The Luftkappe can be installed by anyone who already possesses the tools and the know-how to service their own fork - or by anybody who has the tools and can follow instructions closely. Written instructions and an installation video are included below.

Key things to note before you start:

0. Yes, we know, the dome says 34 on it. The Fox 38 air spring uses the same piston diameter as the Fox 34. We hope to laser etch 38 onto the next batch.  

1. You need a torque wrench. Don't try it without one. Beg, borrow, rent, buy or steal one from a friend. 

2. You need to remove a roll pin from the old piston. You need a bullet tool to safely remove and reinstall the spring shaft through the seal head. And you need shaft clamps to remove the foot stud. We make tools to make your life much easier here. All tools are an option to purchase with the Luftkappe. They can also be purchased separately. We take no responsibility for anything you damage if you attempt installation without these tools.

3. We refer to the Fox service manuals for all aspects of the servicing OTHER than the specific installation of the Luftkappe to the air shaft.

4. The Luftkappe is ONLY compatible with Float forks. It does not work with Talas (travel adjust) forks. 

5. Record your air pressure and rebound settings before you start doing anything else.

6. Don't do it drunk. Even if you're Australian. Especially if you're Australian.

7. You will need some supplies as well as tools. These are outlined below.

8. The Luftkappe only replaces the piston - not the entire air shaft. We will be removing the existing piston from the air shaft, and replacing it with the Luftkappe.

TOOLS & SUPPLIES

Tools:
10mm bullet tool
10mm shaft clamps
Roll pin tool
Torque wrench
12mm wrench
12mm crows foot adapter or universal adapter 
10mm socket
15mm socket
32mm socket 
Ratchet
Bench vise
2mm Hex Wrench
Propane Torch or Heat Gun
Shock Pump

Supplies:
Slick Honey grease
20wt WPL ShockBoost oil or Fox 20wt Gold oil
Fox PTFE 5wt oil
Blue Loctite
Red Loctite
Isopropyl alcohol and clean, lint-free shop towels.

INSTALLATION

Fox 38 specific steps:

3a) Press out roll pin from old piston using roll pin tool and remove piston. Clean shaft with isopropyl alcohol.

3b) Leave the topout bumper and silver spacer in place. (In the Fox service guide the spacer is black, it may be a preproduction model). 

3c) Slide the Luftkappe stud onto the shaft, lining up the lower hole in the stud (furthest from thread) with the hole near the end of the air shaft

3d) Compress the new roll pin to get it started in the hole, then press it all the way in

3e) Slide the plastic Luftkappe piston onto the stud, lining up the slots in the piston with the roll pin

3f) Lubricate o-ring on piston, and inside of Luftkappe dome where it will contact the o-ring

3g) Apply blue Loctite to thread on piston stud

3h) Thread dome on to piston by hand. Clamp the shaft securely in the 10mm shaft clamps and torque the dome to 50in.lbs (5.5Nm).

Step Four

Follow the Fox 38 NA2 air spring service guide from Step 12 to the end of Step 18 onwards. https://www.ridefox.com/fox17/help.php?m=bike&id=1058 

It is not necessary to replace the foot stud orings in Step 12, but do remember to reinstall the one you removed before heating the foot stud to remove it!

NOTE: Make sure the spring shaft is fully extended before reinstalling the foot stud at Step 15. If it's pushed a long way into the air spring tube you can trap too much air in the negative chamber, which will result in your fork "sucking down" even when pressurised as it is not able to extend far enough to equalise pressures between positive and negative chambers.

Step 5

Remove two bottomless tokens from the top cap (if they are installed). 

Reinstall the top cap to 220in.lbs. 

Follow the Fox 38 NA2 air spring service guide from Step 20 to to the end of the guide. Only add about 20psi to the air spring at Step 20, we'll set up the fork correctly once the fork is reinstalled. 

Note: ensure foot bolts are done up with the fork fully extended. If they're done up with it partly or completely compressed, the fork will suck down into its travel.

Reinstall onto the bike once reassembled and checked.

SETUP

Step One
Your token configuration should start with two tokens less than you had previously. The maximum number of tokens you can safely run is TWO LESS than what is specified by Fox for the configuration of fork you have, when it is in stock guise.

Step Two
Your starting air pressure should be approximately the same as your air pressure was before installing the Luftkappe, however it's easiest to get there in two or three steps. 

a) Pressurise the fork to roughly 1/3 of the final pressure you are aiming for. You will notice the fork is now very stiff at the start of the travel, and is topped out quite hard.

b) Compress the fork several times, very slowly, to allow pressure to equalise between the positive and negative chambers. You will feel a soft notch in the motion near the start of the stroke - if you hold the fork at that position you will feel it get softer over the space of a couple of seconds at most.

c) Once the two chambers are equalised fully, the fork will top out pneumatically (not hard contact between two surfaces).

d) After the two chambers are equalised, pump the fork up to roughly 2/3 the pressure you are aiming for and repeat the equalisation process there.

e) Repeat equalisation process at full pressure.

Step Three
Ride your bike and adjust pressure and volume configurations as you see fit.

TROUBLESHOOTING/FAQ

After installing my Luftkappe, the fork is not extending to full travel, what is happening?

After installation, the fork should extend to within about 2mm of its original travel when the fork is unweighted (lift front wheel off the ground to allow weight of wheel to pull on fork) - measure exposed stanchion to check. If it doesn't, this is a sign that one or more of the following things has happened:

1. The footbolts were not done up with the fork at full extension. This must be done or the fork will have a vacuum in the lowers that sucks it down. Undo the footbolts and tap them loose, then do them back up at full extension.

2. The piston was inserted too far into the air spring tube before the foot stud was installed, trapping a lot of air in the negative chamber that the air in the positive chamber is not able to overcome in order to reach the equalisation port. You can try forcibly extending the fork to reach the equalisation point, and/or use higher pressure in there to assist you. If it does equalise but still stays sucked down, this is not the cause. 

3. You do not have the correct size air shaft in there. If you have changed the shaft, this is very likely the cause. Replace the shaft with the correct one. 

4. There is excessive grease in the negative chamber. 

5. There is some fault with the main piston quad ring that is preventing it from sealing properly, such as debris jamming in between it and the stanchion. This will typically cause complete collapse of the fork.

My fork sags just under the weight of the bike, why?

It should sag a couple of mm, because the bike has weight. If your suspension does not sag at all under the bike's weight then it is excessively sticky or preloaded. Think about it this way - if you, the rider, weigh 90kg (200lbs) and the sprung mass of your bike weighs 10kg (22lbs), your bike's sprung mass constitutes about 10% of the total sprung mass. If you run approximately 20mm sag in the fork when the rider is on the bike, then it makes sense that you'd see roughly 2mm sag with no rider on the bike.

I have to run more pressure now to get the same sag, why?

Part of the point of the Luftkappe is that it reduces the initial stiffness of the air spring. As a result, yes, you'll run more sag. Besides that, measuring sag on a fork is very inconsistent and unreliable - use pressure as a measurement instead. If the fork feels like it's riding too low in the travel due to the extra sag, it may simply be that your handlebars need to be a few millimeters higher.

Questions?
steve@vorsprungsuspension.com