That's why choosing the proper type of oil is so important; each fork requires a different oil grade. Manufacturers use a universal code system based on specific criterions. Usually, fork oil needs to be changed every 10,000-20,000 kilometers, depending on the use and riding style. For example, a road bike can easily cover 20,000 kilometers before an oil change is required, whereas a dual-purpose or off-road bike will demand more maintenance, perhaps once every few days or weeks. If you're riding competitively, well, it's a matter of a few hours.

Oil viscosity is available with the following grades: 0 W, 2.5 W, 5 W, 10W, 15 W and 20 W. There are even multi-grade oils like 20 W30 or 10 W40. The lowest-viscosity oil (or the most fluid) is 0; it's mostly used for inverted forks. Normally, sportbike forks will work best with a 5 W oil.


Improper oil grade can result in bad fork operation. Moreover, in the spring or fall, a lower grade than the one recommended by the manufacturer might be preferable. However, during summer, the weather is steadily hotter, so you need to change your fork oil for a higher-viscosity one. Same goes for a loaded or large-displacement motorcycle.

The "W" in the oil grade classification system refers to "multi-grade", meaning that it can withstand both cold and hot temperatures. The last numbers represent high-temperature viscosity. The majority of lubricant manufacturers set oil viscosity at temperatures ranging from 40 to 212 degrees Celcius.

As mentioned earlier, fork oil change should be performed by an experienced mechanic. The tools are specialized and the technique is complex.

If you don't change your oil, the fork will collapse and rebound more quickly, thereby affecting the ride as well as braking power. Also, even if your suspension is adjustable, it won't be easy to compensate for one dynamic without compromising the other. The decrease in braking power is proportional to the quickness of compression; the weight is transferred forward, lightening the rear wheel and reducing contact with the ground before skidding. A loss of control might occur shortly afterwards.

Handling suffers from increased body roll and pitch, hence the potential for a loss of control, especially in corners. And that's not even counting understeer, where the front wheel loses grip and starts to skid.

So please, pay attention to your fork and follow the recommended maintenance schedule. Ride safely and enjoy the road.




Photo Credit : Henri Lebarbé, Philippe Champoux