A bicycle frame hanger straightener and a brake disc straightener are part of the basic equipment of a bicycle repair shop.
A bicycle hanger straightener is a specialized tool used in bicycle maintenance and repair to properly align the derailleur hanger – the small component that holds the rear derailleur to the bicycle frame. The hanger plays a key role in the precise shifting of a bicycle. If bent or misaligned, it can lead to poor shifting, misaligned chain, and even possible damage to the drivetrain. A derailleur hanger straightener is an investment that pays off, especially if you need to do more maintenance or after a fall. Instead of replacing components due to poor shifting, you can often just straighten the derailleur hanger.
A disc brake straightener is a specialized tool used to adjust and align brake discs. Disc brakes on bicycles can sometimes become misaligned due to a variety of factors, such as impacts, rotor warping, or normal wear and tear. Aligning a brake disc ensures that it rotates smoothly and evenly in the caliper, preventing friction between the brake pads and ensuring effective braking performance.
How to use a derailleur hanger straightener?
- Place the bike on a mounting stand (ideal), or stabilize it so it doesn't tip over.
- Remove the rear wheel - it will give you better access to the heel.
- Remove the derailleur.
- Screw the derailleur hanger straightener into the thread where the derailleur is attached.
- Make sure that the straightener is screwed firmly, and the tool can rotate around the axis of the foot.
- The leveller has a measuring stick or indicator that rests on the wheel rim.
- Turn the tool to 3, 6, 9 and 12 o'clock (positions like on a clock face) and at each position measure the distance from the bar to the rim.
- If there are differences in distance (e.g. 5 mm on the left, 15 mm on the right), the derailleur hanger is bent.
- Gently push or pull the tool in the opposite direction of the deviation.
- Straighten gradually and carefully – repeatedly check the distances in different positions.
- The goal is to keep the distance between the bar and the rim the same or nearly the same in each direction (±1 mm).
- Unscrew the tool.
- Put the derailleur and rear wheel back in place.
- Try the shifting and fine-tune if necessary.
How to use a brake disc straightener?
- Watch to see if the disc wobbles as it rotates – moving closer and further away from the brake pads.
- If so, it is bent and needs to be straightened.
- Place the bike on a mounting stand or otherwise stabilize it.
- You don't have to remove the disc - the work is done directly on the bike.
- Slowly spin the wheel and listen for friction against the pads, or watch the disc move through the brake caliper.
- When you find a spot where the disc is deflecting, stop the wheel.
- Insert the tool (straightener) through the groove into the appropriate place on the disc.
- Gently pull or push the disc in the direction opposite the bend.
- Make small, gradual adjustments – then always turn the wheel and check the result.
- You may need to adjust several places around the circumference of the disc.
- The goal is for the disc to pass evenly and without contact with the plates.
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