Mountain Bike Suspension: Sag, Rebound & Compression Setup
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Setting up your mountain bike's three main suspension functions (Sag, Rebound, Compression) is an extremely important step you need to take care of before heading out and riding it. Suspension setup can make or brake the way a bike performs and feels, so setting it up for your weight and riding style is key. For best results, please follow in this order:
This is also referred to as “preload” or “spring” setup. When you saddle up to your whip, the suspension will compress a bit under you (and the burritos you’ve been stashing in your pack). This is normal and helps the suspension to conform to the trail as you pass over it; you’ll not only pass over bumps that compress your suspension, but holes that the suspension extends into to maintain contact with the ground.
This procedure is more or less the same regardless of what spring type (air or coil) that you have. The only caveat is that coil springs have a limited range of adjustment and you need to make sure that you have the right weight spring.
Gear you'll need
- Shock Pump
- Tape Measure
- A friend to help you balance on the bike and measure the compressed shock.
Step 1: Look up your Shock or Fork's Stroke Length
You'll see numbers like 200 x 50 (metric) or 7.875 x 2.0 ('merican).
The first number is the eye-to-eye length (how long, overall) of your shock.
The second number is the shock stroke. This is the important number.
Just the travel will do. Some forks have gradients on them to show sag, making the process easier.
Step 2: Gear up as you would for a ride
If you wear a pack (fanny or otherwise), put 'er on. Helmet, goggles, pads, everything.
Step 3: Set your bike up somewhere level where you can put your full weight on the bike while balanced
You can do this sitting or in a standing position, whichever position's performance is more important to you.
Step 4: Step Onto the Bike and Ensure the Shock or Fork is in the Wide Open Position
Give it a bounce or two to overcome some of the suspension stiffness.
Step 5: Reach down and Move the O-Ring To the Air Chamber Side of the Stanchion (Air ShocKs Only)
This creates a placeholder after you've pumped the shock so you know how much the suspension compressed under your weight.
If you have a coil shock, there is no O-Ring. You may need a friend to measure the eye-to-eye to see how much it's compressed.
If you do not have an O-Ring on your air shock, a zip tie will do the trick.
Step 6: Step off the Bike and Measure the Amount of Sag
Getting off the bike should be done very carefully so the shock and fork are not compressed further than riding weight dictates.
The amount the shock compressed under you divided by the total shock stroke will give you your shock's current sag percentage. For example, a shock with a 2" stroke that compressed 1/2" of an inch has 25% sag. Math is hard, but it makes for good suspension.
Step 7: Adjust Your Shock or Fork's Air PRessure, or Spring Preload as Necessary
Less air pressure means more sag. Start with 5 PSI increments so you don't overshoot your sweet spot.
If you have a coil shock, turn the lock ring to compress. Start with half-turns at a time.
Shoot for 25% to 30% suspension sag. These are good starting values but they should be adjusted based on manufacturer recommendations and personal preference.
That's it! Now it's up to you to get out there, ride your bike, and decide if your sag feels right, or if you want to add more or less sag to your suspension.
Try to keep things consistent as you move towards your goal sag setting. There’s a subjective component to this as well. The faster and harder you ride, the stiffer you’ll need to set your suspension. The fastest guys in the world run their DH bikes’ suspension firmer than XC racers’ bikes. That’s because they need more resistance to withstand smashing into rocks at their unbelievable speeds.
The terrain your ride might factor into your preference. Softer suspension typically is faster over successive hits and firmer suspension will provide more control over bigger hits, landing jumps and drops. Start with the recommended sag and work from there as you get to know your bike and your own riding style better.
Now that you’ve set your sag, it’s time to set up your rebound damping. This is generally a set-it-and-forget-it adjustment that doesn’t require on-trail adjustment, but is best done on-bike with some testing. The goal with initial setup is to set the bike up for an average sized hit (such as a curb). For both shock and fork, you’ll want to set the rebound such that rolling off of a curb results in a single shock stroke.
Set the rebound, initially, full open or as fast as it will go. Towards the rabbit if you have RockShox suspension or towards the minus if you’re on Fox. Get on your bike and roll off a curb and try to be as static with your body position as possible. Use a body position that’s similar to your riding position. If you feel the suspension go up and down more than once, add more rebound damping. Repeat this process until you feel only a single shock cycle. That’s a good baseline rebound setting. Do the same for your other rear shock if you’re on a full suspension bike.
Another thing that’s necessary to check is the balance of the rebound damping. Setting your shock fast and your fork slow is a great way to buck yourself over the handlebars as the springs will return at different rates. You can check this by bouncing on your bike. Use a typical riding position and try to bounce straight up and down, weighted mostly thru your feet. If you find yourself getting bucked forward, speed up your fork’s rebound or slow down your rear shock. If you feel yourself getting pushed into the backseat, slow your fork and/or speed up your rear shock. Try to find a happy medium.
Your local trails and riding style definitely comes into play when adjusting rebound. Generally speaking, rougher trails are going to favor a faster rebound setup. This is due to the fact that the shock is going to get hit successively by smaller hits which can “pack out” the suspension. This means that the shock hasn’t had the opportunity to return to the appropriate length and will be in a portion of the shock stroke that’s firmer than it needs to be to handle the hit.
Smoother flow trails and jump trails are going to favor slower rebound settings. Part of the trick in jumping effectively is timing the rebound of your suspension with the compression provided by the face of a jump. By slowing down your rebound settings, you are widening the window of time that you can compress into the jump face. This can help prevent the dreaded “dead-sailor” feeling that can happen when the timing isn’t right.
Lastly, the amount of rebound damping is going to depend on how much spring force is being used in sag. Less sag means you’ll have to use more rebound damping to slow down the increase in spring force.
Compression damping is a much more subjective setting and depends heavily on riding style and on-trail feedback. Thankfully, most of these settings are adjustable on-the-fly. This setting is priamrily used for controlling how much travel you use in any given situation.
Count your clicks
The single most important thing when it comes to compression damping is to not be afraid to experiment. Most knobs on these suspension settings are detented, meaning they go “click” when you turn ‘em. When you first start setting up your suspension, count the number of clicks ( you may only have one) and keep note of how many “clicks” of compression you’re using. If you have a working baseline, you can always return to that setting after experimenting.
Low speed compression is the most dynamic setting on a shock, with a range of offerings from handle-bar remotes to preset 3 position controls. If your trail demands full plushness for traction and control, leave this setting full open. If you’re noticing that your suspension is moving around too much when pedaling, hard cornering, or braking, then you can add more compression damping. Lock-out settings are no longer “true” lock-outs, but rather very firm compression settings set aside for fire road climbs and the occasional on-road transfer. This is highly personal and you’ll come to know what settings you like as you ride and test.
The same theory applies to high speed compression (if your shock has it). Find a bigger feature that you’re willing to hit a few times and add compression damping until it feels right. The right compression setting should make the experience feel controlled and smooth. Too much damping will make the landing feel harsh. Too little will make it feel like you’re blowing thru the travel and whipping your neck like the bassist for a heavy metal band.
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