Crankarm Keeps LooseningUpdated 6 months ago
If you are only tightening the spindle bolt, it will continue to fall off while riding. The pinch bolt needs to be tightened. A tried and true trick to fix this is to first loosen both bolts, then when you are tightening down the spindle bolt, get it where it feels correct while rotating the pedals (not too much that it causes resistance). Then use the compression bolt to tighten it down until you can't anymore. After the compression bolt is tight, tighten the spindle bolt more to prevent it from falling out.
If you are not confident performing repairs yourself, a bike shop is always recommended.