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2016 BOS VS 2016 Float 40

ridevt

Chimp
Apr 14, 2006
6
1
Opinions on the BOS Idylle Air? My new Maiden WC just came with the Idylle Air fork and I'm torn on whether to run it or not. I put the 16' Float 40 on my old DH bike last year and it performed incredibly well. BOS gets good reviews but I'm worried about reliability and service issues. I could also probably get more $ for the BOS since it's new.

Also, anyone know if the fox SLS springs will the fit the BOS rear shocks?
 

yd35

Monkey
Oct 28, 2008
741
61
NY
I've had multiple Fox 40s and have tried the Idylle Air on a friend's bike, plus listened to all his complaints about it. The short version of my advice is don't bother with the Bos, it's too much of a pain to deal with if something goes wrong. Here goes the long version: I think they are both top notch performers that you would be pleased with however, the Bos has better small bump compliance while still managing to not eat up it's travel too eagerly. The Bos also requires less maintenance. You can go a whole season without changing the oil or seals and the performance is still pretty good. If you did that with a 40, your fork would feel like ass after about a month and you'd ruin your seals and score your stanchions. If something goes wrong with your Bos though, you are out of luck. Seals and oil are harder to find and more expensive. A few years ago, Bos wouldn't even disclose what kind of oil they put in their forks although that may be different now. If something more complex like the air spring or damper went wrong, Bos doesn't publish literature on how to work on their stuff and their customer service is mediocre at best. You also have the added disadvantage that a lot of shops simply don't have the knowledge to work on Bos stuff.

As you know, the 40 is very user serviceable, parts are readily available, and Fox customer service is excellent. Plus, while I give the nod to the Bos for out of the box performance, it's not a big gap, and with some tinkering you could get the 40 to feel the same. Sell your new Bos, buy a new 40, have a few hundred left over for beer.
 
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epic

Turbo Monkey
Sep 15, 2008
1,041
21
I think you'd be nuts to drop the BOS without trying it. I have the Deville on my trail bike and while getting it serviced has been a total pain in the ass, it is worth it. Distribution and service is now through Quality Bicycle Products, so I think it's safe to assume that service will be greatly improved.
 

ridevt

Chimp
Apr 14, 2006
6
1
I bought 2016 Fox 40 last June. Incredible fork and am leaning towards keeping it. Did the 17's change? I don't think they're even out yet..


I've had multiple Fox 40s and have tried the Idylle Air on a friend's bike, plus listened to all his complaints about it. The short version of my advice is don't bother with the Bos, it's too much of a pain to deal with if something goes wrong. Here goes the the long version: I think they are top notch performers that you would be pleased with however, the Bos has better small bump compliance while still managing to not eat up it's travel too eagerly. The Bos also requires less maintenance. You can go a whole season without changing the oil or seals and the performance is still pretty good. If you did that with a 40, your fork would feel like ass after about a month and you'd ruin your seals and score your stanchions. If something goes wrong with your Bos though, you are out of luck. Seals and oil are harder to find and more expensive. A few years ago, Bos wouldn't even disclose what kind of oil they put in their forks although that may be different now. If something more complex like the air spring or damper went wrong, Bos doesn't publish literature on how to work on their stuff and their customer service is mediocre at best. You also have the added disadvantage that a lot of shops simply don't have the knowledge to work on Bos stuff.

As you know, the 40 is very user serviceable, parts are readily available, and Fox customer service is excellent. Plus, while I give the nod to the Bos for out of the box performance, it's not a big gap, and with some tinkering you could get the 40 to feel the same. Sell your new Bos, buy a new 40, have a few hundred left over for beer.
 

yd35

Monkey
Oct 28, 2008
741
61
NY
I bought 2016 Fox 40 last June. Incredible fork and am leaning towards keeping it. Did the 17's change? I don't think they're even out yet..
If anything changed for 2017 then it probably debuted at Sea Otter. I saw they added a climb switch for the Float X2 shock but didn't see anything for the 40.

IMO, the 40 is the best DH fork on the market. Damping, stiffness, weight, serviceability, and customer service are all top notch.
 
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Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
IMO, the 40 is the best DH fork on the market. Damping, stiffness, weight, serviceability, and customer service are all top notch.
Agreed 100%.
Stiffness is class-leading and the damper is the best on the market in my book.

The only thing I don't like is the air spring, but I don't like the air spring in the BOS or Boxxer either - so it's comparable at least. I've run the new 40 chassis converted to coil for a while now and you couldn't pay me to run a different fork.
 

HAB

Chelsea from Seattle
Apr 28, 2007
11,580
2,006
Seattle
The only thing I don't like is the air spring, but I don't like the air spring in the BOS or Boxxer either - so it's comparable at least. I've run the new 40 chassis converted to coil for a while now and you couldn't pay me to run a different fork.
Does the 40 still use a coil negative spring, or did they switch it over to air when they did the 36?
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
Does the 40 still use a coil negative spring, or did they switch it over to air when they did the 36?
Air negative now like the 36.
Both designs have their ups and downs in my book, with both still inferior compared to a full coil fork. I predict that Fox will return to pure coil on their DH fork at some stage.
 

Mo(n)arch

Turbo Monkey
Dec 27, 2010
4,441
1,422
Italy/south Tyrol
I predict that Fox will return to pure coil on their DH fork at some stage.
I don't think so. Air is the bees knees in therms of fashion, marketing and selling numbers.

If you have some sort of support for your BOS products nearby, I'd keep it. I have the 26" version of the Idylle rare and I think that it is a seriously amazing fork. I just love the fact that I can ride the fork all year long without having to service it regularly.
It rides high in its travel, the hydraulic bottom out safed my life a few times and the supreme suppleness makes my desktop-jockey-hands happy. Really happy with that fork.
 
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Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
I don't think so. Air is the bees knees in therms of fashion, marketing and selling numbers.
I honestly thought the same thing, but the last few world cups have seen a strong return to coil suspension - a few pro teams made an active change back to coil (from air) while other pros individually chose coil over air when given the choice of both, and readily published their views / preferences. That kind of thing drives the market and I'm glad to see it, because as I said, functionally and from an engineering standpoint coil is far superior and always will be.

Coil rear shocks seem to be showing up on a lot of pro enduro bikes too, the market is supporting this with the CS-equipped DB coil, and the upcoming Fox X2 coil equipped w/ lockout.

Steve Smith even had a sneaky coil leg back in his Boxxer, not sure if anyone noticed.

In fact, I think Steve Smith's mechanic nails it with his statement on pinkbike:
The beauty of a coil is the initial sensitivity of it, you get a nice linear spring rate that's consistent, especially with a high-quality spring like the SA Racing springs, they are super accurate. The job of the spring is simply to re-extend the suspension, it's not there to hold the bike up, that's what the compression damping is for. The more consistent the spring is, the easier it is to sort out the damping. When you have an air-spring curve, which isn't linear it gives you a much bigger challenge to overcome on the hydraulic side. - Nigel Reeve, Stevie Smith's Mechanic
While the wording might not be instantly clear, he makes some very fundamental points there - particularly the point where air spring curves require excess damping to compensate for nonlinearity, and as a result (combined with the inherent and guaranteed stiction increase of an air spring), peak traction is lower.

We've stuck with the coil because we think it gives better traction. The shock rate of the bike is more suited to coil than air. We are yet to test it properly and would like to do some more testing with the air, we have a short test session planned in South Africa on the way to Cairns. The Fox guys think the coil spring relates to the bike travelling faster down the trail as it can absorb bumps better on the V10. But we will see, you can always try new things and see how it goes. - Jason Marsh, Greg Minnaar's mechanic
http://www.pinkbike.com/news/shock-decisions-lourdes-dh-world-cup-2016.html



 
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Mo(n)arch

Turbo Monkey
Dec 27, 2010
4,441
1,422
Italy/south Tyrol
coil suspension is awesome
I saw that too and it confirmed my opinion about air shocks for DH-bikes.
As you might have read a few testers had problems to find a good setup with the air shock on the new Canyon Sender, which has a pretty normal and constant progressive rate. I am convinced, that this bike needs to be ridden with a coilshock to unleash its full potential.
I might be wrong with my argument, but coilshocks with an eye to eye length longer then lets say 222mm have somewhat of a too big air chamber, which results in a not supportive middlestroke. Really progressive bikes (like the YT is) might work better with these shocks (for example Gwins setup), where the lack of support gets counterbalanced with lots of progression.

On the other hand: How do I get a balanced ride if I have a really progressive rear end, but a linear working (coil-)fork? In that context the air sprung forks make kinda sense, doesn't they?

Edit: I meant airshocks that have somewhat of a too big air chamber. Massive typo here.
 
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ridevt

Chimp
Apr 14, 2006
6
1
Thanks for the input everyone. 40 is currently on the bike and the BOS is up for sale. The hand-friendliness of the BOS is intriguing though as I've had some hand issues develop over the past 6 months...
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
I might be wrong with my argument, but coilshocks with an eye to eye length longer then lets say 222mm have somewhat of a too big air chamber, which results in a not supportive middlestroke. Really progressive bikes (like the YT is) might work better with these shocks (for example Gwins setup), where the lack of support gets counterbalanced with lots of progression.

On the other hand: How do I get a balanced ride if I have a really progressive rear end, but a linear working (coil-)fork? In that context the air sprung forks make kinda sense, doesn't they?
Okay so to cover this point by point:

1. The piggyback size argument is baseless - its impact on overall spring rate curve is completely marginal, and can't actually have a substantial effect on the middle of the stroke anyway. With a tendency towards smaller shaft shocks these days there isn't actually a need for a particularly large piggyback to cover the displacement (which is merely the total volume of the shaft - see footnote), and furthermore, twin-tube dampers reduce the pressure requirement in the chamber drastically (because they need less pressure to prevent cavitation) - which while not really a necessary change (since there wasn't a problem there anyway), means there's even less effect on spring rate now.

2. It's important to define things like "lack of support" and "progression" very precisely in terms of curve shapes if you're going to discuss which bikes work with particular shocks - but the basic fact of this matter is that coil shocks follow an actual spring curve that is very close to linear. Air shocks on the other hand, even with the most modern technologies, suffer from *substantial* nonlinearity which has been discussed and graphed on RM regularly.

This means that the frame's leverage curve needs to address the nonlinearities, which CAN be done successfully with a VERY well-engineered design (this is VERY few bikes in reality - hint: it's none of the ones which claim to do it), and even those that do can only do so for one specific air shock and air can spring curve. In this sense, air springs are less detrimental to performance when used in a rear shock (compared to a fork) because you can use the leverage to curve to attack the problem areas - something you can't do on a telescoping 1:1 system like a fork. However - as I said - it's difficult to do this, most manufacturers don't, and what you get instead is a few DH bikes that by fluke work reasonably well with a modern air shock. Most DH bikes (>90% of them) will work better with a coil shock.

In general, a lack of support will be a result of air springs themselves, and what most people perceive as "increased" support from an air shock is simply a result of increased stiction (there is a *substantial* increase) or running excess pressure / spring rate to compensate for the mid-stroke fall off in rate - which subsequently increases the initial and ending rates higher than an equivalent coil sprung setup - which again is perceived as "increased support". What it really is, is a poor tradeoff of reduced traction for increased resistance in areas other than where support is actually needed - which manifests itself as "increased support" to someone who likely doesn't know any better. To use a practical example, it's like using heavy compression damping or very firm initial wheel rates to fight acceleration squat instead of using correct AS% - sure it vaguely works, but utilising AS nets far less traction loss.

3. On the balanced ride thing - I don't think bikes need a "really progressive rearend" and a lot of DH bikes ARE too progressive. This manifests itself in a bike that blows through the first half of travel too easily and results in instability. At this point a fast rider would run a higher spring rate (or spring pressure on an air shock) to compensate for the blow through, at which point full travel usage becomes difficult and the 8" travel bike is now a 7" travel bike. At the risk of sounding biased, I think the '13-16 Gambler frames all have a very balanced leverage curve, if you want an example of progressive-but-not-too-much. A current GT is too linear, but most current DH bikes are too progressive. I really don't have time to cover fork progression here as well, but if we go back to point (2) and recall the benefit of being able to apply a leverage curve to an air shock on the rear (but not on the front) then I'm sure you can see how it is likely that an air fork is always squarely inferior to a coil fork. I'm happy to elaborate another time though.

4. Footnote - just to give you some quick tangible data on the piggyback thing for a modern shock - shaft volume can be calculated by π*r^2*l where r, l are shaft radius and length respectively. If we use a modern 10mm shaft diameter and compare the 222mm and 267mm shock lenghts, we get volumes of 5486mm3 and 6982mm3. Those are extremes of DH shock sizes and even then the required piggy volume difference is quite small as you can see.
 

TrumbullHucker

trumbullruxer
Aug 29, 2005
2,284
719
shimzbury, ct
not to derail, but I am on the verge of ditching my '11 boxxer w Charger and finally buying a 40 RC2.

I have used nothing but boxxers my whole 'biking life' and I always bitch about my front end diving too much, and would enjoy the stiffness people are talking about.

I do enjoy the small bump sensitivity of the boxxer w charger though.

the vivid coil will stay though.. smooth as shit

( sorry children )
 

Mo(n)arch

Turbo Monkey
Dec 27, 2010
4,441
1,422
Italy/south Tyrol
Okay so to cover this point by point:

1. The piggyback size argument is baseless - its impact on overall spring rate curve is completely marginal, and can't actually have a substantial effect on the middle of the stroke anyway. With a tendency towards smaller shaft shocks these days there isn't actually a need for a particularly large piggyback to cover the displacement (which is merely the total volume of the shaft - see footnote), and furthermore, twin-tube dampers reduce the pressure requirement in the chamber drastically (because they need less pressure to prevent cavitation) - which while not really a necessary change (since there wasn't a problem there anyway), means there's even less effect on spring rate now.

2. It's important to define things like "lack of support" and "progression" very precisely in terms of curve shapes if you're going to discuss which bikes work with particular shocks - but the basic fact of this matter is that coil shocks follow an actual spring curve that is very close to linear. Air shocks on the other hand, even with the most modern technologies, suffer from *substantial* nonlinearity which has been discussed and graphed on RM regularly.

This means that the frame's leverage curve needs to address the nonlinearities, which CAN be done successfully with a VERY well-engineered design (this is VERY few bikes in reality - hint: it's none of the ones which claim to do it), and even those that do can only do so for one specific air shock and air can spring curve. In this sense, air springs are less detrimental to performance when used in a rear shock (compared to a fork) because you can use the leverage to curve to attack the problem areas - something you can't do on a telescoping 1:1 system like a fork. However - as I said - it's difficult to do this, most manufacturers don't, and what you get instead is a few DH bikes that by fluke work reasonably well with a modern air shock. Most DH bikes (>90% of them) will work better with a coil shock.

In general, a lack of support will be a result of air springs themselves, and what most people perceive as "increased" support from an air shock is simply a result of increased stiction (there is a *substantial* increase) or running excess pressure / spring rate to compensate for the mid-stroke fall off in rate - which subsequently increases the initial and ending rates higher than an equivalent coil sprung setup - which again is perceived as "increased support". What it really is, is a poor tradeoff of reduced traction for increased resistance in areas other than where support is actually needed - which manifests itself as "increased support" to someone who likely doesn't know any better. To use a practical example, it's like using heavy compression damping or very firm initial wheel rates to fight acceleration squat instead of using correct AS% - sure it vaguely works, but utilising AS nets far less traction loss.

3. On the balanced ride thing - I don't think bikes need a "really progressive rearend" and a lot of DH bikes ARE too progressive. This manifests itself in a bike that blows through the first half of travel too easily and results in instability. At this point a fast rider would run a higher spring rate (or spring pressure on an air shock) to compensate for the blow through, at which point full travel usage becomes difficult and the 8" travel bike is now a 7" travel bike. At the risk of sounding biased, I think the '13-16 Gambler frames all have a very balanced leverage curve, if you want an example of progressive-but-not-too-much. A current GT is too linear, but most current DH bikes are too progressive. I really don't have time to cover fork progression here as well, but if we go back to point (2) and recall the benefit of being able to apply a leverage curve to an air shock on the rear (but not on the front) then I'm sure you can see how it is likely that an air fork is always squarely inferior to a coil fork. I'm happy to elaborate another time though.

4. Footnote - just to give you some quick tangible data on the piggyback thing for a modern shock - shaft volume can be calculated by π*r^2*l where r, l are shaft radius and length respectively. If we use a modern 10mm shaft diameter and compare the 222mm and 267mm shock lenghts, we get volumes of 5486mm3 and 6982mm3. Those are extremes of DH shock sizes and even then the required piggy volume difference is quite small as you can see.
I have a massive typo in my previous post. I meant airshocks have a too big airchamber! Sorry about that. I know that the piggyback has nothing to do with it.

I also know that the leverage curve shouldn't be too progressive to have actually more useable travel.
But let's say I combine an excessive progressive bike with a linear coil fork, how do I setup ideally the bike for your average DH-track?
 
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Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
I have a massive typo in my previous post. I meant airshocks have a too big airchamber! Sorry about that. I know that the piggyback has nothing to do with it.

I also know that the leverage curve shouldn't be too progressive to have actually more useable travel.
But let's say I combine an excessive progressive bike with a linear coil fork, how do I setup ideally the bike for your average DH-track?
All good, I did think it was a strange proposition.

As for front/rear matching - if you have an excessively *anything* *anything* then the solution is obviously not to replicate the problem elsewhere, that's like cutting your other leg off because you lost one. If the rear is excessively progressive then my solution is to usually do what I can to linearise things there - this includes removing as much progression as possible from the rear shock - so I start with a coil shock and run the maximum possible chamber volume, minimum possible chamber pressure, replace bottom out bumper with softer/thinner part - and then, run the highest spring rate that still allows full travel use. If the frame has VERY high initial leverage and the wallowing is drastic, I'll bring in a fat shaft RC4 to allow some artificial initial resistance (via air-preload effect on shaft) which can be very helpful (*without* adding EOS ramp up like an air shock would) - this shock was a noticeable benefit on the V10.4 (10" travel version blows through first few inches), Evil Undead, and TR450 amongst others.

Of course that's if I'm forced to run the bike (or have to optimise someone else's) - but otherwise - I'd swap out the frame, because all compensation is compromise. But if you're stuck with a frame, then it's impressive how much of a positive change you can make if you make small optimisations in numerous areas.

For reference, increasing the progression of the fork spring curve just tends to result in a lack of support in my experience, usually in the midstroke. I've always found coil forks to be more free-moving initially (which benefits traction any time the wheel momentarily loses and regains contact with the ground) while being more supportive in the middle of the stroke. A correctly set up air fork that offers *equivalent support* to a coil fork will always be harsher in my experience - often due to requiring more compression damping than the coil equivalent and/or a higher average spring rate (aside from the obvious stiction increase). There's also a tendency to run an air fork more progressive to allow a softer intial rate for a more coil-like feel, however this exacerbates dive and can result in turning an 8" fork into a 7" fork, just like the excessively progressive frame.
 

6thElement

Schrodinger's Immigrant
Jul 29, 2008
15,828
13,063
not to derail, but I am on the verge of ditching my '11 boxxer w Charger and finally buying a 40 RC2.

I have used nothing but boxxers my whole 'biking life' and I always bitch about my front end diving too much, and would enjoy the stiffness people are talking about.

I do enjoy the small bump sensitivity of the boxxer w charger though.

the vivid coil will stay though.. smooth as shit

( sorry children )
Changing to a 27.5 front or sticking with a 26" version? (presuming DHR)
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,031
5,921
borcester rhymes
boxxers suck.

well, rather, the older ones (particularly the one you're on) aren't quite as good as the 40 in terms of refinement, lack of stiction, and control over what's actually happening in your fork.

I highly suggest grabbing a 40. I'm on a 40R, which I dropped and RC2 damper in. It has the inferior, not going to ever move non-kashima stanchions, but it's beautiful. Well controlled, adjustments actually work, a huge range of adjustment, and super stiff. I think you'll be glad you picked one up.
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
what is a FIT cartridge? this '12 40 rc2 im looking at has it
Since no one replied (though you probably figured it out by now), FIT = Fox Isolated Technology and it just refers to them using a sealed damper - it's the design RS copied for the Charger. All top-end Fox forks use FIT, but the inverted FIT introduced in 2011 (with the bladder at the top) is a lot more reliable than their old ones. You can tell from the LS/HS compression adjusters being at the top, the '12 40 RC2 will have it.

If you're buying a used one just make sure there's no stanchion/bushing wear, look closely for vertical discoloration lines on the stanchions (usually about 10mm wide), prominent closer to the seals. If you can't see any, you're good to go. I'd do a quick lower oil change and clean of the seals / foam rings before riding it too.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,031
5,921
borcester rhymes
if you don't like it, I have an old, non-adjustable open bath damper that I literally have nothing to do with. It's a nice bit of machine work but too greasy for wall art and has been replaced by the more functional FIT cart in my fork.