Most Rock Shox suspension forks use a lubrication system called an ‘oil bath’. This means there’s a small amount of oil in the bottom of each fork leg and its sole job is to keep the seals, bushings and other internal parts lubricated and free of corrosion. It plays no part in damping the fork. There’s only about 15ml, about two tablespoons, of this oil in each leg so over time it can become contaminated and break down. For this reason Rock Shox recommends you replenish it after every 50hours of riding, or sooner if you ride in really wet or really dry conditions.