In this blog article we’ll be coving the basics of fork anatomy. We'll explain why you might choose to alter a specific setting on your suspension unit. The next section will start by helping you to identify adjustable points on your suspension fork or shock. Finally we will conclude by explaining what adjustability will actually translate too on the trail.
Can Your Suspension Be Tuned?
Not all forks are born the same. Quality suspension can be described as being two things; high quality & adjustable. The first question that needs to be answered is in regards to the adjustability of your fork or shock. You need to know what changes you can actually affect in order to make an informed set-up alteration. Common features may include
Spring Weight/Air Regulation
Air volume adjustment
Spring Weight/Air Regulation
The fundamental function of a suspension fork is to absorb impact. Modern suspension does this either by using a spring or compressing air within a chamber. Springs and air react very differently when compressed.
Spring forks compress in a very linear manner. Meaning that the rate of shock absorption is almost linear all the way through the travel spring suspension this then peaks in resistance as the spring becomes fully compressed.
Air suspension in contrast has a curving compression rate. The more you compress air the harder it is to compress further. Many riders opt for air shocks because it offers small bump sensitivity and resists ‘bottoming out’ at the end of its travel length. This is due to the increased pressure in the air chamber as the suspension fork or shock is compressed fully.
Rebound is the rate in which your fork or shock returns to its original extension after it has absorbed an impact. A fast rebound will ensure your fork is ready to absorb the next impact.
Compression adjustment alters the amount of force required to get the suspension unit moving through its travel. Think of this as the mesh filter in a cafetiere. If there were more holes in the filter, the rate in which the coffee could pass through would be faster. If the holes in the mesh were smaller the coffee would flow slower as you pressed on the plunger.
Lockout works very differently dependent on the quality of the suspension fork or shock. Entry-level forks and shocks often use a mechanical lockout system, which prevents the fork from absorbing impacts.
The second type of lockout system works in a similar manner to compression adjustment. As your suspension moves through its travel, oil flows through an aperture inside the fork. This process slows down the rate of travel. Lockouts on these suspension forks or shocks often utilise this aperture to slow the oil movement as much as possible.
Travel adjustment is specific to only a few models of fork. It is usually operated using a switch or lever similar to compression adjustment on the top of your suspension unit.
A simple turn of the switch will usually increase the travel to its upper limit. The fork will extend naturally as the internals are adjusted by the lever, changing the fork to the lower limit is usually a two-step process that requires you to 1.turn the lever back to its original position 2. Compress the fork back to its original position.
Travel adjusting forks are usually found on specific models of bike. It is worth noting that altering the travel length of your fork will change the geometry and feel of your bike. In some situations longer travel length can be entirely unsuitable. You may be damaging your frame or invalidating you warranty by fitting an unsuitable suspension fork.
Air Volume adjustment
Air volume adjustment allows the rider to fine tune the volume of air inside the fork. This is a relatively easy adjustment that can be made on a lot of modern air forks including but not exclusive to RockShox and Fox suspension forks.
Adjusting the volume of air inside the fork changes how your fork reacts as it moves through its travel. Riders and reviewers that add spacers to their fork set-up reduce the volume of air and often describe their new set-up as feeling more ‘progressive’.
Although this isn’t exactly a particularly technical or informative term it describes the set-up difference perfectly! Reducing the volume of air inside the fork makes the fork fight back much more in the last few inches of travel whist retaining the sensitivity of the small bumps. Essentially having less air volume makes it more difficult to use the full length of fork travel.
This adjustment requires some workshop knowledge but the overall job isn’t as intimidating as it first seems. If you are visiting this page because you are looking to adjust your air volume spacing we have a separate article written specifically on how to perform this on the most RockShox & Fox forks, which can be accessed by clicking the link here.
Why Should You Tune Your Suspension?
Tuning your suspension forks is arguably the single biggest change that you affect on your bike. You wouldn’t buy a new bike without playing around with the saddle height, bar rotation and stack height so why stick to the basic adjustability on your suspension?
Most of us will set the air pressure when we buy a bike or get out after a period of in-activity. However past setting sag, a lot of us don’t know enough about suspension to make an informed change to our existing set-up.
The Biggest Suspension Tuning Mistakes
Not making notes - Write down air pressure, rebound settings, compression settings and air volume. Before you make any changes if a change doesn’t feel right on the trail you can default back to your last known comfort zone.
Not riding a trail back to back – find a trail that has a bit of everything. root sections, fast single track, rock gardens, jumps, drops, berms and pump sections. The more variation the better.
Test - You’ll find what works best for you when you have both a level playing field for comparison and good understanding of how your suspension reacts to different terrain.
Speed isn’t gospel - You may find that you’re getting faster as your suspension set-up session goes on. Don’t assume that this is entirely due to your suspension set-up. You’ll naturally find better lines and become faster. Concentrate on what feels best and weight this against your over-all time if you’re using a computer to time yourself.
Wear your kit – One of the single biggest mistakes you can make is to set your suspension up at home in jeans and a t-shirt. Make sure you have your full riding kit on before you set up your suspension. This includes backpack, tools, helmet, snacks, shorts, jacket, jersey and shoes. This dramatically changes your weight and affects the distribution of weight on the bike.
Service your suspension – A regular service can be your best friend when it comes to riding, you won’t notice the drop-off in performance over time as your oil gets older and your seals deteriorate but a good annual service can bring life back in to the oldest of suspension forks and shocks.
Each fork and shock is different. Sag varies depending on the bicycle the fork or shock is installed on, the type of terrain you’re riding, and the weight of the rider. As a general rule you should allow the suspension to sag by around 25% to 30% of the stroke length.
There is a high likelihood that this percentage will be indicated on the sanction Alternatively may need a tape measure to complete this task.
Setting Up Rebound
As we’ve already discussed rebound is the rate in which your fork or shock returns after absorbing an impact. There is no right or wrong way to set rebound. Just remember that a faster rebound will enable your fork to react to the next impact and a slower rebound will start to feel sluggish in its reaction time. Setting rebound is a balancing act that you’ll need to experiment with to find a preference.
We recommend going to either extreme of the rebound setting to fully understand how your bike feels and then settle on a happy medium.
Setting Up Compression
Compression is the metaphorical mesh filter in the cafetiere that we described earlier. It increases the amount of force required to get the suspension fork or shock moving. Compression can help to compensate for the terrain your riding without needing to stop and adjust your air pressure if you’re riding uphill or over smooth terrain. More compression will help improve your pedaling efficiency.
If your fork is equipped with travel adjustment you can use this to your advantage on steep and more challenging terrain. This is a particularly useful feature to have when you need to switch constantly between up-hill and downhill riding.
Adjusting the amount of travel will change the geometry of your bike and the rider position from over the handlebars to much further back over the saddle.
Lengthening the travel will move the rider back and away from the front of the bike, elongating the wheelbase and slackening the head tube angle. A slacker head angle and longer wheelbase are both traits of a more aggressive mountain bike designed to tackle harsher terrain over a multitude of negative gradients.
Adjusting the travel length to shorten the fork will make the bike more suited to climbing and positive gradients with technical climbs.
A steeper head angle and shorter wheelbase position the rider further over the handlebars increasing front wheel traction on steep climbs. A steeper head angle also improves the low speed handling capabilities of the bike making it easier to navigate tighter turns.
Air Volume Adjustment
Adjusting the volume of air in your fork or shock differs greatly from increasing the pressure. Reducing or increasing the volume of air makes the fork react differently as it moves through its travel.
Reducing the volume of the air chamber will make the fork ‘ramp-up’ as it moves through its travel. If you find that you’re using all of the available travel right away but don’t want to sacrifice the small bump sensitivity you might benefit from reducing the chamber volume with a token or volume spacer.
If you’re effectively using the first few inches of travel but never bottom out your suspension you may benefit from removing a volume spacer. The increased volume will mean your suspension will compress in a similar matter right through to the last inch of travel.
You can read our comprehensive guide to changing air volume in your forks by clicking the link here.
Now you have a better understanding of what your suspension fork or shock is capable of it might be tempting to go out and change every setting right away. Suspension set-up isn’t a exact science. Every rider has his or her own personal preference and every trail is different.
The key to suspension set-up is to experiment and tinker, after all that’s what mountain bikers do best. Make a small change at a time and work your way through our checklist over a few rides. Even a small seasonal change of clothes or getting soaked in a downfall can affect your suspension set-up.