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I read an article on full suspension bikes, explaining antisquat and pedal kickback. They say the bicycle is the only vehicle, where the gear affects the suspension characteristics. This is great, they continue, because the kinematics can be made so that in some gears of the front chainrings the cranks and rear axle are isolated, while in others pedalling blocks the suspension travel.

Firstly, because some people are commenting that the article is grossly incorrect, I would like an opinion on that.

Secondly, as every mountain biker looking to spend some bucks knows, the fuzz is Enduro now. And 1x10 or 1x11 drivetrain. If the article is correct, this setup is robbing FS bikes of a lot of their potential. How come no one is raising the alarm?

  • I see no comments the article is grossly incorrect. Contrary lots of comments of great article. Do you have any specific questions on the article. What do you mean "no alarm"? You are seeing more 1x. – paparazzo Jun 9 '15 at 16:58
  • Hey @Blam. The article is being criticised in a local forum, where I found the link to it as well. Secondly, what alarm are you talking about. My wast paragraph says that enduro bikes (e.g. 160mm front and rear) are fascionable, together with 1x drivetrains, which seems contradictory. – Vorac Jun 9 '15 at 17:24
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    What specifically in the article to you have question about? – paparazzo Jun 9 '15 at 17:49
  • The basic ideas of the article look alright.Whether the claims are as important as they're made out to be, I don't know. – Batman Jun 10 '15 at 11:08
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A few quick points about the article

  • The author did not provide all the math and formulations so we need to take it on faith that the correct formulae were used and there are not implementation errors.
  • The author also only considered one bike, the 2015 Giant Reign 27.5".
  • Finally, the results seem reasonable to me.

The main take home from the article (which is well known) is that the drive train affects rear suspension performance, and that the chain angle (vertical chain line) also impacts rear suspension performance.

Right now there are a myriad of rear suspension designs, each with different characteristics and all optimized to a different set of characteristics the designing engineer considered important. Taking an older design that was optimized for double (or even triple) chain ring set up and putting on a 1x drivetrain could have unintended performance effects as suggested by the author. Running extra wide rear cassettes can also have an effect.

What would be an interesting follow-up analysis would be to look the anti-squat/pedal kickback characteristics of full suspension bikes marketed with 1x drivetrains. I am sure the designing engineer knows of these problems and took a particular path to optimizing the solution.

It would also be interesting to compare the numbers from fundamentally different suspension designs (e.g., virtual pivots, Horst linkages, single suspension arms, free floating designs... the list goes on).

Finally we shouldn't overlook the type of shock used in the design, some are designed to mitigate peddling input and shocks designed to block out pedal bob would facilitate using a design with less anti-squat.

What does it all mean?

I raise all these issues to illustrate that there is no simple single answer. No one is "raising alarm" because gross generalizations are simply not possible. There are a lot of engineering nuances that need to be considered and unfortunately cannot be summarized in a simple one-size fits all statement that might trend on twitter.

Caveat - I am neither a suspension designer or an engineer. It would be nice to hear input from someone who if officially trained and practicing.

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    Quick thought - clutched derailleurs are a bit of a game changer too as you don't have to rely on Big-big gear selection to keep chain slack under control. – Rider_X Jun 9 '15 at 20:09
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    +1: Great detailed answer. Its important theory to bike designers and interesting to bike mechanics who change bike configurations. As tuning a bike extends to seat heigh and suspension sag for 95% of riders, leaving those that think they know more than a professional bike builder maybe getting nothing more than an expensive lesson if they change a bike to 1x, I don't think there is a problem to 'raise an alarm' on. Those with 'the legs' to push a 1x MTB know when they test ride a bike how it feels. For the rest, 1x is a fad - average riders are better off with 2x. – mattnz Jun 9 '15 at 22:49
  • @mattnz - Agreed even though many may not understand the physics behind different setups, they will typically find an optimal set up by feel and trial and error. Looking back I have always noticed the suspension behaving different at different gearing and as a natural reaction choose gearing to get a particular response out of the suspension. At the time I had knowledge, but not understanding. – Rider_X Jun 10 '15 at 6:43

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