Pull the brake lever and ensure there is sufficient tension on the disc brakes BEFORE your ride. Check brakes frequently to ensure they are working properly.
I. If your brake is rubbing, it may need to be adjusted or re-aligned. For example, the brake may have been impacted during transport or a small stick from the road may have gotten caught in the brake pads causing the disc to bend.
Position yourself so you can see the rotor turning in between the brake pads. Ensure that the disc rotor is true. If the disc is turning unevenly you may have to replace it.
I.a. If the inner brake pad is rubbing, loosen the alignment bolts and follow these steps:
- Use your hand to position the caliper so the inside brake pad is as close as possible to the rotor without touching during a full turn.
- Alternate in tightening the bolts, fastening each one a little more at a time while ensuring that the caliper remains in position. Spin the wheel during this process to control perfect positioning of the Inside brake pad. Torque the alignment bolts to 6 N.m.
I.b. If the outer brake pad is rubbing while the inner brake pad is closely positioned to the rotor, remove a little bit of pressure by relaxing the caliper arm position on the cable (see II.b. below).
If the outer brake pad is rubbing while the Inner brake pad is positioned too far away from the disc, reposition the caliper to bring the inner brake pad closer to the rotor following the steps I.a.
II. If there is lack of tension on the brakes (the brakes should engage fully before the brake lever touches the handlebar) consider the following:
II.a. Slight adjustments in braking tension (e.g. as brake pads wear) can be made using the barrel adjuster:
- To increase brake tension, turn the barrel adjuster backwards so that the caliper arm moves closer to the barrel adjuster.
- Don’t forget to tighten the nut afterwards so that the barrel adjuster stays safely in place.
II.b. Bigger adjustments in braking tension should be done by repositioning the caliper arm on the cable:
- First ensure the inside brake pad is correctly positioned and the alignment bolts are properly tightened as outlined in I.a. above.
- Open the cable bolt and reposition the caliper arm closer to the barrel adjuster while pulling on the cable end to keep it straight. Bring the outer brake pad as close as possible to the rotor without touching during a full turn.
- Tighten the cable bolt and torque to 6 N.m.
After any adjustments to the disc brake system, ensure that all bolts are tightened and test the brakes by operating the brake lever with full force before you ride.
In case your rotor is bent and unless you have a severe wobble in the disc, we would actually recommend you try truing the rotor first to see if that will be sufficient. Any smaller wobbles can be easily removed. You can use a tool like this: https://www.youtube.com/watch?v=O0c2Ez2v0PU
Bike shops in your area should be able to help with that as well.
If you are not able to resolve it as per the above instructions, we can certainly provide a new rotor.