Originally Posted by
gmcjetpilot
Thank you bike riding scientist. Good info. Appreciate it. I am going to look at upgrading it. I don't want to change the Shimano gear cassette or shifter, so compatibility is key. I could buy another RD-TY21 and see if it's tighter. If not Amazon free return. The derailleur has to be Shimano SiS Index capable. I am hesitant to mix and match brands. Good news these derailleurs are not too expensive.
Compatibility isn’t a problem. Any 9 speed Shimano derailer will work with your current shifter and cassette. For that matter any 6, 7, or 8 will work with it. 10 speed Shimano road derailers would work as well but they may not have the range you need. Don’t waste your time on buying another Tourney.
I am just blown away with how loose the derailleur and integral hanger connection is. I have to admit it works well, quiet, sifts fast and solid. Hummmm if it ain't broke don't fix it comes to mind. At least I know I have options. This may go with the Shimano Uni-glide twisted teeth on the gear set. That is weird as well, but have to admit it shifts better than other bikes I have or had. The question is how long will it last. What ever I do I will need a spare, this derailleur is hanging way out and low on this folding bike. It will eventually get wacked riding it or handling it. Thanks again.
Tourneys aren’t meant to be sloppy but they just are. I’ve seen some almost new ones that are flexible enough that they won’t hold the gear. They are ultra cheap so lots of companies are now using them on the low price point bikes but they are also ultra poorly built.
On the plus side, a (slightly) more expensive derailer will stand up to a lot more banging around than a Tourney does.