729 Sladge Hammer

Here youīll find complete instructions about servicing and tuning you 729 Sladge Hammer. CAUTION: The AIR RACE needs special knowledge and tools! Look at the AIR RACE service section!

First, I want to give you a short overview about the 729 versions:

729SH R86, R100, Light DSAD Release 1 and 2

These forks were the first Sladge hammer forks on the market. Their stanchion (inner leg) diameter was 30mm (instead of 32mm of later models).
Refer to the ADDITIONAL repair section of the Sladge Hammer Release 1 and 2.

729SH AIR RACE, 729SH R86, R100, Light DSAD Release 3 and 4

Later models of the 729 Sladge Hammer with 32mm stanchions.

729 Sladge Hammer AIR RACE
This fork is quite complicated to service. Please mail us!! Be sure to be or know an advanced mechanic. Knowledge about suspension forks may serve as a basis for servicing this fork.
Please do not open this fork without need, without instruction AND knowledge about air spring and dampened forks!!! Service instruction

729 Sladge Hammer R86, R100, R100S and R120SF
steel spring/open oil bath suspension fork

If you want a more detailed graphic just click: 729 Detail

The 729 is a steel spring, open oil bath damped fork like actual MX-suspension forks. The difference: Only one spring in the right side (if u stand in driving direction and looking down to your fork), and one open damping cartridge in the left side.

Dismounting your 729
REMEMBER: We describe only the steel spring, oil dampened fork!

Change oil

1. Open the right leg of the fork.
2. Take out the spring.
3. Open the left side.
4. Put the fork upside down. Put out the oil. (on both sides)
5. Pump the fork some times.
6. Turn the fork in vertikal correct position.
7. Put in the oil.
In the right side: Put in about 100ml ATF (Automatic transmission fluid) For reducing friction.
In the left side: Put in fork damping oil (available in Motorbike-shops). Viscosity depending on you riding style (speed, jumps) and weight. We use SAE 4-5(very light), heavier riders should use SAE 8 (or ATF like in the right side). Oil level is about 10mm above the cartridge. Is you use a higher oil level you change the characteristic of the fork very much! Remember: The fork has air inside, if you compress the fork, the air will be like an additional spring. If you ride a higher oil level, u have less air inside, and much more progression of the spring rate. Try some different oil leves.
Donīt forget to pump the fork some times to let the air out of the cartridge! (Correct oil level)
R86 .. 140ml
R100 .. 160ml
R110 .. 200ml
R130 .. 210ml
8. Put the stanchions in normal postion. (No load on the fork)
Why? Because if you close the fork both stanchions completely at the end of the travel u have no air inside, and therefore no additional spring. If u want a comletely linear travel, close the fork at the end of the travel.
9. Put the spring inside the right side.
10. Close the fork.

Changing the seals and bushings:

If you want a more detailed graphic just click: 729 Detail

1. Open the right leg of the fork.
2. Take out the spring.
3. Open the left side.
4. Put the fork upside down. Put out the oil. (on both sides)
5. Pump the fork some times.
6. Remove the screw at the bottom of the inner right leg with a long 5mm hex-key.
7a. Remove the seeger-ring. Pull out the stanchion (inner tube). You willl see on the inner tube a small distance ring, the seal, a distance ring, the upper and lower bushing.
Or: If this donīt work, pull out the stanchion until you see a thinner section. Then you take a small screwdriver and remove the seeger-ring and carefully the small distance-ring and the seal. Be sure not to damage the seal! Avoid any contact to the inner diameter of the seal.
7b. Left side: Like right one, but without step 6.
8. Change seals and bushings if you need. Be careful: The seal can be damaged or worn out even if you donīt see any damage! If the fork lost oil, you have to change the seal! In the season 2000 we tested following seals: Grey and black. Use the black seal if youīre a racer an need full performance from the beginning. Or if you have no muddy conditions. Use the grey seal if you riding in muddy conditions and donīt mind about some friction in the beginning. (about 200km).

Closing the fork

1. Clean all parts carefully.
2. Put some grease or damping oil on following parts:
seals, bushings, stanchions, spring guides (the plastic parts which hold the spring), top-cap thread and o-ring
3. Put the lover bushings on the stanchions
4. Put the stanchions in the outer legs
5. Put in the lower bushings and the distance-rings in the outer legs.
6. Put in the seals. Use a screwdriver for that. If you have stanchions with a thinner section, be sure the inner section is in the same postion like the seat of the seal.
7. Put in the small distance ring.
8. Be sure you see the seat of the seeger-ring. If not you have to put the seal and distance-ring lower.
9. Put in the seeger-ring.
10. Close the fork like in the description above. (Changing oil.)

Change the spring rate:

You have a lot of possibilities to change the spring rate:
With the main (steel) spring itself, with the oil level and the elastomers.

Pre-load the main spring: This is a very popular method. Nevertheless itīs one of the most worst. Avoid pre-loading the spring as much as you can! Try other possibilities first. This is no limitation of the 729 Sladge hammer or any other Race Factory forks, that is a general rule in tuning suspension forks.


Curve 1 shows a linear spring rate
Curve 2 shows a linear spring-rate too, but with a softer spring
Curve 3 shows a linear spring-rate in the beginning and a progressive spring-rate at the end of the travel

You achieve the curve 3 with:
- A higher oil level or
- a fourth elastomer at the bottom of the left leg.

Change the settings of the damper:

If you want a more detailed graphic just click: 729 Detail

To open the damper you will need a special tool but itīs simple to make. Click for a drawing!

1. Open the fork like in the description above (Changing seals and bushings).
2. Put the special tool in the leg with the damper cartridge.
3. Screw the tool counterclockwise. You are screwing the oil-cartridge out of the outer leg.
4. Take the tool and the oil cartidge with the internal damping-tube out of the outer leg.
5. Take the damping-tube out of the cartridge.
6. On the damping-tube you see now:

  • An aluminium-nut (maybe couloured).
  • The piston with the small piston-bushing.
  • Some steel valve-shims, standard is 2
  • An aluminium shim.
Now we will talk about some theory:

During compression the oil flows through the piston holes. The oil press the valve-shims back.
That means: More valve-shims directly after the piston make the fork harder for small bumps. A piston with smaller holes will make the for harder for big bumps. Lighter oil will do the same for small and big bumps.

Other tuning possibilities:

Piston : 1 valve-shim : distance-ring : 2 valve-shims : aluminium-shim
This will make the fork sensitive for small bumps, but when the shim moves back, the the other valve-shims will be pushed - harder for big bumps.

During compression the damping tube moves inside the open oil bath cartridge. The oil inside has now to move out, because the tube needs some volume.
If you look at the damping cartridge you will see a hole at the bottom. Depending on the size of this hole, the oil can flow faster or not.
Big hole means: No difference in small bumps, but less damping progression in big bumps.
Small hole: No difference in small bumps, but more damping progression with big bumps.

After compression the fork has to move out:

Now the oil has no possibility to flow through the piston, because the valve-shims are closing the piston. Now look at the damping-tube. You will seee a hole on the side where the piston is located. (Some millimeters up). The oil now flows through this hole, past the damping adjustment needle through the tube and into the open oil bath cartridge.
Itīs now clear that the damping adjustment at the top of the fork regulates the oil-flow when the fork moves out.

IMPORTANT: The nut which holds the piston needs some loctite glue!!!

I hope I give you a short overview about the damping adjustment of the 729 SH.

Please mail us for further information!

race.factory@aon.at