Suspension Tuning Guide

Why a Link is Different: Volume Spacers & Progressive Springs

What exactly do volume spacers achieve?

Volume spacers function by decreasing the air volume in your shock, which increases the compression ratio. This results in a more pronounced pressure increase in the latter portion of shock stroke.

What does a progressive coil do?

Progressive coil springs are coil springs that change spring rate as they move through their stroke. As with volume spacers, the change in spring rate is most pronounced past the first half of the shock’s stroke.

How is ramp from a progressive linkage different than adding ramp at the shock?

Linkages create ramp through altering kinematics whereas adding ramp at the shock is very direct at the shock. How ride quality is affected is noticeably different and we believe that anyone running volume spacers or a progressive spring would be better served by removing those items and increasing ramp through the linkage instead. There are three key areas where progressive linkages sperate themselves here: rebound performance, bottom out resistance, and the “end of travel wall” feeling.

So rebound performance is better? How?

Rebound speed is directly related to how much force the shock is generating. This means the larger the difference in force between the top and bottom of travel, the larger the difference in rebound speed. As such, this is most pronounced with volume spacers. Now you might be thinking “I have HSR and LSR so I can just tune this out.” Unfortunately, it doesn’t work that way because rebound speed is also driven by whether the wheel is supported by the ground. For example, if you’re in the middle of a g-out, you are likely deep in travel where shock force is high, but rebound speed is slow because the wheel is supported. So, if you are running more volume spacers, it’s easy to get stuck in a spot where rebound is too slow at top of travel and too fast at bottom of travel.

By contrast, with a link there’s a smooth ramp over the entire shock stroke and a lower shock pressure at bottom of travel relative to top of travel. This allows for much more consistent rebound characteristics over full travel. On top of that, the lower final leverage ratio relative to initial leverage ratio further decreases the difference in rebound speed between top and bottom of travel. All of this results in a bike that behaves predictably regardless of where it is in its travel and isn’t prone to packing up or feeling like a pogo stick.

How is bottom out resistance improved?

First off, bottom out resistance is often mistakenly thought of as the amount of force at bottom of travel. In actuality, it is the amount of energy your suspension can absorb before hitting the bottom of travel. Why isn’t it force at the bottom of travel? Your shock does work to absorb impacts over its full stroke and not just at the bottom of travel. If the shock does more work early on it doesn’t have to do as much right at bottom out. Bottom out resistance can be separated into two categories: single large impact resistance and successive impact resistance. For both of these, we are going to assume damping is set identically and the shocks have the same stroke.

Our links increase single large impact bottom out resistance by allowing you to run a higher pressure or spring rate without harming small bump sensitivity or ride height. This corresponds directly to your shock being able to absorb more energy over its full stroke.

Successive impacts have an extra layer of complexity added. Available shock stroke is a key bit of bottom out resistance, and while for single big impacts that might be the same, for successive impacts it is not. Since our links are more progressive than the stock link, they use less shock stroke near the top of travel compared to what would be used with the stock link. So, for successive impacts, on top of having the higher shock pressure or spring rate, there is also more shock stroke available to absorb each impact.

How is the “end of travel wall” gone?

Where the ramp occurs here is key. With the link the ramp is over full travel so you don’t get that feeling of the suspension moving through its travel too easily until it hits a wall and doesn’t want to move. There’s a smooth ramp up that leaves it feeling bottomless and because more work is done to absorb impacts earlier in travel it doesn’t have to be so harsh near the end of travel.