Yeah, if we think that each frame size is meant for a rider ~2”/55mm taller, and we think their hands end up somewhere around half that height, stack should increase about 12mm per frame size.
So on a 6 size range (XS-XXL, which seems to be the biggest range available), stack would increase 72mm!
On the Stumpy Evo I just bought for my daughter, the range is 41mm! The steps are only 9mm per size, except for the S1(XS) to S2(S), where it is only 4mm.
It is understandable that there is a lower limit to stack with longer travel forks and big wheels, but then the reach should have a bigger jump shorter to compensate.
And there is no reason the biggest sizes can’t be taller, creating more spread in the rest of the size range.
Trek Fuel does great, especially for short people, with a range of 82mm*, and quite low stack on the smallest sizes, by switching to a 27.5 wheel.
They also add an extra frame size in the middle to create a smaller size step there.
*on the alloy frames, which come in XXL, carbon frames don’t.
May 5, 2022, 6:19 a.m. - Tjaard Breeuwer
Yeah, if we think that each frame size is meant for a rider ~2”/55mm taller, and we think their hands end up somewhere around half that height, stack should increase about 12mm per frame size. So on a 6 size range (XS-XXL, which seems to be the biggest range available), stack would increase 72mm! On the Stumpy Evo I just bought for my daughter, the range is 41mm! The steps are only 9mm per size, except for the S1(XS) to S2(S), where it is only 4mm. It is understandable that there is a lower limit to stack with longer travel forks and big wheels, but then the reach should have a bigger jump shorter to compensate. And there is no reason the biggest sizes can’t be taller, creating more spread in the rest of the size range. Trek Fuel does great, especially for short people, with a range of 82mm*, and quite low stack on the smallest sizes, by switching to a 27.5 wheel. They also add an extra frame size in the middle to create a smaller size step there. *on the alloy frames, which come in XXL, carbon frames don’t.