Differences

This shows you the differences between two versions of the page.

--- techtalk:ref:wheels03 [2024/05/23 04:33] – [Example of outdated (new) bottle of brake fluid] hippysmack
+++ techtalk:ref:wheels03 [2025/10/31 18:30] (current) – [DOT 5] hippysmack
@@ Line 127: / Line 127: @@
 ===== DOT 5 =====
-  * The change to Dot 5 brake fluid was made with HD production motorcycles in September of 1976 ((HD Service Letter M-28)). It is of silicone chemistry and not being water miscible, it must rely on the silicone (with some corrosion inhibitors) as a barrier film to control corrosion. Water is not absorbed by silicone as in the case of DOT 3-4-5.1 fluids, and will remain as a separate globule sinking to the lowest point in the brake system, since it is more dense. ((http://importnut.net/brakefluid.htm))
+  * The change to Dot 5 brake fluid was made with HD production motorcycles in September of 1976 ((HD Service Letter M-28)). As the production month for new models generally starts in June (ish), September is considered to be of the Late production season. 1977 models produced before September would have come with DOT 3 brake fluid and models produced after September would have come with DOT 5 brake fluid. If in doubt, always check the master cylinder cap. The type of fluid the master should run is written there.
+  * DOT 5 brake fluid is of silicone chemistry and not being water miscible, it must rely on the silicone (with some corrosion inhibitors) as a barrier film to control corrosion. Water is not absorbed by silicone as in the case of DOT 3-4-5.1 fluids, and will remain as a separate globule sinking to the lowest point in the brake system, since it is more dense. ((http://importnut.net/brakefluid.htm))
   * When using Dot 3 brake fluid, the brake system should be drained, flushed, and refilled with new brake fluid every year to eliminate any contamination such as sludge. This yearly service was eliminated when D.O.T.-5 silicone fluid was used instead and with improved performance. ((HD Service Bulletin #M712 dated June 16, 1977 pg 1))
   * Silicone brake fluid reduces corrosion, will not degrade the "rubber" components, and sludge will not form in the system. It will not absorb water, does not attack painted parts, and has a higher boiling point than conventional brake fluid. When stored under normal conditions it has unlimited shelf life. However, it is somewhat harder to bleed brakes with Dot 5 because of its viscosity. ((HD Service Bulletin #M712 dated June 16, 1977 pg 1))