Why does my motorcycle have Fork Seals & Fork Oil?

The top most thing on our maintenance schedule and that is very religiously followed is Engine oil. To a point lots of us change it way before its time without any hesitation. While we do that, most of us tend to forget that there are two tubes called “suspensions” that are having a tough life and one important component in it is oil that needs to be changed regularly. In this blog we dive into the workings of the front suspension and what is the role of fork oils and seals.

What do Fork oil seals do?

Firstly let’s get to know what a fork seal is supposed to do in order to understand the importance of a functioning fork seal.

Your forks are two tubes that connect your chassis to the front tyre and help in steering, absorption of bumps, and control your front brakes. Inside them are springs and oil. The springs help in softening the shock and the oil helps in damping the rebound and compression so you get the most out of the shock and it keeps the absorption of the shock consistent.

We then have a fork seal that is a circular ring attached to the bottom part in a conventional shock or the top part in an upside down suspension and it helps keep the oil inside without letting it drain out to the brake rotor or brake pads. OIl seals have “lips” that sit between the inner and outer fork tubes. The inner fork tube and the oil seal needs to be perfect for it to prevent the oil from leaking. In a nutshell If your oil seals get damaged or the rubber has gone hard, it will no longer prevent the oil from leaking and if something gets lodged in between the seal and the fork tube, it will allow oil to leak by. Let’s dive into this.

Leaking fork oil seals

So what is a bad fork seal? Let’s look at a few cases of what can go wrong with a fork seal

●   Dirt or debris buildup

Most of the time the leak that happens is because there is dirt that’s stuck and is causing the two surfaces (metal from the fork and rubber from the seal) to not seal properly.

●   Physical damage

There are instances where seals have got a tear in them due to a damaged fork that has got rusted over time and has a nick that has caused it. It can also happen if you are pressure washing the fork pointing it directly toward the fork seal. Damaged seals can be also due to stones and pebbles that are thrown onto the seal while you’re riding.

●   Age, wear and tear

Fork seals are made of rubber and over a period of time they harden up and lose their sealing ability. They also have their own share of wear and tear and can be a reason for them to go bad.

It’s time to change your fork oil, what should you be looking out for ?

Now that you know that your oil seal is leaking you need to fix it, your old fork seals need to be replaced and it’s a common DIY job or you can take it to a service center. There are aftermarket options from All Balls Racing or your manufacturer should also have these.

So are all fork seals made the same?

We did some research and found out that most fork seals are made of rubber, there are alternatives to this original-equipment seals with a low stiction material that top fork seal manufacturers are now using. In short what it does is reduces stiction or in other words reduces friction when the inner tubes are sliding on these particular types of seals. How it does this is by having a coating on the lip of the fork seal with a brown rulon that is a hard Teflon type of material. All balls racing uses a vulcanized rubber that also helps in achieving a similar effect.

Choosing the right fork oil

A change of fork seals is a good time for you to renew that fork oil. As mentioned above Inside each fork is valving that controls the compression and rebound of the fork going up and down. The job of the fork oil is to work directly with the valves to provide consistent damping when you’re riding.

We asked Maxima about their fork oils and why are they different? They told us their oils have an Advanced, proprietary additive system that prevents stiction and reduces running friction while minimizing foaming and air entrainment. Their oils also have a formulation that eliminates corrosion and conditions seals.

There are many brands and viscosities of fork oils in the market so how do you choose?read on

1. Fork oil viscosity

Viscosity is how the oil flows through the shocks valves, the heavier the oil the slower the rebounds and stiffer the suspensions feel, lighter the oil the quicker the rebound and makes it a more plush ride. Motorcycle manufacturers recommend fork oil weight and this is a good point to start off with. In the world of fork oil one manufacturer’s viscosity is different to another manufacturer’s viscosity unlike engine oil. Hence you need to assess how you want your suspensions to feel when ridden and it’s one of those parts that you can surely experiment with.

2. Look for a higher V.I.

Viscosity index indicates how an oil will change its structure when the temperature changes. A higher VI indicates better resistance to viscosity changes throughout a broad temperature. That translates into consistent shock performance and feel despite the ambient and operating conditions. In addition to the temperature outside your folks are constantly moving and creating heat that is transferred to the fork oil. As it heats the fork oil starts to lose its

composition and starts to get thinner. A high viscosity index formulation maintains film strength and utilizes anti-wear chemistry to reduce wear.

3. Viscosity at 40ºC

So you’re thinking of changing the “weight” of fork oil. What we suggest is to compare the viscosity of the fluid you’re currently using at 40ºC to the same data for the new fluid. The closer the results, the more similar the oils will perform. Reputable manufacturers publish product data sheets for their oils and these are available on their product pages. Once you feel your suspensions are working as per what you want, stick to that!