First Look: The Digit Datum Has Shock Strut Suspension

Aug 31, 2021
by Seb Stott  


Kickstarter product campaigns often aren't that promising, but this one caught our eye. The Datum from Digit Bikes is the brainchild of Tim Lane, the man behind DirtBaggies and several successful road bike designs. It's a trail bike with a pretty interesting suspension arrangement. The bespoke rear shock/strut is housed inside the top tube and is held rigidly in place with a pair of fork bushings; it forms a structural and integral part of the suspension system. The rear triangle is attached to this with a pivot, while a short link connects the bottom of the rear triangle to a bottom bracket concentric pivot.

Digit Datum Details
• 140mm Analog suspension with shock strut claimed to be lighter, stiffer and simpler
• Intended use: Trail
• Wheel size: 29" front / 27.5" rear
• Designed for 150mm-160mm fork
• 12" shock with 2:1 leverage ratio claimed to offer more consistent damping and spring rate
• Made in the USA
• Pricing TBC
digitbikes.com


The design is called Analog because the sliding strut is an analog (equivalent) of the rocker link at the top of a conventional four-bar design. Digit aren't the first to use a sliding element in place of pivots as part of the suspension linkage: Naild and Yeti have done that before with their R3act and Switch Infinity designs, respectively. But Digit's design is different in that the strut is both a structural element and a shock, which cuts down on the number of parts required.

Pinkbike-Polygon-3-2017
Yeti SB5c Turq Review
Sliding suspension elements have been proven to work before.

Digit aren't the first to do this either, as Resistance Bikes, Maverick's Monolink and Boulder Bicycles all used integral shock struts, but the Datum is a little different to all these designs.

Resistance Bikes
The Resistance Insolent also uses a top-tube mounted strut-shock-thingy, made from a Fox 40 stanchion.

When asked to categorize his design, Tim Lane says he started out referring to it as a "3-bar link". He admits that's "not quite engineering correct [but] it's a snappy name that conveys the point that there are fewer parts." He added, "I think it could be called an 'offset slider-crank mechanism with the wheel riding on the connecting rod'." Probably a good marketing decision not to call it that.

There are three pivot locations in total - two on either side of the short lower link, and one where the swingarm drives the shock/strut. That may sound more complex than an Orange-style single pivot, but even those have three pivot locations if you include the two rotating shock bushings. Conventional four-bar bikes (including Horst-link and twin link designs), as well as "faux bars" like Kona use, have four bearing pivot points plus two on either side of the shock, so six in total.

Digit claim that fewer rotating parts mean they can save almost a pound when compared to a four-bar or faux bar design, plus superior stiffness, reliability and lower environmental impact due to the lower part count.

The design also makes it possible to use a straight seat tube, which makes room for long dropper post insertion lengths and two water bottle mounts inside the frame. There's also very little seat tube offset, so the effective seat angle is almost the same no matter the saddle height.

One thing which could be seen as a downside is the need to design a proprietary shock that also functions as a structural frame member. Digit sees this as an advantage, however; because there are no conflicts for space inside the main triangle shared with rockers and water bottles, it allows them to make a bespoke super-long shock.


The damper is at the back of the strut and the air spring is at the front. Two fork bushings allow it to slide while maintaining rigidity.
All the tools needed to service the shock could be found in any good workshop.

The shock strut is 12" long, which apparently allows for larger oil volumes for better damping consistency and larger air volumes for a more linear spring curve, meaning less beginning-stroke stiffness and more mid-travel support. "Because my shock is so long, life is easier for the oil and there's much more of it," Lane explains, "I can have a nice long air spring, and the low leverage ratio puts much less load into the frame and pivots, plus the shock is supported by fork bushings so there's no risk of sideloading the shock shaft."

The damper offers external low-speed compression and rebound adjustment, while the air spring can be fitted with volume spacers to adjust progressivity. The shock is said to be fully self-serviceable using no proprietary tools, and the first service is free to frame buyers. The average leverage ratio is 2:1, meaning the shock moves 70mm over the 140mm of travel. That's a lower leverage ratio than most bikes, which should improve reliability but could increase friction.


The aluminum frame is mullet-specific, offers 140mm of rear travel and is designed to be paired with a 150 or 160mm fork. With a 65-degree head angle and 75-degree seat angle, the geometry is modern without being boundary-pushing.


If the funding round is successful, Digit will make the frames in Southern California and hope to ship the first frames in March 2022. Pricing is still TBC.

Check out digitbikes.com for more.





200 Comments

  • 137 1
 Not sure how well it works, but it looks fantastic!
  • 5 2
 Yeah, waiting for the review tru written or video. I hope someone reviewed it tru video so that we can see how it works.
  • 9 0
 @DirtBagTim: What was your lengthy reply to the question about the shock.
Funny Beta doesn't have the first ride behind a paywall, but your reply is.
  • 4 0
 It does have a very nice silhouette/side profile.
  • 24 0
 @TheOriginalTwoTone: Just before you wrote this I jinxed myself on FB by writing:
"Pinkbike appears to be broken.
1) The comments are positive.
2) It doesn't #lookslikeasession
3) And nobody complained about Outside Magazine paywalls, even when there's a Beta MTB article cited.
We're living in a bizarro opposite world, and I like it."

...and then you posted about the paywall.
  • 1 0
 @DirtBagTim: If they let me on the podcast (I just tried to invite myself on today's podcast page), I'd be happy to read it aloud or paraphrase and discuss it.
  • 1 0
 @TheOriginalTwoTone , @shedsidechuck, @Hyakian If they let me on the podcast (I just tried to invite myself on today's podcast page), I'd be happy to read it aloud or paraphrase and discuss it.

(oops, I replied to myself above, not you guys). I'd recommend making appeals on todays podcast page.
  • 115 2
 Wish me luck!
  • 6 0
 nice work, tup
  • 7 0
 @DirtBagTim: Need any testers? Big Grin
  • 3 0
 Looks awesome!
  • 3 0
 Brilliant looking design. So clean!
  • 2 0
 Looks good. Can you tune the shim stack of the shock to get different properties? Would there be a coil conversion available, like Push ACS?
  • 4 0
 @chacou: Yep, the shim stacks can be adjusted, it's a pretty standard layout. I'm pretty happy with the tune, but interested to see what people do with it. The shock can be fully serviced with standard tools, and the IFP is charged with a shock pump through a Schrader valve.
  • 1 0
 Just donated some coin your way. It looks like a very playful bike. If the compression of the shock was dialed up, would you say it would be a good bike for jibbing around on or taking to the dirt jumps?
  • 2 0
 @DirtBagTim: Nice! Thanks for the explanation.
  • 2 0
 @DirtBagTim: looks very cool man! Good luck with the project. Excellent looking bike, I like what I'm hearing here.
  • 1 4
 You should bring a few full builds to Montana and we can put them through some proper testing. About the only thing I would like to see in MT from California.
  • 1 0
 how to remove the shock internals from the TT for maintenance? seattube in same plane will interfere him
  • 1 0
 My gut feeling says, with no engineering background, that because the shock has nowhere to go vertically, you will see excessive wear/play in the bushes, or even scratches, in a short amount of time.
  • 49 0
 With a trust fork out front it would be like an Mtb with reversed suspension
  • 9 0
 Hopefully Trust makes a comeback one day. Not that I would ever buy one, but at least they were innovative.
  • 8 0
 @stumphumper92: Specialized bought the IP so it might have a future.
  • 9 0
 @NorCalNomad: part of me wanted Cannondale to buy it…. Linkage Lefty.
  • 36 1
 so.... can I put a coil on it?
  • 15 0
 Of course, grab some duct tape and tape it anywhere you want! Doubt it will change the riding characteristics though.
  • 1 0
 @Waldon83: I think it will be possible to build coil versions. But I'm not dwelling on it now because air is appropriate for the 140mm travel model, and the air-spring and linkage leverage profile have been designed in to complement each other.

First I have to get past the funding stage, then build the first production, and then I can think about longer and shorter travel models. If I don't get fully funded however, I won't have to think about any of this (the campaign was more than 50% funded @30 hours, so quite optimistic).

I've tested a strut with a big rubber coil-shock bottom-out cone installed, that could be installed as a tuning option, but I don't plan to include it for production as the progression resists bottoming very smoothly already.
  • 26 0
 What's old is new again... Boulder Gazell, 1991.. shock was in exact same place. Steel frame. 3 inch travel, elevated stay mono-pivot swingarm. It used motorcycle chain links as a swing link to insure the shock shaft didn't bind up by the swingarm's arc of rotation.

mombatbicycles.com/MOMBAT/BikeHistoryPages/Boulder.html
  • 4 0
 I remember lusting after that thing bitd. Glad I never got it. It likely rode terribly like every full sus from the early 90's.
  • 4 0
 I think Maverick cycles had a similar idea back in the day?
  • 6 0
 @m1dg3t: Mavericks were completely different animals. They used a proprietary shock design that formed part of the swingarm.

ep1.pinkbike.org/p4pb18931156/p4pb18931156.jpg
  • 2 0
 @IamZOSO:

I owned a flaming hot pink one (with matching hot pink Rockshox RS1 fork). It rode okay. Ridiculously heavy frames though (like 8 pounds for a medium).
  • 1 1
 @deeeight: In my defense, I did say similar not same LoL. As soon as I saw this Digit with integral mono shock I thought of the Maverick. If I would have read the OP I would've saw that they included a link for comparison reasons. Still working on the 1st coffee of the day, so putting the cart before the horse is not uncommon HaHa
  • 1 0
 balfa called they want their bike back Smile
www.balfa.wooyek.pl/balfa-belair.html
  • 2 0
 Was counting on you deeeight to dispense with mtb history! If history tells us anything, it's that proprietary shocks do not succeed. Remember the pull shocks of the mid 2000s? But best of luck either way.
  • 1 0
 @m1dg3t: Maverick was my first thought too. I expected to read it in the article.
  • 2 0
 @jaame: These were all part of the inspiration. (Except the pull shock - I had one which failed frequently, was impossible to service, and for which seals weren't even standard o-ring sizes. It was great when it occasionally worked.)
  • 2 0
 @deeeight: Hot damn! the Boulder Bicycles November 1991 prototype on your link has got to be the Grim Doughnut of the early 90's! 787mm Top Tube, and 1300+mm wheel base... That thing is SICK!
  • 2 0
 @IamZOSO: My 93 Foes LTS road pretty damn good.
  • 1 0
 @matarratas: I wonder what bikes would be like today if that geo had caught on back then.
  • 1 0
 @ryguy79: The Kamikaze race bike actually wasn't unusual in its geometry at the time. A number of riders were doing one-off long wheelbase bikes for the Kamikaze DH race at Mammoth Mountain given the 60mph+ speeds being reached coming down the fire road from the top of the chairlifts up the main slope of the mountain where the race begins. The actual front reach is only slightly longer than the stock large size Gazelle frame (which matched a 23.25 inch top tube with a 6 inch stem extension). And its not the only bike that paired the ActionTec headshock steerer/crown affair to a set of telescoping suspension fork legs for longer travel. Ended up with a whopping 3 1/4 inches at the time. Now mind you only 2 years later you could get production telescoping leg forks over 3 inches of travel for any bike.The headtube angle on that Kamikaze Gazelle though was still about 70 degrees.
  • 24 3
 The Resistance Insolent made sense since its a linkage driven single pivot. The single pivot point ensures the wheel path is always radial. The load applied on the shock is in the axial direction. But with the configuration, since it has a lower link and a solid rear triangle, the wheel path is guided by the lower link and the shocks travel. That shock will be seeing load in the axial and radial direction. those bushings are going to wear out like crazy and on larger hits its possible to bind.
  • 8 2
 Bind or wear more than a fork, which has to handle _all_ of the front wheel path guiding with those same type of bushings?

Also don't forget that the rear wheel has leverage over the shock in the range to 2-3x, so there could be at least twice the friction at the shock before it's as noticeable at the wheels.
  • 3 2
 @justinfoil: But a fork sees impact loads that are almost directly aligned with the movement. This has to do all the heavy lifting of guiding the rear suspension movement.
  • 1 1
 Two small bone links could help but then you end up with a more complex bike.
  • 3 0
 @G-Sport: Directly aligned with the movement? Not really. A fork takes tons of frontal impacts, side forces from turning and leaning, torsion from turning, vertical impacts from landing flat, etc. Otherwise, why would the Fox 40, Fox 38, Zeb, Totem, and every other big tubed fork be a thing? If the fork only handled loads aligned with movement then we should all be fine on 20mm stanchions.

"This" only has to do part of aligning the rear suspension. The lower links aren't like ball joints or something, they're 1 degree of freedom, so they will also guide the movement.
  • 2 0
 @justinfoil: Imagine sitting on the bike. Your weight is straight down, the pivots at the bottom contribute zero to preventing the rear triangle moving up. So ALL that vertical load is on the fork bushings.
Yes forks take other loads, momentarily, and when they do their performance drops proportionately. But the lions share of the weight of the rider and normal head on bumps, is supported by the spring and damper.
I'm not saying that the bushings cant handle this well, they are down hill from the shock so can probably be really well lubricated compared to a fork, but it definitely isn't a given that they will cope well. Would need to do the calculations.
  • 4 0
 Even in scenarios where you'd think loads should only be only axial, there will more often than not be are some side loads too, that's how clevis mount shocks breack shock shafts.

Accomodating these considerations is what engineering is all about, and why struts use real bushings (shock manufacturers often call the glide-rings "bushings", but that's quite a stretch IMO, they're only really there to prevent the seals from burping out of place if the piston moves eccentrically in it's bore, or from heving metal-on-metal if the eccentric movement is too big. There are glide-rings in the Integer strut for these purposes too, but their supported by long, large, hard built-for-purpose bushings).

I've not done their math, but I imagine the side loading on a Maverick Monolink was much higher than in the Analog system. Those struts have typically outlasted the chassis parts, and are also servicable in the home shop. The side loads must be horrific in a Chapman or MacPherson on a car.
  • 17 0
 Where will it all end?

Shock in the top tube
Dropper post & cable in the seat tube
Mulitool in the head tube
Tubeless kit in the handlebars
Doughnuts in the downtube Swat box,
A motor in the bottom bracket and battery in the downtube
All that's left are the seat stays & chain stays and even they can have internal cable routing in there., but I'm sure we could fit something else in-
lift a little flap in the seat stay and have a trash port so you leave the trails pristine?
Hermetically sealed chamber for smuggling drugs, cheese or dinosaur embryos across the border?

We live in a brave new world of bikes with thinks stuffed inside the tubes
  • 8 0
 It has to be for cheese embryos.
  • 11 0
 We're not quite in that brave new world yet. You still have to choose between doughnuts OR a battery in the down tube.
  • 2 0
 I've started picking up 1 piece of trash per ride on my home trails, I could use a trash port. I don't want somebody's gross Bud Light can in my jersey.
  • 3 0
 Everyone knows dinosaur embryos do best in a miniature cryo-chamber hidden inside a shaving cream can. Menthol being the best shaving cream variety to hide it in, of course.
  • 4 0
 @runbrung: Just bring some biodegradable dog waste bags. Scoop the trash, tie it off, keep your jersey pocket clean. I have them anyway for my dog (though he almost always makes it easy and shits before we leave the parking lot. He knows what's coming, gotta get light!), but I end up using them just to carrying out someone else's trash on a solid third of my rides
  • 2 0
 @excavator666: Are you saying Mozzarella is sold in amneotic fluid? That's messed up.
  • 1 0
 Sign me up for dino-storage
  • 1 0
 I need an aftermarket CO2 or something to help cram the goo from those Gu packets into my tires.
  • 1 0
 Anyone remember the name of the company doing aftermarket swingarms for the Santa Cruz Bullit back in the day? Had a removable smoking piece in one of the seatstays.
  • 18 0
 Something about the second bike looks inappropriate to me.
  • 26 0
 What's wrong with a rigid shaft with minimal friction?
  • 7 3
 @mi-bike: your lady would be better suited to answer that question Wink
  • 3 0
 I think there are too many innovations on it (belt drive, gear box). Its probably best when a bike frame builder applies one incremental improvement at a time.
  • 3 0
 @mi-bike: that's what she said Smile
  • 15 2
 This really isn't a bad structural solution, and could be the way of the future for every mtb suspension application. Probably what I'd use if I ruled my own communist little country.
  • 16 1
 All the other trail bikes are gonna be shocked when they see this thing strutting around.
  • 3 0
 they're going to have to slide out of the way
  • 20 10
 5 quid says that will destroy the shock shaft over time due to the forward end of the shock being pinned in place. The design might give a perfectly linear path into the frame for the rear shock pivot, but there's got to be some flex in there...
  • 41 3
 The damper shafts in your forks don't get destroyed because the fork legs and bushings keep everything lined up and can take immense force compared with the glide rings inside a conventional rear shock. It's the same principle.
  • 1 1
 @DirtBagTim: do you have to pull the strut go adjust/check sir pressure?
  • 2 0
 @RusMan: looks like the valve extends out of the top tube about midway down
  • 2 0
 Any link to the things you said? I’m interested about the frame and its reliabilities.
  • 6 0
 @gotohe11carolina: Yes, there's a valve under the TT. It will be shorter for production and the damper dials will be right next to it. You can just about see them here: www.pinkbike.com/photo/21203082
  • 1 0
 ?? Both ends are “pinned” in place..... Take another look at the design, bud.
  • 2 0
 @DirtBagTim: Awesome! I really like the low leverage ratio on this one as a big dude!
  • 8 1
 It's quite a good design.

The 'loading' of the shock that some are putting forward? It's absolutely Sweet FA compared to a fork.

By comparison to 'normal' shocks, it has quite a large oil capacity. Many here would be shocked (bad pun) at how little oil is in the vast majority of shock absorbers on bicycles.

It appears to have / easily have Big, Serious Bearings at all pivot points. Those and the triangulated swingarm, and a big , boofy 'Dog Bone' make for , potentially, a very stiff structure, which combined with those Big, presumably High quality bearings (and bushings in the shock) the shock shaft and body will have little adverse loading

And, it has a Lot of potential with the 'dog bones' pivot placements and length. A Lot.

It's quite similar to some drawings I did a long, long time ago.

Oh , and for those eyeing up the length of the shock, in comparison to the gap between the seat post and top tube, look to the plate / port on the headtube. A mate of mine was trying to work out the various ways to break down the shock for rearward removal, until I suggested he enlarge the head tube area on his screen. But, he was looking at it all on a phone screen, so.............
  • 1 2
 Doesn't look laterally stiff at all to me... minimum width at the pivot locations.
  • 1 0
 Thanks, I couldn't see how the strut was supposed to come out either.
  • 7 0
 Really interesting idea and my initial scepticism about binding and longevity was nicely assuaged by Tim's responses. Shame it's only mullet, it looks like it would make a great 29er.
  • 3 0
 My thoughts too. a 125mm 29er with a 140 fork would be a sweet rig.
  • 6 0
 Neat design. I like the clean lines. Hopefully, the shock seals and internal wear parts are similar to one of the big-brand forks as that should keep long-term maintenance costs reasonable.

The Kickstarter price for a frame is $2750, which is competitive in today's market.

Good luck to Tim. Hopefully it'll get funded. If I were in the market for a new bike I'd consider it.
  • 5 0
 Alloy and made in the USA? Excellent. Proprietary shock? A little apprehension but it could be awesome.
ESTA and rear center numbers are the same across the size range. Less cool.
Made in the USA means there's a possiblity for a custom program. I hope they consider this as there are very few FS custom shops.
  • 6 0
 Looks like STA=ESTA due to the straight seat tube, so seat tube angle should remain 75 no matter what your saddle height is. That helps.
  • 1 2
 @jwellford: STA should be steeper in the big sizes because XL+ people have longer legs have taller saddle heights. Longer chainstays for the bigger sizes help maintain the same balance as riders enjoy in M and L sizes.
  • 8 1
 Great looking frame. Only available in mullet might be a deterrent for some potential buyers.
  • 3 4
 Just as only available in 29 might be a deterrent, or only 27. Non-issue.
  • 4 0
 That pic with the scales is so disingenuous. It doesn't account for the extra material needed to support the bushings and to handle the loads that the linkage previously handled. Yes, of course removing linkages could potentially reduce weight, but that comparison of linkage to bushings is just stupid.
  • 5 0
 You are correct, it doesn't account for that. But it also doesn't account for the upper and lower pivot supports in the frames of the bikes the links came out of. With those elements in mind the weight saving will be bigger still. This shock is longer though, which might add a little weight back. My apologies if you felt mislead, that wasn't my intention. My intention was to visually explain how the system works when compared with existing bikes and where the advantages lie. The shown links on the scale were typical of a handful that I looked at, I weighed some which were lighter and some which were heavier but seemed willfully disingenuous.
  • 3 0
 How on earth do you remove the strut to service it? It must have got in there, so it must be removable, but there's a lot of gubbins in there that looks too long to get our without hitting the seat tube. Which brings up another question - how do you accommodate this in different frame sizes?

My immediate thought on seeing this was 'Boulder Starship' - a lot has changed since then. This looks light and clean, and if it works, you're onto a bit of a winner - best of luck!
  • 6 0
 reat triangle looks very similar to santacruz 5010/Bronson 1st gen
  • 4 2
 It really does look very similar! That's for the prototype. the production part will be aluminum welded here in SoCal, and it won't use the fine pitch threads.
  • 3 0
 @DirtBagTim: Good on the no fine pitch. Never understood all the fine pitch threads cut into aluminum parts, that was taught to me in my early days of being around a machine shop.
  • 3 0
 @insertfunusername: The problem wasn't entirely the fault of the fine thread pitch, it was that they were used to adjust the angular contact bearings like in a headset. This meant that the threads weren't under proper tension. Inadequate tension could allow play and fretting between the shallow threaded interfaces, which causes them to wear away and eventually fail. Liberal application of Loctite from the factory helped to relieve this, but I think often it was not reapplied or left to cure during services. I guess they moved to deep groove bearings with a spacer between to allow higher tension and thus eliminate movement in these threads.
  • 2 0
 @DirtBagTim: Didn't realize that you were talking specifically about the rear triangle threading. As a former SC dealership mechanic that was a problem for sure, glad to see that you are thinking it through.
  • 4 0
 @insertfunusername: Production parts will use fullly replaceable hardware, no threading in the frame parts, and the bearings push onto the small parts which you can put on the bench or in a vise.
  • 2 0
 @DirtBagTim: That's the way to do it for sure. I always cringed when I'd be doing a pivot bearing replacement on the bikes with bearings stuffed into all the frame parts instead of in the links. You can't get away from it on some designs, but if you can do it that way, you should do it that way.

Looks like a very interesting bike in general. I feel like it is a good example of Colin Chapman's mantra of, "Simplify, then add lightness." I hope to see you get to market soon.
  • 1 0
 @insertfunusername: I tried to shoehorn a Chapman Strut reference into my explanations of the linkage - I think it helped inspire my way of thinking, but too many wheels to be relevant.
  • 1 0
 @DirtBagTim: I think that the reference works, it has similarities to a short link Chapman strut, but having the pivot at the base of the shock does make it at least a bit different. Short link, multi link with the top link having a length of zero... Is the other half of the IC drawing a line down the center of the shock/top tube?
  • 2 0
 Super clean looking for sure. It's like the supercaliber but with worse parts availability. It's all going to come down to how that shock holds up and how adjustable it is, since there's not much for leverage curve on the frame itself.
  • 3 1
 Another Kickstarter hey? Companies like Specialized and Trek were notorious for proprietary suspension. Some of which was actually not bad. The issue however came across when it was time to service the suspension, or there was a need for an update. Let's say on the other hand, you blow up the rear shock, now your waiting to get it serviced or replaced. A company that needs public funding to make a design with an inevitable point of failure concerns me in the sense where not if, but when that rear shock is done, how long would a rider be sidelined? Would the company stay afloat long enough to be able to provide service and parts several years down the road?
Listen, I'm stoked that people wanna create these cool ideas. I would love to see these small companies succeed though. Find a way to use current off the shelf suspension, and you would have my vote. As of now, that's an investment that I personally don't feel I would get any return on.
  • 2 0
 putting tim lane's response to the questions about proprietery specs behind a paywall is such an old timeworn pre1990 lame-ass approach to aquire subscriptions. that alone kills any desire for me to want to know more. who's coaching this guy anyway?
  • 2 0
 I like it a lot. Lower LR and larger shock body are a huge improvement over the current packaging compromised shocks we are using now. I love the simple elegant look as well. For all the concern about a proprietary shock, based on his descriptions it uses seals and tools available at the hardware store, and the suspension shims are also existing parts that can be sourced from any number of suppliers. That means you're really only reliant on some small machined parts, shafts and such. So still proprietary but more serviceable than you might think at first.

If my funds weren't so tight right now and I had a use for a 140mm bike I'd give it a shot.
Tim do you think this could be adapted to a 160 or even 170 design ?

I took part in the Tantrum kickstarted and while my frame was about 8 months behind schedule everything worked out well. Thie bike was interesting and in many ways did what it said it would. I ended up moving on due to weight and some other drawbacks but overall it was a positive experience, although the company did fade away and not make anymore bikes, so there is of course something to the properitary problems argument.
  • 2 0
 Looks promising, but I wouldn't buy it in it's current form. 85% antisquat at sag? too low. Falling antisquat curve? That's why I ditched Horst link. Are the shock bushings replaceable? No high speed compression adjust on the rear shock. That's the most important adjustment! Yes, I am picky, but this is a $3000 product and this is how I spend my leisure time so I want good equipment.

The important thing about knocking another product off the throne is to excel in ONE important metric. This one isn't that cheap, isn't that light, isn't that stiff, and the rear end isn't going to be as good as current offerings.

I can see a good use for the design in cross country or marathon. A 1500g carbon frame including shock with remote lockout would be a killer. Two water bottles, superior weight, who cares about stiffness.
  • 1 0
 I was also looking at anti-squat graph. Seems a bit too low.
  • 2 0
 @bek998: There's really not enough info on that anti-squat graph to draw any meaningful conclusions from it. In addition to the axle path, anti-squat is dependent on gear combo, CG height, and wheelbase. I'm sure Tim could have manipulated the graph to show 100% anti-squat at sag, but that would just be for one gear - still meaningless. The important takeaway is the slope of the curve, which shows that anti-squat falls as the bike goes into its travel. It means that getting good anti-squat performance will be dependent on setting sag properly (might be what JohanG is getting at), but it also means that the total chain growth from top-out to bottom-out (and therefore pedal kickback) is reduced compared to a single pivot with a flat anti-squat curve.
  • 1 0
 @bcmanucd: My first iterations of the design had about 100% AS all through the travel. However focusing too hard on any one aspect of any design is often detrimental to others, (regarding kinematics, chain growth was particularly horrible, sometimes packaging like water bottle or seat tube placement or weld accessibility gets affected). Ultimately it wasn't even worth cutting metal on the designs which were too focused on one aspect.

Making a well rounded package was better for what I wanted from a bike, my riding style and terrain, and apparently for all the test editors who've ridden the bike so far. All design is a bowl of soup, too salty for some isn't salty enough others - this is a terrible analogy, I don't like soup.
  • 2 0
 Great looking bike and good! Wish I could test one! Honestly great job! Very clean!
Just a thought :
Have you thought of Cannondale's Lefty fork technology when building a shock into the frame like this? It may result in a stiffer build, more compact internals and runs on needle bearings so its butter smooth.
Again mate, great job! All the best!
  • 1 0
 I built a prototype with needle bearings. It didn’t bring any benefits, it was overly complex, heavy and they took up space which is better used in the final version by more air and oil.
It’s a very stiff feeling frame as is.
  • 4 1
 Humm.. The shock body look like 3 times longer than the space between the top tube and the seat tube. What do you do if the o-ring of the shock head fail ?
  • 1 0
 Good question. Could work if the top tube itself was the canister body, but then again, how do you machine the inside after welding?
  • 3 0
 how do you take apart the shock from inside the frame? there isn't a collision with the seat-tube? or do the shock disassemble in a special way?
  • 6 0
 My guess is to release all air pressure and collapse the shock tube. Once you do that and disconnect it from the rear triangle it should slide out? I could be wrong Smile
  • 2 0
 @m1dg3t: yep I also see no other solution, other than a new frame/shock Big Grin
  • 3 2
 How exactly can this be worked on in a shop? As is, how exactly do you get the sliding part of the strut out with the seat tube in the way? There looks to be like 4 to 6 inches of strut inside the frame, but only millimeters between the outer end of the strut and the seat tube, so there would be no way to pull the strut out of this frame.

Kinda looks like it was welded up after the strut was installed...
  • 2 0
 head tube exit (edited for spelling)
  • 1 1
 @Spencermon: wow, didn't even notice the little cover up there. but now I'm worried about head tube strength: don't want the upper headset bearing to blow through the front of the head tube on a direct frontal impact to the front wheel. Doesn't look like there is a whole ton of material around that upper headset area.
  • 1 0
 Love to see someone coming in with a different approach! My only reservation is not being able to fit an aftermarket shock, but if this takes off other suspension brands may come to the table. Bit of a chicken / egg situation, so good on ya for making the first move!
  • 1 0
 Really love the look of the frame. That said, I do not think using that linkage between the BB and the swingarm is a clever choice. It means all vertical forces from the rear axle go into that shock stanchion tube, creating bending and friction. A layout like Resistance isolates a lot more forces from the shock.
  • 1 0
 Interesting concept, but I'm wondering something. The distance between the seat tube and the entry to the shock's mounting location in the top tube is clearly shorter than the shock itself. How can it be removed? Or how was it put in there in the first place? Is the shock actually installed in multiple pieces?
  • 1 0
 I wish him the best and hope he can find enough early adopters to be successful with this. As mentioned in the article that wasn't behind the Outside paywall, I personally won't buy a bike with proprietary parts that aren't easily sourced. Even if what I ride has more pivots, I already know I can find and replace them with little or no issue. Also, and this is a personal nit, give me the option of externally run brake lines at the very least or GTFO.
  • 1 0
 Love to see innovation on aluminum frames - a bike like this can be roughly the same weight as a carbon frame, but cheaper and with fewer environmental implications is appealing.

Whatever happened with that story about the university that made filler rod that allowed the welding of 7075 alloys?
  • 3 0
 I had a Boulders Bicycle Gazelle back in 91/92 that had a very similar design.
  • 2 0
 I wish it was 29/29 front and rear, would get behind it as it seems like a super fun trail bike.. Mullet isn't great for that application on my local terrain
  • 1 0
 I had a Macpherson strut frame back in the day. Put nasty side loads on the shock and wears out fast. While a linkage adds weight, it also takes the side load off the shock. The design is doomed IMO
  • 1 0
 so, Storia and Nikolai puts shocks on angular bearings, here is the opposite;

I like the idea of integration seatpost and shock into the frame as such;

It needs gearbox integration
  • 3 0
 Honestly, I'd rip on that.
  • 1 0
 Reminds me of my old Balfa Bel Air, which was a great bike. The in line shock was a normal shock in the top tube though,not proprietary such as this
  • 4 0
 Balfa didn't do it first either. These sorts of shock in the frame tube designs all trace back to some rear suspension bikes in the late 1800s but in mountain bikes specifically with the shock inside the top tube, Boulder bikes out of Colorado did it first thirty years ago.

mombatbicycles.com/MOMBAT/BikeHistoryPages/Boulder.html
  • 1 0
 @deeeight: The Monolith is also from around that time, 91/92.
www.youtube.com/watch?v=d76PFjH1SJA
  • 2 0
 @DavidGuerra: Monolith came about four years later. Spencer Owyang later became the product manager at Specialized Bicycles when sales of Monoliths didn't exactly excite his bankroll. I still have the issue of MBA it was debuted in (which reminds me I should get around to selling my collection of MBAs). Incidently the suspension fork was also designed by Spencer and was called the Rebound.
  • 2 0
 Incidently the alloy of filler rod used in part 3 of the video series, 5356 is as strong in its natural untreated 0 state as 6061 is after being heat treated and artificial aged to the T6 temper. Heat-treated 5356 is even stronger at that point and that is why you usually don't see properly welded aluminum frames failing at the weld zone in overload tensile strength failures. The tubing itself is weaker and where the bike frame buckles/bends/snaps apart.
  • 3 0
 meh, Resistance to say "looks like a session"
  • 2 2
 "Kickstarter *BIKE product campaigns often aren't that promising..."

Fixed it for ya. Lots of neat stuff comes through Kickstarter, but the bike stuff on there is usually hot garbage.
  • 2 0
 example?
  • 3 0
 @stumphumper92: there are quite a few, but this example and write-up was appalling.

cyclingtips.com/2019/06/what-happened-to-speedx

This outfit actually produced something (which was hot garbage)... more than other KS initiatives did.
  • 2 0
 @twozerosix: That was a pretty interesting read!
  • 3 0
 Brb, going to perform an air can service on my frame.
  • 3 1
 Well, I’ve been looking for a 140mm bike and this is intriguing… funded!
  • 2 0
 I would love to see a XXL size with 530mm reach and 130mm head tube for the tallest among us. Thank you.
  • 2 0
 That is possible. Check out the comment below the geo chart on the Kickstarter page.
  • 1 0
 And longer chainstays too.
  • 3 0
 The most interesting part of this article is the Resistance Insolent
  • 1 2
 This is not a good design for anytjing other than a commuter or lightweight xc bike... There is a reason we want to eventually change from telescopic forks to linkage ones... The stanchion will create huge friction, the kinematic properties are not very tuneable and in this design it's air with a low leverage ratio. It's like he has took everything you shouldn't do and do it for the sake of weight and simplicity. For those saying bigger stanchions don't make noticeably more friction, push down on an air ZEB compared to a cheap air recon fork with thin stanchions...the ZEB may be stiffer and have a better air spring and damper, but it also has a fairly noticeable amount more stiction.
  • 7 0
 Fair point, but comparing to a fork——- with only one stanchion, stiction forces are cut by half. Then, with a 2:1 leverage ratio, they are cut in half again. Then, the fact that weight distribution usually means there’s 50% more weight on the rear tire means that the influence of those stiction forces on this suspension are a much much less prevalent factor, than on your fork.
  • 1 0
 @AckshunW: The leverage ratio refers to a linear force compressing on the shock - there's no side loading whatsoever. Leverage ratio has absolutely nothing to do with it. You could compare it to a fork by viewing the whole lenght of the seatstays as an extension of the fork stanction (or in this case, the shock's "stanction"), in which case the leverage from the wheel axle would be (and is) substantially higher on the shock seals, in comparison with the leverage from the front wheel on a fork's seals. However - and crucially - the wheel axle is also connected to the BB via the chainstays and link. A fork doesn't have this. And not only that, there is also the strut from the shock mount to the BB link. So the side load ends up being extremely reduced in comparison to that of a suspension fork, in which there are no supports of any kind. A fork's seals are really supporting 100% of all lateral and frontal loads, and even some of the vertical ones.
  • 2 0
 @DavidGuerra:

Bringing leverage ratio into the discussion was regarding “stiction” only ——- as in:

When your fork compresses 4”, you’re overcoming seal drag/ stiction on 2 seals traveling 4” each.

When this bike’s rear suspension compresses 4”, you’re overcoming the drag of 1 seal traveling 2”
  • 1 0
 @AckshunW: Yes. I think I read your comment completely backward!
  • 2 0
 It's refreshing to see such a CLEAN simple design. Looks almost like a hardtail. PB needs to review this thing!
  • 2 0
 Saw one of these at the Chattanooga airport in June and was wondering what it was.
  • 2 0
 So I see someone brought back the Boulder Bikes Starship/Defiant....history repeats itself...
  • 1 0
 The Resistance Insolent does look like it's shafting itself when it's working through the travel lol. Still looks nice and clean!
  • 1 0
 Interesting design but I'm not seeing the problem this solution is solving. Put the shock in the frame so I can fit more bottles?
  • 3 1
 Lots of side load on the shock...
  • 3 1
 Same with a fork, which this bears more resemblance to than a typical linkage driven shock.
  • 4 2
 Same order of magnitude as what's on a fork's tube.
  • 2 0
 relying on the rear shock to help guide the wheel path. huge axial loads.
  • 3 0
 could be solved with another swing link coming down from the seat mast to the shock mount?
  • 4 2
 From which fork legs also suffer, but here's it's not as bad.
  • 1 2
 @faul: Twice as much, 2:1 leverage ratio vs a fork which is 1:1
  • 2 0
 @EdSawyer:

Sure, forces could be higher than a fork. Or maybe less—- Leverage ratio does not come into this question at all.
  • 3 1
 @EdSawyer: LR describes the relationship between axial forces at shock and vertical forces at wheel. It doesn't help to know what happen in term of radial loads.
As the lower link is pointing more or less toward wheel contact point (and obviously the IC), it doesn't hold much in term of vertical forces, so the vertical forces at rear wheels are more or less directly transmitted as radial loads on the shock.
The horizontal fore/aft forces will be more or less transmitted in line with the shock, with or without leverage from the lower link. And the horizontal lateral forces will be held by both lower link and shock, depending on their relative stiffness.

A fork's leg mainly sees fore/aft forces, but with leverage, but they are two, so it's more or less the same order of magnitude. And well, a factor 2 would still be the same order of magnitude.
  • 2 0
 Dinging your top tube could get a whole lot more expensive....
  • 2 0
 Beautifully simple looking. Love it.
  • 2 0
 Finally a frame that will eat shock bushings faster than a trunion mount!
  • 2 0
 If it wasn’t a mullet I’d be interested…
  • 2 0
 Digit with Analog design?
  • 1 0
 @DirtBagTim I'm curious about one thing: how to completely remove shock from the frame?
  • 1 0
 If the shock is so long, doesn't top tube bending affects its performance while heavy using?
  • 1 0
 I will never again invest a single EUR in a frame with a non-standard shock. NO GO!!!
  • 2 0
 Hmmmmmm
  • 3 3
 Love the comments about loads, yet no one questions the fork on the front of their bikes.
  • 1 0
 That's because a fork has 1) two legs to distribute the force, and 2) it doesn't then double the loads with a 2:1 actuation ratio, to result in a 400% increase in load for the same style of fork bushings.

Also, if your Fox/RS has short-lived internals, you can curse them out and rely on them still being there to buy overpriced parts from. If you bought a no-name novel fork that got started on Kickstarter 3 days ago, and it turns out to have the lifetime of a junebug... that's all you.

Which situation between the two does this seem like to you?
  • 2 0
 @dtew: well, considering it's already been indicated that the shock is using off the shelf parts and the chance of breaking the actual hard parts is slim- don't think there is much to worry about.
  • 3 1
 no thanks
  • 1 1
 Is the design compatible with carbon frames? Is a sub-20 lb trail bike in our future?
  • 1 0
 Looking great! Hope it's not all about fashion over function.
  • 1 0
 You know those people who swallow swords... just because they can....
  • 1 0
 is that a rear triangle off a Santa Cruz?
  • 1 0
 Yeah I was thinking the same thing. Looks great though.
  • 2 0
 Tallboy V2 rear end!
  • 3 0
 Might be a bronson v1 rear end since 27.5
  • 1 0
 I LIKE, this... =] PS: What about Effigear gearbox versions though? =P
  • 1 0
 Looks like the old commencal meta
  • 1 0
 Looks sweet, Boulder Gazelle anyone?
  • 1 0
 So retro, it has IS Brake mounts!
  • 3 0
 Haha. It’ll be post mount in production according to the kickstarter page
  • 2 0
 Boulder Bikes did it.
  • 1 0
 Why the same chainstay length across all sizes? Is it a cost factor?
  • 1 1
 Isn’t the top tube structural though? That offset to the seat tube is creating a shear point in my mind.
  • 2 0
 DONT SCRATCH THE KASHIMA
  • 1 0
 where's the negative air spring in the rear shock?
  • 1 0
 Cool
  • 1 0
 Cool but super pass

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