How To Address Common Complaints Of MTB Suspension 

November 14, 2024 Ryan Kershek

Have you ever felt like your mountain bike suspension set up wasn’t quite right, but didn’t know how to correctly address the issue? Luckily, the team here at Fluid Focus has been living and breathing suspension tech, service and custom tuning for over a decade and are here to help you with the most common complaints of MTB suspension. Here are some of the suspension issues we hear about regularly.

Too Soft or Too Firm
Feeling harsh
Bottoming out or not Bottoming Out
Lack of Sensitivity
Lack of Traction and Support

1. Too Soft or Too Firm

If your suspension feels too soft or too firm, it’s time to check your sag. Sag is the amount the suspension compresses under the weight of the rider. Sag is measured in percentage of the total travel (stroke) of the fork, or the stroke length of the shock. We typically recommend ~20%-25% sag on your fork, and ~25%-30% sag on your rear shock.

On air sprung forks and shocks your sag is adjusted by increasing or decreasing the air pressure using a shock pump. If your equipment is coil sprung, you can adjust your sag using the preload adjuster. Preload is the amount the coil spring is compressed using the preload adjuster and changes the amount of force required to initiate compression. Tightening the preload adjuster on your shock will decrease sag, loosening will increase sag. We recommend 0-2mm of preload. Zero preload is when the preload collar just touching the physical spring, so the spring has no vertical movement. One full turn of the preload adjuster equals 1mm of preload. If you need more than 2mm of preload to achieve proper sag, the physical coil will need to be changed. We find that 1mm of coil spring preload is best on a shock or 0 to 1mm preload on a fork. Typically coil forks will utilize a dial or spacers to add or remove preload.

Always take the time to measure sag yourself and never go off the manufactures recommended psi. Make sure to put your compression adjusters fully soft and rebound fully fast when setting sag. If you need help setting sag click here

2. Feeling Harsh

If your sag is set properly and your suspension is feeling harsh the next step is to address your rebound adjustment. Adjusting rebound is increasing or decreasing the speed in which the fork or shock extends after compression, so they are ready to compress out of the way for the next rock, jump, root, etc. You need your suspension to extend fast enough to absorb consecutive hits and to track back to the ground after those hits. We work with so many different types of riders and skill levels and we find that appropriate rebound speed is typically much faster than you think. Balanced front and rear rebound speeds are crucial to a good suspension setup, you need the fork and shock to rebound at the same speed.

How do you know if rebound is too fast or too slow? If your rebound is too fast, it can make your bike feel uncontrolled and difficult to track a line as well as a pogo feeling when landing off a jump or riding rough terrain. In this case, slowing your rebound can give you more control and comfort. If your rebound is too slow it can cause your suspension to remain compressed through consecutive impacts, this is often referred to as “packing”. Packing is when suspension compresses, sits too deep into the stroke and the fork and/or shock are stuck in place. The equipment can’t compress because the compression force of you hitting the rock, root, etc. isn’t strong enough to go deeper into the travel and rebound isn’t fast enough to extend. This causes your bike to deflect instead of absorbing. In this case, faster rebound can make your bike feel more compliant and supple. Either too fast or too slow of rebound can make your bike feel harsh and uncontrolled.

When testing and adjusting rebound, we recommend starting with a bounce test. Riding on flat smooth ground, bounce your bike and adjust rebound to achieve roughly even rebound speeds front and rear. Then on a familiar and repeatable section of trail increase rebound speed one click at a time on each suspension component on each pass down the trail. Do this until the rebound is too fast, IE a pogo feeling or difficulty tracking a line. Note the position of the adjusters (we use clicks from closed) where this sensation begins. Then repeat this process but slowing the rebound until the suspension begins packing or feeling harsh. Note the position of the adjusters. Your ideal setting is in the middle of the two noted adjuster positions. Note that these points of too fast or too slow may occur at different points in the range of your fork or shocks rebound adjustment. It’s important to try to discern what the components are doing individually and adjust accordingly. If you have both high-speed and low-speed rebound, we recommend starting with your high-speed adjuster in the middle of its range and performing the above steps with your low-speed adjuster. Once your low speed is dialed in, you can adjust your high-speed using the same method.

Now that your rebound is set, we can start to look at compression. When bikes start to feel harsh most people will turn the compression adjusters to the soft direction. However, this is often the wrong thing to do. Suspension can be very counter intuitive! Too soft of compression damping can make your bike feel unsupportive or unpredictable and may cause your suspension to use more travel than necessary per input, which could be described as harshness. By adding damping (stiffer compression) this will help get your fork and shock riding more in your sag range. If your fork or shock ride mainly in the sag area, they can react and move out of the way more easily and feel more supple. Too firm of compression damping and your suspension may not move fast enough or far enough per input, which could also be described as harshness. Repeat the same steps as the rebound test explained above to find your ideal compression settings.

Which Adjuster do I turn? HSC/LSC/HSR/LSR: This is determined by the shaft speed of the fork and shock. This is hard to gauge while riding without Data (we use BYB Telemetry). The main thing to know is coming in or out of a corner, berms, and going off the lip of a jump are generally low speed compression or rebound adjustments. Landing off a jump, landing off a drop, and square edge rocks, tend to be high speed compression or rebound adjustments. How to use the adjusters: Say you want the front end taller coming into a corner. You could do all these options, slow LSR on your shock, soften LSC on the shock, make fork LSR faster, or make the fork LSC stiffer. They will all achieve similar results but think about how this adjustment will affect the overall picture.

3. Bottoming Out or Not Bottoming Out

Bottoming out is when you use all available travel on your suspension. It’s ok to bottom out on big hits on occasion, and “big” hits are relative to the rider. But it shouldn’t feel like running into a wall and for average trail riding it shouldn’t occur excessively. You may experience more frequent bottom outs if you are often hitting 4ft+ drops to flat and/or riding very steep and technical downhill trails. Even in these instances, a good suspension setup will have you feeling supported through the entire travel of the bike without a harsh bottom out sensation.

If you are still bottoming out with properly set sag, you can increase compression damping. With today's suspension designs it’s possible to get more bottom out resistance by increasing the low-speed compression. Try adding low speed compression first and then high-speed compression. If adding compression results in undesirable ride qualities, you can increase spring progression, or ramp up, and bottom out resistance of air sprung components with volume spacers. If you need to add volume spacers to prevent bottoming out do so one at a time and be sure to check your sag once installed. The pressure you need to achieve the same percentage of sag shouldn’t be too different depending on the amount of volume spacers used, but it’s a good idea to measure sag again. Only use volume spacers as a tuning tool. Never run less sag and lots of spacers, or more sag and less spacers. If you find yourself doing this, look into our Fluid Focus custom tune options.

If you aren’t using your bikes full travel, don’t worry! It's ok to NOT achieve full travel. Ideally you get most of it but don’t become fixated on getting full travel. If you aren’t sending to flat, or your trails are smooth it’s possible to have a good suspension setup without using full travel. What is important is when the fork or shock stops compressing, they don’t feel like you are hitting a wall and it’s a seamless transition into rebound. Read that again. If you want more travel and you’ve set your sag properly then remove volume spacers if you have them installed. Another thing to look at as your compression adjusters. Remember how we said low speed adjustments can make more of difference? Typically bottoming out is a high-speed compression adjustment but try softening of low-speed compression first. If you do this and the bike starts to feel like it’s diving, then go back to where that feeling goes away and then open high-speed compressing. If you are still fighting the fork and/or shock, we can help by our custom tune options.

4. Lack of Sensitivity

We frequently hear about how much better riders' equipment feels after a service. The steps outlined above can help you dial in your settings, but dirty and worn seals, oil, and grease could be the culprit for lack of sensitivity. If it’s been over 12 months since your last service, we highly recommend servicing your equipment. We cannot stress enough how important it is to regularly service your mountain bike suspension! Whether you notice it or not your suspension performance is deteriorating. Damper fluid, the fluid responsible for your compression and rebound damping, deteriorates over time and through heat cycles. Grease also deteriorates and dissipates causing increased friction and lack of sensitivity. E-bikes require more frequent services due to the added weight, speed and stress on components. Manufactures will have recommended service intervals, but we recommend a full teardown and rebuild every 8-12 months for E-bikes and 12-18month intervals for standard mountain bikes. Obviously, this will vary by how much you ride and the conditions you ride in, but in general these are good guidelines to follow. During the servicing of your fork make sure the company doing the work has proper tooling to burnish bushings. Overly tight bushings will cause lack of performance, lack of traction, and horrible compliance. Here at Fluid Focus we include bushing work with every fork service or custom tune. Our tooling has 4 sizing dies for each size stanchion. This allows us to fine tune your fork and get you the supplest feeling possible.

5. Lack of Traction and Support

Over the years the manufacture compression and rebound tunes and overall design of the dampers have gotten better. However, we still see that compression damping is either too much or not enough for most riders. If compression damping is too soft, it will mimic the harshness feeling of too much damping. When your fork or shock damping is too soft there isn’t adequate support, and the damper isn’t pulling its own weight so to speak. This is still an issue with fork coil conversions, you’ll still be fighting lack of damping. Since you removed the air spring and lost its friction, without proper damping your fork will feel unsupportive and divvy. One of the main issues we see in mountain bike forks is that people are forced to rely on the air spring and volume spacers to do all the work, and the damper is an afterthought. All this leads to lack of traction, lack of support, and harshness in the hands/wrists/arms. Assuming you’ve read all the above information, and you are still having issues maybe it’s time to explore custom tuning. Fluid Focus’ philosophy is to have proper damping which we do through our custom MTB fork and shock tunes that we develop ourselves in house. By modifying shim stacks, we can better control the oil flow and how the damper is working. We utilize different types of shims stacks for example, single stage valving, two stage valving, and mid valve settings. We verify all our tunes on our CTW linear actuator dyno.

Tire pressure plays a huge roll in the overall performance of mountain bike suspension. Too much pressure and the bike will have decreased traction. Too little air pressure and your tires can roll. There isn’t a magic number and ultimately it comes down to rider preference, but you should aim to have a soft enough tire that still offers support and grip while cornering. Adjust accordingly.

General Tips

Regular Maintenance: Service! Get in the habit of +/-12-month intervals for best suspension performance. If you need suspension service click HERE.

Never Compensate with too much or too little psi: This will cause more of the same issues you are currently fighting.

Add compression damping: Try this if your fork or shock are feeling harsh or stiff. Suspension is very counterintuitive!

Speed up rebound damping: Another good thing to try if your suspension is feeling harsh and non-compliant.