Ride steep descents safely: saddle down, weight back with pressure on the front wheel, brake smoothly, emergency exit. With milestones and clear limits.
The honest answer: you ride a steep descent under control when you lower the saddle, stand low with your hips behind the saddle, bend arms and legs, keep the front wheel loaded and brake smoothly with both brakes. The mistake that sends you over the bars is almost never courage but a front-brake grab that is too late and too hard.
How hard is it really? Steep sections feel much steeper than they look. The Single Trail Scale, a widespread standard for trail difficulty, puts gradients up to about 40 percent in S1 and up to about 70 percent in S2 [3]. 70 percent means: over 10 metres of distance you drop 7 metres. For practice that is very steep.
Why is the topic serious? In a video analysis of 534 mountain bike crashes, going over the handlebar was the most common crash type at 55.2 percent, mostly through sudden deceleration, in over half the cases on moderately steep terrain and at speeds above 30 km/h [1]. Descending technique is therefore crash prevention, not show.
On steep sections it is not your courage that is tested but your brake modulation.
Lower the saddle all the way. Walk the slope first: how firm is the ground? Where is the run-out? Are there roots or ledges at the end? A slope you cannot see is not a practice slope.
Milestone: before starting you can say where you brake, where you let it roll and where you stop.
Bring your hips behind the saddle, arms and legs bent, heels down. Your upper body does not lie back, though: the front wheel needs pressure so it does not slide away [1]. Weight back, pressure front sounds contradictory. What is meant: hips back, chest toward the handlebar, arms bending.
Milestone: in the side video your hips are back, your arms are bent and the front wheel stays on the ground.
One or two fingers per lever. Brake early and evenly, not with a jerk just before the steep section. The rear wheel must not lock, the front wheel is used only in a measured way. A sudden front-wheel grab is the mechanics of going over the bars [1].
Milestone: you can stop in the steep part without either wheel locking.
Look to the end of the slope, not at the front wheel. If you look ahead, you ride with more foresight.
Milestone: you can name a target at the bottom of the slope and arrive there.
Practise stopping and dismounting before you have to do it in a steep section. The BASPO dossier lists "stopping on a slope" and "dismounting backward (emergency exit)" [6], the DIMB lists dismounting on slopes [4]. That it pays off is shown by a video analysis of 300 crashes: riders who dismounted in a controlled way while descending had a 89 percent lower chance of a head impact (odds ratio 0.11) [2].
Milestone: you dismount in the slope in a controlled way without sliding and place the bike across the slope.
Steep descents are safety-critical. Heads and upper limbs are most often affected in mountain biking [7]. In a fall forward the risk of a head impact was almost five times as high (odds ratio 4.9) [2]. In a meta-analysis of cyclists a helmet reduced serious head injuries by about 60 percent [8], a guide value for cycling in general.
Work in steps. Start on slopes up to about S1 (around 40 percent), only then S2 [3]. Slopes where the rear wheel or your strength might fail, you push. Pushing is not weakness: dismount when fatigue appears or weather and ground get worse. Anyone aiming at S4/S5 needs supervised training and protective gear. This guide explains and motivates; it does not replace supervised training.
Do the stop test on the slope: brake in the middle of the slope to a standstill and ride off again. If you can do that in the saddle, you have the brake under control. If you are already shaking, you know the slope is still too steep. That is an honest gauge that protects you.
And a practical detail: use your index finger instead of all fingers on the lever when descending. That saves grip strength, and you need it: hand strength was among the factors explaining ride time in the downhill study [5].
Saddle down, hips behind the saddle, arms bent, front wheel loaded and brake early and evenly with both brakes. Going over the bars usually results from sudden deceleration [1]. Never lock the front wheel.
To start, about 20 to 30 percent on firm ground is enough (practice). The Single Trail Scale puts S1 at up to about 40 percent and S2 at up to about 70 percent [3]. Move to the next level only when the stop test works cleanly.
Both, smoothly. The rear wheel stabilises, the front wheel provides the deceleration. Braking too hard with the front triggers the flight over the handlebar [1]. Practise the stop test until you feel the limit.
When you cannot see the bottom of the slope, the ground is wet or loose or your hands shake. In one video analysis a controlled dismount was associated with an 89 percent lower risk of a head impact [2].
Rolling Down Ledges and Steps: Riding Small Edges Safely Without a Drop