Formula Selva - a Second Look

When the opportunity came to test the Formula Selva fork, I didn’t jump at it. I was starting my suspension data acquisition journey, putting in the work to get my Fox 36 working for me, and throwing another fork into the mix felt like a lot of work. Did I really want to spend a bunch more days chasing settings? Would there be a payoff at the end? Well, many months removed, I’m glad that I decided to find out.

Killer Features

What we have here is sort of half a fork review and half a part of my series on suspension data acquisition. This felt like a good time to check in on both of these as:

a) Formula just announced that the standard Selva S has been given all of the features of the Bryceland Signature Edition.

b) I need a kick in the pants to get going again on data acquisition.

The biggest change is the implementation of the new low progression air spring from the Bryceland into the standard Selva S, which should allow for more tuning options for all users (it’s quite easy for a user to make a fork more progressive with spacers, and a lot less easy to make it go the other way). This spring is also backwards compatible, so if you own a Selva, you can buy the new spring as an upgrade to your fork (and you can see the internals of that fork here, and AJ’s thoughts on the coil version here).

This modularity is impressive. Any of the three springs that Formula offers (the single air tested here, dual air or coil) will fit in any Selva. Throw in the CTS valve system, and you have a very, very tunable fork.

On the topic of CTS valves, for those new to Formula, the CTS valves are small little cartridges that pop into the top of your fork to control your compression damping. Formula offers 8 different valves (9 with the Bryceland specific valve) and through differences in shims and orifices, each provides a unique tune for your fork. While the valves are the same, Formula has updated their literature and naming convention so that things make a bit more sense. You can see the old guide here, and the new guide here. I’d also highly recommend this Chris Porter video to get an understanding of both how the CTS valves work, as well as some observations on compression damping in general.

Now, new literature isn’t generally something to get all that excited about, but I found that these updated descriptions allowed for something to click in my brain and send me to a better place on my fork (more on that in a minute). Formula now has the valves split into two handy categories:

Traction Series – for those looking for a spring forward setup with a light touch of low-speed compression damping and varying degrees of high-speed damping.

Support Series – for those looking for a damping forward setup with a heavier touch of low speed compression damping and varying degrees of high speed damping.

There’s a lot of detail to take in when you look at each CTS valve. Most obvious is the difference in hole architecture on the piston, with varying numbers and sizes of holes altering the oil flow into the shim stack. Less obvious, and I haven’t gotten Formula to confirm this, is the little bypass notch that shows up on the Traction series. Compare and contrast the valves, and you can start to wrap your head around how each valve leads to such dramatic changes in your fork.

Put this all together, and you have an interesting package from Formula. What you’ll like is the modular spring system and the easy tuning via CTS valves. What splits the difference is the 35mm stanchion architecture (bruisers may prefer something with a bit more girth, but others will be fine), the coil negative spring (by definition this is not adjustable and doesn’t vary with the fork's air pressure) and the Italian rarity (you won’t see many other Formula forks out there on the trail, and you’ll probably struggle a bit more than you would with the big two if you need a last minute part). What you probably won’t like is the 160mm post mount architecture.

My Tuning Journey

Lucky for me, I had two things at my disposal that most don’t. The first was access to the Motion Instruments data acquisition tool. The second was Formula employees willing to spend way too much time answering my questions and providing advice via e-mail. Both of these caused me to put way, way too much energy into thinking about suspension tuning.

I started my journey with the custom Bryceland valve, which is essentially the stock Red valve with even more high speed compression damping. This wasn’t too far off from how I had my 36 set up, with not much low speed compression and a firm spring providing support. “Firm” would be the key word for this setup, but I liked the aggressiveness of it. I could have left it there and been happy enough, but the Formula folks encouraged me to experiment.

My next step was the Gold valve. This is what ships stock in the regular Selva S so will be what most of you first experience if you buy a Selva. Compared to the Bryceland valve it dials up the low speed compression, and dials down the high speed compression. I have zero notes from my first ride on this fork, but I left it in for quite some time so it must have been okay.

At this point, what I really wanted was to figure out if I could actually see a difference in how the fork rode with each different valve. It’s one thing to watch a histogram shift right or left in the Motion Instruments app, but I wondered if I could actually see a difference on a micro level. I also wanted to determine if I could feel a difference with each valve running them back to back. So I packed a handful of CTS valves into my bag and set up shop at the top of Ned's.

CTS Valve Testing

Bracketing is a buzzword that you’ve probably heard many, many times by now. Basically, pick a short section of trail that typifies your riding, pick a specific adjustment, and methodically work through it (up and down from your starting setup, hence the term 'bracketing') until you arrive at a setting that you prefer.

Trail Choice – My goal was to find something that kept the speed up, had lots and lots of small and medium-sized bumps, and that was very repeatable. To me, this is the sort of terrain that one thinks of when they think of “suspension performance”. If you can get your suspension working well on fast, repetitive hits, that’s a good place to be.

Pick one setting, but don’t be afraid to bite off a chunk – Most people advise you to adjust one or two clicks each way. Honestly, I’ve made more breakthroughs playing around with big chunks of change. My biggest revelation on the Grip X damper was when I swung the HSC from fully open to almost fully closed. Deniz found something similar when he was playing around (the same day I did my CTS valve experiment) with his pike and 34. There’s a time and a place for subtle changes, but if you’re just starting out with a fork or a shock, don’t be afraid to try the extremes. Though, one change at a time please.

With that, I decided that the top section of Ned’s would be perfect for my test, and I decided on the silver (now called bronze), red, gold and green CTS valves. This would give me a broad sample across the range of CTS valves. I also decided that I was going to keep my air pressure and rebound damping fixed, and just swap in different CTS valves.

Run 1 - Gold Valve (medium LSC, medium HSC) – Baseline settings. I had been running the fork with this valve for several weeks, so I kept stock settings for my first run.

Run 2 – Silver/Bronze Valve (light LSC, light HSC) - This valve felt terrible! The bike felt really pitchy and sketchy. I did not like it at all. I eased up about halfway down the run.

Run 3 – Red (light LSC, Heavy HSC) – The bike felt much more stable and supportive. My speeds felt much faster and I was able to ride more aggressively, to the point that I blew up my wheel at the bottom of the run!

At this point, I thought about packing it in. The wheel was holding air though and what was the worst that could happen with a cracked sidewall? So I kept going. In hindsight, I think this compromised my test. I was pretty focused on my rear wheel placement and trying not to totally blow the wheel up. This caused me to put too much thought into everything but my suspension, and I missed some key feelings as a result.

Run 4 – Green (heavy LSC, heavy HSC) – In the moment, I didn’t pick up the change in LSC. There is a lot of overlap on the HSC front between the Red and Green valves and, to me on this day, they felt similar.

Run 5 – Gold (medium LSC, medium HSC) – Back to baseline – This felt really different! While rideable, the bike felt pitchier. I assumed it would be slow.

Based on feeling, everything was pointing me back at the Red valve. I liked how stable the bike felt and it certainly felt faster. Once I dove into the data, things were muddy. In addition to suspension data, the Motion Instruments system can give you very precise timing. Just match up key bumps, determine the time between them and you have a very, very accurate timing system. Here were my key takeaways:

Differences in Feeling – The feeling between different cartridges can be very noticeable, but sometimes it takes certain things to spot the difference. The silver cartridge felt very different and would likely be noticeable against nearly any cartridge. The change from Red to Green was less noticeable given the circumstances, and with my low sag/high pressure setup, it didn’t feel all that different. Moving back from Green to Gold though, was very noticeable.

Differences in Speed – With most of the cartridge changes, the speed that I was riding at felt noticeably different. Gold to Silver felt like I was miles slower. Moving to the red cartridge felt like a huge bump up in my speed. Red to Green didn’t feel like much of a change, and then moving back to gold felt like I was probably a bit slower as well. Throw in a blown up wheel, and I was confident that my red run was going to be fastest, by miles. Granted, the point of the exercise wasn’t to ride the trail as quickly as I could. I was searching for consistency of effort, and it felt like both Red and Green put me in a place where I was travelling faster.

Once I looked at the numbers, I was surprised by the consistency! My route was the top of Ned’s down to just before the new bridge, and my times were all within 2.5 seconds, from 46.9 up to 49.4 seconds. Silver was my slowest run, but only 0.2 seconds slower than Gold #1. Red was noticeably faster than Silver, but it was Gold #2, my final run of the day on a broken wheel that was fastest! What felt good and what felt fast didn’t actually play out in trail speed.

Difference in Data – From the data side, there was no smoking gun. Increased damping amount from each valve caused very slight changes. Compression speeds slowed, slightly less travel was used, and dynamic sag was slightly lower. I couldn’t look at the position graphs and definitively say “this was very different”, just subtle differences in certain peaks.

Bad Decisions – I took all of this information and I made some correct decisions and some bad decisions. I was fairly certain already that my settings were all a little bit too stiff, so I was going to slowly start increasing my sag. I also decided that more hydraulic resistance was a good thing…but I went the wrong way with it. Based on how it felt, I decided to move to the red cartridge with lower air pressure, thinking that lots of high speed compression and not much low speed compression would be the ticket. And then right after I decided to do this, a different test bike showed up.

Bad Compression Damping Head Juju

This is where all of the nonsense we’ve told ourselves about damping comes into play. Even with my recent attempts to change the way that I’ve been thinking, I’ve been hung up on high speed compression damping. It never entered my brain to consider running more low speed compression. That’s to control the bike while pedalling, right? Less makes things more plush, right?

Compression damping that is working correctly shouldn’t feel harsh! In fact, if it’s done right it’s almost the key to smooth feeling suspension. Where I’ve gotten things wrong is that I’ve taught myself that I like suspension that rides high in its travel (this is good), but I’ve been convinced that I need a lot of spring to make this happen (this isn’t necessarily good). There are other ways to keep your suspension running high.

When I finally hopped back on the Formula fork a few months later I had the red cartridge in and I had bumped my air pressure down a few psi. And it felt terrible! I was riding horrendously! I had thought that minimal low speed compression, a bit more sag and a bunch of high speed compression was going to be smooth off the top and have lots of bottom out resistance. The bottom out resistance was fine, but it felt harsh everywhere else. Two things convinced me to change my tack.

The first was the new Formula verbage on CTS valves (I told you we were coming back to this). Just reading things laid out like that convinced me that I was probably thinking about it wrong. So I dropped a line to Formula and they encouraged me to follow this train of thought. More sag, more compression damping (both high and low), and less rebound damping would give me something that would remain high in travel while being very compliant. And my god, it worked!

For the next ride I kept everything else largely the same and swapped in the Orange cartridge (I would describe this as medium levels of both high speed and low speed compression damping). This offers a similar shape to the Gold cartridge that I was used to, but with more damping across the range, and it was an immediate revelation. Through fast, repetitive hits, the front end felt glued to the ground. Through large drops and rolls I still had bottom out support. Right away I felt I was in more control, and I was riding smoother, cleaner and with less fatigue. This was a home run improvement and I’d barely started tweaking.

Conclusions

This is both the beauty and the curse of the CTS valved Formula fork. If you want to play around with settings, you can stay busy for months. The two caveats are that first you must invest in the full set of CTS valves in order to do so (you can buy the valves individually at 90 CAD each, but if you plan on trying 3-4 different ones you’re better off buying the full pack from Formula for considerably less), and second, you can pretty easily take yourself in the wrong direction.

However, if you’re a patient person and like to experiment, you likely cannot get a similar experience from anybody else. While Rock Shox and Fox spend a lot of time tuning their products for the average consumer, they’re tuning it for the average consumer! For most of us, most of the time, this is just fine. I was on my way to a great feeling fork with the latest 36/Grip X. But if you’re on the margins, or looking for something special, the CTS valves are essentially a total re-tune of your suspension that you can do (carefully) trailside. This is like having the Fox or Rock Shox race pit at the bottom of each run, only you’re doing all the work yourself and don’t have access to all of the highly paid brains.

For me, I’m really, really happy with how the fork is feeling, but I still have work to do. I need to head back up to Ned’s and do another round of CTS valve bracketing. This time though, I’m not going to hold myself to keeping my air pressure fixed. While I’m going to be hunting the right settings for me, I also hope that I can come up with a way to really visualize the difference in how a high spring/low damping setup compares to a low spring/high damping setting. Maybe it didn’t work for you, but my rebound damping article was a revelation for myself! Being able to visualize the difference in recovery time as rebound damping was reduced made it so clear to me what was going on. Is there something similar to be seen with compression damping? We’ll find out. If it’s possible, the Formula fork will be the tool that lets me see it.