Datalogging with Formula

"Do you want to come datalogging?" It's not the kind of invite any self-respecting bike nerd should say no to. So when the guys at Formula asked if I want to come play with a rigged- up Selva fork for a day, there was only one answer I could offer...

Datalogging in mountain biking has its roots in the early 90s, when the Sunn team, lead by Nico Vouilloz, rigged up their race bikes to find an edge on the rest of the field. It was ahead of its time, that level of technicality approaching a race arguably still isn't seen today - in no small part thanks to Vouilloz completely ignoring the sponsorship conventions of the DH circuit and, rather than accepting sponsor product, he paid for his suspension to get the best. Since those days it has had something of a halo around it, a mythic tool that most mere mortals never have the chance to get their hands on. Seeing as I'm never likely to worry the sharp end of any race result, it's something I had resigned myself to envying from afar. So when I got the call from Forumla it's fair to say I was rather excited about the prospect.

I am familiar with Formula suspension - I have had their 35 fork on the front of several bikes since late 2014. In that time I have fiddled and tweaked to find a setup that works for me and while I'm not here to review their suspension, it is fair to say that I rate their forks among the very best on the market right now. The Selva fork I would be testing is very close to the 35 I run at home, the chassis is revised, but the internals are more or less the same. The idea would be that I spend a day with their engineers on one of their test bikes riding on a short section of track they have used for testing a lot. We would only collect data on a 20-30 second section in order to keep the results precise and concise.






There was no clear outcome defined before I arrived. While talking to their engineers, we agreed that I would use the day to try and get a baseline on where my setup for the fork should be and Luca, their chief engineer, was keen for me to try a new compression tune he had developed. It should be made clear here that from a scientific point of view the test would be flawed. I would be riding a track I don't know, on a bike I have never ridden before. There is fundamental basis for experiments: more data is better. This day wouldn't provide enough data on any front to provide real answers, but the hope was that it would provide some insight.

With their roots in the moto side of things, it should be no surprise that Formula are applying this kind of technology to their mountain bike line. Few people realise that Formula were making shocks for motos long before their original mountain bike brake. Luca was also keen to stress that datalogging in mountain biking is not as exact a science as it is in, for example, track sports like Formula One or Moto GP. Having worked in Moto 3 (the Moto GP feeder series), Luca understands this fact intimately. In motorsports the results are so consistent that you can fine-tune the driving/riding to exact points - in Formula One they can use these numbers to coach the drivers on precise braking, acceleration and turning arcs. That isn't possible in mountain biking. There are so many more variables, from changing track conditions to the difficulty of exactly repeating your technique, which means that you don't get as clear and precise a picture of what is actually happening. Ideally, Luca advised me, I would ride the same line in the same manner each time so they could compare performance. However, that is easier said than done - especially with a new track and bike to get your head around. I will put my hands up here and admit that I probably was not a very useful test subject as my riding adapted to the changes in suspension and my line choices evolved as I got more comfortable on the test track.





For the first run the fork was in the stock configuration - that is, medium compression piston and no reduction in the air volume. For this run we set the bike to find a basic balance - my preference tends to be stiffer and higher at the front, with a little lower pressure at the rear, so the bike sits into its travel a bit more and gives me a feeling of riding behind the fork. I set the fork to 70psi, which is slightly harder than they recommend for a rider of my weight, and added 5 clicks of low-speed compression from closed. For the rear we tried a couple of options, before settling with 190psi, which was the best compromise we could find between it riding too high or, alternately, blowing through its travel. This would remain as our rear configuration until the final run, as the focus of our testing was on the fork (and Formula don't currently produce a rear shock).

The run was completely blind this time, so the time should be taken with a pinch of salt. What was clear was that the fork was not where I needed it: With the standard compression damping and air volume it didn't stand up enough in the travel or remain composed enough for how I like to ride. On the trail this translated to a holding-on style of riding - without that support it was hard to place the bike as I would like to and I felt like it all passed by before I had a chance to react fully.


For the second run we added 25cc of oil to the air spring with no change to the compression damping. This does the same as adding tokens in RockShox or Fox forks - it reduces the air volume to offer a more progressive spring curve (until recently, Fox used the same method to adjust air volume). This means that while it felt the same at the start of the travel, the force needed to compress the fork later in the stroke was much greater, so it stood up more in the travel and resisted bottoming-out more. It is worth noting here that on this particular test track there was no moment where the bike should be bottoming out.

On the trail the difference was immediate, I started to feel like the bike was more in the position I like, where I am riding behind the fork. It is hard to explain the sensation, but I felt like I had more time to see what was coming and to react to it. I could pick and change lines with more confidence.


With the air-spring volume where I like it, the next step was compression damping. Formula have a unique system for adjusting compression damping. There are two ways you can tune a fork - with the piston or shims. Most mountain bike forks use shims to tune the characteristics, Formula do not, they use the piston. In a system adapted from Moto GP technology, you remove the piston from the top of the fork and pop a new one in. Changing the compression profile is a two-minute job. Easy. It does, however, also come at the cost of adaptability, as shims can be added and removed at will, whereas with this system you need to produce a precision-drilled piston. As stock options, Formula offer soft, medium and hard pistons. The medium piston is considered "stock" and was what we were using up to this point. For the third run we switched to the hard piston - the same one I run at home on my bikes. Compared to the stock piston this offers more compression damping across the board.

At the trail head I backed the low-speed compression off by one click to five clicks as I found that at six clicks there was some vibration coming back through the fork. Unsurprisingly, on the trail this felt comfortable - I had the confidence and support to start riding the bike how I wanted to, picking my lines.


The first three runs essentially validated how I set my bikes - testing each of the adaptations I like. For the fourth run Luca introduced his new, custom piston. This is designed to be somewhere slightly beyond the hard piston. There is more low-speed compression, but ever so slightly less high-speed compression - the result is a more supportive ride throughout the stroke. Air pressure remained unchanged and the low-speed adjust stayed at 7 clicks.

Rolling into the trail the fork felt firm, but despite this there was a level of comfort to the ride - there was none of the vibration I found when I added more low-speed compression to the hard piston. While descending the firmness was instantly forgotten, the fork felt comfortable still, but the additional mid-stroke support was immediately noticeable - even on my first run with the piston I felt more confident and more able to pick and chose where I put the bike and how I rode it. The clock backs this up - I was notably faster than on the run with my standard setup.


With the bike feeling good the question was, what direction now? We decided that with the compression set we would try and adjust the air. As the fork felt firm, we took 5psi out of the air spring. In the car park this felt amazing, the fork felt much plusher, but still with support and nice ramp-up on the spring.

On the trail leading up to our timed section the difference was much less pronounced and when I actually dropped in, the fork had definitely taken a step in the wrong direction. The comfort you could feel in the car park made no difference, because there was no difference in comfort out on the trail. To make matters worse, the fork no longer felt as precise and the lowered ride height made it harder to get comfortable on the bike.


At this point we felt that we had found the best setup for the fork we were going to find in the time available, so we put the 5psi back into the fork and started to look at the rear shock. Up to this point the best you could say about the shock was that it had been acceptable. Luca spent a few minutes fiddling and came back with the bike where he felt it would be better - after trying some different air pressures he settled on simply switching up to the "trail" compression setting. We had tried this in the morning, but, when paired with the stock fork, the front and rear suspension hadn't felt balanced. Now with the additional compression damping up front, the extra compression damping at the bike's rear end made the bike feel more balanced than it had all day.

In honesty, I cocked-up the final run. Formula's test rider, Benjy, had been following me all day and suggested that I was getting one of my lines wrong (at home his riding buddies include a couple of guys called Loic Bruni and Loris Vergier, so he knows a thing or two). I tried changing that line and blew it, I virtually stopped, lowering speed through the longest straight on the section. If you look at the telemetry you could see where I braked harder and earlier than my other runs, how my average speed was ruined, yet despite this I came out of the run only a couple of seconds off and we reckon that without the time lost I would have been on for my best time of the day.



So, what can I take away from all this? The main thing is that more data is needed. As I said at the beginning, this was a flawed test and sitting here looking at that mass of lines there is no clear statement from. What is reassuring is that Luca (who is much smarter than I am) can take little away from this too. Without more context, more testing and more data it is hard to tell you too much, which tells you a lot about datalogging--it takes a lot of time and repetition to yield useful and reliable results. Anybody can wire a bike up with this kit, but to get useful data from it you need experience and understanding, it doesn't magically make your suspension better. This is also a very limited test track. There were no moments where I should have been anywhere near full travel. On a more varied track you would get a more complete picture of how the suspension is working. Also, without rider feedback all the data are of little use.







But that's not to say that this was wasted time or that I didn't learn anything. Now that I know a little bit, I want to know much more to really understand what is going on with my bike. Certainly this small test has helped confirm my preference for suspension settings on the aggressive side of things. One thing that has bugged me every day since our data logging, however, is the matter of air volume - the evidence here suggests that I am more comfortable with a progressive spring curve, but with the modified compression profile, do I still need such a ramp-up? Could I remove some oil from the spring leg as I am not using all the travel? Looking at the numbers it is clear that the compression damping had a far greater effect on how much travel the fork was using - it also shows that I was more comfortable when the fork used the travel more sparingly. Although the average fork travel remained consistent all day, with the custom valve I was using around 20mm less travel at max. The same goes for the rear, on the run when Luca re-worked the shock the average went down substantially and the max decreased slightly too. To me, all this suggest exactly what one World Cup tech told me recently, "Just because your suspension is moving, it doesn't mean it is working." However, looking at the compression and rebound speeds it is hard to draw any conclusion from such limited data.

Then there is the question of balance - as flawed as run six may have been, it has left me more certain than ever that balance is the most important thing - the fork was feeling better than any fork I can remember using, but without a rear shock matched to it I wasn't reaching my full potential. The day also reminded me of how useless the car park test is - the fork for run five felt best in the car park, but it was demonstrably worse on the trail than with the higher air pressure. Of course, one day of testing only elevates these things to the level of strong suspicions. I just have to hope that one more of those calls comes through one day...