The cogset consists of an aluminum body, covered with aluminum cogs and hardened steel cogs. The outer 2 cogs (usually 11 &12) are made from hardened steel to withstand the incredible chain-torque generated on these small cogs. The torque from the chain is much higher per area on the smaller toothed cogs, simply because there is not enough cog-material to displace the torque. The bigger diameter of the larger cogs does provide sufficient displacement of energy to justify the use of aluminum ( ie the softer alloy). That’s why you get a mix of steel and aluminum cogs, – any questions? Good.
The cogs are made for both Shimano 9-speed and Campy 10-speed hubs, and come in a variety of combos ranging from 11-21,23, to 12-21,23,25, and 28 for your steep climbers out there.
The main body of cogs are bolted together, to allow for future replacement of worn cogs, and also to strengthen and displace the loads generated from the chain.
The weights vary from 109grams to 161 grams depending on ratios, so you know they’re light. The spacers are made of glass-filled plastic that are light but won’t compress of bend (like the aluminum spacers will do when you drop them…).
You Learn Something New…
Bill strongly recommends using a new chain with the new cogset, because an old stretched chain will actually “forge” the teeth on the cogs – wearing them out faster. File this under “you learn something new every day”, and thanks to Bill for actually explaining to me how chain-wear really works… It goes like this (dummied down so we non-engineers can understand it):
A new chain wraps around the cogs evenly, applying an even amount of torque and energy transfer to the cog. When a chain gets worn, and stretched, the chain links no longer fit evenly into the cog teeth, thus concentrating the energy transfer (and forces) into the top teeth on the cogs. The same amount of energy being applied across fewer teeth results in higher friction and pressure on those fewer teeth, leading to early burn out.
When I saw they were releasing a 12-28 I got pretty excited. Living in a land of many hills, I can actually look forward to some winter rides at a decent cadence, and can forget about pedaling like a granny wishing I had one on my bike…
Get more info on the new Aluminum Cogsets from American Classic at their website www.amclassic.com