fritz1255

We have at least five bikes with Shimano freewheels or casettes. Almost all of them, including my son's, which is fairly new (probably less than 500 miles), have bent teeth on the rear cogs to some degree. One of the older ones even has a few teeth badly worn down and a couple broken off (I replaced this one). The Shimano cogs themselves look pretty thin and weak, which is probably where the problem is. Replace with a better brand? Which brand? What degree of bending of bending is likely to cause problems?

HillRider

Are you sure they are "bent" or you are just seeing the shaping and profiling that is done intentionally to improve shifting performance? If all five of your bikes show this, either you are mis-interpreting what you are seeing or your all are incredibly harsh on your equipment.

I've ridden 100,000+ miles on Shimano cassettes and freewheels and am familiar with dozens of other high-mileage Shimano cassette equipped bikes and none of us has ever bent or broken any cog teeth.

fritz1255

By "bent" I mean twisted - looks like they are stressed by the action of the chain over time. The teeth on a brand-new freewheel are straight. I should point out that most of these bikes are Toys-R-Us specials with low-end components.

HillRider

Toy-R-Us specials have the lowest of the low components and tend to be ridden by children who seem honor-bound to try to damage them. You asked; "Replace with a better brand? Which brand?" Shimano cassettes and freewheels are among the very best, just get a higher line version and don't abuse them.

My son-in-law is a very strong rider and a serious racer and he has never bent ot broken any Shimano cassette including 105 and HG-50 level components.

Retro Grouch 

Nope. Shimano produced twist tooth freewheels for a time. They were supposed to improve shifting. Newer freewheels use differently shaped teeth to improve shifting.