The new thing

I was walking along when I heard this almighty racket. It was this lad on a bike; it sounded like it was more rickety than the ricketiest of bridges.

It turned out that him and his mates, who he met behind me, had stuck stuff between the bike frame and the rear tyre. He had also stuck a thing on the end of the frame beside the wheel. I fear for the longevity of the tyres.

These modifications must make the bike make the noise, but I don’t see the point. I’m assuming they think it makes them cool to have such noisy bikes. But are they meant to sound like engines? If so, they’ve failed.