Other materials used for o rings include ptfe universally noted for its chemical resistance but difficult to install due to minimal elasticity. These seals have a simple donut shaped ring technically called a toroid and are manufactured using pliable material such as elastomers like silicone buna n and ethylene propylene.
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O rings for brake fluid. I dont think viton flurocaron would be the best. Im told dot 3 will call that o ring to swell. Grob requires the use of dot 3 fluid because of the master cylinder. Nitrile o rings are not advisable for use with automotive brake fluid ketones phosphate ester hydraulic fluids and nitro and halogenated hydrocarbons. Buna n viton and epdm. Virtually any size o ring is available off the shelf in nitrile butalene or neoprene but ep needed for resistance to brake fluid is impossible to find.
Fep encapsulated fep is similar to ptfe and is used to cover viton or silicone o rings to offer the chemical inertness of ptfe with some elasticity. Many bike shops will have tackle boxes full of specific parts for hydraulic brake systems. For the purposes of this article we will focus on just three common rubber types found in o rings and similar automotive seals. On a recent tour on an old and rare bike i had a problem with the seal on the hydraulic clutch. O ring materials compatible with brake fluid select a material to show its compatible chemicals aflas 4 buna n nitrile 1 butyl 4 chemraz 0 epichlorohydrin 1 ethylene propylene 4 fluorocarbon 1 fluorosilicone 1 hypalon 0 kalrez 0 natural rubber 1 neoprene 1 nitrile hydrogenated 3 polyacrylate 1 polysulfide 3 polyurethane cast 1. I discovered that bearing houses and seal companies do not carry o rings made of ep.
The recomended materail for brake fluids would be epdm. The o ring in the piston is designed for 5056 fluid. So we need to replace the. As for size using the parker handbook ord 5700 would let you see what sizes are available. Nitrile o rings which have a temperature range between 54 and 149 degrees celsius are suitable for use with water petroleum oils and some hydraulic fluids. Id recommend looking for a replacement from the manufacturer or a good bike shop.
Closest to your dimensions would be a 013 which is 0070 cs x 0566 od. Standard o rings will degrade very quickly in dot fluid as it is highly corrosive. O ring are one of the most commonly used fluid power seals. Water coolants both ethylene and propylene glycol and glycol based brake fluid. Of all three rubber types epdm is the only one that should be considered for use anywhere in a braking.
Gallery of O Rings For Brake Fluid
