All of those who are seriously into motorcycles know that they need top quality brake fluids for their safety. Unfortunately, these quality brake fluids are found to be highly sensitive to the UV light. To keep the fluid safe from the environment they usually put a sock on the reservoir cap to block the UV rays from causing any damage to the brake fluid.
Since there are many debates on the subject of brake fluid getting degraded by the sun’s UV rays maybe we can add that looking at MSDS (material safety data sheets) it states to store brake fluid away from sunlight, also this is the reason why they are not sold in clear bottles, but brake are clutch fluid reservoirs on most sportbikes are opaque which lets sun/UV rays to reach the brake fluid, aesthetically thinking these will also cover up the ugly plastic brake and clutch reservoirs.
The reservoir sock covers also help prevent spillage or leakage from either the brake or the clutch reservoirs. These are basically designed like wristbands wrapping the brake and clutch reservoirs to absorb any fluids that may spill or leak from the cap of the brake and clutch fluid reservoirs as in such cases of hard braking. And yes brake fluid does expand and anyone who is real hard on their brakes will know it. The danger is the highly corrosive fluid can damage paintwork, metalwork and get onto riding gear such as your visor which could cause real visibility problems. For those who are into motorcycle racing, the reservoir covers will also keep the reservoir caps firmly in place during a race and/or spirited riding. It can also help the brake fluid from getting contaminated with dust or dirt by keeping the brake/clutch fluid reservoirs clean and away from debris.
Many of the brake reservoir fluid sock covers are made from cotton and manufactured in such a way that each of the socks fit properly since you don’t want them to come flying off down the road or track. When it comes to the clutch fluids, it is basically the same principle. The brake and clutch fluid reservoir sock covers keeps the fluid from environmental degradation which can eventually lead to poor braking and shifting performance. And as most that use these covers are involved in motorcycle racing, poor braking and shifting performance and brake fluid spillage bike would not be any help on the track.
For those who are wondering if they could just go buy generic wristbands for their brake or clutch fluids, they can, at their own risk. But wristbands tend to fit very loosely and will eventually fly off going down the road or track. Obviously the bike aficionados would probably get horrified if they see their precious Honda, Yamaha or Ducati motorcycles getting dressed with poor fitting low quality products. They would want to get matching Yamaha reservoir sock covers for their Yamaha’s and Ducati’s, rather than having an ill fitting wristband with a sport shoe brand covering up their brake and clutch reservoirs.
Many of these motorcycle brake and clutch covers can be bought online or at reputable motorcycle shops. They are relatively affordable; the generic ones are particularly cheaper but are lower in quality and have heat pressed logos which tend to peel off after a few months. Higher quality reservoir sock covers will be made of high quality cotton, specifically made to fit your motorcycle application and have matching logos which are embroidered on.