Bike Repair – Downhill Suspension – Shock Set-Up

Bike with downhill suspension

A mile of suspension travel is worthless without a well tuned shock. We show you how to get the best from yours.

Setting up sag 1

Sit on your bike fully kitted up in riding gear. Get a mate to measure the shock’s compressed eye-to-eye length while you’re sitting on it. Subtract the compressed (sagged) measurement from the total eye-to-eye shock length. This is your sag in mm.

Setting up sag 2

You need to know your shock stroke to calculate your sag percentage; it’s written in the shock’s user manual. Divide the sag measurement (mm) by the shock stroke and multiply it by 100 to get the sag percentage. For downhill we’d recommend 35%. Alter spring preload by up to two turns or switch the spring to achieve optimal sag. If using air, add or remove as necessary.

Setting rebound 1

The rebound adjuster may be marked + and –. Turning the adjuster clockwise in the + direction will give more (and therefore slower) rebound damping, and turning the rebound adjuster in the – direction will give you less (faster) rebound damping.

Setting rebound 2

To check rebound, push down on the rear of the bike and let it spring back. If you can lift the rear wheel high off the floor before the rear shock extends, it has too much rebound (so is too slow). If you feel the bike trying to push you away and you can’t lift the wheel off the floor, it hasn’t got enough rebound (so is too fast). Experiment until you find a happy medium. If in doubt, it is best to set the rebound on the slow side.

Compression

Locate your shock’s compression adjuster/s. Compression damping determines how fast the shock can compress when hitting an obstacle or bump. More compression damping and the shock will be less sensitive to small bumps, less and it will be more prone to falling through its travel and will feel horribly mushy.

Low-speed compression

If you have a separate low-speed compression adjuster, it affects how the shock behaves at lower shaft speeds, like when pedalling or compressions into berms. Too much low-speed compression damping and the rear wheel will tend to deflect off objects easily. Too little and the suspension will dive, using more travel than it needs to.

High-speed compression

High-speed compression damping affects higher shaft speeds such as hard landings, square-edge hits and G-outs. Too much high-speed compression damping and the shock will give a rough ride and feel too hard. Too little and the shock will dive through the travel easily and feel out of control in rough sections.

Bottom-out resistance

If your shock has a bottom-out resistance adjuster, it’ll affect the last part of the travel, much like the air pressure. If you’re finding yourself bottoming out all the time, try winding it on a quarter turn at a time. It’s best to start at the minimum and add more slowly until you find the optimum setting for you.

Air pressure

If your shock has adjustable air pressure on the reservoir, it’ll affect the shock toward the end of the travel, making it harder to bottom-out. Too much air pressure though, and you’ll find that you’re not using enough of the travel and have a harsh ride. Too little and you’ll be bottoming-out too often.

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