High-Speed Compression and Low-Speed Compression are two suspension settings that are easy to mix up. The biggest thing to know is this:
They refer to how fast the suspension is moving, not how fast the bike is moving.
A slow ride over a sharp rock can create a high-speed compression event, while a fast ride through a smooth berm can still create a low-speed compression event.
What Is Low-Speed Compression?
Low-Speed Compression (LSC) controls slower suspension movements.
This usually includes things like:
- Braking
- Cornering
- Pedaling
- Pumping through terrain
- Rider weight shifts
- Smooth takeoffs and compressions
Adding more LSC makes the suspension resist these movements more. That can give the bike more support and reduce things like brake dive, but too much can make the suspension feel firm and reduce traction. A good way to think about it is:
LSC = support and chassis control
What Is High-Speed Compression?
High-Speed Compression (HSC) controls faster suspension movements caused by sharper impacts.
This usually includes:
- Rocks
- Roots
- Hard landings
- Drops
- Square-edge hits
- Rough technical terrain
Adding more HSC gives the suspension more resistance during bigger or faster impacts. This can help prevent the suspension from blowing through its travel, but too much can make the bike feel harsh and cause it to deflect off rough terrain. A simple way to think about it is:
HSC = impact control
High-Speed vs. Low-Speed Compression
| Low-Speed Compression | High-Speed Compression | |
|---|---|---|
| Controls | Slower suspension movement | Faster suspension movement |
| Common situations | Braking, cornering, pumping | Rocks, roots, landings |
| More damping can provide | More support | More impact resistance |
| Too much can cause | Harshness and less traction | Harshness on sharp hits |
Bike Speed Doesn't Determine Compression Speed
This is where the names can be misleading. If you're slowly riding through a rock garden and the wheel hits a sharp edge, the suspension may compress very quickly. That's high-speed compression. If you're riding quickly through a smooth berm and gradually loading the bike, that's mostly low-speed compression. It's all about the speed of the suspension shaft.
How to Adjust Them
Start with the suspension manufacturer's recommended settings. From there, make small changes and test them on the same section of trail.
Add More Low-Speed Compression If:
- The fork dives too much under braking
- The bike feels unsupported in corners
- The suspension moves excessively while pumping
Reduce Low-Speed Compression If:
- Small bumps feel harsh
- The bike lacks traction
- The suspension feels overly firm
Add More High-Speed Compression If:
- You're blowing through travel on large impacts
- Hard landings feel uncontrolled
- The suspension bottoms out too easily
Reduce High-Speed Compression If:
- Sharp rocks and roots feel harsh
- The bike deflects off obstacles
- You're struggling to use full travel
The Bottom Line
The difference between LSC and HSC is pretty straightforward: Low-Speed Compression controls slower suspension movements and helps provide support. High-Speed Compression controls faster suspension movements and helps manage harder impacts.
Neither setting should be adjusted in isolation. Air pressure, rebound, spring progression, tire pressure, and bike setup all affect how your suspension feels. Start with the recommended baseline, change one setting at a time, and make small adjustments until the bike feels controlled without becoming harsh.
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