How To: Servicing Fox Suspension Forks (Quick and Easy!)

Words by: Max Morgan

Servicing your mountain bike suspension can sometimes get pushed under the rug. For those who don't want to spend the money sending their fork back into the manufacturer to get serviced, or don't have the knowledge to do it at home, we are here to remind you the importance of servicing your suspension and walk you through the process. Just like changing the oil in your car, changing the oil in your mountain bike suspension needs to be on your to-do list certainly at least once a year. Over time, the oil in your suspension breaks down and gets contaminated with dirt and grime. With a quick service, your fork will feel like new again!

In this installment of our mountain bike How To series, we are going to be doing a lower leg fork suspension service on a 2020 Fox 36 Factory Series fork. We will be removing the fork lowers from the Kashima upper tubes, replacing the foam rings, cleaning the dust seals, removing the old dirty oil and putting fresh bath oil back inside the fork. We won't be tearing into the damper or the spring side of the fork, rather just giving the fork a quick freshen up. This service can play a major role in the overall performance of your fork out on the trail. Follow along and don't be afraid to dig into your own fork! This same step by step process can be followed for all Fox forks. Just be sure to reference the oil bath volume chart to find your fork.

What Tools Do We Need?

• We need to make sure we have all the right tools for the job. For starters, you will need Fox 20wt Gold Fork Fluid, Fox 5wt Teflon Infused Fork Fluid, Fox 36 foam rings, and Fox crush washers. (DO NOT use the old crush washers) We offer a variety of Fox dust wiper refresh kits.
• To also help keep the fork lubricated, you will need either Slick Honey or Sram Butter. We will be using Sram Butter for this fork service but either will work.
• You will need two generic syringes to put fresh oil into the fork legs, 2 small plastic containers to soak the new foam rings, and an oil drain bucket to catch the used oil.
• Next, you will need some kind of degreaser and cleaner. Here I am using Maxima Contact Cleaner. This degreaser is great so that you don’t leave extra oil residue behind on the fork that could potentially contaminate your brakes once the fork is mounted again on the bike. Having some clean microfiber rags/shop towels will also be helpful. 
• Lastly, you will need a shock pump, a rubber mallet, a torque wrench, a standard socket wrench, a 15mm socket, a 10mm socket, a pick, and a 2mm hex key.

Before we get started, remove the fork from your bike and make sure it is nice and clean. Also, make sure you have a clean work environment that way no dirt or grime can get into your nice fork. The easiest way to service your fork is to hold the fork by either the steerer tube or the lower leg in a bike stand. Now let's get to it!

1. Release Fork Air Pressure

• Before releasing the air pressure, make note of the pressure in your fork so you can set it back up the same when we are all done. Even though we aren't getting into the air spring side of the fork, it's always a good habit to release all of the air pressure in your fork when ever you are doing any kind of suspension service.

2. Remove Rebound Knob Cap

• First, unscrew the black rebound knob cap. Then using a 2mm hex wrench, loosen the pinch bolt on the side of the rebound knob. It is not necessary to remove 2mm pinch screw entirely. Lift and remove rebound knob. The fork we are servicing here uses Fox’s Grip 2 damper with both high speed and low speed rebound. Because of that, there are two rebound knobs you will slide off. The Fit 4 and Grip 1 dampers use only one rebound knob.

3. Remove Damper Side And Air Side Bottom Nuts

• Before removing the bottom nuts, make sure the bottom of your fork is raised higher than the steerer tube so that once the bottom nuts are removed, oil will not spill. 
• Using a 15mm deep socket, remove the damper side bottom nut and crush washer. Keep the bottom nut close by, you will need it in just a minute. You might need to use a small pick to remove the plastic crush washer. 
• Using a 10mm socket, remove the air side bottom nut and crush washer. Keep the bottom nut close by, you will need it in the next step. 

4. Knock The Damper Rod And Air Spring Rod Free

• Because we don't have the Fox specific damper leg removal tools, we will be using the bottom nuts to help knock free the damper legs from the bottom of the fork lowers. All we are doing here is compressing the damper leg and air spring leg to detach them from the bottom of the lowers. This will allow us to remove the lowers in the next step. 
• Thread both bottom nuts halfway on to the threads showing. On the damper side, place the 15mm socket on to the bottom nut so that you do not damage the rebound adjuster. Use a rubber mallet to knock the damper leg and air spring leg free. Remove both bottom nuts. 

5. Pull The Lowers Off Of The Upper Tubes

• Now that both the damper leg and air spring leg are free, the lower legs will slide right off of the Kashima coated upper tubes. Now swing the fork down and slide the lowers off above your oil drain bucket to catch all of the old oil. Rest the lowers up against the oil pan to allow all of the old oil to drain out. 
• You can also spray Maxima Contact Cleaner down inside the lower legs to clean out all of the old bath oil.

6. Remove Foam Rings

• Now that we have the lower legs separated from the upper tubes, it's time to remove the old foam rings. The foam rings sit right underneath the dust wiper and are designed to catch any dirt that gets past the dust wiper. Over time the foam rings can collect a lot of crud and dry out.
• Carefully use your pick to fish out each foam ring and throw them into the trash. It’s best to always replace the foam rings when doing a lower leg service.

7. Clean Dust Wipers

• Instead of replacing the dust wipers, we are just going to clean them and throw everything back together. This is a good time to inspect the dust wipers and make sure they aren't damaged. Using a clean shop rag or microfiber towel, wipe them clean.  

8. Clean Upper Tubes

• Take your Maxima Contact Cleaner or Maxima Suspension Clean, spray off the Kashima coated upper tubes and wipe them down clean. This is a nice easy way to make sure you aren't reintroducing any contaminants into the new bath oil. 

9. Install New Foam Rings

• Before you put the new foam rings into the fork lowers, you will want to soak the foam rings in a small container of fork fluid. The damper side for the Grip 2 damper specifically uses Fox 5wt Teflon Infused bath oil and the air spring side uses Fox 20wt Gold bath oil. Give the foam rings a few minutes to absorb as much of the fork oil as possible. 
• The best way to install the new foam rings is to take one at a time out of the oil soak using your pick and set them inside the dust wiper. Then push the foam rings in to place with your fingers. 
• If you aren’t sure what bath oil to use inside your Fox fork, check Fox’s bath oil volume chart to find both the type of oil and oil volume used for each model fork.

10. Pump Up Air chamber

• Before you slide the lower legs back on to the upper tubes, attach the Fox Digital shock pump on to the fork and pump up the air chamber to 60 psi. This will make things easier to reinstall the lower legs.

11. Apply Slick Honey/Sram Butter To Dust Seals

• When the fork is right side up, a majority of the bath oil finds its way to the bottom of the fork lowers. Slick Honey or Sram Butter is a light grease specifically designed to lubricate the dust seals and stay in place.
• Here we are using Sram Butter. Apply a layer of Sram Butter to the inside of the dust seals. This will help keep the fork lubricated and feeling supple.

12. Slide Lower Legs Back On To Upper Tubes

• Before the lowers go back on, tilt the upper tubes slightly inverted so that once the lowers are slid back on we can add bath oi
• Make sure you orient the lowers on to the upper tubes correctly. The damper side is on the rider's right, and the air spring on the riders left side. Gently slide the upper tubes through the dust wipers without pushing the damper rod and air spring rod all the way through the bottom of the lower. That way we can add bath oil!

13. Add Bath Oil

• Fill each syringe with the correct amount of bath oil for each side of the fork. The fork we are servicing here is a 2020 Fox 36 Factory series fork with the Grip 2 damper. For this particular model, we are adding 10cc of Fox 20wt Gold to the air spring side, and 40cc of Fox 5wt Teflon Infuse oil to the damper side of the fork.
• It is very important to use the correct amount of bath oil in both sides of your fork. See the photo below to make sure you are using the correct oil type and oil volume for your fork. **Fox forks with the Grip Damper use Fox 5wt Silver Teflon Infused Fork Fluid on the damper side. 

14. Slide Lower Legs Into Place And Reinstall Crush Washer And Bottom Nuts

• Now that the fork is full of the correct bath oil, slide the lowers far enough on to the upper tubes so that the damper rod and air spring rod come out of the lower legs. Place the appropriate Fox crush washers in to place and thread both bottom nuts on by hand. 
• Using a torque wrench, torque both bottom nuts to 5.7 Nm (50in lbs). No need to over tighten. 

15. Reinstall Rebound Knob And Rebound Knob Cover

• Slide the rebound knob back on and tighten the pinch bolt using a 2mm allen key. Then thread on rebound knob cover.

16. Clean Fork and Set Your Fork To The Desired Pressure

• Make sure to wipe the entire fork down to clean all of the oil residue off the lowers. We will be using Maxima Contact Cleaners to get everything nice and clean.
• Remember to set your fork back to your desired pressure and equalize the positive and negative air chambers when you do. Throw it back on your bike and go for a rip!

You Made It! Now, your Fox fork will be rolling like new again. Feel free to contact us at the shop with any questions and we would be happy to help. 

This article was written / authored by Max Morgan. Max has been a professional downhill mountain bike racer for the last 10 years, competing in the UCI World Cup downhill series and U.S. Pro GRT series. Having ridden all different kinds of bikes on trails all over the world, Max's experiences being out on the circuit give him a unique perspective on what makes for a quality cycling component. Max also has degrees in Mechanical Engineering and Physics, and so if you don't see out on the trail, chances are he is probably in the garage tinkering on the next project.