retaining Ring 343 External 2 CA 92 Cage CD Clasp 343 Diameter 3 RR 12 Retaining Ring 343 External 4 CA 90 Cage CD Top Hat 343 Diameter 5 VW 91 Washer Valve 1 475 x 010 VW 88 Washer Valve 1 350 x 008 VW 66 Washer Valve 1 200 x 006 VW 44 Washer Valve 1 050 x 0...

Page 11: ...portionally to the axial load applied With this arrangement the low speed bleed orifice still meters fluid during high speed shaft movements but the extra forces generated are handled with the shims which have less resistance to flow at higher velocities They are designed to virtually bypass the low speed orifice and form a new fluid circuit The force at which this occurs can be varied by turning ...

Page 12: ...ir Valve Port O Ring Aluminum IU 04 Valve Core 2000 psi IU 06 Valve Cap High Temperature Incomplete Part Number PART NO 1 JT 76CDSH Jet High Speed Shaft 2 RR 12 Retaining Ring 343 External 3 CA 92 Cage CD Clasp 343 Diameter 4 CA 90 Cage CD Top Hat 343 Diameter 5 VW 91 Washer Valve 1 475 x 010 VW 88 Washer Valve 1 350 x 008 VW 66 Washer Valve 1 200 x 006 VW 44 Washer Valve 1 050 x 004 VW 28 Washer ...

Page 13: ...he jet causes the oil to hydraulic In turn the oil is forced through another piston in which it s orifices are covered by another shim stack This shim stack is preloaded with force from the CD cage and preload shims By turning the high speed adjuster clockwise stiffer you are preloading the CD cage and shims making it tougher for the oil to flex the shims The operation of the high speed adjuster a...

Page 14: ... 8900 Series Rebound Adjuster The rebound adjuster screw on the 8900 Series shock absorber is located in the adjustable platform at the base of the main shaft The rebound adjuster has 25 to 30 clicks of adjustment Note the external rebound adjust ment is only a fine tuning device for the main valving located inside the shock absorber During the rebound extension stage of the shaft movement fluid f...

Page 15: ...ps against high speed hex 6 Before the oil lowers insert the floating piston and 8100 piston band or 8700 8760 quad ring into the reservoir body Make sure the quad ring is not twisted 7 Hold the remote reservoir below the level of the shock with the hose pointing up allowing any trapped air to flow up into the shock body Using the handle of a mallet push the floating piston up into the reservoir b...

Page 16: ...r valve needs replacing reservoir cap o ring needs replacing leaking quad ring or dowty seal OIL LEAK AROUND SHAFT Shaft seal o ring or wiper needs replacing Note minimal oil seepage is normal OIL LEAK AT RESERVOIR Teflon tape seal on hose needs replacing reservoir cap or CD housing o ring needs replacing OIL LEAK BETWEEN SHAFT BEARING AND BODY Shaft bearing o ring needs replacing SHAFT WILL NOT F...

Page 17: ...ual shims determines the amount of damping force the shock will produce By changing the thickness of the individual shims damping forces will be altered For example if you are running an A compression valving where all the shims in the stack are 006 thick and you replace them with a B compression valving which consists of all 008 thick shims the compression damping will increase When the shaft is ...

Page 18: ...when making a big adjustment in high or low speed the change will affect the other in a small percentage As an example the high speed is set at 4 and the low speed at 6 Now you want to set the low speed to 2 this will also increase a percentage of the high speed force figure By dropping the high speed from 4 to 3 would compensate for this low speed change so the overall damper curve would remain i...

Page 19: ...l soft add 5 flats 8100 or clicks 8760 of rebound adjustment at a time then return to continue the process until the bike becomes skittish or the rear wheel hops under braking At this point you know you have gone too far on the rebound settings back off one flat at a time for final balance Once again this is a basic procedure for finding your initial setup for a given track If you find that you ar...

Page 20: ...012 Constant VS DM D 012 012 010 010 Constant VS D D 012 012 012 012 Constant VS DP D 012 012 015 015 Constant VS EM E 015 015 012 012 Constant VS E E 015 015 015 015 Constant VS EP E 015 015 020 020 Constant VS FM F 020 020 015 015 Constant VS F F 020 020 020 020 Constant 1 350 O D 1 200 O D 1 050 O D 900 O D 750 X 020 Constant Compression Valve Stack Rebound Valve Stack Constant When refering to...

Page 21: ...of 0 40 The flow rates can also be added so a piston with three Ø 015 and three Ø 020 holes would have a total flow rate value of 0 68 1 20 1 88 which would be the same as three Ø 025 holes VDP and Digressive Valving Information Options Part Part Part 004 VW 2NX 004 004 VW 5NX 004 004 VW 8NX 004 006 VW 2NX 006 006 VW 5NX 006 006 VW 8NX 006 008 VW 2NX 008 008 VW 5NX 008 008 VW 8NX 008 2 Notch 5 Not...

Page 22: ... 032 1 02 2 05 3 07 4 10 5 12 6 14 7 17 8 19 9 22 0 034 1 16 2 31 3 47 4 62 5 78 6 94 8 09 9 25 10 40 0 035 1 23 2 45 3 68 4 90 6 13 7 35 8 58 9 80 11 03 0 036 1 30 2 59 3 89 5 18 6 48 7 78 9 07 10 37 11 66 0 038 1 44 2 89 4 33 5 78 7 22 8 66 10 11 11 55 13 00 0 040 1 60 3 20 4 80 6 40 8 00 9 60 11 20 12 80 14 40 0 045 2 03 4 05 6 08 8 10 10 13 12 15 14 18 16 20 18 23 0 050 2 50 5 00 7 50 10 00 12...

Page 23: ...near Piston 1o 2o 55mm PI HF14005 High Flow Linear Piston 1o 4o 55mm PI HF21005 High Flow Linear Piston 2o 1o 55mm PI HF22005 High Flow Linear Piston 2o 2o 55mm PI DL00_ Digressive Linear Piston 45mm or 55mm DESCRIPTION PART NO PI DL005 1DG Digressive Linear Piston 1o 55mm PI DD00_ Double Digressive Piston 45mm or 55mm PI VDL45 VDP Linear Piston 45mm PI VDPL55 VDP Linear Piston 55mm PI VDPL55 1DEG...

Page 24: ...sing the compression side dishing to 2 the shims become increasingly preloaded causing a slight delay in opening during compression movement The dishing causes the shims to snap open in return giving the car a snappier feel as opposed to a smooth roll once again this modification is for driver feel If you have questions on piston dishing call our technical staff for information and recommendations...

Page 25: ...varied by adding or subtracting a series of shims under the main shim stack The high flow piston design is offered in two variations The double digressive piston is preload variable on both the compres sion and rebound sides The digressive linear piston is preload variable on the digressive side only leaving the other side with linear characteristics In most cases the linear side of the piston wou...

Page 26: ...n Rebound Rebound Flow á Compression Flow á This graph illustrates the way in which the two different circuits operate on compression This graph illustrates the way in which the two different circuits operate on rebound side LOW HIGH LOW HIGH Low speed works the digressive stack and high speed works both ...

Page 27: ...e outer stack helps to seperate the high and low speed circuits in the piston resulting in more compliancy over bumps and curbs 1 The Low Speed section is controlled by the amount of bleed the outer valve stack configuration and the amount of preload to determine the nose profile 2 The Digressive profile is set by the thickness of the outer stack The amount of time that the curve stays digressive ...

Page 28: ... take a set quicker Figure 2 shows the effect of increasing the stiffness of the shim stack Increasing the thickness of the shim stack i e 004 to 010 stiffens the damping rate of the shock across the whole velocity range While the other two adjustments only affect the lower shaft speeds the shim stiffness is the best way to adjust damping at higher shaft speeds The shims give the damping that chas...

Page 29: ...29 Damping Adjustments Figure 3 Figure 2 ...

Page 30: ...his section of the manual illustrates different valving combinations in the form of graphs The graph shown is force vs displacement graph The force vs displacement graph is a very accurate and simple way to assess valving characteristics If you are not familiar with this type of graph it is ex plained on the following page along with the graph above showing the four different quadrants ...

Page 31: ...tarts over again in quadrant 1 QUADRANT 1 This is the beginning of the compression stroke Where the graph crosses the zero line pounds in quadrant 1 begins the compression stroke Approximately the first 1 2 of displacement is formed with relation to the low speed bleed bypass When the shaft reaches a certain velocity the low speed bleed bypass shuts off and the compression valve stack begins to re...

Page 32: ... to react QUADRANT 4 This quadrant begins with the rebound valve stack open Where the graph crosses the zero line inches in quadrant 4 is the maximum force produced by the rebound valving As the shock approaches the full extension point the rebound valve stack begins to close as it approaches the compression movement At this point the cycle starts over again in quadrant 1 Force Velocity Average Th...

Page 33: ...Activate knee Low Speed Bleed Bypass nose Shaft Velocity In Sec Rebound Low Shaft Speed slope Note Remember that low speed damping characteristics are controlled by bleed through the low speed adjuster and the bleed hole in the piston not the valve stacks 500 400 300 200 100 0 100 200 300 400 500 Damping Forces Lbs ...

Page 34: ...34 Notes ...

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