Gear Tooth Wear

Here are a few pictures of worn gears recently extracted from the gearbox of my vintage race bike. The box wasn't misbehaving nor even making any untoward sounds. Most of the gears are in good condition, the pictures are of sleeve gear and it's mating gear on the layshaft which are transmitting power whenever 4th or "top" is not engaged i.e. for as long as all the other gears combined.

Here is the layshaft gear: -


Here is the Sleeve Gear: -


And another view of the Sleeve Gear showing how the driven flank of the tooth has had the involute profile worn flat: -

Nice post , & thanks for the photos.

Nice photography and educational views. Note the nice machined finish reveal where not worn out to compare to the crappy new cogs, ugh. I've put some hard miles on some my teeth but they looked more polished away and hammered away. Wonder if the wear is from pure mileage or lots of 4th lugging with some throttling up now and then chugging slowly up steeps? Likely could run a long time further if not drag racing.