Can You Use Car Brake Fluid On A Mountain Bike? (Explained)

Can You Use Car Brake Fluid on a Mountain Bike

When maintaining your mountain bike, it is crucial to use the correct brake fluid to keep it working correctly.

Or, if you’re looking for how to get the most out of your MTB, you may wonder if you can use car brake fluid. 

It is an important question to consider before modifying your bike’s brakes. 

However, you may wonder if using car brake fluid instead of bike-specific brake fluid for your bike is safe and effective.

Yes, you can use car brake fluid on your mountain bike, but you should be careful about which oil you use. That’s because cars also use some DOT fluid MTB uses, but some MTB brake systems are incompatible with the car brake fluid. Their incompatibility is because brake fluid has a different boiling point than MTB fluid.

In this article, I’ll explain whether you can use car brake fluid in your MTB. Then, I’ll explain the difference between your bike and car brake fluid.

By the end, you will know whether it’s safe to use car brake fluid for your MTB.

Can I Use Car Brake Fluid on My Mountain Bike?

Can You Use Car Brake Fluid on a Mountain Bike

You may use car brake fluid on your MTB but be careful with the fluid you put in your bike. 

That’s because there are some instances whereby the car brake fluid isn’t compatible with the fluid your bike uses.

So, check the type of fluid your bike uses to know if it’s the type your car brake uses, or ask your mechanic what to use.

Your mountain bike uses mineral oil or DOT fluid as brake fluids. So if you use car brake fluid and your MTB uses mineral oil, it is bad for your bike and can damage it.

Car brake fluids are for automotive applications and can be corrosive to the internal parts of a bike brake system. So you should ensure the fluid you put in matches.

Sometimes, you see that your MTB uses DOT, and your car brake fluid is also DOT. 

But there are different DOT available, and if you use one incompatible with your bike, it will become a problem.

For instance, using a DOT 3 with your mountain bike will be unsuitable because it has a different boiling and freezing point

Also, in some cases, the boiling point of car brake fluid may be too high for certain mountain bike brakes. So it is important to use the correct type of brake fluid for your mountain bike.

I recommend you use only brake fluid designed specifically for mountain bikes for maximum safety and performance. 

This fluid type has been designed specifically for hydraulic disc brakes, commonly found on mountain bikes

It is also important to use fresh brake fluid when replacing your brakes. If you expose the brake fluid to heat or moisture, it can cause damage to your brakes.

When changing or servicing your brakes, you should always read the manufacturer’s instructions before using any fluid or lubricant.

If you have any doubts about the type of fluid to use, consult a certified bike mechanic or dealer.

What Brake Fluid Do I Need for My Mountain Bike? 

The brake fluid suitable for your mountain bike is the one stated by your manufacturer and depends on the type of brake it has.

It would be best if you didn’t use a brake fluid different from what your manufacturer’s specified for your bike model to avoid damage to your bike.

There are two types of brake fluids that your mountain bike uses mineral oil or DOT. 

Although they are different, just because they are both used with MTB doesn’t mean you should use them together.

Each of these brake fluids has specific mountain bikes they are compatible with. 

The table below shows some mountain bikes and the brake fluid they’re compatible with.

Mountain BikeBrake Fluid Type
ShimanoMineral Oil
CampagnoloMineral Oil
GiantMineral Oil
TektroMineral Oil
MaguraMineral Oil

So if you need help deciding which brake fluid to use for your MTB, speak with a qualified bike mechanic before making a purchase. 

Using the right type of brake fluid in your MTB is essential to ensure that your brakes remain in good condition and work well when needed. 

Follow the manufacturer’s instructions when filling your bike’s brakes with brake fluid so you don’t make a mistake. 

Also, always wear protective gloves and eyewear when handling the brake fluid. 

That’s because it is highly corrosive and can cause skin burns or eye damage if it comes into contact with your skin or eyes.

Additionally, ensure to fill the brakes up slowly and evenly to avoid accidental spills. Finally, check and refill your bike’s brake fluid periodically to keep your brakes in peak condition. 

If your brakes aren’t working well again, you may need to check the level of your brake fluid and top it off as needed. 

Is Bike Brake Fluid the same as Car Brake Fluid? 

No, they are not all the same. In the case of DOT brake fluid, they are the same, but if it is mineral oil, it isn’t because your car doesn’t use it.

Instead, they have similarities that allow you to use a car’s DOT bike brake fluid.

So, for example, if the specification for your bike brake fluid is DOT 4, it’s the same DOT 4 you’ll use for a car.

In this case, there is no difference between the bike brake fluid and the car brake fluid.

So the difference between the brake fluids for both your car and bike is the type of fluid they use. For example, your bike uses mineral oil or DOT brake fluid, while a car uses DOT.

Only use the type specified for your mountain bike to avoid damage caused by using the wrong brake fluid. 

Using anything else could cause serious damage to your bike and jeopardize your safety.

How to Add Brake Fluid to a Mountain Bike?

Adding brake fluid to your MTB is fairly simple. But first, you have to be sure you have the correct type of brake fluid for your bike, if it’s mineral oil or DOT.

After knowing the right brake fluid to use, you should bleed out the fluid in the bike before adding your brake fluid.

To access where your brake fluid is, check near the brake levers. It has a small cap or lid, which you’ll open with a Hex wrench. After bleeding the bike, clean the reservoir with a cloth.

It would help if you moved your bike a bit to shake the bubbles and get a kit to help add brake fluid.

From the kit, insert a funnel into the hole where the fluid is, then add the new brake fluid to it. Be careful not to spill it and not put too much.

It will go in bit by bit because of the hole in the funnel, and the bubbles in it will come up. Then, after it successfully goes into the reservoir, you’ll see the dirt/remnant in the funnel.

Use the stick in the funnel to block the funnel hole and remove it to dispose of the dirt. Then, add more brake fluid and repeat the process till you’re satisfied with the fluid you’ve added.

After that, you close the brake fluid reservoir and tighten it very well to prevent leaks. You can then test if your brake now works well after adding the brake fluid.

If everything looks good, you’re ready to hit the trails!

Josh Matthews

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