I’ve tried making fender flaps from empty plastic milk jugs and rubber stair tread materials. The result of my on bike testing is:
- milk jug is stiffer and not as attractive, but it lasts through years of tough use.
- rubber stair tread material is more flexible and nicer, but it lasts about 1 year before the material will fail at any stress points and need to be replaced.
So if you want fire and forget flaps use the milk jug.