HOW TO REFRESH YOUR MOUNTAIN BIKE’S FORK – IT’S EASIER THAN YOU THINK

HOW TO REFRESH YOUR BIKE’S FORK

Over years and years of suspension development there is one thing that has never, and will never, change—the need for servicing. This is an often neglected aspect of bike maintenance and is something that many people wouldn’t dream of doing themselves. However, we’ve partnered with our friend Jonathan Dunbarr at Trail Tuned Suspension (we call him Jon) so he can show us just how easy a basic fork service can be to execute. Fork performance and longevity are greatly affected by your choice to service regularly, so it’s definitely worth the effort. You don’t even need all of the fancy tools Jon uses either, just a little bit of determination and creativity. The fork we are servicing in this “Garage Files” is a RockShox ZEB Ultimate using SKF seals, but this process works for most fork designs.

 

NECESSARY TOOLS

• Articulating bike stand

• Assortment of Allen wrenches

• Torque wrench

• Fork seals kit (look up requirements for your fork)

• Fork oil (look up your fork’s manufacturer recommendations)

• Crush washers (look up your fork’s requirements)

• A mallet

• Lint-free towels or shop towels

• A shock pump

• A syringe

• A wide flat-head screwdriver, moto tire irons, or box end wrench

• A small cup or dish

• Isopropyl alcohol or fork-cleaner solution

• Narrow wooden dowel

• A catch bin to drain the oil into

• A small metal pick

• Light fork grease like Slick Honey

• Gloves and eye protection are recommended

Step 1: Workplace Setup

There are a lot of easy-to-lose small parts being taken off and on in this service, so it’s best to have a clear bench or tabletop to put things on. We recommend laying out a length of shop towels to put things on when you’re not using them. This helps with the organization and cleanliness of your workspace. Lay out all the tools and items we listed above on and around the shop towels so they are all within reach when needed.

You’ll also need a solid work stand to hold the fork aloft while working. It’s best if this stand has some level of articulation as you will need to rotate the fork a couple of times to complete steps properly. We also recommend you work on a mat or carpet you don’t mind getting dirty, as there will most likely be unavoidable leakage.

 

Step 2: Fork Preparation

Before you do anything, you’ll need to remove the front wheel and brake caliper. Be careful when you undo the clamp that holds your brake hose in place because it is one of the easiest to lose parts of this process (believe us, we know). If you are able to remove the fork to complete this service, now is the time to do so; however, it is possible to complete the service with the fork still installed on the bike, but some steps may be harder to complete

 

Step 3: Air Removal

If you have an air fork, it’s important for safety purposes to release the air from the air spring before you begin the process. Be sure to use a shock pump with an accurate gauge so you can write down the air pressure inside on a piece of paper or on your phone. Then release the air pressure slowly through the pump’s release valve until there is no air left in the system. Jon likes to remove the valve core, but that’s not necessary.

 

Step 4: Pre-Soaking the Foam Rings

The foam rings’ primary purpose is to collect oil and keep it so the seals and bushings remain lubricated even when sitting unused for a little while. This extends their lives and helps the fork wake up a little quicker after being stored. Grab a small cup or dish and fill it with a couple of centimeters of fork oil and submerge the foam rings into it and let them sit there until they’re needed. The fork oil Jon used in this demonstration was Motorex SuperGliss, but ideally, you should be looking up the recommended fork oil for your specific fork. This is typically found on the brand’s website with a chart of oils and the volumes needed for that fork.

 

Step 5: Removing the Foot Nuts

For this step it’s best that you have your fork inclined so it’s just over parallel to the ground. This is where some forks differ from others, but generally, they all have a removable rebound knob, often using a small Allen key; in this case, a 3mm. Once that’s removed, you’ll need a 5mm Allen key to loosen the foot nuts until they’ve been backed about ¾ of the way out. Then, to unseat the shaft, you’ll need a mallet to bang on the head of the foot nuts until you hear a pop. This may need to be done a couple of times. This releases the inner shaft from the outer fork body so you can take the lowers off. When this is complete, finish unthreading the foot nuts and place them on your bench towel for later.

 

Step 6: Draining the Oil

Depending on how long it’s been since this service has been performed on your bike, there may not be much oil left or it might be incredibly dirty. Either way, using a catch basin, tip the bottom of your forks vertically to the ground so the openings you have just made are at the bottom to let the oil drain. This may take a minute or so.

 

Step 7: Removing the Lowers

Once the oil has fully drained, it’s time to remove the fork’s lowers. It’s best to remove the lowers slowly to not cause damage to anything on the fork. This should be relatively easy, just be aware that any remaining oil will drop out at this point, so do this over your catch basin if possible.

 

Step 8: Removing the Old Seals

Now that you’ve separated the lowers from the stanchions, it’s time to start swapping parts. This can be a tricky step, but don’t worry, it’s not too hard. Before removing the seals, carefully reach in with a small pick to dislodge the old foam rings, making it easier to get at the seals.

Using a wide flathead screwdriver, motorcycle tire lever or open-ended box wrench, carefully place one end under one side of the first seal and slowly leverage it back. This may take a little effort, but it will pop out eventually. Be careful not to damage any part of the inner fork.

 

Step 9: Clean and Inspect

At this point, it’s important to carefully clean every part of the interior of the fork. We used 90-percent isopropyl alcohol for this task, but there are also fork-cleaning products available to buy that do just as well and are not harmful to any part of the fork itself. Take a dowel and lint-free cloth or shop towel and, after soaking the inside of the fork in the cleaning solution, carefully insert the dowel with the towel on the end and rotate. This is a good opportunity to clean the outside of the fork and bridge, as it is now easily accessible.

 

Step 10: Seal Installation

Now, this is probably the most important part of the whole process. Before installing the seals, you want to make sure both the seals and the surface you’re inserting them into are cleaned with isopropyl alcohol and a lint-free cloth. Once that’s done, take your tool—Jon is using a Push Industries 38mm seal press—and carefully knock them in with a mallet. Seal presses are available online. If you don’t have a seal press, bring your seals to a hardware store and buy a small section of PVC pipe that fits over the outside edge of the seals. You will have to be a little more careful this way, but it will work just as well when finished.

When hammering them in, it’s crucial that you get them fully seated in place with no gaps between them and the fork. If not, they will be tilted and won’t fit over the stanchions right, making it harder to install and keeping them from sealing effectively.

 

Step 11: Foam-Ring Installation

This is where we add the foam rings. Why now? Well since they’ve been soaking in fork oil, it would get all over the surface of the fork where the seals are going, making it slippery and giving them a higher probability of popping out, which is not what you want. Best to put them in now after the seals are already installed. All you have to do is get one side into the slot between the seals and the bushings, and then just feed them around until they are fully seated.

 

Step 12: Reinstalling the fork lowers

Before reinstalling the fork lowers, use the isopropyl alcohol and a lint-free towel once again to wipe down every part of the fork uppers making sure to clean all excess oil that may have lingered. Now coat the seals in a light suspension grease, which will allow the lowers to slide on more smoothly.

Once that is done, carefully guide the lowers up to meet the stanchions, being careful not to fold the new seals under themselves, which can cause problems later. Once they’re on, slide them all the way up and tilt the fork horizontally for easy access to the bottom holes to refill the oil.

 

Step 13: Refilling the Oil

Now is when you’re going to need to consult your fork’s rebuild chart to figure out how much oil you’ll need on each side. Some manufacturers use slightly different oils for the damper side and the spring side, but most of the time you don’t need to worry about that. Most forks will take about 10cc of oil on each side using a syringe.

 

Step 14: Crush Washers

This is something you may need to take a trip to your local bike shop for—crush washers. You can find them on Amazon, and sometimes they come with the seal kit depending on which one you buy, but they’ll need to be replaced, so make sure you have them before you start the process. These are located on the foot nuts you removed earlier, and if you look at them carefully, you can see why they’re called crush washers. They’re small nylon washers designed to be crushed at torque so no damage is done to the fork itself.

 

Step 15: Reinstalling the Foot Nuts

For this you’ll need a torque wrench, because if you over-torque this particular component, it can cause a lot of damage, so be careful. Make sure you pay attention to the torque spec in your fork’s chart. Ours called for 7 Nm of torque on both sides, which was measured using a Park Tool torque wrench. Once you’re done with that, go ahead and reattach your rebound knob.

 

Step 16: Air it up

Remember that piece of paper or file you put the fork pressure number on? Well, it’s time to get that out again. When airing up your fork, it’s important to balance your negative air chamber as you fill it. To do that, you must cycle the fork every 25 psi or so until full. This allows the fork to come to pressure in a balanced way, allowing it to perform at its highest level. This is easiest when the fork is fully reattached to the bike.