BOS Idylle Rare Air FCV Fork
MSRP: $2,350
Street Price: $2,090
Travel: 208mm
Wheel size: 27.5”
Stanchions: 37mm
Axle to crown: 586mm
Offset: 56mm
Blister’s Measured Weight : 2798 grams
Days Tested : ~25
Locations Tested: Whistler and Fernie, BC; Whitefish, MT; Kellogg, ID
Reviewer: 5’9” 155 lbs
When I bought the BOS Idylle, I knew exactly three things about it: (1) it’s French, (2) it’s expensive, and (3) the guys over at Canfield Brothers said that it was “INSANE” (that’s a direct, case-sensitive quote).
So in a bit of a leap of faith, I bolted one on to my Canfield Jedi, and I’ve spent the summer putting it through the paces.
A quick look at BOS’s website confirms that the company is thoroughly French, and I’ve definitely confirmed that the Idylle is expensive. But how about that insanity? Read on…
Initial Impressions and Installation
Out of the box, the Idylle’s fit and finish looks nice and clean. It doesn’t quite have the polished graphics of a RockShox Boxxer or Fox 40, but the paint is high quality and thus far has held up better than my previous Boxxer. The anodization on the top caps is decent, but over the summer, they’ve faded out to be different colors.
Pretty clearly, BOS goes through some effort to remove weight from the Idylle. Throughout the fork, excess material has been machined off or removed (moreso than on a Boxxer or 40). The crowns are fairly sculpted, the lowers slimmed down wherever possible, and even the stanchions step down and are slightly narrower between the crowns.
That machining on the stanchions did somewhat limit where I could position the fork in the crowns. It worked fine for my preferences, but if I was looking to drop the fork down in the crowns, there’s some limitations there due to the reduced diameter.
The axle is a straightforward aluminum 20mm affair that uses a 6mm wrench for removal, and is secured with 4mm pinch bolts (two on each side). The pinch bolts thread into a removable nut, so if you get ham-fisted and strip something, it’s a relatively painless fix.
Up on top, bleed screws are integrated into the top caps on both sides. Unscrewing these releases any air pressure that might build up in unwanted places. The only downside here is they require a 2.5mm wrench, as opposed to the push button bleeders found on some other forks. I used these periodically, and a bit of air would squirt out, but I can’t say that I noticed much of a difference after the purge.
Installation went uneventfully, which is always nice. Cable routing is perfectly functional with a zip tie, although it doesn’t have the integrated cable clamp like a Rockshox or Fox fork. The brake mount is a traditional post mount, and the fork uses a normal straight 1 ⅛” steerer tube. The stem mounts via a standard Boxxer-configuration direct mount.
On my scale, the Idylle weighs in at 2798g, which is roughly 160-170 grams more than either a Boxxer (2637g) or a Fox 40 (2629g). That extra weight could presumably be attributed to the Idylle’s open bath damper, which has more oil in it than the enclosed bladder systems in the Boxxer or 40. The Idylle is quite a bit lighter than some other open bath forks, like the DVO Emerald, which weighs in at 3490g.
Setup
BOS includes a one page quick start guide, which was the only piece of documentation included with my fork. One side was in English, the other side was in French. Other languages are out of luck. The guide includes suggested settings for air pressure, low and high speed compression, and rebound, and some basic measurements to make sure you don’t set the crowns too low.
For my weight (155 lbs), I started with those suggested settings, which meant I had about 170 psi in the fork, 15 clicks (out of 26) of low speed compression, 18 clicks (out of 24) of high speed compression, and 18 clicks (out of 32) on the rebound. And no, that’s not a typo—the Idylle runs at a really high air pressure.
So I went and bounced around on it in my driveway, and got really worried that I’d made a terrible mistake. The fork felt horrible, and on every compression, it was gasping and wheezing like an asthmatic donkey.
But, slowly, it got better. After a few minutes of bouncing around on it, it quieted down a bit, the air circulated into the negative air chamber, and the fork started to feel pretty good.
Skip forward a bit: after a ride or two to break everything in, the fork was functioning as it should (details on that below), but I found that BOS’s initial suggested settings for the air pressure were way off from what I like.
I’ve settled on running 205-210 psi as opposed to the recommended 170 psi, and I’m running 17 clicks (from open) on the low speed, 14 clicks (from open) on the high speed, and 15 clicks (from open) on the rebound. I tend to run my suspension somewhat on the stiff side, but I’m also not all that heavy. Big folks that like stiff suspension should take note: it seems plausible that you’d exceed 250psi, which BOS says is the max pressure for the Idylle.
Those settings yielded roughly 18% sag while standing in a slightly forward position. Interestingly, changing the air pressure in 5 psi increments had relatively small effects on the sag, but would make a noticeable difference in the mid-stroke support and ramp up late in the travel. I’m guessing this is due to the relatively large air chamber.
One note (and gripe) is that you need a wrench and a flathead screwdriver to change the damping adjustments. Especially when I was first getting the fork dialed in, it was pretty annoying to have to carry that stuff around with me. I’d expect a high end fork like this to go through the trouble of including knobs. I ended up making this little tool to bring with me:
All of the adjustments worked as advertised, and made a noticeable difference. I’m comfortably in the middle of the range in all settings, and the increments between clicks were appropriately sized, no issues there.
NEXT: The Ride, Stiffness, Etc.
Interesting. Seems like BOS is in a chicken and egg situation. They need better service in NA to sell more forks, but they need to sell more forks in NA to justify funding better service options.
I wonder if the FCV is closer to the Penske-developed Reaktiv valving in some of the newer Fox shocks on Trek bikes than it is to a Spec Brain? I’ve been on the Reaktiv stuff for over a year now, and it is significant. Super supple early travel, but still stays high in the travel, like you noted on the FCV system. Hoping Fox gets Reaktiv valving into a fork in the next year or so!
Agreed on the chicken and egg thing.
I haven’t really played around with one of the Reaktiv shocks yet, but from what I’ve read, those valves are designed to open at higher shaft speeds (and thus higher oil pressures). It’s working towards achieving the same basic goal as the FCV, but it appears to be going about it a bit differently. The brain and the FCV are both inertia valves, meaning that they open when the valve is physically rattled open (as opposed to a speed sensitive damper that’s opened via oil pressure). But I think the similarities between the brain and the FCV end there – the actual execution seems to be a bit different.
I feel like, BOS is missing out so much in terms of profit, among others by being so restrictive in the whole rebuild and DIY maintenance thing. I know a lot of people can afford BOS and would want to get a BOS fork, but the lack of parts, the lack of service centers, among others really kills it. I want one no doubt about it, but what a deal breaker that you’d have to send a fork for servicing to their headquarters or for any of there service centers, if any exist. I’m somewhere in Asia and I don’t know if they have a service center here.
I do understand the do it yourself and your warranty is void thing. Still they should at least offer parts available for everyone and how to do maintenance themselves. I feel that it doesn’t affect warranty at all. After all, the customer already knows that if they touch the innards or do repairs or do maintenance themselves, they already know what they’re getting into.
C’mon BOS! Want to love you but you’re pushing me away!
Thank you for a great review. I’m running the BOS myself on an new bike so I have spend quite some time now setting up a decent set-up. I’m exactly same size and weight as you so I was very surprised about your settings and would be very pleased if you could clarify / confirm a few things: I run 195 psi so given you like a harder set-up 205-210 psi is probably okay, However, looking at the LSC, HSC, Rebound settings I’m counting like BOS. Meaning from fully closed and then anti-clock wise (I understand you count opposite?). So in BOS-terms I’m running this setup: LSC:12, HSC:18, Rebound 20-22. I’m trying to count where you are. My simple observation tells me something like LSC: 9, HSC:10, Rebound 16-17. Combined with the 210 psi it looks like a damn hard and slow setup compared with mine. Can you confirm or correct the numbers above? Finally, any chance you would test the Void? Could you some reference there as well…
Hey Martin,
That’s correct – I’m counting clicks opposite from how BOS talks about them. I guess I’ve just always counted from fully open since that makes more sense to me; more clicks = more damping, whereas with the way BOS counts, more clicks = less damping. So counting them the BOS way, I’m running 9 clicks LSC, 4 clicks HSC, and 17 clicks Rebound.
So yeah, I’ve got the compression circuits dialed in quite a bit stiffer / more supportive than BOS’s recommended settings, and my rebound is a smidge slower than what they recommend (which probably makes sense, given that I’m running higher air pressure – more air pressure means more force on the rebound circuit).
And I’d love to test the Void. I just need to figure out how to get my hands on one!
-Noah
Thank you Noah. I give it a chance and try this stiffer setup. Sometimes you got to try something new. Again thank you for a great review.
Great review!
I know you have touched on this, but I’m looking for some reassurance. I just purchased a Rocky Mountain Maiden, that has come with the Idylle Air. Right out of the box the fork sounds horrible, like a suction or wheezing noise anytime it is compressed and released. I expected some noise, but not this amount.
You say this stopped after some use?
Yup, that was exactly how mine sounded. It probably took ~10 minutes of bouncing around on it before it quieted down and started to feel good. It continued to get quieter and feel better for the first 2-3 rides. Since then, it’s been great.
Thanks for this awesome review! I was simply searching around for what other riders thought of the BOS air. My Opinion and observations about how the fork functions and what its like to own one is parallel with yours Noah. I ve been on a jedi since 2013, 3 years with the 2013 frame on a 40 FIT and the last few months on a 2016 jedi first with a boxxer WC now with the BOS Air fcv. It was actually pretty nerve racking being presented with the opportunity to get on a BOS after canfield offered the upgrade as i have heard Nightmare stories about their customer service. in the end i sold the boxxer and made up the difference to upgrade to the BOS. An upgrade it truly is.
One advantage of not providing user friendly tool-free knobs is reducing chances to get pranked by friends :)
It also gives opportunity to aftermarket solutions. Will try 3D printing a tool (depending on how stiff the flat screws turn).
I accidentally found someone offering blow-off screws with integrated buttons :)