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Teardown

Formula Selva C Fork

Words A.J. Barlas
Photos A.J. Barlas
Date Jul 27, 2021

Previously I thought my teardown articles would be better if completed before spending any time on the product. The teardowns are an opportunity to see the guts of a product before riding it, providing a better understanding of how it works. At least that's what I thought…

This approach was intended for the Formula Selva C test fork but the world had other ideas. Covid restrictions here in B.C. once again locked us down hard when the fork showed up at Alba Distribution. But Alba co-founder, Ben Arnott wanted me to get going with some ride time on the fork and dropped it by at a social distance, forgoing the teardown until later.

As it turns out, my initial process for completing a teardown on a review product may have been short-sighted. The chance to get a few rides on the product and initial tests with the two supplied CTS compression cartridges was great. In half a dozen rides, I was able to form a solid idea of the fork’s performance and then bust it open to see why certain things may be happening, with the help of an expert who knows the product inside and out.

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Formula's Selva C is their coil sprung, 160mm travel 29er fork. The 27.5 fork is also available with 170mm.

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Before digging in, fresh cherries from my tree were consumed.

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There was a beer close by for safety…

Unfortunately, I stumbled across an issue around the sixth ride that, combined with continued health and safety protocols and personal health challenges, prevented us from completing the teardown until recently. The seals used on this batch of the fork – late 2020 – weren’t the most durable and the cold, wet conditions of Coastal B.C. in January quickly brought them to failure.

During the teardown, Ben addressed this, changing the old seals for a set from SKF. Formula has since started using an updated seal of their own and I’m informed all has been smooth since. I’ll go into more detail in the final review but for now, let’s dig into these Italian beauties, see what makes them tick and how they differ from many available competitor options.

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The lowers were quickly dropped to get started.

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With only eight rides on the Selva C, the oil was like new, not that you could tell once it drained into Ben's catch pan.

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The ends of the shafts are keyed, making it easier to pull the lowers. Formula's forks don't rely on the pressure fit of others and there's no hammer needed to bash the shafts free from the lowers. The damper side…

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And the spring side. The keys also make it easy to put the fork together. They slot into the lowers and prevent spinning while tightening things down.

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The foam rings from the new seal package were soaked in Formula FX oil. I'm told it's similar to a 20wt oil.

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With the lowers off, the damper lockout lever was removed so Formula's special tool – provided with the fork – can access the keyed interface on the top cap.

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The same is done on the spring side. I've had no issues removing the spring top cap with the Formula tool and it provides a more secure feeling connection than a regular socket.

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Spring removed. The heat shrink pieces have migrated toward the centre of the spring from the recommended 60mm from each end. Also, note the white nylon pieces just beyond the spring. These sit between the preload adjuster and the spring, with the open cylinder capping around the top of the spring.

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With the upper spring assembly removed, Ben gets into the spiral retaining ring.

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The spiral retaining ring is used instead of a more common standard clip with an opening that's squeezed together. These are said to provide improved retention thanks to the 360 degrees of contact.

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Spring side disassembled (with a couple external adjusters from the damper side).

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The negative spring. It sits at the bottom of the stanchion, with the spring on top.

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The spiral retaining ring (right) holds everything in the stanchion. A wave washer (left) sits against the bottom of the negative spring and a washer in between.

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The damper utilizes a rubber bladder, similar to what's found on some other forks. It allows the displacement of oil as the shaft compresses with minimal friction.

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This little seal head houses some interesting parts that make the damper function a bit differently to others.

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The top of the seal head with the low-speed rebound needle visible at the top of the shaft.

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The seal head and its internals. The pieces to the right, particularly the bushing next to the seal head housing, and their rounded edges. It doesn't seem like much but the square edges of a typical bushing in this part of the damper easily bind when a side load is added. Formula use rounded edges to allow unimpeded movement while the fork experiences lateral loads. This is noticeable on the trail, with the fork remaining very active and minimizing feedback when the front wheel is being hit from angles.

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The components of the lower damper. The shaft moves through the seal head and its bushings and seals with rounded edges, and on the right is the rebound circuit.

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The high-speed rebound circuit. As with most suspension brands, this is set by Formula. On the right is the shim stack and on the left of the piston is the check valve.

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During a rebound cycle, the spring pushes the oil against the piston but on compression, it releases and allows oil to flow freely past the piston. Without it, every rebound adjustment would also affect behaviour during compression.

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The low speed rebound needle inside the damper shaft (what you're adjusting with the external knob at the bottom of the fork).

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The high-speed rebound circuit back on the damper shaft.

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Formula use a unique method to tune the compression damper of their forks. Their CTS (Compression Tuning System) cartridge provides riders with seven different compression settings by changing the cartridge. Each cartridge can be fine-tuned externally with a blue dial at the top of the fork.

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A series of holes in the cartridge valves provide the different compression characteristics. My Selva C came with gold and blue CTS cartridges. The gold valve has more, smaller holes, while the blue has bigger holes, but less of them, and a relief (on the right side of the blue valve pictured) that changes how the oil flows during a compression. The valve on the right is a special super-light option that allows the easiest oil flow.

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Ben shows the shim against the bottom of the blue valve. The rounded edge of the nut beneath allows the shim to flex when oil is forced through the circuit.

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Formula's Selva forks come with a lockout, too. When flipping the lever on and off it lowers or raises this needle in the compression damper. The chamfered edges create a strong seal (there's a more natural stop for two chamfered edges as well).

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Bleeding the damper is easily done from the top of the fork. It doesn't need to be taken apart to do so, either.

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Before the lowers are slid back on, the foam rings are removed from their fresh soak and place in the fork.

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After putting the internals back together and sliding the lowers on a little, a syringe is used to fill each lower with 15cc of Formula FX oil.

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This isn't very different to other forks but is always a satisfying part of tearing down a fork. It's almost ready to ride.

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A quick clean to the bottom of each lower leg after pressing the lowers completely on, engaging them with the keyed part of the shafts.

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Formula use a copper washer and o-ring to seal the lowers, rather than the crush washers found on some other forks.

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Tighten down the damper side…

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Then the spring side.

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Give the fork a wipe to clean any oil from it and it's ready to mount back on the bike.

Formula's CTS cartridges provide a notable change in how the fork behaves during compressions when on the trail. It was interesting to see the internals and discuss the inner workings more with Ben during the teardown, helping me to see some of the parts that give the fork its interesting ride qualities.

External fine-tuning of each compression cartridge is controlled by an external adjuster with a range of 12 clicks. There is no separate high and low-speed compression tuning for the user and I'll share more on this in the review. But the difference of each cartridge so far has been pronounced, providing different ride qualities to each other. Initial impressions are very good with the fork remaining incredibly smooth and active throughout its stroke – it may be the most friction-free fork I've ridden to date.

More on the Forumla Selva C...

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Comments

Wapti
Wapti
1 year, 2 months ago
+6 ackshunW Émanuel Valex Endur-Bro Velocipedestrian ollyh Zayphod

The World welcomes the return of Italian coil forks.

Reply

AJ_Barlas
AJ Barlas
1 year, 2 months ago
+2 Émanuel Valex ollyh

It would be great to see more coil forks available for those that prefer it. Thankfully, there are some good options for coil fans, even if they are few. 

Though not Italian, I was recently informed that Öhlins will not be producing coil forks come MY22, which is sad as their coil sprung 36 is a beauty. Blame the supply chain bottlenecks.

Reply

Wapti
Wapti
1 year, 2 months ago
0

pity, i was looking forward to the coil 38 m.2

Reply

AJ_Barlas
AJ Barlas
1 year, 2 months ago
0

You and me both!

Reply

Wapti
Wapti
1 year, 2 months ago
0

I'm waiting for the future article explaining how to use a 36 spring to make your 38 coil.

Reply

Wapti
Wapti
1 year, 2 months ago
0

This comment has been removed.

Spooky817
Spooky817
1 year, 1 month ago
0

But why go 38 when you can can go dual crown instead? I only see advantages in an equal or lighter weight dual crown fork… it just makes so much sense!

Reply

Endur-Bro
Endur-Bro
1 year, 1 month ago
0

Yeah no idea.  DH38 can be had @180mm travel and 46mm offset.  Many BOOST15 hubs can be converted to 20mm via end caps. Even then one should be able to swap the DH38 20mm lowers for the 38SC 15mm lowers.

Wapti
Wapti
1 year, 2 months ago
0

This comment has been removed.

JakeE.Pooh
Jake Smith
1 year, 1 month ago
0

Like never again, or just until the supply chain settles down?

Reply

ackshunW
ackshunW
1 year, 2 months ago
0

Haha ahah so true

Reply

Endur-Bro
Endur-Bro
1 year, 2 months ago
+3 Konrad Velocipedestrian ollyh

Good to hear a Selva review is coming.  I'm highly interested in the upcoming Selva MK2 single crown and dual crown models.

Selva 29 extended is available in 170mm now.

Reply

AJ_Barlas
AJ Barlas
1 year, 2 months ago
+5 Endur-Bro Konrad Mammal Roman S ollyh

The Selva dual crown is certainly interesting. It’s great to see someone tackling the trail dual crown setup. 

Thanks for the update on a 170mm Selva 29, too!

Reply

kyle-doherty
Kyle Doherty
1 year, 2 months ago
+1 ollyh

So, for the keyed damper and air shafts, do you have to align them in a special way before inserting back into the lowers? I like the idea of not having to get the mallet out, but wonder how it goes in practice.

Reply

LAT
LAT
1 year, 2 months ago
+2 AJ Barlas ollyh

all you need to do is face the flat sections at the end of the shafts forward. it’s very simple in practice and emotionally easier than taking a hammer to your suspension fork.

Reply

AJ_Barlas
AJ Barlas
1 year, 2 months ago
0

Not having put the lowers on myself I can only comment on what I saw, but Ben had the keyed portion lined up to slot in. It wouldn't go in if it were a quarter turn off, but it didn't seem difficult for Ben to get it aligned close to where it needed to be.

Reply

1nixxxo
Nikita Morozov
10 months, 2 weeks ago
+1 Zayphod

Huge thanks for Selva teardown. I was very interested to look inside the damper.

I have Formula Selva S and I also bought R dual air spring for test. R modification didn’t inspire me at all, but S is brilliant performer. I previously had Lyrik Ultimate with custom tuned Charger RC2.1 damper, DSD Rund and later installed Vorsprung Secus which is now relocated to friend’s Z1. I thought it was amazing fork until Secus refused to work! I was mad, I got tired of investing in Lyrik performance and I ordered Formula Selva S after looking through different reviews.

To my surprise, after only 1 km I became a believer =))

Than I got Orange, Silver, Red, Electric Blue CTS because of curiosity. Right now I have settled on Blue CTS. 

Recently I have tested fox 36 2021, Z1 with Secus (air spring really does it job amazingly, but let down by the damper) and had a short ride on fox 38. Well, all of them are crap, sorry. Selva S outperformed all of them with Blue CTS. And having the ability to completely change the compression knocks down the whole competition.

How it feels? My weight is 116 kg geared for reference. It’s super plush in the initial 40% of travel due to coil negative spring, and than the magic starts to happen. It doesn’t choke on repeated bumps, it doesn’t bottom out, it eats almost all types of obstacles and it’s performance doesn’t fade on long descents. Next, I’ll convert it to coil just to see how the ultimate enduro fork should perform. I haven’t noticed any unwanted flex even under my weight. Electric Blue CTS was an overkill on our trails, or maybe I’m to slow to bring it alive, cause it feels like a rally car. Silver CTS is sooooooo plush, but bottoms out easily and dedicated more towards lightweight riders, or I got it completely wrong. Red CTS is like Blue CTS, but in the second part of the stroke it refuses to give back remaining travel, simultaneously keeps eating chatter and big hits. I haven’t tried Green and Orange, but will give them a try in 2022.

There are some minor details, like lower axle to crown height (though it rides much higher during the braking, but it depends on chosen CTS), it needs Mudhugger Evo front fender (others will hit the tire during compressions, I have experienced it already), there are no bleeding buttons on the lowers (but didn’t experience any internal pressure when dramatically changing the altitude), spare parts are available, but you need to hunt them down using SKU numbers, which Formula provides in direct messages on Facebook if you ask what you need.

Reply

resistemptation@gmail.com
resistemptation@gmail.com
10 months, 1 week ago
0

Hey Nikita, also sent you a DM. I've been interested in a Selva for a while, and was going to order the R. Can you expand on your experience between the S and R? Thanks.

Reply

trumpstinyhands
trumpstinyhands
1 year, 2 months ago
0

"The spiral retaining ring is used instead of a more common standard clip with an opening that's squeezed together. These are said to provide improved retention thanks to the 360 degrees of contact."

Fox had these 10+ years ago. On the same note, Fox's air bleed system and floating axles are straight out of Marzocchi forks from the turn of the millennium. Funny how old ideas keep getting re-hashed as new. Oh and yay more proprietary tools for no reason at all :D

Reply

LAT
LAT
1 year, 2 months ago
+5 Endur-Bro DancingWithMyself AJ Barlas ollyh Zayphod

to be fair to Formula, the tools for the top caps and the CST cartridge are supplied with the fork.

Reply

AJ_Barlas
AJ Barlas
1 year, 2 months ago
+2 Endur-Bro ollyh

True! And the longer someone's been involved in the sport, the more instances of something already being tried come up. Some things were before their time, others were deemed bad at the time and maybe improved now with updated technology. We're definitely seeing a lot of it though!

Agreed with the proprietary tools, but honestly, it fits great and doesn't slip. I haven't had to be as careful as I am with my flat sockets, which could eventually be dangerous…

Reply

Spooky817
Spooky817
1 year, 1 month ago
0

There’s only really one proprietary tool, the CTS tool… for the top caps you can get a a socket from any hardware store and modify it a bit (face it and turn it down a little) it will do the same job… honestly, I think Formula are doing a great job at making suspension that requires very few proprietary tools to work on…

Reply

Sethsg
Sethsg
1 year, 2 months ago
0

Wow, it is so cool to see how it all works it is so simple yet complicated at the same time.

Reply

AJ_Barlas
AJ Barlas
1 year, 2 months ago
0

Fully! I was thinking the same as I put the article together. It seemed like there wasn't much happening but once it was all done, there's actually a fair bit going on.

Reply

BenHD
BenHD
1 year, 2 months ago
0

Hey A.J., you may have a typo in there. The seals should be manufactured by SKF and not SKS, right?

Besides that, I love your photos and the review.

Reply

AJ_Barlas
AJ Barlas
1 year, 2 months ago
+1 BenHD

Hey Ben, thanks for the catch. All fixed.

Reply

LeeLoo
Sarah McBain
1 year, 2 months ago
0

This comment has been removed.

LeeLoo
Sarah McBain
1 year, 2 months ago
0

This comment has been removed.

Zayphod
Zayphod
1 year, 1 month ago
0

When can we expect the review?

Reply

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