This is how to align the brake caliper
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Loosen the two screws pictured (the right screw is removed in the picture but the screws should/need not to be removed). When they are slightly loose you can spin the rear tire with one hand and move the brake caliper with the other. Keep aligning the brake caliper until you don't hear noise from the rear brake anymore. Then re-tighten the screws. Support the brake caliper with the other hand when you tighten the screws so that it doesn't move around after you've aligned the brake correctly.
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If this doesn't help or the brake was stuck when you tried to spin the rear tire contact Augment.eco customer service through the chat or by email.