[By Manufacturer] Types, Features, Pros and Cons of Hydraulic Brake Oils

    Posted at: Mar 27, 2024

    This article explains the types of hydraulic oils used in bicycle hydraulic brakes, their characteristics, and the brake oil types used by each manufacturer.

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    Hydraulic Bicycle Brakes Require Compatible Brake Oil

    Hydraulic bicycle brakes use different types of brake oils depending on the manufacturer. Generally, there are two types:

    1. Mineral Oil
    2. DOT Fluid

    In theory, even water could be used in a hydraulic system. However, because water has a low boiling point, it may evaporate due to brake heat or ambient temperature, leading to air bubbles in the brake system and loss of proper hydraulic pressure.

    Therefore, oils with high boiling points and low volatility are chosen. Still, depending on the type, hydraulic oils differ in properties such as boiling point and hygroscopicity, which affect braking performance and maintenance requirements.

    Item DOT Fluid Mineral Oil
    Main Manufacturers SRAM, HAYES, etc. Shimano, Campagnolo, etc.
    Base Components Glycol
    Silicone    		 Petroleum-based oil
    Boiling Point Above 200°C Above 200°C
    Viscosity Low Low
    Hygroscopicity High Low
    Corrosiveness High Low

    Properties, Advantages, and Disadvantages of Mineral Oil

    Mineral oil is currently the mainstream choice for hydraulic brake systems in bicycles. Shimano, for example, uses mineral oil in its hydraulic brakes.

    Due to its low hygroscopicity, mineral oil maintains its properties even after long periods of use. While its boiling point is generally considered lower than that of DOT fluid, Shimano’s mineral oil is reported to exceed 200°C1.

    Advantages Disadvantages
    Low hygroscopicity allows long-term usage
    Low corrosiveness protects paint and metal parts    		 Higher cost

    Characteristics, Advantages, and Disadvantages of DOT Fluid

    DOT fluid is also used in the hydraulic brake systems of motorcycles and automobiles.

    Due to its high hygroscopicity, its boiling point decreases over time. In some cases, if left unused for too long, certain DOT fluids can even solidify into a gel-like state. Therefore, regular replacement is necessary.

    There are several types of DOT fluid, such as “DOT 3,” “DOT 4,” “DOT 5,” and “DOT 5.1.” In bicycle hydraulic brakes, “DOT 5.1” and “DOT 4” are commonly used.

    DOT 5.1, for example, has a dry boiling point (when new) of over 260°C, offering high stability even under high temperatures.

    Advantages Disadvantages
    High boiling point
    Low cost
    Widely available    		 High hygroscopicity requires regular replacement
    High corrosiveness may damage paint and metal parts

    While it is technically possible to use DOT fluid intended for motorcycles or automobiles in bicycle hydraulic brakes, it is generally not recommended by most component manufacturers. This is because the composition and additives can differ, which may result in improper braking performance or even damage to the system.

    Brake Oil Types by Manufacturer

    Below is a list of the types of hydraulic brake oil used by various bicycle brake manufacturers.

    Manufacturer Mineral Oil DOT Fluid
    Shimano ⚪︎ -
    SRAM ⚪︎ ⚪︎
    Campagnolo ⚪︎ -
    TEKTRO ⚪︎ -
    MAGURA ⚪︎ -
    HOPE - ⚪︎
    HAYES - ⚪︎

    Notably, SRAM used DOT oil for both road and MTB models up until the 2024 models, but it has been announced that the 2025 MTB brake models will adopt mineral oil.

    Each manufacturer formulates its brake oil to ensure optimal performance of their own hydraulic brake systems. Therefore, it is generally best to use the manufacturer’s genuine hydraulic brake oil.

    1. SAFETY DATA SHEET HYDRAULIC MINERAL OIL | Shimano ↩︎

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