Ask a Mechanic: Basic Suspension Setup

Joseph asks: “I’m new to full suspension mountain bikes and don’t quite understand all that goes into setting up my suspension. Can you give me the basics?”

Properly setting up mountain bike suspension can seem like a magic trick to many people, but fortunate for you, following a few simple guidelines will have you pointed down the right track in no time.

The first step is determining sag, which is the distance your bike settles into its travel when weighted. Make sure that your fork and shock have travel indicators and if there are none, install a zip-tie yourself, but not too tightly.

Place the bike next to a wall or have a friend hold the bike while you climb aboard. Wear what you would on a ride, including hydration pack, and armor. Stand on your pedals in the attack position, centering your weight over the bike. Gently bounce a few times, then slowly reach down and push the travel indicator against either the shock or fork. Avoid compressing your suspension by slowly dismounting the bike in the opposite direction. With your air pressure properly set, the travel indicator should move 20-30% of the stroke and about 35% for longer travel applications. Increase or decrease air pressure five PSI at a time until proper sag is achieved.

Now that you’ve got your air pressure dialed, it’s time to set rebound damping. Less damping—turning the adjuster counter clockwise— means the shock or fork will return from compression faster, and vice-versa. If rebound is too fast, you’ll get a skittish, bucking ride. Too slow, and your suspension won’t be ready for the next impact, making for a harsh ride.

The easiest way to get in the ballpark is to use the “top-out test.” Turn your rebound adjust knob so it’s fully open. Now compress the fork or shock as much as possible by pushing down on the saddle, and quickly let go. If the suspension extends too quickly, coming to an abrupt stop at the top of its travel, you’ll need to increase rebound damping to slow it down. Repeat the top-out process on your fork, pressing down on the handlebars instead of the saddle.

You will most likely need to fine-tune your rebound one or two more clicks on the trail. If the front or rear of the bike bucks, increase the rebound damping a click to slow the rebound down. If the bike seems like it’s overly harsh through successive hits, speed up the rebound a click so the suspension will be able to extend for the next impact. Err on the slow side of rebound for the shock so you won’t get bucked, and on the fast side for the fork, so it won’t pack up and throw you forward. A general guideline is to set up your rebound 1 or 2 clicks faster for trails with small, high frequency bumps and 1 or 2 clicks slower for trails with big hits.

Compression damping is more involved and requires time on the trail to dial in. Most trail components only offer low-speed adjustment, and DH components offer separate high and low-speed adjustability. High-speed compression handles big, square-edged hits and bottom outs, while low-speed compression affects small bumps and pedaling platform, along with brake dive and ride height in corners. It’s helpful to think of low-speed damping as a blow-off gateway to access the high-speed damping.

The best way to set up compression damping is to back the damping all the way off and get out on the trail, paying attention to specific ride characteristics which apply to both the fork and the shock. If you find yourself bottoming out harshly or too often, increase high-speed compression damping. Adding volume reducers to your fork and/or shock’s air chamber is another option to deal with this problem.

For low-speed damping, focus on brake dive and ride height as your indicators. If the fork compresses excessively when braking or when driving through turns, increase low-speed compression damping until ride height remains stable and brake dive is under control. For your rear shock, small bump compliance and pedal bob will direct you in adjusting your shock’s low-speed compression.

It’s important to record all your suspension settings. This lets you see how changes affect your bike’s behavior and will help get you back to the sweet spot if your settings are altered. Once you finalize your settings, you might write them on pieces of tape affixed to your fork and shock so you’ll always know where you should be, or stash them away in your little black book.

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