Originally Posted by
HillRider
Tiagra should be equivalent to 105 in quality and durability but will probably weigh a bit more.
I expect Tiagra will use plate cogs rather than the spidered cogs on 105/Ultegra, so yeah, I bet there'll be a notable weight difference, but equivalent longevity. SRAM PG1050 cassettes are an alternative, and have aluminum spiders for the bigger cogs.
I'm glad to see Shimano expanding the range on the road and sport-touring stuff like this, props to SRAM for providing the necessary competition by doing it with Apex.