You bought a new hydraulic disc brake for your bike and when installing it, you notice that the brake lines are too long. Especially Magura supplies brakes with a decent cable length, but also SRAM and Shimano equip their brakes in most cases with lines that are too long for practically any bike.
This is a good thing because, as you will learn in our guide, shortening the line is no problem at all. Extending it would be much more complicated, as it would require a complete replacement of the brake lines.
In this tutorial, we will show you how to shorten the brake line with just a few simple steps and perfectly adjust it to your bike. We demonstrate the necessary steps on a SRAM G2, but shortening the lines is similar for all manufacturers and models.
What do you need to shorten a brake line?
Of course, you can't shorten a brake line without tools. In addition to the new brake (and your bike, of course), you'll need some tools.
The most important tools for shortening a brake line on a bicycle.
To shorten a brake line on a bicycle, you need the following tools:
- Hammer (not for SRAM brakes)
- Pipe wrench
- Cable cutter
- Tool for removing the brake pads
- Torque wrench with various bits (suitable for your bicycle)
- Torx or Allen key for the handlebar clamp
- Protective gloves
- 8mm open-end wrench
- Spacer for the brake pistons
- Clamping jaws for the brake cables
↪ You can find tools and bicycle tools in the BMO online shop
The delivery scope of most bicycle brakes includes the following accessories:
• Olive (clamping ring) for the hydraulic line
• Insert pin for the hydraulic line
• Torx angle key T10/T25 (only needed for SRAM)
Shortening bicycle brake lines – step by step
The first step is to prepare the bicycle for the upcoming maintenance session.
Preparation before shortening
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To have free hands, it's best to secure your bicycle in a repair stand. Then remove the front wheel to protect the brake disc from dirt and oil.
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Also the brake pads you should ensure this, because when shortening the brake line, some brake fluid may leak out, which would ruin it.
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The brake pistons inside the caliper are carefully pushed back and fixed with a spacer.
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To avoid losing too much brake fluid later on, the brake lever is loosened and aligned upwards. Due to the vertical alignment, the line connection is tilted upwards and the brake fluid cannot flow out freely.
Loosening the Brake Line
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Step five gets exciting. Pull back the protective cap of the brake lever to expose the locknut.
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Next, loosen the locknut with an 8 mm open-end wrench to remove the end of the brake line from the brake master cylinder. When pulling out the line, you should proceed very carefully, as brake fluid may leak out. Skin contact should be avoided at all costs, which is why wearing protective gloves is recommended. The locknut and protective cap remain on the line so you don't lose them.
Determine the Length of the Brake Line
Now comes an important step: You can determine the appropriate length of the brake line.
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To do this, turn the steering wheel to the maximum and hold the cable up to the connection of the brake lever. The line should pass closely by the frame but not touch it, so it does not damage the paint. The vertical position of the brake lever provides a few extra millimeters of buffer in the length, so you can ensure that the line does not become too short.
Now the brake line is being shortened!
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Mark the required length, that is, the point where you will cut the line. Then you can shorten it with a cable cutter. It may be tempting to just use side cutters here, but the straight blades can crush the brake line, and in the worst case, it won't fit into the fitting anymore.
Assembly of the shortened brake line
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After the actual shortening, we clamp the line using a pipe wrench and clamping jaws. You should never work without the clamping aid here as otherwise the line can be crushed or even damaged. You should also check again that both the protective cap, which we loosened in step five, and the compression nut are in the correct order on the line (first the protective cap, then the compression nut).
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Note: For other manufacturers (i.e., not SRAM), the olive must also be threaded onto the brake line after the compression nut. Observe the correct order: protective cap, compression nut, olive. Important: The order cannot be changed after the insert pin is mounted. With a SRAM brake, the olive is screwed on only after inserting the insert pin. |
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The next step involves the assembly of the shortened brake line. To reattach it to the master cylinder, a new insert pin and an olive must be installed. Both parts are included in the package of almost all new brakes.
- Since we are performing the assembly of a SRAM G2 brake, the pin is screwed in. The appropriate Torx key is also included.
- For other manufacturers like Magura or Shimano, the insert pin is carefully driven in with a hammer.
- In both options, we first press the pin by hand a bit into the line, to then drive it into the sleeve up to the head using the appropriate tool.
For SRAM brakes, the olive, also called clamping ring, is now screwed onto the insert pin. For other manufacturers, the clamping ring has already been pushed onto the line.
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Now, the brake line is fed back into the brake lever and mounted. When tightening the lock nut, the cable must be pressed firmly into the opening the entire time. Only then is an error-free installation possible.
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Tighten the nut with about 8 Nm and check if the line holds. A slight pull on the brake line will show you whether the brake line is securely seated in the lever.
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Afterwards, you slide the protective cap back into its position and the main work is done.
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Now all that's missing is the reassembly of the bike. Align the brake lever appropriately again and mount the brake pads and the wheel, which were removed at the beginning for protection
Test the brake setting
In the last step, you check the pressure point of the brake.
15. If this is not optimal after multiple actuations, you may need to bleed the brake. Another reason for insufficient function could be the loss of brake fluid. Actually, setting up the lever in step four should prevent this, but fluid can still be lost.
The brake line is shortened and mounted...
... and when everything is perfectly adjusted and controlled, the trail fun can go to the next round. This assembly is absolutely doable for experienced mechanics, but if you are (still) unfamiliar or have an uncertain feeling about it, you should ask a professional or at least have your work checked by someone. The brake of your bike is truly essential for your safety, if something is wrong here and the brake does not work properly on the trail, it can lead to painful accidents.
