One of the most common terms bandied about to describe a full suspension bike’s pedaling performance is “Anti-Squat”. Which means, for many riders, it’s a marketing term with no clear meaning, but obviously it must be good because everyone’s touting it. Right?

Mostly, yes. But like chocolate cake, too much of a good thing can be bad. To cut through the hype and explain what you need to know, we spoke with three engineers and designers from Niner Bikes (George Parry, Engineering Manager), Esker Cycles (Tim Krueger, Managing Partner) and Fezzari (Tyler Cloward, Director of Product Development). Here’s what they have to say, followed by our own take on why it matters and what you should look for…

BIKERUMOR: In simple terms, what is “Anti-Squat”?

KRUEGER: Anti squat is a trait of a suspension design that resists the compression of the suspension caused by mass transfer during acceleration.

CLOWARD: Anti-Squat is the force on a suspension system that is generated by the drivetrain. As you accelerate and the bike moves forward, the rider’s weight moves rearward causing the suspension to compress or squat. The biomechanics of pedaling (downward force of legs) also produce a downward force causing the suspension to compress or squat. As the chain is pulled forward by the pedaling motion, it creates a force on the suspension system opposite of the “squat” caused by the rider and weight transfer, and that’s why it’s called Anti-Squat.

new fezzari le sal peak carbon 29er enduro mountain bike has adjustable geometry to work with different tire and wheel sizes
The new Fezzari La Sal Peak uses Anti-Squat to maintain efficient pedaling performance on a Horst Link suspension.

BIKERUMOR: If you had to explain it more technically, is there anything you need to add to that description to help people understand the concept better? (as in, if a bike has “50%” anti-squat, what does that number mean?)

PARRY: Bicycle suspension designs typically use the chain tension resulting from pedaling loads to reduce the amount of force on the shock. Thus, reducing or eliminating the amount of suspension squat when force is applied to the pedals. This is directly related to chain tension. So, higher pedaling force, or chain tension, results in more anti squat.

CLOWARD: If a bike has 50% anti squat that means that the opposite force from the drivetrain is 50% of the squat force caused by the rider weight shift during acceleration. A bike with 50% anti-squat will have a fair amount of pedal-bob because there is only half of the opposite force on the suspension from the drivetrain compared to the downward force caused by the rider weight shift from acceleration. 100% anti-squat means that the force of the drivetrain on the suspension is equal to the opposite force caused by the weight shift. 150% means there is more force caused by the chain in the opposite direction of the squat caused by the weight transfer from acceleration. In this case, when pedaling, the bike will literally rise.

KRUEGER: The best thing to understand is the point of 100% anti-squat. That is what everyone is trying to achieve at the right point in time. 100% anti-squat is when mathematically, there is nothing causing the suspension to extend or compress under acceleration – it is literally the point of perfect neutrality amongst all the variables that can cause suspension movement from things other than bumps in the ground under acceleration. In the case of your question – 50% anti-squat is when there is a re-active force pushing back against the mass transfer under acceleration that is 50% of the force created by the mass transfer.

BIKERUMOR: What’s the benefit to the rider?

PARRY: When force is applied to the pedals there is a shift in the rider’s center of gravity. This can cause the suspension to compress and results in lost energy and pedal induce bob (suspension compressing and extending throughout the pedaling cycle). Anti-squat can eliminate this pedal induced sag, resulting in more energy being translated to forward movement and, ideally eliminating pedal induced bob.

KRUEGER: Squat would be the trait of a suspension bike to compress or “squat” under acceleration. Acceleration in a bike is not even because we have a very low rpm, high-torque motor with a lot of unbalanced mass (legs). This unbalance of the motor, along with the suspension compressing under acceleration would be referred to as “bob”, or the suspension constantly compressing and extending with the rythym of the pedaling cadence.

CLOWARD: (Basically, it’s) the pedaling platform of a bike.

2019 niner bikes prototype long travel trail enduro mountain bike with adjustable geometry
Smart pivot placement and a lot of engineering helps keep the bike from bobbing around while you’re pedaling.

BIKERUMOR: Is there a downside?

KRUEGER: Maybe – since anti-squat partially deals with chain torque as one of the forces involved in the overall situation, one of the ways to get to an ideal place is to have the chain pull the swingarm towards an extended position. The opposite of this movement though is when the swingarm compresses rapidly, it would be pulling on the chain. Some people call this “pedal kickback”, and it’s generally not a desired trait. So, you have to be careful about allowing too much extension of the chain through the swingarm travel so that the person riding the bike does not feel that potentially negative behaviour.

PARRY: There is no set equation for the right amount of anti-squat. All riders have different riding styles. So, some may prefer more anti squat where others prefer less. It’s up to the frame designer to find that sweet spot that will accommodate the greatest number of riders. Too much anti squat and the suspension will extend under pedal loads, too little anti squat and the frame will compress under pedaling loads.

CLOWARD: (Too much) can cause the suspension to stiffen up or even lock out while pedaling. Over rough, rocky terrain, a design with too much anti-squat turns your ground-hugging bike into a hardtail.

Esker Cycles uses the new Dave Weagle Orion Dynamics suspension platform to create better anti-squat and improve pedaling performance

BIKERUMOR: How much Anti-Squat do you want?

KRUEGER: In an ideal world – 100% exactly at all times you are pedaling, at any given travel. But that’s not possible. Due to that, most bikes that are competently designed have more than 100% in the initial travel, settle down to around 100% at the sag point, and then fall off from there. Really well designed bikes can manipulate the curve, how fast the rate changes, and even have multiple rates at different points in the travel, based on the desired traits of the type of bike.

CLOWARD: If you modify a suspension design to have the perfect anti-squat value, it will affect the other characteristics of the suspension system. How much anti-squat you want really depends on the bike’s intended purpose. On a DH bike, for example, you are more worried about downhill performance, so things like leverage ratio, anti-rise, pedal kickback, axle path and shock curve will usually take precedence over anti-squat. On an XC race bike, on the other hand, where pedaling efficiency is usually more of a priority, the anti-squat value usually takes precedence over the other riding characteristics.

BIKERUMOR: How do you design Anti-Squat into a frame?

CLOWARD: This can get very technical quickly. In very general terms anti-squat is designed in a frame by controlling the Instant Center, or IC, of the rear axle. The IC is the point around which the rear axle pivots during suspension compression. The IC can change location at every point of suspension compression. The IC is controlled by changing the position of the pivots. The art of suspension design is balancing all of the above mentioned forces, and additionally geometry, frame shapes, bottle cages, drivetrain, shock placement and specs – together to make the best riding bike for the intended purpose and use.

PARRY: Anti-squat is a result of the relationship between the chain force vector and pivot location. So, the simple answer is by manipulating the pivot location. However, there are many variables to consider here including leverage ratio, axle path, rate of chain growth and anti-rise.

KRUEGER: To truly answer this, without leaving parts out, or create arguments by glossing over certain areas – there is a 555 page book out there that is required reading to truly understand and then explain the answer to this question. There are also patented methods to doing this, which someone would need to be aware of. The short answer is math, geometry, and using them both to line up artificial points in space that affect how the bike reacts when mass (the human) shifts backward under acceleration, and how certain forces can have an effect on the frame. One mistake a lot of bike companies make is trying to design a bike first for a visual or manufacturing reason, and then hoping to make the suspension work. When designing a suspension bike, the very first thing that needs to be done is a proper layout of the suspension kinematics to ride properly, then visual and manufacturing concerns come in after.

prototype niner full suspension gravel bike now in carbon fiber will launch in 2019
Hard to believe, but we might be soon talking about Anti-Squat for gravel bikes, too!

BIKERUMOR: So, what’s the takeaway?

Getting a bike with the right Anti-Squat is both easy and hard. It’s easy because most brands nowadays are designing their bike to keep up with the competition. A bike without good Anti-Squat simply couldn’t keep up and you’d know about it pretty quick (thanks, social media!). But it’s hard because brands don’t usually publish a number, relying instead on nondescript terms like “good” to describe their Anti-Squat performance.

And, as our experts mentioned, different types of bikes and riders will need different things. Different terrain benefits from different designs, too. For example, if you have technical climbs that often have you off the saddle, then you probably want a little less so the rear wheel can track the terrain even though your pedaling hard. But that means you’re likely to get more pedal bob when hammering on the flat sections. By designing the Anti-Squat characteristics into the kinematics as opposed to relying on firm low-speed shock damping, you can get a suspension that’s supple when floating over the little stuff yet still resists pedal bob.

As always, we recommend you ride as many different bikes as you can before you buy. Look for demo schedules on your favorite brands websites, head to events like Interbike’s Northstar Free-Ride Festival or Outerbike to sample the smorgasbord, and see what feels right for you.

Stay tuned, next week we explore Anti-Rise…


The fun never ends. Stay tuned for a new post each week that explores one small suspension tech, tuning or product topic. Check out past posts here. Got a question you want answered? Email us. Want your brand or product featured? We can do that too.

 

29 COMMENTS

    • I would suspect the book is Tony Foale’s Motorcycle Handling and Chassis Design. It is a very well regarded book on the topic, and happens to be right around 555-560 pages, depending on which website you check.

  1. My 2018 S-Works epic squats and bobs so much I keep thinking Ive got a flat tire. The shock blew out in the first week and now they are sending me a second shock with a stiffer tune. I wish I knew before purchase date that they turned it into a comfort bike aimed at fat bankers vs a full blown XC race bike like it always was.

    I even rode a Trek Top Fuel the other day and that locked out still had heaps of bob. What is going on these days lol! Where are the old skool full lock out dual sus bikes gone??

    • Try a bike that doesn’t have a 4 bar rear suspension. It’s not about having a shock lockout, it’s about having a properly designed bike. Specialized has been using that same garbage rear end for years now.

    • Sounds like the OP needs to work on their technique – you don’t ride a full sus bike the same way you ride a hardtail, if you want it to be fast/efficient. Full lockout bikes have died because full lockout is slow and inefficient compared to active designs. If it wasn’t, we’d all still be riding hardtails.

    • Sounds like you need to set the Epic up correctly, with the correct air pressure and rebound setting with the brain set to the course it will be firmer than most, the Top Fuel locked out should have zero movement, sounds like a badly cabled lockout to me.

      Or maybe you are trolling, Durian? 😉

    • My experience with the 2018 Epic is different. I bought the aluminium version and immediately did my own version of the EVO model just before Specialized released their own. Upgraded fork to SID 120mm bigger tyres and a dropper. I run the Brain as soft as it goes and adjust the air pressure to suit. It is a fantastic trail bike now only limited to the size of the drops I can take with only 100mm of rear travel. I am thinking of removing the Brain and just running a standard shock.

      The 4 bar FSR is still a great system when used properly. The new Stumpjumper is an amazing trail bike and the rear end is as good a pedaling big travel bike as I have ridden. Very smooth and refined.

  2. A lot of the details above are either wrong or oversimplified. Kreuger’s first comment about mass transfer is not quite right. Also, Cloward calls AS a force, when it is clearly a percentage as documented in the rest of the article. 100% is not the optimum value of antisquat either (Kreuger). The AS calculation assumes constant acceleration and assumes that the rider mass is stationary (no chest heaving up and down or legs frantically flailing at 100 rpm). To counter act the actual movements of a cyclist, often times a number somewhat above 100% is optimum.

    I just wish folks didn’t oversimplify things. We are a smart audience and can handle the facts, even when they are complicated.

    • This website is “Bike RUMOR”… not “Bike ENGINEERING”, the purpose of this content is to simplify the information so MANY people can understand it. The quoted engineers get it…

    • Andrew – you are not wrong. When I was writing my replies to the questions, I had to write them 4 or 5 times because I got way too technical and had to be sure I kept on the subject of Anti-squat alone. Anti-squat is only one of many considerations that goes into a suspension design, a point I tried to make in my answer of how to design AS in a frame. I think the point of the article is to make it simple because Anti-squat is a term that gets thrown around, but is seldom quantified, kind of like “That bike feels balanced” or “The short chain stay makes the bike maneuverable”. What do those statements actually mean and how will they translate on the trail? I think Bike Rumor Tyler is doing really good job in his articles to help riders understand how some of these terms will translate into trail feel.

      Technically, Anti-squat is a measurement of a force and the equation to calculate it is a force over a force, so the force part cancels out and you get a percentage. Good catch on that one.

      The 100% number is the point where the force of the rider’s weight transfer from acceleration and the force from the drivetrain in the opposite direction are equal. This does not take into consideration the vertical movement of the rider’s legs or other rider inputs, as we both mention in our comments. It is up to the designer if, and how, they want to account for this (higher AS, lockouts, shock tune, etc.) and how accounting for these extra forces in the suspension caused by rider input will affect other characteristics like braking, leverage ratio, pedal kick-back, etc.

      I’d be more than happy to talk suspension theory and design with you anytime. Give me a call here at Fezzari.

      Tyler Cloward
      Fezzari Bicycles

      • I think one of the things Andrew was stating was that a percentage of anti-squat requires one to fix the mass and mass center of the rider, the acceleration, and the chain force required by the rider to get that acceleration in whatever gear (even for 1x as the vector still changes). None of these variables are actually fix from one rider to another for obvious reasons. Therefore, the entire concept of an “ideal” anti-squat, as defined for a bike sold to a multitude of people, is very “marketing”.

        End-users…hardly anyones makes a bad bike. TEST RIDE!!!! Something that works wonderfully for one, may not be ideal another, both in theory and in feel. Will it work. Sure. But take two “great” bikes and give them to 10 different people, and they will come back with distinct preferences.

    • Have you been reading the comments on the various articles over say the last year??? There are in fact SOME smart people here, but plenty I wouldn’t put in that category.

      Beyond that, the persons interviewed clearly stated multiple times, that they were very much simplifying, and that it get very complex very quickly (meaning far outside the intent of this article).. From having taught various classes, and worked with people from all levels of education, and you never assume too much, and always know your audience.

  3. Thanks for providing a forum for the ideas of designing suspension kinematics based on the goal of the bike’s riding purpose and forwarding the idea that riders ride in different ways and that different riders want different types of engagement with their suspension that fit their riding style.

    Too much dogma on this topic in MTB…

  4. These real working engineers making real products are all wrong. Waiting to read the “truth” by the venerable armchair engineers who will refute everything these “real fake” engineers said.

  5. Perhaps the most amusing thing I am finding is that back in the dark ages of the 1990’s, they found that a hig-ish, forwqard single pivot design, optimised for the middle chainring pedaling (as the good ones were), did the antisquat thing really well. In fact they did a lot really well.

    But then began the giant circle of ‘development’ that saw single pivot designs ditched for far more complex designs to accommodate gearing and travel. Now, some 25+ years later we’ve ended up at bikes now running single 32-36T rings upfront that are the ideal candidates for those early designs that tended to work really well, even better when mated with a modern shock.

    Wheels within wheels….

  6. If the linkage is designed so the IC is tracking Chainforce, there is no squat tendencies from Chain Force, thus Anti Squat is designed in to counter … wait for it… nothing. In this case, Anti Squat just means Rise. A well designed linkage bike will not respond to Chain Force, thus, needing a considerably smaller amount of AntiSquat in the design… If a bike has a high Anti-Squat, assuming it’s being measured via an industry standard method, it will either “Rise” or “Jack” or it will bind the suspension countering a squat force from a poorly designing linkage, that binding of Squat and Anti-Squat will cause a reduced bump sensitivity under hard pedaling efforts. Anti-Squat is just a new buzz word for “pedal platform” designing in the linkage that tends to have considerable pedal input into the linkage.

    Love this topic. Put the better part of 25 years into demystifying it. New words, same concepts, Compress the shock, it’s Squat, extend the shock, it’s Anti-Squat… The holy grail remains a mechanism that decouples the Chain Forces from Suspension Articulation. Nothing does this as effectively or perfectly as the Chain Force Tracking an Instant Center.

    • It’s like this guy knows something. Always great to hear your input and thoughts on bikes and suspension Tony. You are a legend in the industry and it’s an honor to work in the same field as you. I hope all is well!

  7. All respect Tony but…

    “Anti-Squat is just a new buzz word for “pedal platform”

    and then…

    “Nothing does this as effectively or perfectly as the Chain Force Tracking an Instant Center.”

  8. “There is a 555 page book out there that is required reading to truly understand and then explain the answer to this question”

    What’s the book?

  9. A bike with the IC lined up with the chain will absolutely have anti-squat. Tony Ellsworth has either constructed his own lexicon for describing bicycle dynamics that no one else uses, or he doesn’t have a firm grasp on the concepts. I’m leaning towards the latter.

    For those who don’t want the dumbed-down version, this is a great read:
    http://members.home.nl/vd.kraats/ligfiets/pa/index.htm
    There’s a whole sub-chapter on the bogus marketing in Ellsworth’s Instant Center Tracking.

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