Suspension Fork Service: Everything for the Flow!

Loosen the axle on the front wheel with a hex key or, depending on the fork model, with the integrated quick-release lever and remove the front wheel.

Loosen the two caliper bolts (depending on the brake with a 4mm or 5mm hex key or with a T25 Torx key for SRAM and Magura). The caliper along with the adapter, if any, can now be removed. You can then simply let the caliper "hang" by its line.

Now you gotta remove the cable holder to detach the brake line from the fork. If you're dealing with an older fork, often a zip tie is used to secure it - just cut the zip tie then.

Loosen the two stem clamp screws that hold the stem to the fork steerer.

Loosen the Ahead screw responsible for the headset preload and remove it along with the Ahead cap.

Heads up: as soon as the screw is loosened, the fork might slide down – so please, hold onto the crown!

Take off the stem and (if present) the spacers from the fork steerer, then gently pull the fork down and out of the frame's head tube.

To prevent the handlebars from swinging around and kinking the lines, you can stick a big hex key through the stem and head tube. This keeps the cockpit in place somewhat.

If you've got a fender (mini mudguard) mounted on the fork, unscrew it. For a zip tie version, you’ll need to cut them.

Now, it's cleaning time for the fork. You can do this with a damp cloth, some soapy water, brake cleaner, or penetrating oil. We prefer the latter (Brunox, WD40, or Ballistol) because it's excellent for cleaning.

Be super thorough when cleaning the fork. When it's "open" later, no dirt or dust should get inside!

Our patient: A RockShox Lyrik Ultimate RC2 with 140mm travel. However, the approach is similar for most forks.

Once the fork is completely clean, seize the opportunity to check for any damages: Are the stanchions scratch-free? Do the seals look intact and aren't brittle or cracked? Are all adjusters working? Also, inspect the axle receiving area for cracks or anything similar.

Unscrew the air valve cap on the air side of your fork (for most forks, that’s on the left when viewed from the rider's perspective)

Use a slim tool (screwdriver, hex key, etc.) to open the valve and release the air from the fork. Pull down on the lower tube unit. This empties both the positive and negative chambers, preventing the fork from compressing and making it much easier to disassemble later.

Remove the Air Top Cap: For current RockShox forks, you'll need a cassette tool, but for most other forks, a thin wrench will do.

The removed Air Top Cap with a volume spacer. Their number and shape can vary, depending on the fork model, of course.

Now unscrew the rebound adjuster (on the bottom of the damping side, on the rider's right). It's fixed with a hex socket grub screw. You only need to loosen it, not remove it entirely.

Once the grub screw is loosened enough, you can pull out the adjuster.

Next, loosen both screws on the bottom of the lower tube unit – but only 3 turns! Why will be clear in the next step.

Take a soft hammer and tap gently on the screws loosened by 3 turns. This needs to be done to disconnect the conical piston rods inside from the lower tube unit. If the screws are flush with the bottom after the hammer tap, the piston rods are disconnected.

Subsequently, remove both screws completely. Watch out: From this point, the fork might start to drain.

We're putting the fork back in the repair stand to pull down the lower tube unit. Make sure to place a suitable container underneath. Both parts of the fork should be standing or hanging vertically so the old oil can drain out.

When pulling the lower tube unit down, make sure you pull it straight down. The piston rods shouldn't be stressed sideways. If you don't have a repair stand and can't secure the upper part of the fork, pull the two parts of the fork apart by hand.

Next, wipe the main seals, also known as dust wipers, inside and out with a cloth until they're completely clean and dry.

With tweezers or a small screwdriver, carefully remove the foam oil rings sitting in a groove under the main seals.

Check the foam rings and also feel the main seals inside with your finger. If they show no damage, aren't brittle and the fork is relatively new, you might reuse the rings and seals. If you spot any damage, they need to be replaced. Here you can find our service kits. 

Manufacturers recommend installing new foam rings at every service. But if they are completely intact, not swollen or damaged, and not black from old oil, you can reuse them. Squeeze the old oil out with your fingers.

Then dip the rings in fresh oil, allowing them to soak up. The same oil used for lubrication in the lower tube unit is used here.

Next, we spray the lower tube unit with brake cleaner or degreaser. Don't be stingy: There should be no residue of old oil or grease left afterward. Place the lower tube unit vertically in a bucket so the brake cleaner can drip off and the rest can evaporate.

To remove the air shaft, the retaining ring securing it in the stanchion must first be removed. Work gently and carefully. A scratch on the stanchion or piston rod could mean a total fork failure! Lift the retaining ring all the way around until it pops out completely. With some other brands, it's equipped with 2 holes – then you'll need Retaining Ring Pliers.

Now you can gently pull out the air unit.

The stanchion on the spring side is now completely open. Pull a cloth through it several times to clean the inside.

Use a long, slim object to push the cloth through the tube. Be careful: If you're using a metallic object, make sure not to touch and scratch the inside wall.

Now, we've gotta clean the air shaft thoroughly. Both the piston rod and all seals need to be clean and dry afterward. While you're at it, you can check if the piston rod is scratch-free and the seals are intact.

The cleaned air unit and some SRAM Butter for lubrication.

Slather a bit of SRAM Butter on all the seals. Don't be stingy with it – any excess grease will be wiped off during reassembly. The seal shown here separates the positive chamber from the negative chamber, is always in motion, and thus has a groove to constantly provide a "sliding layer". 

The glide surface of the air spring guide rod also gets some SRAM Butter. Best to apply it with your finger. The O-rings of the lower seal and the spacer (red components) are also greased up with SRAM Butter. 

Now, the cleaned and freshly lubricated air unit is reinserted into the cleaned stanchion tube. 

Next, slide the red spacer on. It positions the negative chamber's end seal correctly, ensuring the proper volume ratio of the two air chambers. 

Push the spacer all the way into the stanchion tube. Finally, you might need to use a screwdriver to help a bit around the edges since the spacer is a few millimeters recessed into the stanchion tube in its correct position. 

Now, the snap ring is reinserted for securing. Be patient if it resists. It often likes to pop out halfway through. Here, too, be careful with the piston rod. Once the ring is completely in its groove, press around with the flathead screwdriver to make sure it sits properly. 

The foam rings have by now soaked up fresh oil and are ready for installation. 

Insert the freshly oiled rings back into their groove below the main seals. Be careful: They shouldn't twist or tilt. 

This is how it looks when the rings sit correctly in their groove. 

Now, the main seals are lubricated. We're also reaching for the SRAM Butter for RockShox. Again, don’t hold back with it. Anything that's too much will push itself out later. 

Best to spread the SRAM Butter inside the main seals with your finger. 

Now it's time to reassemble the fork. Ideally, do this in a repair stand, clamping the fork shaft and keeping the fork vertical. First, check the oil rings in the lower tubes to make sure they're sitting properly in their groove and not protruding inward, or else they'll get squished by the stanchion tubes. Slowly insert the stanchion tube unit into the lower tube unit. 

As soon as the stanchion tubes reach the main seals, be careful: The stanchion tubes need to slide into the seals without getting jammed. Pay close attention. The fork should now slide together quite easily. 

Only slide the fork a little bit together, so the stanchion tubes still "stick out too far." You can find documents with the necessary lubricants and quantities from the respective manufacturer online - in this case, at www.sram.com 

We use a clean syringe to draw the required amount of oil. Definitely do not add more than prescribed to the fork. The saying, "The more, the better" does not apply here! Depending on the manufacturer and model, different amounts and even different oils are used in the two lower tubes.

The oil is now injected into the openings of the lower tube unit. It's important that the piston rods inside don't reach the openings, otherwise, the oil would end up inside the piston rods and not in the lower tube unit itself. That’s why we only pushed the fork together a little bit. 

Once you've filled both sides with oil, the screws are reinserted. Watch out: Don't mix them up! The "simple" screw goes on the spring side, the special screw with the adjuster slot goes on the damping side. Depending on the manufacturer, there are special sealing rings that go under the screw head. With some models, these should be replaced during service. 

Tighten the screws with the torque specified by the manufacturer. For RockShox and Fox, it's usually about 7Nm. 

Now, you can stand the fork upright again. The positive air chamber gets a few milliliters of oil to keep the stanchion tube's glide surface permanently lubricated. You'll find the exact quantity again online at the manufacturer's site. Our Lyrik Ultimate gets here 3ml.

Now the air chamber is sealed again. The seal on the Air Top Cap also appreciates a little grease. 

For current RockShox models, here's where we use our cassette tool again. Pay attention also here to the manufacturer's specifications. RockShox, for example, sometimes recommends 28Nm, Fox Racing Shox 25Nm.

Don’t forget: The rebound adjuster must also be put back in place. Just stick it on all the way and tighten the grub screw by hand. 

We pump the fork back up. To balance the pressure between the positive and negative chambers, you should lightly compress the fork a few times while pumping. 

Before we put the fork back, we clean the headset bearing cups on the top and bottom, as well as the bearings, since dust and dirt tend to accumulate here. 

The bearing cup, here fully integrated, is greased. For carbon frames with integrated cups, please make sure that the grease is compatible with carbon. The bearing itself can also be greased. A generous amount of grease prevents water ingress and creaking noises. We do the same with the lower bearing cup and bearing. 

The fork cone, here with a sealing lip, is also greased, as it faces a lot of splash water. 

Now, the freshly serviced fork goes back into the frame. If you had spacers installed, of course, put them back in place. 

The cockpit is slid back onto the fork shaft. 

We tighten the Ahead screw by hand. 

Now, the brake caliper is reattached. Make sure the adapter and washers, if present, are positioned as before. Don't tighten the brake caliper yet, as it needs to be aligned to the disc. 

Now you can reinstall the front wheel, slide the axle in, and tighten it with the specified torque.

The cable clip is reattached.

If you've aligned the brake caliper without any rubbing, you can also tighten it with the correct torque. Unless otherwise specified, use about 7Nm.

If the pressure set works for you, screw the valve cap back on.

If you've adjusted the headset without any play using the Ahead screw, the stem can be clamped. Also, make sure to adhere to the manufacturer's specified torques here.