What do you have to match to go from suspension to rigid?

Above all the axle-to-crown (A2C). Because suspension is measured with dynamic sag, the rigid should be close to the corrected A2C (extended minus the sag), not the fully extended length. You also have to match the wheel size, the axle type (Boost 15x110 or QR) and the steerer tube.

Why not use the extended A2C?

Because mounted and under your weight the suspension fork sinks by the sag, so the real ride height is less than the extended one. If you match the rigid to the extended figure, the front of the bike sits higher than it was; that's why the corrected A2C, extended minus the sag, is used.

Suspension & dropper cluster · Rigid

Converting to a rigid fork

Q: What happens if the rigid is too short or too long?

Too short lowers the front and closes the head angle: the bike becomes twitchy. Too long raises the front and opens the angle: the steering becomes slow. That's why you should get close to the corrected A2C, not go over or under it.

Quick answer

The key to not wrecking the geometry is matching the axle-to-crown (A2C). Because suspension forks are measured with dynamic sag, the corrected A2C is roughly the extended length minus the sag, and the replacement rigid should be close to that corrected A2C, not the fully extended length. Too short closes the head angle (twitchy); too long opens it (slow). Also match wheel size, axle (Boost 15x110 or QR) and steerer tube. Before deciding, review rigid vs suspension and check what fork fits your bike.

The number almost everyone reads wrong is the A2C: match it to the extended length instead of the corrected one and you change how the bike steers.

Why the A2C decides everything

The axle-to-crown is the distance between the wheel axle and the fork crown. That number sets the front height and, with it, the head angle. If the rigid has an A2C close to what your suspension had while riding, the geometry holds. If not, the bike's character changes.

The detail almost no one accounts for: a suspension fork, mounted and under your weight, sinks by the sag. So the real ride height isn't the extended one but the corrected A2C, roughly the extended minus the sag. That's the figure the rigid should get close to.

The procedure, step by step

1 · Corrected A2C of your suspension — Start from the extended A2C of your fork and subtract the sag you ride with. That corrected A2C is the real ride height you need to keep.

2 · Pick the rigid by that A2C — Look for a rigid whose A2C is close to the corrected one, not the extended one. Getting close is what matters; you don't need it to the millimetre, but you shouldn't overshoot or undershoot.

3 · Match wheel, axle and steerer — Same wheel size, same axle type (Boost 15x110 or QR depending on your bike) and a steerer tube compatible with your headset. Without this, it won't mount or won't fit.

How to measure a fork's axle-to-crown and compare the extended A2C against the sag-corrected A2C when going rigid — The corrected A2C (extended minus the sag) is the reference, not the extended one.

What happens if you get the A2C wrong

A rigid that's too short lowers the front and closes the head angle: the bike becomes twitchy and quick in the hands. One that's too long raises the front and opens the angle: the steering becomes slow and lazy. That's why the goal is to get close to the corrected A2C.

Common mistake: picking the rigid by matching the fully extended A2C of the suspension. That ignores the sag and leaves the front of the bike higher than it was, opening the angle and making it slower than you expected.

Need help with the A2C?

Send us your current fork model and your sag and we'll tell you which corrected A2C to aim for on your rigid. Message us on WhatsApp

Frequently asked questions

What do you have to match?

Above all the corrected A2C (extended minus the sag), not the extended one. Plus wheel size, axle type (Boost 15x110 or QR) and steerer tube.

Why not the extended one?

Because under your weight the suspension sinks by the sag; the real ride height is less than the extended one.

What if it's too short or long?

Short closes the angle (twitchy); long opens it (slow). Get close to the corrected one.

Rigid vs suspension → What fork fits my bike? → Suspension & dropper cluster →

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BikeLab-pedia · Suspension & dropper cluster / Bicycle compatibility and standards / Carlos Eduardo Ravello Joo · BikeLab Studio · Trujillo, Peru