This bladder is a good tool (or maybe) if.1. The magnet did not always come out when separated from the wheel or disc. Reinserting the magnet may affect the repeatability of readings. So I had to check the calibration every time. The solution when you hold it, add it to the cup.2. the magnetic cup holds securely. It is only held in place by a Phillips screw and must be checked for tightness before using the bubble level. calibration has taken place. You will need to use a pad of paper to hold the adjustable part of the spirit level in place or give it more friction to stay in place. degrees on both wheels. Not too bad for the money. A device will probably be made to hold the level if the tire comes off the rim.