Adhesive force in relation to the air gap between magnet and steel plate.
This huge ring has drill holes with two different diameters. On one side, the drill hole diameter is 6 mm and the depth is 20 mm...
... on the other side the diameter is 16 mm and 10 mm deep.
You could also fasten it with a large screw (but be careful - the slant is not 45 degrees - a normal counter-sunk screw would therefore not be sufficient, a rubber buffer or something similar would be necessary.)
Incidentally, Euro coins are magnetic and will be attracted by this magnet.
The cardboard pieces between the giant magnet and the nails are over 40 mm thick.
A single nail flies to the magnet from a distance of 10 cm.
Luckily, we laid a thick piece of cardboard on the cutting board before we started this experiment - otherwise we could barely have removed the magnet again. I also recommend this precaution to you - so that you don't end up scratching the paint off your filing cabinet when pulling the magnets off...
The weight of a bicycle is naturally no problem for this magnet.
Even when the magnet is only in contact with a small piece of the bicycle...
For details, see the cross-section sketch. If you need a higher resolution to see all the dimensions, please click on the sketch.
Note that the slant can be slightly different than 2 mm - this sketch is only to give you a general idea of the layout.
The north pole is located on the are with the larger opening.