I was looking for a 10 Speed Tiagra Casette but was not able to find one. A good deal for a 105 10-Speed Casette caught my eye, so I wanted to ask if it would be possible to pair a 10-Speed Derailleur (Tiagra) with a 10-Speed Cassette (105) even though they are two differnt models? Another small thing, does the size matter of derailluer because I saw some short and long ones? Thank you!
Yes you can, provided that the cassette range approximately matches the range and capacity the Tiagra derailleur expects.
Any Shimano 10 speed cassette works with any derailleur subject to the range constraints.
There are two variants of the Tiagra derailleur: RD-4700-SS short cage (33 tooth capacity) and RD-4700-GS medium cage (41 tooth capacity).
The specs are as follows:
- Short cage: 11-14 T ... 25-28 T, 33 tooth capacity
- Medium cage: 11-12 T ... 28-34 T, 41 tooth capacity
So for example if you have 11-28 tooth cassette and 34/50 chainrings then the capacity requirement is 50-34 + 28-11 = 33 teeth. That will work even with the short cage because the 28T fits to the range of big sprocket size (25-28 T) and the capacity of 33 teeth is enough.