Agleck - You need to combine stem length and bar roll to get an effective stem length (ESL) - position of grip centre relative to steering axis (centre of steerer tube).
Example - a 300mm stem with bars that roll back 300mm gives you an ESL of 0mm which is the same as a 0mm stem and 0mm bar roll - and should feel the same.
So the stem length allows you to adjust the location you start the bar roll from. Andrews example of a BMX with 10" high bars is a good one. The stem length almost doesn't matter as you have so much scope to change the ESL.
Front / Rear weight balance is another factor that is affected by all this - as Andy E points out above it's spiderweb - pull one thing and it effects another.
Nov. 2, 2022, 8:54 a.m. - fartymarty
Agleck - You need to combine stem length and bar roll to get an effective stem length (ESL) - position of grip centre relative to steering axis (centre of steerer tube). Example - a 300mm stem with bars that roll back 300mm gives you an ESL of 0mm which is the same as a 0mm stem and 0mm bar roll - and should feel the same. So the stem length allows you to adjust the location you start the bar roll from. Andrews example of a BMX with 10" high bars is a good one. The stem length almost doesn't matter as you have so much scope to change the ESL. Front / Rear weight balance is another factor that is affected by all this - as Andy E points out above it's spiderweb - pull one thing and it effects another.