BOS Idylle Rare Air FCV Fork
Street Price: $2,090
Wheel size: 27.5”
Axle to crown: 586mm
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.
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.