Good point Vic!
There are many people remarking that they don’t understand how bikes fit differently than what they expected based on the geometry chart. I think there are two issues that cause this confusion:
1. They don’t set up the bike to their own fit. In other words, they don’t set the saddle to the same height and set-back from the bottom bracket, and they don’t set the grips the same distance and drop from the saddle. (And they use different saddles and shaped/widht bars)
2. They don’t understand the relationship between stack and reach.
With modern mtb’s, the head angle is so slack, that a lower stack makes for a significantly shorter effective reach.
‘_Effective reach_’ being the horizontal distance from bottom bracket to the center of the steerer tube at _your_ handlebar height.
Imagine two nearly identical bikes, the only difference being that one has a tall head tube and the other one has a short head tube. let’s say you run no spacers on the tall head tube bike. If you owned the short head tube bike, you would add spacers to get the bar at the same height. These bikes would fit, feel and handle identical. Yet, the second one would have a longer reach, and shorter stack.
If you want to approximate this when looking at geometry charts, you can subtract 0.4 times the difference in stack from the reach of the lower bike.
May 28, 2019, 7:05 a.m. - Tjaard Breeuwer
Good point Vic! There are many people remarking that they don’t understand how bikes fit differently than what they expected based on the geometry chart. I think there are two issues that cause this confusion: 1. They don’t set up the bike to their own fit. In other words, they don’t set the saddle to the same height and set-back from the bottom bracket, and they don’t set the grips the same distance and drop from the saddle. (And they use different saddles and shaped/widht bars) 2. They don’t understand the relationship between stack and reach. With modern mtb’s, the head angle is so slack, that a lower stack makes for a significantly shorter effective reach. ‘_Effective reach_’ being the horizontal distance from bottom bracket to the center of the steerer tube at _your_ handlebar height. Imagine two nearly identical bikes, the only difference being that one has a tall head tube and the other one has a short head tube. let’s say you run no spacers on the tall head tube bike. If you owned the short head tube bike, you would add spacers to get the bar at the same height. These bikes would fit, feel and handle identical. Yet, the second one would have a longer reach, and shorter stack. If you want to approximate this when looking at geometry charts, you can subtract 0.4 times the difference in stack from the reach of the lower bike.