A more correct nomenclature for Fork Oil is “Suspension Fluid” or “Hydraulic Fluid”, however for the sake of general understanding we will stick to “Fork Oil”. This differentiation is very important, and will be discussed later on. Since the primary function of fork oil is to provide damping rather than lubrication, in terms of its character, it is much nearer to Hydraulic Oil/Fluid as compared to lubricating oils/engine oils/gear oils etc. For this reason, the fork oil grade will be determined by the damping requirements and not by its lubricating requirements.įork Oil / Suspension Fluid / Hydraulic Oil: So, the primary function of fork oil is to provide damping and not lubrication, ofcourse it lubricates some of the internal moving parts, but that is its secondary function. It does so by moving the oil / fluid from one side to other through a small orifice or valve. In simple terms, how fast the front fork depress on hitting an obstacle and how fast it bounce back is decided by oil. viscosity and quantity of oil (along with a lot of other design factors, ignored for simplicity) determines the rate of compression and rebound. The job of fork oil is to provide damping, it provides both compression and rebound damping, i.e. Spring basically provides compression and rebound whenever our bike hits a pothole. The following information is a result of internet research, discussion with friends, mechanics & authorized service centers.įirst let us understand the working of motorcycle forks. It was infact Motul, which started my thought process in this direction, since they have two options available in India (5wt & 20wt) and four internationally (5wt, 10wt, 15wt & 20wt) Untill now, like most others, I was happy with whatever my mechanic used to put in my bike’s fork, which was mostly one of these brands -Veedol / Gulf / Bosch / Endurance and/or more recently Motul. Everything, from the grade mentioned in service manual, to service center recommendation, to grades mentioned on fork oils available in market, to biker buddies advise was so confusing and dangerous mix of half correct half incorrect information, that I decided to fully understand the topic and decode it completely. Recently I had to change the fork oil of my P200NS, and started my search to find the best possible oil for my bike’s forks, unfortunately I was shocked when I found out that very little information is available on fork oils. Since very less information is available on xbhp about fork oils, I am starting this new thread.

Motorcycle fork oil viscosity chart