I want to see how big of a rear cassette I can go on all of my bikes so they can be better at climbing while keeping the same RD.
First bike 9 speed Tiagra SG RD. It’s a 2011ish masi speciale strada. Current cassette is 12-25. Can I go to 11-28? Can I go bigger? Front cassette is 34/50.
2nd bike is a 1995~ Gary fisher Aquila mountain bike 7 speed. Has a shimano STX GS rear derailleur. Current cassette is 11-28. Front cassette is 22/32/42.
3rd bike is a 1995~ gary fisher marlin 7 speed. Should be a 11-28 as well. Front cassette should be 22/32/42.
by FerretFiend
10 Comments
Depends on the capacity of the RDs
I am not going to look up the data sheets for you lol
Short cage RD, not going to accept a much larger cassette if at all.
I’ve got that STX doing 8 speed 12-32 with a triple in front.
I bet that Alivio can go up to 32 too.
You can calculate chain wrap with all the numbers that you have given. Then just do internet search for the chain wrap capacity of each derailleur.
Find the model numbers stamped on the back of the rear derailleur (starts with RD) and put it in to Google or si.shimano.com > technical specifications and you’ll find exactly what you’re looking for.
28t maybe 30 max
You could find a 2nd hand tiagra 4500 long cage for a few pints of beer for 34T
If you find a broken or for spare mech you can swap the cage even.
Not sure about the other two but I’m running an 11–34 7 speed with my STX derailer with no issues.
Try harder dude. The internet…
I can tell you you’d get up to a 40t with an inexpensive Shimano Acera RD-M3020, 45t total capacity
The tiagra short cage derailleur will take a 28, at least. All my derailleurs are short cage, I never use a cog larger than a 28 but they work fine with a 28.