Originally Posted by
Iride01
Seems like a important thing to know. At least it is if we are talking about what range you want on the cassette. This is your opportunity to change to something else if you need it.
If you seldom use the 30 tooth cog, then you might just get something with less teeth on the low gear. 28 or even less. If you need that 30 tooth cog and there are somewhat frequent times when even it is not enough, then a 32 or 34 tooth might be the thing to look for the low cog. However then you'll have to know exactly what your rear DR is so you can see if it'll handle bigger or not. The part number for the DR will be stamped on the backside of the parallelogram if it's Shimano and can be difficult to see with the wheel in. Might be gunked up too.
It's a trek-domane-4-3-compact-56cm with a Shimano CS-4600 10spd, 12-30t