Suspension tuning is a dark art. Those who have mastered it are wizards ... Or they’ve made a deal with the devil. At least that’s how it might feel when you’re struggling to set up your own suspension.
My last couple of mountain bikes came with suspension that had a lot of adjustment options: high-speed and low-speed compression damping, as well as high-speed and low-speed rebound damping. Add in air pressure/spring rate and air volume reducers and you have a lot of settings to consider.
I researched as much as I could, but soon I fell into a black hole of confusion and doubt. Sometimes, I wasn’t sure an adjustment did anything. Other times, I was sure I had made my bike worse. Tuning your suspension is challenging, especially when you’re going off ride feel.
I turned to data and put a Motion Instruments system on my enduro bike.
Pro riders rarely have to struggle like this. They work with dedicated tuning experts and high-tech equipment to analyze their suspension. Now, that technology they use is finally trickling down to us mere mortals.
My co-worker Spencer and I brought our bikes to Derek Cuny of Gnice Riding to get the pro treatment. Cuny is an engineer who worked in robotics and now is branching out into mountain bike suspension. He’s partnered with Motion Instruments to develop the budding field of professional suspension tuning using data acquisition.
What is data acquisition?
Suspension data acquisition uses special sensors that measure and record your suspension’s movement. This helps engineers set up suspension to work optimally for the given circumstances. Motorsports have used this technology for decades, but it’s been too bulky to adapt to bicycles until recently. Professional mountain bike teams only started experimenting with data acquisition over the last few years.
Loic Bruni is the most high-profile rider using data acquisition. The three-time downhill world champion uses a system developed with Ohlins. Since he’s been so dominant lately, it seems his bike isn’t holding him back.
Downhill World Champion Loic Bruni uses data to get his suspension dialed. | Photo credit: Bartek Wolinski/Red Bull Content Pool
In an interview with VitalMTB titled, “Why does Loic Bruni’s suspension work so well,” Bruni explained how his data acquisition system sets his team apart.
“We know how to exploit it,” Bruni says. “Every time I’m lost ... the data can bring us so many answers. The engineers and team know how to read the data and numbers, and it’s so much more efficient. In one year we’ll do what some teams take three years to do because we have so much more information.”
How you can get data for your suspension
Bruni’s World Cup-level system is likely out of reach of normal riders. Instead, Cuny and Gnice Riding use sensors produced by Motion Instruments, which get you very close.
The whole system was developed with the help of downhill legend, Greg Minnaar, and other high-level racers. Motion Instruments has several sensor packages that can be mounted to different mountain bikes. They interface with an app called MotionIQ. Everything connects via Bluetooth and easily delivers the data to an engineer like Cuny. It even connects with Strava so you can match segments to your data.
The sensors are relatively expensive, retailing for $479.99-1,299.99 depending on the bike, and the MotionIQ app requires a monthly subscription to use. For the average rider with one or two bikes, it doesn’t make much sense to buy your own setup. So, Cuny started Gnice Riding as a way to lend his expertise and give more riders access to the technology. He has multiple sensor set-ups available and, as a MotionIQ partner, can give riders access to the MotionIQ app.
The Motion Instruments system collects 200 data points per second and displays it on complex graphs. As much as I wanted to decipher all of this on my own, I needed some help. That’s the benefit of having an expert like Cuny to work as your suspension guru with this technology. He can interpret the data for you and suggest changes for your riding style or terrain.
Bruce’s tuning experience
Cuny recording my initial settings.
I brought my current enduro bike, a 2020 Reeb Sqweeb V3, to Cuny’s garage. It’s set-up with a Fox Factory 36 Grip2 fork and a Fox Factory DPX2 shock. The Motion Instruments sensors attach using various mounting pieces and adhesive.
Mounting the fork sensor is fairly straightforward, but rear suspension configurations are different for every bike. The rear often requires some clever positioning and potentially some custom mounts. It all adds about a half-pound to your bike, but I couldn’t tell they were there while riding. The sensors connect easily to the app, and then the fun starts.
First, Cuny recorded all of my current settings. This would serve as a baseline for his tuning suggestions. Then, we measured my sag using the app. Before, I had measured sag with a tape measure, but using the app, I noticed the numbers were a bit off from what I thought they would be.
My sag before and after. The sensors are sensitive enough to detect tenths of millimeters.
Cuny added a few psi to my fork and shock to bring the sag down a few percentage points in the rear and a half-percent in the front. This is the type of extreme detail that data allows us to achieve. The tech nerd within me was extremely pleased.
Then I went riding. I went to my favorite trail system and focused on one specific trail that had a very long descent with a good combination of high-speed flow, jumps, and chunky rock gardens. I rode this trail multiple times over the course of several days.
This graph shows suspension movement on a segment with two jumps and a section of braking bumps before a hard corner.
Before each descent, I pulled out my phone to hit record on the MotionIQ app, and when I finished, I’d stop the recording. It would then upload automatically to Cuny so he could analyze the data.
It was clear I wasn't using much of my fork's 170mm of travel. Cuny wanted me to achieve at least 85% travel on my normal trails, leaving ~15% for big impacts.
After analyzing my data, Cuny made a couple of key discoveries about my set-up: I was severely over-damped and my bike was off-balance, with the rear being far too slow.
This scatter plot shows how my fork is rebounding faster than my shock.
Cuny had me reduce the compression damping in my fork by 14-16 clicks, a large amount. I had grown accustomed to running a lot of compression damping to prevent bottoming out on the largest jump at my local bike park. It made my bike feel harsh in chattery sections, but I just sucked it up and dealt with it.
To compensate for the reduced compression damping, Cuny added a volume spacer to increase bottom-out resistance.
He then had me slow the rebound in my fork a couple of clicks and speed up the rebound in my rear shock a couple of clicks. We repeated this process several times, slowly speeding up the rear shock one-to-two clicks at a time until I was running a rebound setting over twice as fast as my original setting.
This transformed my bike. The rear wheel felt incredibly smooth over braking bumps and chunky rock gardens. I had traction on loose off-camber sections where I would usually lose control and drift the back end.
With my old setting, my shock was packing up deep in its travel. Speeding up the rebound kept it higher up in its travel, where it works best, and balanced it with the front. This made my bike feel more planted and confidence-inspiring.
Spencer’s tuning experience
Spencer's Santa Cruz Megatower with the Motion Instruments system installed. Note the different rear sensor placement.
Spencer: I also went through the tuning process with Derek, but I knew Bruce’s set-up would be so messed up that I figured he should write this story instead… Just kidding!
But in all seriousness, I had a 2020 Santa Cruz Megatower to test, and frankly, I was overwhelmed by all of the tuning options. My typical approach to suspension is to put it to the factory-recommended settings and forget about it.
Surprisingly, that’s actually a pretty good approach! Cuny told me that some of his clients have tried extreme settings because they heard about how pro racers tune their suspension, or they’ve been doing too much reading on the forums. So thankfully, I didn’t have to totally revamp my settings.
Like Bruce, I sped up my rebound slightly and added a bit more air to both fork and shock. I actually didn’t do much with the compression damping settings.
The difference was noticeable — my Strava times on particularly rocky, fast, and loose descents started to go down. The Megatower got faster, more stable, and more predictable. Next to regular maintenance, I think a professional tune like this is a great way to maximize the performance of the bike you already have without spending money on new parts.
Would I have achieved my new set-up on my own? I’m not sure. A lot more went into my new set-up than can be written here. Without the data to look at, I don’t think I would have gone the direction I did.
When I tuned by feel, I made a common mistake and over-damped my bike. I got so used to the hard compression and slow rebound that I couldn’t bring myself to change it. If I made a drastic change in settings, my bike would feel so unfamiliar, I assumed I had messed up and would go back. I was stuck in a cycle of bad decisions.
Cuny pushed me to make the changes I had avoided. The faster rebound settings felt wild at first but Cuny showed me the data to support his suggestions and assured me I would get used to it. He was right. I trusted the data and over time I gelled with my new settings.
We kept making positive, incremental changes until we arrived at my final settings. My bike still feels stable over big jumps (and if anything it has much more pop now), but it also feels better everywhere else. We achieved a fantastic balance, and I now have data to back it up.
Is a data acquisition system like the Motion Instruments system for everyone? Probably not. But would most riders benefit from using it? Probably. I encourage anyone who’s curious to give it a shot, especially if you plan on racing or are chasing an elusive perfect set-up. Having someone like Cuny help definitely makes the whole process easier.
It should be noted that the Quarq ShockWiz is another tuning option, but it operates differently. It mounts to the air valve on your suspension, so it doesn't work with coil suspension, and it analyzes changes in air pressure. It can provide some general air pressure and tuning suggestions, but if you want to get granular with tuning and really maximize your bike's potential, experts like Cuny and systems like Motion Instruments are the way to go.
Above all, this experience gave me a solid starting point. Set-ups have to change. Temperature and elevation will affect your settings. I’ll likely have to make small changes for specific trails or races. Plus, my weight and speed will change as I get older. With the knowledge I’ve gained from using data acquisition, I’m confident that I’ll always be just a few clicks away from the perfect set-up.
If you’re interested in renting a Motion Instruments data acquisition system or working with an expert tuner like Derek Cuny of Gnice Riding visit the Motion Instruments partners page to get set up.
If you'd like to see more bikes go through the tuning process, follow @gnice_riding on Instagram.