Many people are not aware of what quality the different gears of their bikes have. Shimano, Campagnolo, and SRAM makes gears in all types of quality and price, and they are listed under here, from worst to best:
Shimano
2300 (Cheapest)
Claris
Sora
Tiagra
105
Ultegra
Dura Ace (Best)
Campagnolo
Xenon (Cheapest) (not made anymore)
Veloce
Mirage (Not made anymore)
Centaur
Chorus
Record
Super Record (Best)
SRAM
Apex (Cheapest)
Rival
Force
Red (Best)
You can see a list of the mountainbike geargroups here
Written by René
