16/02/2016
Servicing Your Fox 36: A Comprehensive Guide to Oil Replacement
The Fox 36 is a legendary piece of mountain biking hardware, renowned for its robust build and exceptional performance on the most demanding trails. However, like any high-performance component, it requires regular maintenance to ensure it continues to deliver that buttery-smooth feel and unwavering support. A key aspect of this upkeep is the regular servicing of the lower leg oil. This oil acts as a crucial lubricant and protectant for the fork's internal moving parts, including the stanchions, seals, and bushings. Over time, this oil can become contaminated with dirt, grit, and even tiny metal particles from normal wear, significantly reducing its effectiveness. Furthermore, some oil loss is normal due to the nature of suspension fork seals. Therefore, understanding how to drain and replace this oil is an essential skill for any Fox 36 owner. This guide will walk you through the process, ensuring your fork remains in peak condition.
Why Service Your Fox 36 Oil?
The lubricating oil within the lower legs of your Fox 36 fork serves multiple vital functions. Primarily, it ensures that the stanchions and seals move freely against each other, reducing friction and providing that plush suspension feel. It also helps to keep the dust seals clean and lubricated, preventing dirt and water ingress, which can cause significant damage to the internal components. Additionally, the oil helps to cool the lower leg assembly, especially during heavy use. When this oil degrades or becomes contaminated, several issues can arise:
- Reduced Suppleness: Stiff or notchy suspension action, making the fork feel harsh and unresponsive.
- Increased Friction: This leads to poorer small bump sensitivity and can make the fork feel like it's 'sticking' when initiating movement.
- Seal Wear: Contaminated oil can act like liquid sandpaper, accelerating the wear on your fork's seals and bushings, leading to leaks and premature component failure.
- Decreased Lubricity: The primary function of the oil is compromised, leading to increased wear on the stanchions and internal structure.
Regularly replacing this oil, typically as part of an annual service or more frequently if you ride in harsh conditions (e.g., dusty, wet, or muddy environments), is a proactive way to prevent costly repairs and maintain the optimal performance of your high-value fork.
What You'll Need: The Essential Toolkit
Before you begin, gather all the necessary tools and fluids. Having everything ready will make the process smoother and more efficient. Here’s a breakdown of what you’ll require:
| Tool/Fluid | Description |
|---|---|
| 10mm & 15mm Socket Wrenches | For undoing the foot nuts on the lower legs. A deep socket is often beneficial. |
| Soft Mallet | For gently tapping components apart if they are a little stubborn. Avoid using excessive force. |
| Pick Tool | Useful for carefully prying out the foam rings without damaging the lowers or seals. |
| 2mm Allen Key | To remove the rebound adjuster knob. |
| Syringe | A clean syringe (ideally with a narrow tip) is crucial for accurately measuring and dispensing the new fork oil. A 20ml or 30ml syringe is usually suitable. |
| 20wt Gold Fork Fluid | This is the specific, high-quality oil recommended by Fox for their suspension forks. Using the correct fluid is vital for optimal performance and longevity. Do not substitute with other oils. |
| Tub or Bucket | To catch the old, dirty oil as it drains from the fork lowers. |
| Shop Towels/Rags | Plenty of clean shop towels are needed for wiping down components and cleaning up spills. |
| Suspension Grease | A light application of suspension-specific grease on the seals will help with installation and initial lubrication. |
| Bike Stand | To securely hold the bike or fork while you work. |
The Step-by-Step Oil Service Process
This guide assumes you have basic mechanical knowledge. Always work in a clean environment to prevent contamination. The estimated time for this service is approximately 45-60 minutes, and the difficulty is rated as medium.
Preparation and Fork Removal
Begin by removing the Fox 36 fork from your mountain bike. Clamp the steerer tube securely in a bike stand. It's imperative to thoroughly clean the exterior of the fork, paying special attention to the area around the dust seals. Any grit or dirt here could be pushed into the fork during the service, causing damage. A quick spray with a degreaser and a wipe down will suffice.
Rebound Adjuster Removal
Locate the rebound adjuster knob, typically found at the bottom of the damping-side leg (usually the right leg). Using your 2mm Allen key, carefully loosen and remove the small grub screw that secures the adjuster. Once the grub screw is out, gently pull the rebound adjuster knob off the shaft.
Loosening the Foot Nuts
Identify the foot nuts at the very bottom of each fork leg. The damping side will likely require a 15mm socket, while the air-spring side often uses a 10mm socket. Using the appropriate socket, undo both foot nuts by approximately three full turns. Do not remove them completely at this stage.
Releasing the Inner Shafts
With the foot nuts slightly loosened, you need to release the inner shafts from their seats within the lower legs. You can use the corresponding socket wrench on each foot nut or, if you have one, the specific Fox fork removal tool. Gently tap the socket or tool with a soft mallet. The goal here is to dislodge the inner shaft assembly from the lower leg, not to force anything. A few gentle taps should be enough.
Draining the Old Oil
Once the inner shafts are loosened, you can fully unthread the foot nuts. Ensure that the small crush washers come away with the foot nuts; these will be replaced with new ones during reassembly. Now, carefully turn the fork upright so the fork lowers are pointing downwards. Position your catch tub or bucket directly underneath the lower legs. Slowly allow the lower legs to slide down off the stanchions. This will allow the old, contaminated oil to drain out into your catch tub. Be prepared for a bit of oil to escape; this is normal.
Cleaning the Components
With the lowers removed, take this opportunity to clean all the fork components thoroughly. Use clean shop towels to wipe down the stanchions, the inside of the lower legs, and any other parts that were exposed to the oil. Ensure all traces of old oil and any accumulated dirt or debris are removed. A clean workspace is paramount for a successful service.
Inspection for Wear and Damage
Carefully inspect the fork's seals and the stanchion tubes for any signs of damage, such as nicks, tears, or excessive wear. Also, check the bushings inside the lower legs. If you notice any damage or significant wear, it's advisable to replace the affected parts. Compromised seals or worn bushings will prevent your fork from performing optimally, even with fresh oil.
Foam Ring Removal and Cleaning
Inside the lower legs, you'll find foam rings that sit around the stanchions, just above the seals. These rings are designed to hold a small amount of lubricant. Use your pick tool to carefully pry out these foam rings. Be gentle to avoid damaging the lowers, seals, or bushings. These foam rings can trap dirt particles, so if they appear excessively dirty or degraded, it's highly recommended to replace them. Replacing them will help prevent premature wear on your stanchions and seals.
Cleaning and Soaking the Foam Rings
Clean the removed foam rings using a clean shop towel. You can use a tamping method to gently wipe away dirt and old oil. Once cleaned, it's beneficial to soak these foam rings in a small amount of fresh 20wt Gold fork fluid. This will re-saturate them, preparing them to hold fresh lubricant. Let them soak for a few minutes while you proceed with other steps.
Re-fitting Foam Rings and Greasing Seals
Take the now-soaked foam rings and carefully refit them back into their housing within the lower legs. Ensure they are seated correctly. Next, apply a light application of suspension grease to the inside of the dust seals. This will aid in the smooth reassembly of the lowers onto the stanchions and provide initial lubrication.
Reassembling the Lowers (Partial)
Carefully slide the fork lowers back up onto the upper stanchion tubes. Take your time and be extremely cautious not to pinch the seals or the foam rings as you insert them. You don't need to slide them fully on just yet. Leave them partially fitted, with the inner shafts still exposed at the bottom.
Adding New Fork Oil
With the fork still slightly inverted (lowers partially on), you can now add the new 20wt Gold fork fluid. Use your syringe to accurately measure the correct amount of oil. The exact amount can vary slightly depending on the specific model year of your Fox 36, so it's always best to consult your fork's service manual or the Fox website for the precise oil volumes for each leg. Inject the oil through the lower holes in the bottom of each leg where the foot nuts were previously located.
Final Assembly and Tightening
Once the oil has been added to both legs, carefully slide the fork lowers completely up onto the stanchion tubes until they are fully seated. Now, refit the crush washers (using new ones is recommended) and thread the foot nuts back onto the shaft threads. Tighten the foot nuts securely. The recommended torque for the foot nuts is typically 5-6 Nm. Overtightening can damage the threads, so use a torque wrench if possible or tighten them firmly but carefully.
Refitting Adjuster and Final Touches
Refit the rebound adjuster knob onto its shaft and secure it with the grub screw. Give the entire fork a final wipe down to remove any excess oil or fingerprints. Reinstall the fork back onto your bike, ensuring all bolts are tightened correctly. Give the suspension a few good bounces to allow the oil to circulate properly.
Frequently Asked Questions (FAQ)
Q1: How often should I service the oil in my Fox 36?
It's generally recommended to perform this lower leg oil service every 50 hours of riding time, or at least once per year. If you ride frequently in very dusty, wet, or muddy conditions, you may benefit from doing it more often.
Q2: Can I use a different type of oil?
No, it is crucial to use only the specific Fox 20wt Gold suspension fluid. Other oils may have different viscosity properties, contain additives that can damage seals, or simply not provide the correct lubrication and damping characteristics.
Q3: My fork feels stiff after the service, what could be wrong?
Ensure you used the correct amount of oil. Too much oil can increase hydraulic resistance. Also, check that the seals weren't pinched during reassembly, as this can cause significant stiction. Make sure the foam rings are properly soaked and seated.
Q4: Do I need to replace the crush washers?
While not strictly mandatory for every service, it is good practice to replace the crush washers when you remove the foot nuts. They are designed to crush and form a seal, and reusing them may compromise that seal.
Q5: What if I don't have a bike stand?
While a bike stand makes the job easier and safer, you can perform this service with the bike resting on its wheels. You may need to prop up the rear of the bike to keep it stable. However, clamping the steerer is highly recommended for ease of access and safety.
Conclusion
Performing this lower leg oil service on your Fox 36 is a rewarding task that will pay dividends in the form of consistently smooth and responsive suspension. By following these steps carefully and using the correct fluids and tools, you can maintain your fork's performance and extend its lifespan. Regular maintenance is key to enjoying your ride to the fullest, so don't neglect this important aspect of your bike's upkeep.
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