Status quo? Not so much for Ashley Kalym.
On a scale of one to ten, how much of a do-it-yourselfer are you? Burnt-out lightbulbs and hanging picture frames are the limits for some of us, whereas others are happy to DIY their way through just about anything short of a shuttle launch. Back in 2018, we saw Jean-François Boivin's homemade carbon downhill bike that used a gearbox and a stanchion tube from a Fox 40 for its rear shock
, as well as Vladimir Yordanov's dual-link carbon downhill bike
Next up in the DIY Hall of Fame is Ashley Kalym with his 160mm-travel single-sided, carbon fiber linkage fork.
Most modern suspension forks all follow the same basic principles: Two stanchion tubes sliding on bushings, a set of lowers held together by an arch and axle, and there's probably some type of spring in one leg and some type of damper in the other. That layout has worked really well for two or three decades now, depending on how you define 'really well,' and it's the recipe used by most of the traditional suspension manufacturers out there.
None of that is going to change anytime soon, of course. Sure, Trust, Structure, and Motion Ride are convincing some of us there are other ways to get the job done, but linkage forks will likely always be on the fringe. Interesting and always promising, but too bizarre for most of us to actually consider.
But Ashley Kalym didn't just consider one; he designed and built his own single-sided, carbon fiber linkage fork.
''I don’t have any engineering background at all, apart from teaching myself CAD over the last three or four years,'' Kalym told me, with the only other product that he's designed being a relatively simple archery release aid. Jumping straight into the deep end of the DIY pool, Kalym taught himself by using online resources and insists that what he's created could be built by anyone with the desire and stubbornness to get it done.
There's surely lower hanging fruit than such an important, consequential component like a fork. ''I think that most other parts of a bike are pretty solid in terms of their function,'' he replied before admitting that there's little to no way for him to improve on a stem, handlebar, or other relatively straightforward parts. On top of that, the major brands focus their time and efforts on telescoping suspension, leaving plenty of room for the smaller outfits to experiment.
Kalym's focus was on the chassis, not the spring and damper, which greatly simplified the process. ''This meant that all I had to worry about were wheel path, leverage curve, and a few other bits and pieces,'' a process that took about two years of on and off work and ten different iterations before he decided on what you see here. Some of those were dual-sided, but the simpler single-leg layout won: ''Of course, this caused some packaging headaches, but I got there in the end. Also, going single-sided meant that I could increase the diameter of the fork leg to 50mm, and therefore increase the stiffness while keeping the overall weight the same as if it were two-sided."
A 20mm Hope Pro 4 hub works, as does a standard rear shock. Kalym was careful to only use existing parts.
If you've spent any time on Cannondale's single-sided Lefty, you already know that a fork doesn't require two legs to be torsionally rigid. The Lefty is a very different chassis, though, and its abilities come from a square (newer models are three-sided) stanchion that rolls in and out of the massive upper tube on strips of roller bearings. But Kalym wanted his fork to offer anti-dive abilities, and to increase trail as it goes into its travel to stabilize handling, neither of which are possible when using stanchion tubes. And he didn't want it to look horrendously complicated or require a one-off, non-standard hub, all of which led him towards the leading-link layout you see here.
What do you think: Is it better looking than a Trust, Motion Ride, or Structure, and should that even matter?
The benefits of increasing trail and anti-dive have been proven, with those traits creating handling that can't be matched by a telescoping fork, and Kalym admits to still learning what this means on the trail. ''It makes sense on paper to keep the head angle consistent and slacker when braking and cornering, but is that more beneficial than having the suspension completely free and active? I’m not sure yet, and there’s a lot more testing to be done,'' which is a rather refreshing attitude.
"The link itself moves through 47.16 degrees of rotation from full extension to bottom-out, which means that the brake caliper rotates around the disc a large amount, which equates to a lot of anti-dive.'' The trail grows from 130mm to 165mm at bottom-out, he says, which, ''equates to an offset of 45mm at rest, and 17mm at full compression.''
Kalym is working on a second version of the fork that will have a four-way adjustable floating brake arm to suss this out.
While the kinematics are still in the works, Kalym knew from the outset that he'd be using an off-the-shelf shock to handle the spring and damper duties. ''If you think about it, the rear of your bike is incredibly adjustable in terms of the shock choices you have. You can simply buy a new shock, bolt it on, and ride. You also have a choice of cheap or expensive, feature-poor or feature-rich, air or coil, and so on. However, if you want to change the spring and damper in your telescopic fork it’s a lot harder, and sometimes it’s not possible, especially if you want to go from air to coil and back again.''
So instead of thinking classic front suspension, Kalym wanted to design a chassis that could accept most shocks on the market. Prefer a simple air-sprung shock with a lockout lever? Not a problem. Want to bolt on an exotic coil-sprung shock from EXT, Push, or someone else? Go right ahead.
The rear suspension approach to front suspension also requires a progressive leverage curve to resist bottom-out, whereas a telescoping suspension fork is a straight 1:1 ratio. ''I was limited in what I could do because I went with a directly driven shock design, but I ended up with a curve that starts at 3:1 and ends at 2.54:1, which feels good even with a coil shock,'' he explained. An air-sprung shock would provide more ramp-up if that's what you're after.
The massive aluminum link pivots on 20mm x 32mm x 7mm bearings, there's a 20mm diameter axle through it all, and an M10 bolt holds it all together. ''It's pretty bombproof,'' Kalym told me, and it uses a normal Hope Pro 4 hub.
The massive upper leg was made by Carbonwasp, an outfit in Yorkshire that specializes in one-off, prototype carbon components. ''I’ve known Adrian for a little while, as I’ve done a few other 3D printed prototype things before doing the fork. He probably got sick of my emails, to be honest! But he was great in advising me the best way to go about certain things, and the way they do carbon made the whole project economically feasible." The single-sided leg was new to them, but Kalym says that the finished product is overbuilt and, "insanely stiff." Even so, he's planning to go with an aluminum leg for the next version as it'll make anti-dive adjustments and other modifications easier.
After a few year's worth of time and a hell of a lot of work, Kalym is ecstatic with how his fork performs: ''The sensitivity and activeness are like nothing else, much plusher than anything I’ve ridden. The amount of grip that the fork gives is really confidence-inspiring, and the increase in trail is noticeable (I think). Stiffness is also noticeable, with steering feeling much more precise and less delayed. I think the only thing that needs more exploration is the anti-dive."
Ashley Kalym with his homemade linkage fork.
There are no proper plans for a production version, though, with Kalym having been down that road before with the archery release aid. ''It just took the fun out of it for me,'' he said. ''If it grows organically then that would be awesome, but if it never happens I’ll be happy just to ride around on a fork that I designed and built. Obviously, something like this would be a niche product, and I think would be for people who are simply interested in performance above all else. There will be other forks that look better, weigh less, and cost less, but I’m certain there’d be a small group of people that would love to reap the benefits of a fork like this.''
The fear of using the bathroom when your boyfriend is in the house.
For Sale - One off Carbon single sided rear shock fork
"Hands down, the most plush best suspension I've ever used"
Reason for sale - "Upgrading"
I think your design looks dope. I'm a believe of form folows function and, while telescopic forks do the job well, your design could be a better performer handling-wise and in maintainance. Ofcourse the shock has to be serviced just like forks but the shock can easily be swapped out for a serviced spare to minimize/eliminate down-time. And most importantly: no sliding bushes taking lateral forces. And three pivot points including shock mounts is not a lot! Keep it up!
And then we can expect production?
i think it's badass!
*full discolsure - previous Lefty owner here
I believe what he has done is carbon wrap his plastic 3D printed model. It certainly looks that way. Happy to be proven wrong though.
Also I really like the way it looks man! Awesome design right there.
The article states you don’t have an engineering back ground - What do you do for a job/career? This would be an undertaking to say the least for someone trained in design!
Does you fork's chassis have fork crown and steerer tube as single monocoque? Have you calculated the change of front wheel offset throughout the travel? Your design would be very interesting to compare with Trust's forks.
Do you happen to know about Josh Gore from USA who built two prototypes very similiar to yours one? It's very interesting as well:
Hope this can be made cheaper!
Yes it is a single monocoque. Yes I have calculated the change. For a 63 degree head angle bike it goes from 45mm to 17mm, but for different head angled bikes it will be different.
Keep going with yours, looking forward to seeing it mate.
You predicted: the E-Verb & eagle-tap, the CAD single crown lefty, linkage forks, the Grim Donut's headtube angle, DH bikes in wind tunnels, helmets with built in airbags, e-bikes (still waiting for front-wheel drive to come out), and more.
Whatever you do... please don't predict new wheel sizes or hub and BB standards... or else they will come true!!
I'm hoping for a 603mm bsd rim - that's halfway between 29" (622mm) and 27.5 (584mm) rim diameters. 9.5mm change in rim radius.
No new forks needed, just a couple good rims and a handful of tires.
I think it could be a good chassis modifier for a fairly low cost. I think there is a big enough gap to warrant an intermediary size. One could fine tune tire radial height (cushon) without having to compromise dynamic wheel radius. Just as we have many stem lengths, crank lengths, frame sizes etc; i think having the ability to fine tune one of the most important aspects of a bike would be truly beneficial.
Convert to coil: "nothing matches the suppleness and responsiveness of coil."
Linkage fork: "sliding forks can never match the suppleness and responsiveness of linkage pivots."
Patiently waiting on magnets...
But yeah I remember, basically based on road conditions a computer tells the fluid by way of electric current that the shocks should be more rigid sometimes and soft at other times.
/s if you couldn't tell
The aluminum 20mm axle is unsafe, imo. If you got a solid steel axle turned, that would be slightly less likely to knock your teeth out.
The better solution would be to have an oversized, tapered axle, like the lefty.
Edit: I've found a steel axle of the correct size so will order that for the time being.
Honestly, I don't think you need FEA done on that part of it. Some pretty straight forward hand calcs will get you a good idea of where you need to be since you're not really worried about weight savings or eeking out the last bit of stiffness. FEA on the chassis and the linkage may be a good idea at some point, or just keep it beefy AF!
An issue i see (constructive criticism): to make the pivot stiff enough, that lower linkage is WIDE. is that not the widest point of the bike (off the centre line) by some margin? I suppose pedals stick out further actually, but i would be concerned dropping it into deeper ruts and gullies, especially considering your wheel is going to want to sit in the middle of a rut, effectively doubling the actual width of the fork?
Your fork is compatible with standard parts and that's why you gonna win this one
That linkage fork is simply stunning Next-Next-Next level DIY engineering. Everything about the design and part sourcing. Total package. Wowser!
Tip o' the cap, and then some, my friend! : )
[Full disclosure: I have a Trust Shout on my main whip, and I love it!]
It does look like a big hit/landing/Gout where there are rocks that are close the the left side of the wheel could be an issue? Normal forks get scraped up, loose a cap now and then on the end of the fork, but that at least is a fixed drop.
Random thought I had to address the lower link clearance issue:
This is hard to explain. What if you set it up so that the lower link as oriented like a swing arm, with the axle positioned at the back?
Picture a mirror image of what you made. Then adjust crown angle, shock angle, and linkage path to accomplish the same objectives you achieved. This would place the link in the front and above the axle, or mostly above. It would significantly increase ground clearance on that side.
How well do the hope bearings do under the single sided loading? Looks like quite a large bending moment around the left hand bearing?
Wondering though, do you need to remove the brake caliper when taking out a wheel?
Either way, of course props for making this happen!
Higher pivot or shorter arm will both reduce dive.
It actually rewards very aggressive riding, and being over the front wheel a lot. The suspension actually stays very active when braking, just that if the front is unweighted it wants to extend the spring, depending on how hard you are braking. Without getting too technical, the brake calliper on this one goes through nearly 50 degrees of rotation, which equates to a lot of anti dive. Version 2 will have four settings, going from 0, 10, 20, and 30 degrees of rotation, which should give enough adjustment to suit most riding styles. Although testing will confirm this.
Also need a few more moving parts, throw in a handful of acronyms, then he can call it a linkage!
(Good to see someone finally put this idea in practice in a MTB)
I'm sure it has a grest personality though.
But my question is:
Why don't some people devote themselves more to auto eroticism?
and it's the best bike I could ask for, I'm sorry to see one with an abortion like that ......
Me: Hi! I'm here for the periodic maintenance.
Service Guy: daily, weekly or monthly?
M: I don't know, a week ago was made the monthly for $500 - all the bearings were replaced, and now i'm having problem again with the articulations.
SG: No problem, we will change the bearings again for another $500.
M: But...Isn't that a steal?
SG: Sorry bro, You made the decision to buy this fork. But if you want, you can buy a "club card" from us for $2000, and you'll be covered in the next 2 months with free service for your fork.
M: Oh, really? Sounds nice! Take my money!
I ride a lefty and a conventional fork and the lefty blows me away every time I ride it. So stiff so smooth. But the damper is meh
My evil has a Fox 140 on it. If were talking lycra, then sid.
Honestly what would you say the leftys market share is? and why?
The other market barrier is knee-jerk reaction dipshits who think a lefty is unsafe or ‘stupid’. Yes it’s funny looking, but if people knew anything about mechanical engineering, tube stiffness vs weight, bushing friction vs roller bearings, they’d realize it’s a superior chassis design. Cannondale Damper and air spring designs are archaic.
He is just showing his creation and I wouldn't bet against the quality of his work just because he doesn't have an engineering degree.