Does headset stack height matter?

Yes as long as the part they’re measuring above and below the head tube are actually supportive – like threaded headset cups or threadless external headset cups pressed into the head tube. They actually structurally add to the length of the head tube, making it “longer”.

Do I need a spacer under top cap?

The extension above the stem clamp can be as little as 1mm. Obviously, you need to put a spacer above the stem clamp that extends above it by at least 3mm to allow the top cap to push down on the stem via the spacer; otherwise, the top cap would bottom out on the steerer.

How do I know my stack and reach?

Stack is the vertical distance from the centre of the bottom bracket to the mid point at the head tube. Reach is the horizontal distance from the centre of the bottom bracket to the middle of the head tube.

Is stack more important than reach?

For a given reach, a greater stack puts you into a more upright riding position; your hands will be moved upwards and your body position will rise more towards the vertical.

Is longer reach better?

A longer reach can be very helpful to have room to move around. Also, it helps if you prefer running a shorter stem and having a quicker turning front end. A longer wheelbase keeps the bike in control on high-speed sections. The bike becomes less twitchy and can help smooth out some rough sections.

Should I slam my stem?

If you’re flexible enough, there’s no reason not to slam your stem. If you can hold the position and keep your head and shoulders low, there are certainly aerodynamic benefits, especially when combined with narrower bars.

How do I know what stack and reach I need?

The stack is the vertical distance between the bottom bracket and the headset. It’s the imaginary line that you needed to measure the reach. Stack is the difference in height between the headset and the middle of the bottom bracket.

Why are MTB getting longer?

One of the ways frame designers have been able to grow reach without changing effective top tube lengths too much is through the use of steeper seat tube angles, which we’ll cover below. After declining for a number of years, trail bike chainstay lengths also got longer between 2018 and 2021.