Originally Posted by
mstateglfr
I'm kinda confused on the issue.
A 42t ring with 11-45 cassette is what you currently have and you want to move to a 15-40 cassette?
If that's correct, you are looking to reduce both the low and high gearing. So you don't use the first few small cogs or the last couple large cogs?
If that's correct, then wheelsmcgee ha a solid suggestion- get a smaller ring and smaller overall cassette range.
compare gear inch options on a website and go from there.
That's how I understand it. Maybe just using a few gears in the middle and not the largest or smallest. A wide range 9 speed cassette has big jumps between gears. It would be annoying on flat road riding where you're only in a few middle gears to deal with that.
A narrower range cassette solves this problem. Given that the OP is riding in the middle of their current cassette with a 42T chainring, I'm not sure what problem a smaller chainring solves. If the OP is really on flat roads only, a 42x32 is likely more than enough for any minimal climbs they encounter. A smaller chainring would just move everything down to the smaller cogs and limit top-end. For flat road riding, I'd rather have extra gears on the high-speed end vs low speed.