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Demystifying MTB Suspension: All About Adjusters

Demystifying MTB Suspension: All About Adjusters

Words & Photos: Ryan Kershek – Owner of Fluid Focus, LLC in San Marcos CA.

The balance of your suspension is crucial to the performance of how well your bike handles. One way to address balance is with air pressure and sag, which we discussed in the first article, but you can fine-tune the suspension characteristics with adjusters. Most of the time, adjusters are blue and red knobs on the top and bottom of the fork and shock. The more expensive the suspension, the more adjusters are typically at your disposal. Let’s look at what adjusters do and how to use them.

Two types of damping circuits are Low Speed and High Speed. This is true for both compression and rebound. If your fork or shock only has one adjuster for compression and one for rebound, these are Low Speed adjusters. Inside the damper, the Low Speed adjuster is a tapered needle that determines the oil flow rate through the Low Speed pathway. If the needle is further into the pathway, it will restrict oil flow (stiff compression and slow rebound). More oil can flow if the needle is further away from the pathway (soft compression, fast rebound).

Once the Low Speed circuit is overcome with too much oil flow, the oil must bleed off somewhere, and this is when the High Speed circuit takes over. Most High Speed circuits are controlled via shims stacks. When the oil flows through the piston, it bends or deflects the shims. The more resistant the shims are to bending, the stiffer the compression will be, and the slower the rebound becomes (and vice versa). In most dampers, the High Speed compression adjuster puts preload on shims or a poppet valve spring, which helps restrict the oil flow at the adjuster. This works with the mid-valve piston shim stacks to complete the High Speed circuit.

What adjuster should you be adjusting?

It’s important to remember that what you adjust is dependent on how fast the fork or shock is cycling, not the wheel speed. Your wheels could be moving at 80 MPH, but the trail is smooth and flowing; any adjustment made in this situation should be Low Speed. Landing off a jump or drop or smashing through a rock garden with square edge hits, should be a High Speed adjustment. Get the idea? Rebound speeds are arguably more important than compression because the idea is to have your fork or shock return to the sag point, or about the full extension, before the next hit. This allows the suspension to absorb the bumps, keeping the bike feeling plush and compliant.

The more extended your suspension is when it hits the obstacle, the less force it takes to compress the fork or shock. If you are constantly too deep in the travel, this is called “packing,” meaning the fork or shock cannot extend, so it packs up. If this happens, your suspension deflects, causing the bike to feel harsh and non-compliant. Many people confuse this with compression being too stiff and then make an adjustment that makes compression softer, which makes the situation worse. If you make the suspension stiffer and faster, the bike will track better and be more comfortable. It’s very counterintuitive!

For example, picture yourself entering a corner, and you are on the brakes. Your fork dives, and your shock extends. What could you adjust to level the bike out? This usually would be a Low Speed adjustment, and you could stiffen the fork’s Low Speed compression to keep the front end higher. Or slow the shock low-speed rebound to keep the shock lower in its travel—or both. There isn’t a wrong adjustment. It’s recommended only to make one adjustment at a time so you don’t get confused and you can learn what each adjustment does.

In summary, don’t be scared to use the adjusters to see what they do. You should figure out where you are in the adjuster’s range to return to that spot if you get lost. F-Ftuned.com is a great website where you can log your bike settings and adjustments, and it’s all free! It is essential to remember that you do not adjust for one part of the trail but think about how the adjustments you make will affect the overall big picture—some people like a set-it-and-forget-it method; others like to tinker with settings depending on the trail. There is so much more to this, but hopefully, this is the start of making the adjustments you have hesitated to make!

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