Nothing wrings out an idea like the passing of time. You can do all the engineering and testing you want, and maybe you'll even speed the process up, but there's no getting around the fact that it takes many, many years - decades or longer, even - for a design to near its full potential. And something funny happens when that point gets near: designs can start to converge and appear quite similar as people learn what works and what doesn't. An obvious example is the mountain bike's distant motorized cousin, the dirt bike; most of us would probably have a difficult time telling modern specimens apart if they shared the same plastic bodywork. One could make the same argument about all sorts of things: internal combustion engines, squash racquets, the common fork and spoon.
Oh, and of course the mountain bike. There's a reason that the "Looks like a Session" comment is so pervasive... it's because, well, a hell of a lot of bikes look like a Session.
The vertical shock, big ol' rocker link, four-bar layout makes a load of sense, so it's no wonder that many brands employ those basic principles in one way or another. This was happening long before the Session was even a twinkle in Trek's eye, too, don't forget. But as we get closer and closer to there being only a handful of truly different suspension designs out there, albeit being executed in distinct ways, it's the outliers, those who go in a different direction, that stand out more and more.
No, an engineer doesn't need to be an artist. This is an initial sketch of the Insolent by Boivin from 2013.
One man going his own direction is Jean-François Boivin, a thirty-seven-year-old mechanical engineer from Quebec, Canada, who wanted to work in the cycling industry so badly that he relocated his entire life to Europe to chase that dream. ''I moved to France hoping to find work in the bike biz, but it was actually pretty hard,'' Boivin said of that period. ''However, I had the opportunity to work as a consultant with Cedric Braconnot at Labyrinth bikes.''
That led to Boivin designing the linkage on Labyrinth's Minotaur and Agile models before returning home to Quebec where pedal-power took a back seat, at least professionally, to electricity and automobiles: ''I moved back to Montreal and worked as a professional engineer for ten years in the field of electric drive systems (motors and inverters) at TM4 and continuously variable transmissions for heavy vehicles at CVT Corp.'' You know, just your normal, everyday CVT engineering job.
A rendering of the 203mm-travel Insolent.
But like a lot of us, bikes were always in the back of Jean-François' mind regardless of what he was doing professionally: ''I still had that wish to be a full-time bike designer. Then I had this idea of integrating the suspension in the top tube and thought it would make for a great looking bike.'' Which, was the genesis of Boivin's 27.5'' wheeled Insolent downhill bike that's surely one of the more interesting - and best looking - machines I've seen in ages. ''I began to work on the project during my spare time." Said Boivin. "And then, from initial sketch, through 3D modeling and supplier selection, the bike slowly became a reality.''
Did it ever. The 203mm-travel carbon frame, which was manufactured for Boivin in the UK by Carbon Wasp, has an Effigear gearbox bolted to the bottom of it, uses a belt-drive system, and has its shock located inside
of its top tube. Oh yeah, Boivin also made his own shock, as you do, by cutting up a Kashima-treated Fox 40 stanchion and plugging in a FIT damping cartridge from a 36 fork that he heavily modified to suit his needs. More on that later, though.
Gearbox jewelry. Boivin designed the Insolent's carbon frame to accept an Effigear 'box.
Boivin's creation lit the internet up after he shared a video on Facebook, with every major mountain bike website lifting photos and what little info there is on the sparse (and very French) Resistance Bikes website
to get something posted ASAP. The handful of photos and speculation-filled words that I put together on Boivin's Insolent DH bike a few weeks ago did nothing but make me more curious, and judging by many of the nearly three hundred comments, it had the same effect on others as well.
Of course, both the Insolent and Boivin himself deserve more than my microwaveable dinner of an Internet story
, and while the cheeky name of Boivin's bike hints at his thoughts on the mountain bike industry, the man himself is eager to share his ideas.
Building The Frame
Picture this: you've got a great concept for a bike, one that you're sure has potential, but as clever as you are, manufacturing your own carbon frame isn't on the cards, at least not yet. What do you do? The obvious way to solve that dilemma is with a welding torch and having someone build a one-off frame for you, but not if you're Jean-François Boivin. A chance find on YouTube of a Red Bull-curated series called 'Fettlers' introduced Boivin to Carbon Wasp, a small operation in the UK that specializes in producing low-volume carbon creations.
Surprise surprise, you can't just ring up China and have a single frame made for you, but Boivin now had a plan and a way to carry it out.
Wouldn't it have been easier to turn to aluminum? In some ways, yes, but going that route presented its own share of concerns. ''My original intention was to make the frame out of aluminum, but the distortions during welding would require a lot of alignment and machining, and that might not even procure proper performance. Carbon manufacturing doesn’t have this problem. The frame has a straight shape out the mold, so it was the way to go,'' Boivin said, which means that while carbon isn't the obvious choice for a first go, it turned out to be the material that made the most sense for his needs.
Being a hands-on chap, Boivin didn't just send Adrian Smith at Carbon Wasp his design and then wait by the mailbox for the frame to show up. Instead, the Canadian traveled to Leeds to see his creation come to life in person, and even got a bit hands-on himself, although not as much as he would have liked. ''For the next model, I will definitely participate in the carbon layup process, as I want to understand and control every detail of the process,'' he said, before going on to explain how what began as a one-off project has now morphed into a long-term goal of being able to manufacture his own carbon frames in Quebec.
Every small business owner knows that having a product is only part of the battle, and Boivin is realistic but also sanguine about his chances: ''In the beginning, the intent of the project was only to make my own bike," says Boivin. "I have been racing downhill for a few years here on the Coupe du Québec, so making a downhill bike was an obvious choice, especially with a gearbox. Right now, there is only one frame in existence and it kind of serves as a proof of concept. When I started, I didn’t even know if all the parts would fit together and that the suspension would move freely. Now that the bike is assembled and performing very well, we are sure looking at making a small production. We are quoting parts with our suppliers as you read these lines and will come up with a price tag for a very limited run of ten units when ready. Then you will be able to pre-order through our website with around a 30-percent price commitment. If enough customers step in, production will begin; if not, customers will be refunded. There is also the financing side of things that we have to cover. We are evaluating our options right now. So, if any serious investors out there feel the project has potential and would like to join us, we will be glad to discuss.''
Boivin decided to use carbon fiber because the mold method essentially eliminates the possibility of misalignment.
While they might be the Formula One cars of our little world, the demand for high-end downhill bikes is roughly similar in size to the goat rental market, and Boivin is well aware that a downhill frame on its own probably isn't going to keep Resistance Bikes around for the long haul. That's why he's looking at bringing an enduro-focused bike to the market as well, presumably of a similar design to the Insolent and making use of both carbon fiber and a gearbox.
So, how much does one have to lay out to get their hands on a limited production, carbon fiber, gearbox-equipped downhill bike with a custom designed shock hidden inside the top tube? Boivin doesn't have an MSRP locked in yet, but his goal is to ''remain competitive compared to other gearbox bikes.'' Let me translate that for you: it won't be an inexpensive option, even if he does go ahead with his plan to sell direct to consumers through his website, thereby cutting out the distributor's mark up, and to accept crypto currencies like Bitcoin, Litecoin, and Ethereum.
The Suspension and Custom Shock
If you're going to build your own one-off carbon downhill frame, you might as well make your own shock because, well, engineer. There is, however, another reason that Boivin built his own shock using part of a Fox 40 stanchion tube: because the 203mm-travel Insolent's shock is a stressed member of the frame, and an off the shelf shock would simply not suffice. The 40mm diameter Kashima-treated tube provides the lateral support that the frame requires, and it's also home to the damper and spring element that, you guessed it, Boivin pieced together himself. However, he admits it was not a simple task: ''The design of the internal suspension parts was definitely the hardest part. It had to have the damper and spring in the same tube and be compatible with air or coil springs. Disassembly, access to adjustments, and low friction were all challenges as well.''
Is that a stanchion tube or a shock? Turns out that it's both.
When I first saw the Insolent's rear end, I suspected that the 40mm gold tube was hiding a normal, production-spec damper of some sort, but I was only partly right. Boivin did try to fit a production shock and damper inside the 40mm tube, but that idea was eventually shelved when nothing usable came of it. Instead, he's heavily modified a Fox 36's FIT damper cartridge to do the job: ''I don’t want to give many details now," said Boivin. "But, we are evaluating the possibility to use off-the-shelf parts integrated into a custom-made slider. We will see how this turns out. For people interested in the project, we plan to make the next phase of development public. Which means I will post any advancements, design techniques, questions or problems we might encounter has it happens. We think it will be very interesting for the customers to be invited in our design space. That is surely something other companies would not allow. You can probably begin to see we intend to do things somewhat differently at Resistance Bikes.''
The FIT damper retains its low-speed compression, low-speed rebound, and high-speed compression adjustment dials and function, and all of the new internal components, which were manufactured by Machine Pro, have been inspected and approved by Boivin's suspension specialist consultant, S4 Suspension.
Boivin modified a Fox 36's FIT cartridge to use as the damper for the Insolent's shock.
The FIT cartridge was shortened down to 92mm of stroke to provide 203mm of travel at the wheel, and the shim stack was reconfigured to work with the Insolent's slightly progressive leverage ratio that goes from 2.36 in the initial stages to 2.0 at bottom-out. ''The average ratio is about 2.2, which is low, to improve damping performance,'' said Boivin before pointing out that, because the main pivot is concentric to the gearbox's output, there also won't be any feedback from the belt drive.
He's prioritized having an active suspension system over one that firms up under pedaling loads to feel more efficient, but Boivin is well aware of the consequences and compromises that come with such a design: ''It will come at the expense of some suspension compression during pedaling. We think the pros defeat the cons here. I remember smiling when Aaron Gwin and Neko Mullaly had tremendous race runs with 0-percent pedaling efficiency.''
Of course, Jean-François doesn't have to adopt the "It's the best at everything'' marketing spiel, given that the French Canadian isn't aiming to sell the thousands of frames that he's ordered from China and already had to pay for. Being a low-volume outfit means that he can be more straightforward and open, which is a refreshing change from what we're used to seeing.
The shock can be fitted with either an air spring or a coil spring, and Boivin is planning to use progressively wound coils to provide ramp-up.
Boivin came up with his own dual-chamber air spring, hence the two external air valves that can be seen on the non-drive side of the frame. Boivin says the setup process is similar to a two-chamber air-sprung fork: ''To set up the suspension, a rider would begin by adjusting positive air chamber pressure to get the right sag, then add enough pressure in the negative chamber in order to balance the forces at zero travel. At this point, the suspension becomes very sensitive. We use Viton quad rings on the dynamic seals, so the movement is super smooth. I was impressed myself when I tried it the first time. We don’t have a bottom out control per say. There will be a rubber bumper to absorb hard hits like is found on standard rear shocks.''
The slightly progressive leverage ratio that goes from 2.36 in the initial stages to 2.0 at bottom-out.
Without a linkage of any sort to manipulate the rate, the Insolent depends on the air spring to provide more or less ramp up. To tune this, a rider can adjust the position of the main air piston that divides the two chambers; a smaller positive chamber would provide more ramp-up and vice-versa. Volume spacers are on the cards as well, and Boivin is considering going with progressively wound springs for the coil-sprung setup.
Yup, unlike any other shock out there, Boivin's creation can be fitted with a coil spring or run air internals - it's your choice. ''We began with air springs because custom coil springs would have been more expensive considering many spring rates would need to be purchased. Air springs provide more tuning options for us in the beginning,'' he explained of why air made the most sense for these early days.
Alright, it's one (impressive) thing to make your own shock, even if you've done it by modifying existing components, but it's a whole other ball game to go from that to making a reliable version that can be manufactured over and over again. I had to question Boivin as to if he could make the shocks using his own parts, and if the tolerances would be good enough. ''That is a good question," he says. "And, being a professional engineer, I certainly know not to overlook manufacturing tolerances. I will admit that the internal suspension sleeve was pretty hard to produce. This design will probably have to change a bit in order to be economically competitive.
"But, we have very good machining suppliers, and we got them involved early in the design phase, so we didn't get big surprises during fabrication,'' he replied, before also explaining that his plan is to consult with some well-established bike studios in the future, and to not get in over his head: ''Production is always a challenge; we will begin with low volume and build from there gradually in a safe and reliable way.'' If you ask me, that sounds like a very un-bike industry-like approach.
Boivin says he isn't dead-set on the shock design you see here: ''On the following design, we will try to make the shock system more like a fork, with bushings or maybe needle bearings in the top tube. Again, we would like to know what you think in the comments section." I'm picturing a four-sided stanchion with needle bearing strips, much like the torsionally rigid Lefty chassis employs, but we'll have to wait to see what he's cooking up. One thing is for sure; he'll need to manufacture his own suspension components for the customer version rather than modify Fox parts - I doubt that Fox is all that keen on having their chopped up bits in a production bike, as neat as it is to see.
If we had X-ray vision, we'd be able to see the shock inside of the Insolent's top tube.
Why is the Shock Inside the Top Tube?
It surely would have been an easier project had Boivin gone with a more conventional shock mounting location like, oh, I don't know, not inside the bike's top tube. Then again, there are a bunch of things that would have been easier had he taken a different approach, but we'd be looking at a much more conventional - and not nearly as good looking - downhill bike.
Boivin happily admits that the internal shock placement is largely for aesthetic reasons, and I can't argue with him that it worked. ''I really like a direct slopping line between the head tube and rear axle. The shock integration inside of this line made much sense,'' was his answer when I asked him why he went this route. And while I can't tell you there's a performance advantage, even the uneducated, non-engineer in me knows that the internal frame mounting provides support for the custom made shock that must also supply lateral rigidity on top of its bump-absorbing duties.
While the shock plays a vital role in the rigidity of the Insolent's rear end, the majority of its length being nested inside the top tube means that it does have help.
A comment that popped up under that original article a few times questioned if the shock's temperatures would be quite high given that it's nested inside a carbon tube. Boivin doesn't believe that this will be an issue, though: ''As for the shock getting too hot, we don’t think it will be any worse than a fork. Moreover, on a future version, we would like to have the slider be the damper’s body, so in that case, the oil would be in contact with a metallic external surface, same as a regular shock, so no problem there.''
As it is right now, the heavily reconfigured FIT damper is a separate unit that sits inside the Fox 40 stanchion, so there are two aluminum 'walls' between the damping oil and the outside air that act as an insulator. If the stanchion tube was the damper body, as it is on some forks and pretty much all shocks, the damping oil should stay a bit cooler because there's a single 'wall' between the oil and the cooling atmosphere outside.
Another valid concern that was raised by forum engineers was about service, and if the shock could be removed from the frame when required. The answer: sort of.
The plan is to have the shock's body bonded into the top tube on the production version, but riders will be able to disassemble and remove all of the shock's components from the body as needed. While Fox obviously doesn't recommend it, a FIT cartridge can be rebuilt by someone with the right tools and knowledge without having to ship it to a service center, so I don't see why someone with the same skills couldn't give the Insolent's shock some love if it were needed.
Many of those same commenters questioned Boivin's decision to not employ a rocker link of some sort, if only to add rigidity to the frame while removing much of the side-loading from the shock. ''It is our belief that the bike is going to be sufficiently stiff without a rocker,'' was his retort when I laid that concern on him.
''The 40mm diameter stanchion tube is pretty stiff in itself. And then, inside the suspension tube there is a 60mm long Igus linear slider combined with a piston ring giving a 150mm span between the two supports. This distance even becomes greater as the suspension compresses, meaning it gets stiffer along the travel. Also, the intent of the design is to be as sleek as possible, and we think a rocker would not have looked as good.''
If it turns out that more rigidity is required, Boivin's first-gen prototype is ready to be tested with an SKF linear ball bearing setup, although this would require a heavier hardened steel slider rather than the aluminum tube that he lifted from the Fox 40 downhill fork.
From a Simpler Future
Even if you're not a believer in the design or in gearboxes, I bet that most of us can agree that Boivin's creation is a thing of beauty. To me, it looks as if it's been shipped back in time from a future that's actually simpler rather than more complicated; the lack of a conventional drivetrain contributes, of course, but it's the integrated suspension and sleek lines that do it.
A gorgeous bike is not necessarily a fast bike, however, and let's be honest with ourselves and admit that a Session, Glory, Tues, et al. aren't about to hold any of us back, which raises the question: why choose the Insolent over those examples, or any other off the shelf downhill sled? What, exactly, does the Insolent bring to the table that a mass-produced downhill bike isn't able to?
''First is good looks, which many traditional off the shelf bikes don't have,'' replied Boivin to that slightly pointy question. Sure, I'll give him that, but what about reliability? Performance? Weight? You know, the things that really do count. Take it away, Jean-François: ''The maintenance will be reduced compared to traditional derailleur design. I, for one, absolutely hate to clean dirty chains. The belt design with no lubricant sure is an improvement. The internal suspension should not require any more attention than the fork. The suspension is coil-spring compatible, so low maintenance. The frame is free of small, hard to reach details, so you will waste no time cleaning the bike after a ride. Low unsprung weight and low-middle center gravity are immediately noticeable, but any gearbox bike provides that. Then the suspension becoming part of the structure and having direct, minimal tubing has the potential of being the lightest design of all [the first prototype weighs 35.24lb]. The current unit is not optimized, but when we are done, the result might be surprising.''
With a gearbox, belt drive, and integrated shock made using parts from Fox's 40 and 36 forks, the carbon fiber Insolent is not your average homemade mountain bike.
In another time, Jean-François Boivin might have been the guy welding together a race car chassis in a French garage in the 1930s, or even tinkering as an early innovator in the aviation field. Instead, Boivin's attention has been focused on the humble bicycle and, as bikes look more and more alike every year, he's an outlier who stands apart for going his own way. Whether the Insolent is better than a common, run-of-the-mill downhill bike is almost beside the point when the point is that Boivin created exactly what he wanted, for better or worse.
And that, dear Pinkbike readers, is something that we need more of.