For 1X single chainring setup, how to achieve both close ratio and wide range gearing?
the easiest way of course is to adopt 11-speed setup like 11-32T, then you will have
11-12-13-15-17-19-21-23-25-28-32T.
but what if you are in 9-speed setup?
if you use 11-32T, then your ratio would be
11-13-15-17-19-21-24-28-32T, then you are missing 12 and 14T.
1T difference in small cog makes bigger speed difference than 1T difference in big cog above 19T. not to mention your cadence higher on flat and that will make the speed gap larger and cadence lower on climb and that will make the speed gap smaller.
let me show you the calculations based on 349 wheelset on 54T chainring and 406 wheelset on 48T chainring:

at 80rpm cadence, 12T jump to 11T there will be 2.55km/h difference while 13T jump to 11T there will be 4.71km/h difference.
at 80rpm cadence, 14T jump to 13T there will be 1.85km/h difference while 15T jump to 13T there will be 3.46km/h difference.
any gap larger than 4km/h will be very noticeable.
then how to fill in this 12T gap while you still want to use 11-32T 9-speed setup?
you can learn from bro azam that combine 2 set of cassette.
at 80rpm cadence, 28T jump to 24T there will be 2km/h difference while 32T jump to 24T there will be 3.51km/h difference.
at 80rpm cadence, 24T jump to 21T there will be 2km/h difference while 24T jump to 19T there will be 3.69km/h difference.
you can combine 11-32T with 11-23T and form
11-12-13-14-15-17-19-23-28T or
11-12-13-14-15-17-19-24-28T or
11-12-13-14-15-17-19-24-32T or
11-12-13-15-17-19-23-28-32T or
11-12-13-15-17-19-24-28-32T.
*25 May 2022 updated: optimized gear ratio with 28T for those who don't like big jump from 24T to 32T*this is same theory like how shimano introduce their megarange freewheel/cassette during 7 and 8 speed.
this is how 11-12-13-14-15-17-19-24-32T looks like:

this is how 11-12-13-14-15-17-19-23-28T looks like:

p/s: not all brand cassette are combine-able, some you might need to drill the rivet screw off or break the spacer to have space to dremel the rivet screw.
This post has been edited by BOTAK_WAI: May 25 2022, 06:43 AM