hi,
on all my bikes as a kid there was always a large metal or plastic
round disk behind the largest cog on the rear cluster between the
largest cog and the spokes ... I assumed this was to protect the
spokes in case the chain overshifted and tried to jam between the cog
and the spokes, right?
by the time i bought my last adult bikes in the late 90's this was
normally reduced to a very thin lexan piece which was barely visible
and didn't weight much.
It still seems like a useful thing (right?) and on my old Trek the
plastic was broken so I went my a LBS to obtain another and was given
a lot of attitude by the shop worker's ... something like they are
only for kids bikes, they aren't needed, and I shouldn't have such a
sissy thing on my bike! I did notice that they didn't seem to be on
the better bikes in the shop.
So?
S