4 Simple Solutions If Your MTB Fork Leaking Oil!

Seeing the smallest leak from your MTB’s fork is enough to sink your heart. Because this leak, if not dealt with, will turn into a gusher springing from the fork seal. And the aftermaths of that are not something to look forward to. 

But what are the reasons and solutions if your Mtb fork leaking oil?

Basic wear and tear over time can cause your MTB to leak oil and you might need to replace the fork seal. Also, dirt and debris might cause the leaking, which might need proper cleaning. Moreover, if the fork tube is faulty or the excess pressure from the tie-down system can cause the leaking too. 

And there are specific fixes for all of these issues. So, you don’t have to worry at all! All you need to do is follow our instructions and fix all the issues you may have with your bike.

So, what’s the delay then, get right in!

Diagnosing the MTB Fork

There may be many reasons behind why is my fork leaking oil. To solve the problem we must first find where the problem originates. The solution may change depending on the problem. 

First, make sure that there is no mismatch. Mismatches like a 150mm fork on a 130mm frame can sometimes cause trouble. 

If there are no mismatching issues, you have to begin by looking for traces of oil. Locate where the oil is leaking from.

4 Simple Solutions If Your MTB Fork Leaking Oil!

Source: Reddit

Now there might be different reasons for the leakage. Let’s look into all of them. 

Reason 1: Leak Due To General Wear And Tear

Fork seal takes a lot of beating over time. Harder riding causes even more harm. Riding over tougher terrain can wear it down and lead to fork oil leaking from bottom.

Ideally, the fork seal should be properly maintained or changed after around 40 hours of riding. Even so, check the seal every now and then for leakage just in case. 

Solution: Replacing The Fork Seal

The fork seal needs to be replaced every so often. But replacing it yourself may not be the best choice. 

Replacing the fork seal requires complex tools, like the fork seal drivers, to get the work done. These fork seal drivers are very useful and easy to use. Here’s a tutorial about how to use it.

These tools are expensive and using them requires experience. However, you can actually make your own fork seal driver as well to save money.

So, having a professional replace the fork seal is ideal. A visit to your dealership will do the job. Local mechanic shops can be visited as well. 

Replacing a fork seal might set you back around $100 to 400. It depends on the components of your MTB that need to be worked on. 

But it is a lot of load on your pocket so it’s better if you change it by yourself. You can follow this guide to change your fork seal though.

Reason 2: Dirt And Debris

Fork seal is not just affected by age. Dirt and debris can mess it up as well.

Dirt, mud, or any other kind of junk can get in between the seal and the inner fork tube. This creates an imperfect seal. Dust might accumulate under the dust cover as well.

This gap between the seal and inner fork tube might cause oil to leak too. 

Solution: Cleaning the Fork Seal

The whole process of cleaning the fork seal is not that complex. Anyone can do this with some basic tools that lay around in our tool shed or in the toolbox. So no need to be worried about the things that you might require to clean the fork seal.

Let’s get into it, shall we?

  • Begin by carefully prying apart the dust seal. Try using a flathead screwdriver for this. But exercise the utmost caution to not damage the seal or scratch it. 
4 Simple Solutions If Your MTB Fork Leaking Oil!

Source: ProX Racing Parts

  • Then use a lint-free cloth or a cotton swab for cleaning. Carefully remove the dirt stuck under the lip. After finishing, put everything back together again.

Sometimes this is not enough to solve the problem. In that case, pieces of camera film or any other flexible and thin object can be used. 

Remove the dust seal and wrap the flexible object around the shaft. Then continue pushing up until you reach beneath the lip. Anything missed by the cotton swab can be cleaned using this method. After cleaning, put everything back together. 

There is a downside to using a camera film or similar object. This process pushes the dirt into the suspension. This may cause even further damage and lead to oil leaking from suspension.

Reason 3: Inner Fork Tube Imperfection 

Even normal riding will inevitably cause dents and scratches in the inner fork tube. Flying rocks or any other debris might be the cause of it. 

4 Simple Solutions If Your MTB Fork Leaking Oil!

Source: Cyclinic

Imperfection in the fork tube can cause oil leakage. Even brand new fork seals can start leaking because of the tube. 

Solution: Buffing Out the Dents

If you see any dents or scratches in your fork tube, you will have to buff them out. 

Things you’ll need: 


  • Use Isopropyl to clean the area properly.  
  • Now, very lightly file or sand down the scratch marks. Make sure that there aren’t any raised surfaces.
  • Then, clean the smooth area with isopropyl alcohol again.
  • After that, use a clean microfibre cloth, polish using Autosol, or something similar. 
  • Finally, inspect the area to make sure that there aren’t any more bumps.

After fixing the imperfection, the fork seal needs to be replaced as well. But replacing the fork seal without fixing the imperfection will just damage the new seal. 

We discussed how to replace a fork seal previously. 

Reason 4: Excess Pressure from Tie Down Straps

Fork seals wear down eventually just by normal riding. Tie-down systems just fasten the wearing-down process. 

Tie-down systems compress the fork seal during transportation. This puts constant tension on the fork seal. This may cause it to leak.

Solution: Using Seal Doctor Or Replacing The Fork

There is an answer to how to stop fork seals from leaking without replacing the seal. Using Seal Doctor by Risk Racing is the quickest solution to fork seal leaking. Using it is easy and the sealing can be done anywhere at any time. 

4 Simple Solutions If Your MTB Fork Leaking Oil!

Source: canva

To apply Seal Doctor first lower the dust seal of your MTB. Then snap the Seal Doctor on the fork tube. Put the tooth into the leaky seal and start twisting.  

We have already mentioned how you can replace your fork seal. 

Tips On How to Prevent Future Leaks

Hopefully, you have been able to deal with the leak. It was a frustrating process and something that you would rather not do anytime soon again. 

But what can we do to stop the fork seal from leaking? 

Installing the Fork Seals Properly 

Improper installation might cause the fork seal to leak immediately after replacing it. Sharp edges of the fork tube can cause damage to the seal while installation. The damage might happen during crosstrail fork upgrade as well.

Having an experienced mechanic do the installation process should not lead to such cases. 

Completely Cleaning the Fork Seal

Even a little dust or debris can cause the fork seal to leak oil. So be sure to clean it thoroughly. Clean it until you are sure that it is sparkly clean. 

It is a good practice to clean the dirt from the fork seal after every ride. It keeps the fork seal in a good condition for a long time.

Transporting the Bike Differently 

You might notice that your fork seal starts leaking after the bike has been transported. In that case, the problem is in the way you transport your bike.

Tie-down systems are known to damage the fork seal of bikes. Try using different transportation methods. You can look into Lock-N-Load Pro for transporting your bike. 

That’s all for today! Hope this helps.


What is the Difference between Fork Oil and Fork Fluid?

The difference between fork oil and fork fluid lies in their quality and capacity of being slick. Fork fluid is slicker and of higher quality than fork oil. The drag experienced while riding is reduced by fork oil. But fork fluid reduces the drag even more. So fork fluid is better for legs.

How Much is a Fork Seal Replacement Cost? 

The cost of replacing fork seals costs vary depending on your geographical location. It may even vary slightly from shop to shop. But you can expect the prices to be as low as $150 and as high as $400. It should cover the full removal of the forks and replacement of the fork seals.

What are Good MTB Fork Oil Alternatives?

An excellent substitute for fork oil is ATF. ATF works well as fork oil because of its anti-foaming properties. Many motorbikes used have ATF specified for usage for forks as stock. ATF is equivalent to about 7.5 weight of fork oil. So using it will make you a bit lighter.


And now we know the reason behind your Mtb fork leaking oil and how to solve it. 

The reasons for the leakage are plenty. The solution will generally require you to replace the fork seal. Sometimes you will need to buff out imperfections from the fork tube. Using Seal Doctor is an option as well. 

That’s it for today!

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