If the bicycle has a very rounded frame

but on the other hand

Made of magnetic tape with self-adhesive back

we can recommend a magnet separator

Jernspåner til magnetiske eksperimenter (200 g.) Auto-translated (SE) If the bicycle has aUse iron filings to visualize a magnetic field the iron powder is attracted to the magnet and settles in a new, interesting pattern on top every time. NOTE! Remember to use a thick piece of paper or similar between magnet and iron filings! It is difficult to remove iron powder from a permanent magnet again. You therefore need a layer inbetween such as cardboard or a piece of glass, so that you can create a distance between the magnet and the iron