Getting the gearing right is quite tricky, but very worthwhile. The bike gearing charts on the internet are a good place to start. You could see from a gearing chart what the percentage is for the lowest gear you use at the moment, and then using the chart see how bigger chain rings change the percentage of each of the cogs on your rear cassette and find the point where your actual lowest gear on your current cassette matches the percentage of the rear cassette cog you use now. I would ideally have a lowest gear that is a bit lower than the lowest you use now in case you encounter a steeper hill at some point.
For me I used a hard tail Yamaha Haibike to commute to work and back. I rode cross country to work, and then back home on the road. So I still needed my lowest gear to be able to get me up my steepest off road section, but also wanted higher gearing so that I could travel home o n the road at a faster pace.
For me the sweet spot was a 12/36 9 speed cassette coupled with a 42 tooth chain ring. I could travel 10 miles at an average speed of 20mph, and this means being able to cruise in the 20/23 mph range on level slightly down slightly up gradients.
If you do not venture off road you might be able to have higher gearing than I did, but going from 38 to 48 is a massive jump in gearing on a bike.
For me I used a hard tail Yamaha Haibike to commute to work and back. I rode cross country to work, and then back home on the road. So I still needed my lowest gear to be able to get me up my steepest off road section, but also wanted higher gearing so that I could travel home o n the road at a faster pace.
For me the sweet spot was a 12/36 9 speed cassette coupled with a 42 tooth chain ring. I could travel 10 miles at an average speed of 20mph, and this means being able to cruise in the 20/23 mph range on level slightly down slightly up gradients.
If you do not venture off road you might be able to have higher gearing than I did, but going from 38 to 48 is a massive jump in gearing on a bike.
