# Brake fluid

> Brake fluid is the high-boiling-point fluid that carries pressure from the master cylinder to the caliper.

- **Also known as:** Hidrolik, DOT 4, Fren yağı, Brake fluid
- **Turkish term:** Fren hidroliği
- **Category:** [Master Cylinders & Calipers](https://motorsikletparcasi.com/en/category/master-cylinders-and-calipers)
- **Page:** https://motorsikletparcasi.com/en/glossary/brake-fluid

The most common types on motorcycles are glycol-based **DOT 3, DOT 4 and DOT 5.1**; use the type printed on the reservoir cap. Silicone-based **DOT 5** must not be mixed with them.

- Glycol-based fluid absorbs moisture from the air (it is hygroscopic); as moisture builds up the boiling point drops and the brakes can fade under hard use. That is why it is usually changed **every 2 years** regardless of mileage.
- Dark, brown fluid is due for replacement.
- Brake fluid damages paint and plastics; wash any spills off immediately with plenty of water.

## Related terms

- [Brake master cylinder](https://motorsikletparcasi.com/en/glossary/brake-master-cylinder): The brake master cylinder converts force on the brake lever or pedal into hydraulic pressure and sends it to the caliper.
- [Brake caliper](https://motorsikletparcasi.com/en/glossary/brake-caliper): A brake caliper uses hydraulic pressure to move its pistons and press the brake pads onto the disc.
- [Brake pad](https://motorsikletparcasi.com/en/glossary/brake-pad): A brake pad is the friction-lined part that the caliper pistons press against the brake disc to slow the motorcycle.

---

- Source page: https://motorsikletparcasi.com/en/glossary/brake-fluid
- Last updated: 2026-10-09
- Türkçe sürüm: https://motorsikletparcasi.com/sozluk/fren-hidroligi.md
- Site overview: https://motorsikletparcasi.com/en/llms.txt
- Append .md to the URL of any product, category, motorcycle, brand, blog or company page on this site to get its Markdown version.