Frequently Asked Questions

Provide DOT 5 brake fluid is generally not recommended for most motorcycles, and here's a breakdown of the key reasons why:

1. Chemical Incompatibility and Mixing Issues

Different Base: DOT 5 is silicone-based, while the more common DOT 3, 4, and 5.1 fluids are glycol-based.

• Cannot be Mixed: These two types of fluid are chemically incompatible and should never be mixed. Doing so can cause the fluids to gel or coagulate, leading to major brake system failure and damage to seals.
• Difficult to Switch: If you want to switch a system from a glycol-based fluid (DOT 3/4/5.1) to DOT 5, you must completely flush and clean the entire system. Any remaining residue of the old fluid can cause problems. It's often recommended to replace all the seals and lines to ensure there's no contamination.

2. Performance and Feel

• "Spongy" Feel: One of the most common complaints about DOT 5 is that it can lead to a slightly spongy or "mushy" feeling at the brake lever. This is because silicone fluid compresses slightly under pressure and tends to aerate (absorb air bubbles) more easily than glycol-based fluids, which can make brake bleeding more difficult.
• Not for ABS: DOT 5 fluid is not suitable for motorcycles with an Anti-lock Braking System (ABS). The rapid on/off pulsing action of an ABS system can cause the silicone fluid to become frothy, leading to a loss of braking efficiency.

3. Moisture and Corrosion

• Non-Hygroscopic Nature: Unlike glycol-based fluids, DOT 5 is non-hygroscopic, meaning it does not absorb moisture. While this might sound like a benefit, it can actually be a major drawback.
• Water Pooling: Any water that gets into the brake system (and it inevitably will, as no system is perfectly sealed) will not mix with the DOT 5 fluid. Instead, it will settle in the lowest points of the system, most often in the calipers. This can lead to localized corrosion and, in extreme situations, the water can boil under heavy braking, creating steam and causing a complete loss of braking power.

4. The Only Real Advantage (and why it's a niche one)

• Higher Boiling Point: DOT 5 has a high boiling point, which can be beneficial in certain extreme conditions. However, many high-performance DOT 4 fluids (sometimes called "Super DOT 4") and DOT 5.1 fluids now have comparable or even higher boiling points than DOT 5, without the significant drawbacks.
• Doesn't Damage Paint: One of the most cited benefits of DOT 5 is that it won't damage painted surfaces if it spills, unlike glycol-based fluids.

In summary: While DOT 5 has a high boiling point and won't strip paint, its disadvantages—incompatibility with most systems, a spongy feel, and especially its unsuitability for ABS and the risk of water pooling—make it a poor choice for the vast majority of modern motorcycles. Your motorcycle's manufacturer will specify the correct DOT fluid (most commonly DOT 4) on the brake reservoir cap or in the owner's manual, and it's always best to stick with that recommendation.an answer