The motorcycle front fork is a critical part of the bike because it affects steering, overall handling, and it smoothens out the bumps on the road. But you might be wondering if there are any alternatives to using fork oil on your motorcycle.
There aren’t many suitable alternatives to motorcycle fork oil, as the role of this fluid is very important and specific on your motorcycle. However, many people will recommend automatic transmission fluid (ATF) as a fork oil substitute thanks to its similar properties.
Fork oil cannot be blindly changed as it could do more harm than good. Keep reading to find out your best choices when the time comes to change your fork oil, and how to decide between them to keep your motorcycle in perfect working condition.
What Can You Use Instead Of Motorcycle Fork Oil?
Before doing anything, read your motorcycle manual to find out which grade of oil is best for your front fork. Different bikes use different oils as their front load, and fork construction varies. A heavier bike is going to use a thicker oil when compared to a lighter bike that does not have to take the same front load.
Gearbox oil is used primarily for lubrication, so any oil used in the gearbox must have high lubricative properties. Any oil that can maintain these characteristics over a temperature range can be substituted for fork oil, as long as the SAE grade is the same.
The viscosity of fork oil is important as it has to maintain its properties over a range of temperatures. The oil cannot freeze up in winter, and in summer if it heats up excessively, it can affect handling. Most of the alternatives provide no extra benefits, so it’s best to simply stick with fork oil.
Oil Compressibility And Viscosity
The entire premise of using oil as a dampener is because of the compressibility that the oil inside the fork provides when going over a bump. Even though the twin springs on either side of the wheel absorb some of the energy, the oil also acts in conjunction with it to smooth out the bumps.
Using oil of lower SAE grade than recommended in your manual is only going to degrade the front fork performance and could even damage it. On a lighter bike, this is not as much of a problem as on a heavier bike.
Can You Use ATF Instead Of Fork Oil On A Motorcycle?
You may be able to use ATF instead of fork oil on your motorcycle. Automatic transmission fluid has similar properties to fork oil, meaning it can be a viable substitute. However, it’s best to stick with whatever your manufacturer suggests you use just to be on the safe side.
If you don’t know the SAE grade number of the oil that you’re using to fill the front fork with, then you’re risking degraded performance along with front fork damage.
How Motorcycle Forks Work
A front fork isn’t as complex as it seems, but remember that not all front forks are constructed the same way. Basically, each side of the fork consists of a spring and a small cylinder with a piston moving inside it. After removing the cylindrical cover, you can access the spring fitted around the cylinder and the piston.
There are two types of forks used on motorcycles: damping forks and cartridge forks. Cartridge forks are more modern and claim to make damping more linear by using two stacks of shims that work as a valve. In both types, the piston uses oil to do the damping, although the mechanical parts inside the fork are different.
The spring is responsible for absorbing most of the shocks caused by potholes or bumps while the oil inside the cylinder slows down the spring movement. When there is no oil inside the fork, the sound of the piston hitting the cylinder metal can be heard, and is a sign that the oil seal needs to be replaced as well.
The springs used inside the front fork are costly and typically made from steel alloys or chrome vanadium. Over time, they lose a lot of their springiness. When this happens, instead of buying new ones, you may want to see if you can get them refurbished to restore them to close to their original condition.
How To Change Your Motorcycle Fork Oil
If you are going to change your fork oil at home, make sure that you have the necessary tools to open the front fork, and the new fork oil ready. When changing front fork oil, you might as well fit new oil seals. The oil seal is just a rubber cap that fits on top of the cylinder. They are very cheap and well worth the protection they provide against oil leaking out.
Your owner’s manual will tell you the exact amount of oil you need to fill it with. Do not use more or less oil than is specified. Remove the handlebar and headlight assembly from the top of the fork so that you can access the oil cap. It is usually held in place by a bolt. After opening the bolt, unscrew the oil cap and pour out the old oil.
Then pour in the new oil and replace the oil seal before fitting it all together again. If you’re in any doubt as to the procedure, take the bike to a service center and watch how it is done so that you can do it the next time!
How Often Should You Change Your Motorcycle Fork Oil?
You should change your motorcycle’s fork oil once every 18 months or every 20,000 miles. Rather than having a fixed schedule to change the fork oil, we recommend you change it when you feel the suspension getting weak.
Any small oil leaks could signal that the oil seals need to be replaced along with the front fork oil. The biggest tell-tale sign is when the fork damping gets degraded. This is the case when the front fork becomes too easy to compress. While standing over the bike, push down on the handlebar as hard as you can and see how much the fork compresses.
If the front suspension compresses very easily, the fork springs need to be checked to see if they need replacement. Fork springs are usually long-lasting, but they might need to be replaced if the bike is used a lot over very rough terrain that stresses the suspension a lot.
Final Thoughts
Although alternatives to front fork oil can be experimented with, it is hardly worth the trouble. Very little benefit can be obtained, and if the wrong oil is used, you can damage the front fork. For the cost difference, it is better to stick with your manufacturer’s recommended fork oil.