Suspension is one of the most important elements of a modern mountain bike, generating grip and control on the trail to help you ride smoother and faster.
There’s no doubt that the best forks and the best shocks work incredibly well. But tuning your suspension can help eke that extra bit of performance from your fork and shock by optimising their setup for you, your bike and your riding style.
Once upon a time, suspension tuning was reserved for a handful of pro riders. Now there are tuning services that mean anyone can refine their suspension.
We spoke to Jim Williams at J-Tech Suspension, a UK-based suspension-tuning centre, to find out what suspension tuning is, how it works and what kind of benefits you can expect.
What is suspension tuning?
Your mountain bike suspension relies on two main components – the spring (air or coil) and the damping (rebound and compression) circuit.
Air springs, which are the most popular, are highly tunable. The spring rate is infinitely tunable and even the volume of the air chamber can be tweaked with the use of volume spacers.
The damping circuit works by using a combination of piston, shims and suspension oil. As the suspension is compressing or rebounding, oil is forced through shim stacks. How quickly and freely oil can flow through the shims determines how readily the suspension compresses and extends.
“When we do a full tune, we tune the shim stacks and also look for areas of friction in the suspension. To do this, we hone in on your riding style and ability, the type of riding you do as well as your weight and the kinematics of your bike,” Williams explains.
By tuning the pistons, shims and oil in the damping circuit to make it less (or more) restrictive, you can control the oil flow and manipulate the suspension’s damping performance.
How does suspension tuning work?
Custom fork and shock pistons
A less restrictive damper (with more oil flow) will compress and rebound more willingly, freely absorbing impacts before extending again.
While, in many cases, a less restrictive damper is useful, there are scenarios where the extra support from a firmer compression tune is desirable. Custom pistons can improve oil flow in certain areas of suspension performance while increasing support (by decreasing oil flow) in others.
According to Williams, changing the dynamic piston can improve oil flow while generating more mid-speed damping, which is the speed of damping involved in rider inputs (think pumping downslopes, compressing the bike for a bunny hop, etc).
Improving oil flow also helps the oil to stay cooler on long descents, further improving the performance of the suspension.
Oil tuning
The suspension’s oil plays a big role in the damping circuit, as well as lubricating the entire system as the suspension moves through its travel.
The oil’s job is to keep everything running smoothly, minimising friction. Over time, oil volume can reduce, and dirt and dust from the trail can make their way past the wiper seals. This grit has a detrimental effect on the suspension’s performance, increasing friction and wear on the components.
Getting an oil change will have a big effect on how smoothly your suspension works. However, you can go one step further by using an aftermarket oil.
Williams says: “At J-Tech, we use a special oil. It has a Teflon additive, which uses micro-particles that adhere to the porous surface of your stanchions, air shaft and other moving suspension parts. This creates a Teflon film and reduces friction even further.”
Nitrogen shock tuning
Many MTB shocks use an internal floating piston (IFP) design. These pistons have to be highly pressurised, using nitrogen or air. Getting a nitrogen recharge is another way of subtly improving the performance of your shock.
“The difference between nitrogen and air is that nitrogen is more inert – it’s more stable. At higher temperatures (reached during long descents), its pressure doesn’t increase as much compared to air and shock performance stays more consistent,” Williams says.
How to get the most from your suspension
All the tuning in the world won’t get you the maximum performance if your basic suspension setup and maintenance aren’t up to scratch.
Williams recommends getting on top of the basics first, before delving into the world of suspension tuning. Here’s how you can make sure your suspension is working optimally right now, without spending any cash:
- Set your sag correctly – sag refers to the amount of suspension travel used solely by the weight of the rider, bike and kit. Following the manufacturer’s guidelines will get you into the right ballpark, from which you can experiment to suit your preferences. For more advice, you can read our in-depth guide to setting your suspension sag.
- Set your rebound – once your sag is set, it’s time to move on to the rebound. Once again, consult your manufacturer’s guidelines first and then go from there. Most riders aim for a rebound setting that is fast, without being so fast that it starts to unweight the bike. A good front/rear balance is important too.
- Set your compression – next, it’s time to take a look at the compression settings on offer. These will vary depending on your suspension. In general, you want to use your spring rate to influence how much travel you use, and just use the compression settings to fine-tune levels of support.
- Keep on top of your suspension maintenance – friction is the biggest enemy of smooth suspension performance. Keep your stanchions clean and make sure to stay on top of oil and wiper seal changes when required.
After some experimentation with the steps above, your suspension should work optimally for weight and riding style. Some riders prefer to set their suspension and stick with it, whereas others might dive into the world of subtle tuning based on riding conditions. Whichever approach you choose, make sure to take note of your base settings, so you can always return to them if needed.
