The top one is the guide pulley. The bottom one is the tension pulley.
spyro66 on
Guide pulley at the top (it guides the chain into the correct gear and keeps it there) and tension pulley at the bottom (it keeps tension on the chain and takes up the slack of small gears vs big gears). The bushing on the tension pulley allows it to float back and forth which helps with chain alignment. The guide pulley is often more square shaped and the bushing has very little side to side float.
If you’re looking to find the right one to replace the guide pulley that you broke, I’d highly recommend cutting your loss and getting a cheap shimano derailleur. They’re pretty cheap these days, you’ll dodge a half-dozen pitfalls of putting it together wrong (it may work but it would bind or back-out the bolt), it would probably be a special order anyway for the parts you need, so that’s either shipping cost or time to ship. Cheap shimano derailleurs are way better quality and avoid the risk of braking another pulley and chain. Every shop has them. Or Amazon. Much easier/quicker to install.
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How did you do that?
The top one is the guide pulley. The bottom one is the tension pulley.
Guide pulley at the top (it guides the chain into the correct gear and keeps it there) and tension pulley at the bottom (it keeps tension on the chain and takes up the slack of small gears vs big gears). The bushing on the tension pulley allows it to float back and forth which helps with chain alignment. The guide pulley is often more square shaped and the bushing has very little side to side float.
If you’re looking to find the right one to replace the guide pulley that you broke, I’d highly recommend cutting your loss and getting a cheap shimano derailleur. They’re pretty cheap these days, you’ll dodge a half-dozen pitfalls of putting it together wrong (it may work but it would bind or back-out the bolt), it would probably be a special order anyway for the parts you need, so that’s either shipping cost or time to ship. Cheap shimano derailleurs are way better quality and avoid the risk of braking another pulley and chain. Every shop has them. Or Amazon. Much easier/quicker to install.