Why does "Front pumps / dives harshly under hard braking" happen?

The most common causes are: Compression, Oil height, Trail braking to the apex. Check them in this order; it is often the setup, sometimes the technique.

All symptoms

Front pumps / dives harshly under hard braking

When your bike shows "Front pumps / dives harshly under hard braking", these are the most likely causes - ranked by relevance: Compression, Oil height, Trail braking to the apex. LAISA separates setup causes (adjusters, components) from riding technique.

Short answer for this problem

Recommended starting point: Check first: Fork: Compression
Most important change: Smallest documented change: 1 click - clicks out from fully closed
Why: The compression is too soft - the fork dives fast and pumps; add compression.
How to test it: Read the current value off the bike and compare it with the recommended one. Write it down before you change anything.
Source: LAISA diagnosis catalogue, drafted automatically and editorially released Methodology →
Last reviewed: No review date documented

Pick your bike to apply the fixes directly →

The order comes from the stored strength of the symptom-cause link in the catalogue - per symptom, not across symptoms. These are not probabilities and not measurements.

Suspension

Fork: CompressionCheck first

Why this could fit: The compression is too soft - the fork dives fast and pumps; add compression.

How to check it: Read the current value off the bike and compare it with the recommended one. Write it down before you change anything.

Smallest change: 1 click - clicks out from fully closed

Fork: Oil heightCheck first

Why this could fit: Check the oil level first - the wrong air spring makes the dive harsh and pumping.

How to check it: Read the current value off the bike and compare it with the recommended one. Write it down before you change anything.

Smallest change: 1 mm - from top, fully compressed, no spring

Tires

Tire: Front tire pressureCheck next

Why this could fit: Too much front pressure makes the carcass skip/pump - set the hot target.

How to check it: Read the current value off the bike and compare it with the recommended one. Write it down before you change anything.

Smallest change: 0.05 bar

Technique

Trail braking to the apexCheck first

Why this could fit: Slamming the brakes spikes the dive - squeeze progressively and trail off smoothly.

How to check it: Ride the drill deliberately for a few laps on the same section and watch whether the behaviour changes.

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Related symptoms

Bike will not hold a tight line Front chatter on corner entry Front pushes (understeers) on entry No front feel / grip when tyres are cold

A starting point to verify on the bike - not a safety guarantee. Change one thing at a time and check on track.