On 10/11/2018 12:07 AM, Emanuel Berg wrote:
On my racer, there is a wire under the
top tube. On this wire hangs three very small
plastic washers. Unless someone forgot to
remove them, the only thing I can think of is
they are there to prevent the wire from
rattling against the tube. Not that that would
happen very often for a stiff wire, right?

I'm guessing you mean a brake /cable/ runs under your top tube. ("Cable"
is the common term for brake and derailleur-control wires.)

If the washers are soft and rubbery, vaguely doughnut/torus shaped, yes,
these are commonly used to keep cable from rattling. If the length of
exposed cable is long, it doesn't take so very much bouncing of the bike
to get the cable to bounce against the frame tubes. Brake cables aren't
all that stiff.

Mark J.