Originally Posted by
dsbrantjr
It seems to me that just the fact that smaller wheels have to make more turns to cover the same ground they would wear chains, etc. faster.
Also, throw away your chain checker and measure your chain with a good steel rule, if you want to know what is really going on.
^^^This.
Per the late Sheldon Brown's
online gear calculator, a bike with a 50T front sprocket, an 11T rear sprocket, and 700c x 25 tires rolls approximately 9.6 meters for each turn of the crank. A bike with 20x1.75 BMX wheels/tires and the same front/rear gears rolls only 6.8 meters for each turn of the crank - or approximately 70.83% as far. The crank (and chain and sprockets) on the bike with smaller wheels thus must turn more times in order to cover the same distance - in this case, around 41.2% more. They can therefore be expected to wear out after covering less distance.