i-track Suspension Is Going All-In On The Quest For Kinematically Perfect Suspension

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There are essentially two ideas in bicycle rear suspension right now, and that is designing the suspension to be kinematically correct and using a wide-open shock, or designing a suspension that is simpler or lighter, and uses a shock with valving, sensors or other methods of controlling the ride. For instance, Specialized with their Brain shocks, Trek with DCRV, Cannondale’s DYAD, and even electronically controlled shocks introduce the technology into the shock to control the ride, whereas DW-Link, VPP and Split Pivot work to keep the kinematics correct in the chassis, and then use a simpler shock.

Sometimes we see each of these ideas go to the extremes. Most typical consumer goods are a balance of manufacturability, appearance, performance and cost, and bicycles are no different. Lapierre’s electronic suspension takes shock control to a new level, and i-track appears to be the company that is taking chassis kinematics to that far end of the spectrum.

Check out the complicated, yet brilliantly engineered bikes, and their process, after the break…

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One of the primary things that suspension designers talk about is anti-squat. Also known as anti-bob, it is a trait of the suspension to resist compression or extension as the mass transfers rearward during acceleration. It is not just a simple equation, as it changes throughout every bike as the overall frame geometry changes, since it involves series of lines through the drivetrain, suspension pivots, tire contact patches and center of mass of the rider, and then all the corresponding intersection points of those lines. The challenge of a suspension designer is making all of those lines and intersection points end up where you want them, but also make the bike look like a bike, so typically, there is a balance in there of the design and the appearance, as well as how the bike will work.

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i-track seems to be working through their design process publically, which is pretty cool to see the versions as they work on their design. Interestingly, i-track seems to be focused on achieving some very specific kinematic traits, and taking the more difficult engineering way to get there, using rollers and guides that move with the suspension through it’s travel. This allows them to continue to alter one of the forces that affect anti-squat, which is the line of force that the chain torque follows. Other companies in the past have used rollers to change the angle in which the chain pulls on the suspension, but i-track is actually mounting this roller to a moving suspension part such as the swingarm or linkage, and it is actually moving throughout the travel of the bike.

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i-track has made these first three prototypes from steel, in their shed in Australia. They don’t appear to be ready for production, and in fact they say they are going to keep prototyping, and are looking for a manufacturer that may want to use their design, instead of making it themselves.

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The guys at i-track even put all of the suspension rate curves and anti-squat curves of each prototype on their website. It is really interesting to peruse through and see the drastic differences in anti-squat that can be made in bikes that do not look too terribly different. This is where a lot of suspension designers try to start to protect their product, as its easy to make a bike “look” like another, but it may not ride anything like it. Some of the smarter suspension designers have not protected their actual design, but have protected specific methods to get to specific anti-squat lines.

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What do you think? Is there a proper balance of working with existing parts and drivetrains, and making sacrifices to the suspension design? Or should suspension designers go to the extremes to make the suspension work, regardless of the special parts or complexity?  Let us know in the comments!

www.i-tracksuspension.com

 

 

 

 

 

 

 

Comments

26 thoughts on “i-track Suspension Is Going All-In On The Quest For Kinematically Perfect Suspension

  1. Why should I buy a Model T when I have two perfectly good horses? Consumers don’t want these new fangled horseless carriages, it’s just the automobile industry trying to ram their products down our throat by making horses obsolete.

    I don’t want to go back to 1″ steerers, cantilever brakes, 8 speed shifting, or anything else that’s been burned at the altar of progress. If it’s better, bring it. The same people complaining today are the one’s buying it tomorrow when the price comes down.

  2. “one of the forces that affect anti-squat, which is the line of force that the chain torque follows”
    So if you are using a derailleur the line move when you change the speed !
    You have to use a single speed or a gearbox.

  3. Make the suspension as complicated and with as many parts as possible if you want it to be attractive to large companies. Like car manufacturers ,they are probably not interested in engines that do more with less , the idea is to have lots of parts to wear out and replace so they can keep the circle of surrounding businesses growing and profitable . How bout a brain for each different pivot points with a dw link stuck somewhere near a vpp ,oh and stick a couple of proprietary springs in that require some special tools to remove and install ,yeah now you got something they’ll want .

  4. Moving idlers aren’t entirely new, but that’s by far the neatest implementation I’ve seen. Looking at those bikes I wonder if they’ve been talking to Luis Arraiz (formerly of K-9), looks like similar sorts of ideas going on.
    .
    Best of luck to them, if it works someone will buy it. Although having said that, I have always been of the two bearings, a swing arm and send the shock to Avalanche train of thought.

  5. The complexity of this design, and others similarly complex, needs to be put in the proper context. Few people would argue about the usefulness of modern computers or smartphones, regardless of how complex they get. Once the design is ubiquitous, complexity doesn’t matter; it’s accepted as functional technology, and people cease to be intimidated by it.

    The transparency of their process is rare, and I applaud them for it. Iterating through the different designs within full view of the public leaves no doubt as to who is inventing the technology, which may or may not be intentional. Regardless, it’s a notable achievement.

  6. The concept is ingenious. The idler pulley adds a whole new dimension of tuneability to the suspension independent of the shock currently not found on any MTB suspension designs… and allows the use of a high pivot for rearward axle path. The result is supleness, quick response and plushness like you’ve never experienced before. I sure hope one of the larger manufacturers open to new concepts will jump on board with I-Track.

  7. Having been seduced by marketing-ese previously, it is refreshing to see actual evidence of function in the form of reproducable graphs, and understand the reasons behind the design decisions made.

  8. Balfa, Brooklyn Machine Works…been there; done that. Lotsa extra complication for a ride that is good, but not vastly superior to it’s peers.

  9. The advantage of this approach is that you can have a very rearward axle path which provides superior bump absorption and allows for long travel without long chain stays. In addition, you can have very high anti-squat values without high pedal feedback. The downside is the extra drivetrain losses and the need to use a 1x drivetrain. If you’re not careful you can have bad rear brake performance as well.

    Personally, I think this is the way to go but the chainline gadgets may limit the marketing appeal. With wide range 1x gearing the worst downside is no longer a big problem.

  10. All suspension design is a compromise between different factors. Some people put extra emphasis on different aspects. What I like about the i-track idea is that the pivot location is not dependent on the “normal” chainline dictating a sub-optimal pivot location.

    Also, to answer sf, yes the chain torque force line does change depending on which gear you’re in. Usually this does not make a whole deal of difference with the rear cogs but can make a huge difference with big ring to granny ring changes.

    And hellbelly- Balfa and BMW were different. BMW was a jackshaft concentric pivot and Balfa (whilst similar) didn’t use the idler to significantly alter the chain torque force line.

    Finally, after the experience with my Zerode I now think that a bit of Brake Squat is no bad thing. It tends to keep the bike more level under hard braking into a corner.

  11. “Trek with DCRV, Cannondale’s DYAD, and even electronically controlled shocks introduce the technology into the shock to control the ride, whereas DW-Link, VPP and Split Pivot work to keep the kinematics correct in the chassis, and then use a simpler shock.”

    This statement contradicts itself. Trek and SplitPivot are the same thing.

    I am of the camp that thinks correct Kinematics are where you start and this allows a finer less drastic jumps in tune of the shock making the entire system better for the average rider.
    Yeti and Dave Weigle are the masters of this.

  12. chasejj –

    I do not think that is contradictory, because it is extreme oversimplification to say that Split Pivot and Trek’s ABP are the same thing. There has been lawsuits around the idea that Trek’s ABP infringes on certain aspects of the Split Pivot patent, and they appear the same, but that does not mean they are the same thing. The primary difference here is that Split Pivot bikes are designed to run with very low-tune shocks, and just that, where as Trek has said that DCRV is needed to make the bike ride correctly, and then furthermore, the Penske shock makes the bike ride better, so Trek is relying on whiz-bang shocks to do the work, whereas Split Pivot is actually asking for the shock that does the least.

  13. I saw a guy riding something like this a year or two ago in NC, He was doing his best to angle the bike away so I could not see it. It looked like it would do the job of isolating pedal forces, but at what cost? Lots more chain and complicated routing. This ranks up there with the Alsop suspension beam or the Slingshot bike. DOA

  14. “Lots more chain and complicated routing.”

    Once you’ve dealt with a recumbent you won’t consider this either “lots more chain” or “complicated routing”. It’s not a big deal.

    This design only adds one pulley anyway. The return side pulley is just a tensioner and isn’t required in the design. The additional chain is meaningless. The cost of this is a slight amount of weight, a small loss in drivetrain efficiency, and a commitment to 1x gearing. People should stop making a big deal over what they don’t understand.

  15. Hmmm…. 13.8 kg / 30.4 lbs for the prototype AM bike, and that’s with steel front and real triangles. Not bad actually, not bad at all. Looks promising in the prototype stage at least.

    I wonder if it would be possible to package the links and idler in a smaller package with eccentric bearings, kind of like how Yeti does it.

  16. @Tim Krueger: thanks for a great write-up Tim!

    @Burnt Orange:
    Ghost uses a 4-bar axle path with a fixed idler. i.e. the idler is attached directly to the front triangle. With this setup, anti-squat decreases continuously through suspension travel (which makes for an unstable pedalling platform – like 90% of other bikes out there).
    I-track has the idler mounted on a separate member, so that it moves relative to the rear axle AND the bottom bracket. This allows the anti-squat curve to be tuned much more precisely, so that it can be made to increase throughout the pedalling zone (which makes for a stable pedalling platform).

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