I lost control of my bicycle, crashed, and was seriously injured shortly after having the brakes repaired. Can I sue the repair shop?

The key is, what caused the accident? For example, if there was a pothole, and that pothole is what caused the accident to occur, and it had really nothing to do with the brake repair, then there's no claim to be brought against the bicycle repair shop. If, however, the accident was caused by some sort of negligent repair of the bicycle and the brakes, such as they didn't put a screw in the brake pad correctly, and the brake pad fell off, causing the accident, then you certainly would have a right to bring a claim against the bicycle repair shop, because of their negligent maintenance and repair of the bicycle.