Properly setting up the suspension on your mountain bike can make a huge difference in how it rides. Too much pressure, and you won’t use all your travel; too little, and you risk bottoming out, which can damage the shock, your bike, or your body. So before you just hop on and start pedaling, take a moment to make sure your suspension is set up properly.
Here are the key measurements that will put the right bounce in your bottom—and take the bottom out of your bounce.
Sag and Preload
Sag is the amount of travel you use simply by sitting on the bike in a neutral position. It’s the main point of reference you’ll need to set up your rear suspension.
Preload usually only concerns coil spring suspension (though people sometimes use it when referring to air spring suspension as well). This is where the spring is pre-loaded to set its initial firmness, in order to attain the correct sag. It’s important to start with a spring that’s correct for your weight, then sag can be fine tuned using the adjuster.
Luckily, sag is also one of the easiest adjustments you can make on your bike. All you need is a shock pump and your normal riding gear. If you don’t have a shock pump, most local bike shops will be happy to let you borrow one—but it’s a good idea to get one of your own (like this $30 one on Amazon) in case you want to make adjustments later, or even on the trail.
In order to get the best performance from your suspension, you’ll want to calibrate the sag when you’re close to the weight you’ll be while riding. That means wearing everything you would wear for a day on the trail during the test—including shoes, a full hydration pack, and a helmet, all of which can add significant weight. It’s also important to make sure you reset the indicator (the rubber O-ring on the shaft of the shock) before every test.
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To test sag, have someone hold the handlebars while you get on your bike. With feet on the pedals, bounce up and down a bit, then sit neutrally and slide the indicator back up against the canister. Then carefully get off the bike. There should now be some shaft showing between the air canister of the shock and your indicator. The distance between those two is your sag measurement. You’ll set the sag for your fork the same way, using the indicator on the stanchion. Most air shocks and forks come with those percentages already labeled on them, to make measuring and adjusting sag easier.
Ideally, you should be able to engage the suspension without worrying about using too much on big hits and bottoming out. Anywhere between 20 percent to 30 percent sag is the standard for shocks, and 20 percent sag is the standard for forks. Check the manufacturer’s recommendations for your particular model. It can also depend on your riding style.
Compression
The compression setting controls the time it takes for your suspension to slow a downward force. Starting with the control knob completely open (counterclockwise), you adjust compression by turning the knob clockwise. Turn the knob too much, and your suspension will take too long to go through all of its travel. Turn it too little, and your suspension will bottom out on small bumps. Experiment to find the sweet spot that best matches your riding style and terrain.
Rebound
Rebound is the speed at which the suspension comes back to full travel after it’s compressed. Though rebound is a preference thing, in general you want your suspension to rebound as fast as it can without the shock topping out or feeling too springy. Set it slow and the suspension can’t extend back into its travel before you hit the next bump, resulting in a harsh ride. Set it fast and your bike will bounce like a pogo stick. To adjust, use the clearly marked control on your fork or shock.
Maintaining Your Suspension
Remember to check your suspension throughout the season, since weather, travel, storage and general use can change the pressure in your shock slightly. If you notice that your suspension feels sluggish or strange, sag is a good starting point for shock troubleshooting. If you spot excessive oil on the shock (trace amounts are okay), or the stanchion tube shows wear, take it in for service.
Lube the pivots and linkage according to the manufacturer’s specs after every 10 hours of riding, or after every muddy or wet ride. Check the tightness of the pivots and linkage bolts. It’s important to use a torque wrench here—too tight and the rear suspension won’t work properly, too loose and things could come apart on the trail. You should also regularly check the rear linkage (including swingarm, chainstays and shock mounts) for cracks or other damage. If anything feels loose after you tighten all the bolts, then the bushings or bearings are worn, and probably need to be replaced.
Another easy way to help keep your suspension in working order is to clean the fork stanchions and the shock shaft after every ride. Gently wipe away any grit and dust, especially around the base where the compression happens.
