Behind the Numbers: Yeti SB140

Jun 19, 2020
by Dan Roberts  
Behind the Numbers Yeti SB140 Title Image


Behind the Numbers is made possible by Creaform Portable 3D Measurement Technologies.

We now come to the final bike in the trail category and a slight, and hopefully welcome, difference in wheel size and suspension system compared to the bikes we’ve already looked at. 27.5” wheels are certainly not dead.

Yeti have always had an alternative take on a suspension system. Sliders and spinning elements have graced their designs for a very long time and the bike we’ll take a look at, the SB140, uses their latest incarnation dubbed Switch Infinity.

While we’ll look at what the SB140 looks like on the graphs, we can also do a bit of explaining on just how the Switch Infinity system works.


Behind the Numbers Yeti SB140 Grenoble Scan


Scanning

As you’ve seen, all the bikes in the trail category we looked at have been 3D scanned. But between the actual scanning and output of kinematic graphs there are some important steps in the process that often get forgotten about. A quick thank you again to The Factory Bike shop for letting us borrow one of their highly expensive bikes.

The output of the scan is directly a file format called STL or stereolithography. This is the build-up of all the small triangles to form the surfaces of the bike scan. During the scan and post-treatment we used VXelements, a software from Creaform that works with the scanner hardware and is used for the following alignment, entity extraction and decimation steps.

Behind the Numbers Yeti SB140 Alignment
Aligning the scanned bike in space using the center plane, floor and crank axis is the first crucial step. A different alignment can result in different measurements further down the road.
Behind the Numbers Yeti SB140 Entity Creation
Extracting entities uses the scan data to create clean geometrical entities that can represent parts of the bike scan and easily be used later in the analysis. Here the shock shaft scan area is being turned into a cylindrical entity.

The first crucial step in post-treatment is the alignment. This allows us to extract the dimensions most relevant to the application, in our case the kinematic and geometry points. The alignment uses the middle plane of the bike, the floor and the BB axis to position the bike in space and give us our reference planes. Aligning is crucial as a different alignment can result in different measurements.

After that we extract the entities, where we take surfaces, shapes and features on the scan data and reinterpret them as cleaner entities that are easier to then deal with and take our kinematic from.

Inside the VXelements software is VXmodel, which enables the user to quickly and accurately create all kinds of entities and measurements. The software will automatically select from thousands of points the best fit for the desired geometrical entity, like the shock shaft shown. There are also options to constrain the entities, in their orientation and diameter for example, to help fit them to the scan. The created entities can be coloured to help validate them in comparison to the STL scan file.

Behind the Numbers Yeti SB140 Before Decimation
The original scan consisted of around 14 million small triangles, which makes it a pretty hefty file for working directly with.
Behind the Numbers Yeti SB140 After Decimation
Decimation reduces the number of triangles without disturbing the quality of the scan. It puts the small triangles where the detail lies and uses fewer larger triangles on flatter surfaces. After decimation we were down to around 2.5 million triangles.

With the scan STL file often compromising of millions of triangles, it’s pretty data heavy and can need some processing power or time when opening or working with in other software. Decimation reduces the number of triangles to help reduce the overall file size without altering the quality of the scan. Typically, the number of triangles can be reduced by 75-80% without reducing the quality of the data, as only the small triangles are kept in the places where there is detail. There’s no need for small triangles on flat surfaces.

Behind the Numbers Yeti SB140 Sections
Splitting the bike scan into sections allows to have individual parts that we can then assemble together and move around to animate the bike as it goes through its suspension.

After that, and mainly for your viewing pleasure, the bike scan is also split into sections. This 5-10-minute job per bike allows us to have individual models for the frame and bike parts which we can then tie into the kinematic and animate to show you how the suspension moves and how the characteristics we analyze change throughout the travel.

Once we’ve got our STL files of the full bike scan, the decimated version and the entities we can move over to PTC Creo to begin importing and extracting the kinematic, as well as setting up the model to provide our animations.





Behind the Numbers Yeti SB140 Instant Centre
The Yeti SB140 is essentially a four-bar suspension system, but their Switch Infinity design mimics an infinitely long lower link packaged into the space of a smaller link. The instant center, or IC, is depicted here by the engineering standard for showing an instant center - a cat.


The SB140 is a 27.5” wheeled, 140mm travel trail bike with a 160mm travel fork.

Of late, Yeti have split their range into Rip and Race categories, and the SB140 falls into the Rip segment of bikes, intended to have a bit more of a focus on the play aspect of riding rather than the fastest point to point time, which can also be fun sometimes.

As mentioned, Yeti use a system called Switch Infinity. In the same way that the Ibis Ripmo we looked at had a name associated with its suspension system, DW-Link in that case, we can actually look at the Yeti as falling under the same four-bar suspension design.
SB140 Analysis Details

Travel Rear: 140.1mm
Travel Front: 160mm
Wheel Size: 27.5"
Frame Size: Medium
CoG Height: 1,100mm
Chainring Size: 30T
Cassette Cog Sizes: 50T, 24T and 10T


Categorising aside, though, there is a major difference between the designs of the Ibis and the Yeti. With the Ibis it’s clear to see the two links that connect the rear triangle to the front and even extrapolate where the instant center lies.

With the Yeti we can see one recognizable link connecting the top of the rear triangle to the main frame, but the other connection is the sliding element down by the bottom bracket.

Now, if we imagine the path a link takes when it rotates around a fixed pivot, it draws an arc. If we were to rotate it completely, we’d have a circle, with the radius of the circle being the link length. If we were to increase that link length our circle would increase in size too. Seeing as the links in bike suspension systems only rotate through a small angle, we can zoom in on that segment. The short link would have a much more pronounced arc to it than the long link, with that looking a lot straighter to our eye.

If we were to keep increasing the link length, longer and longer, that segment would get closer and closer to a straight line. If we were to make the link infinity long then the segment would actually become a straight line, just like the path that the slider takes. And also, hence the Switch Infinity name.

So, what we have is a four-bar design with one short link and one effectively really damn long link.

Behin the Numbers Switch Infinity explanation
If we take a short link, like the top link from a Santa Cruz, we can visibly see the arc the link moves through as the bike goes through its travel. If we make the link length longer and longer then the arc becomes straighter and straighter. If you make the link infinitely long, then the arc becomes a straight line, and this is exactly what Yeti have done with their Switch Infinity system. Trying to package a link that long gets tricky, so having it packaged into their small proprietary slider system is a clever trick from a kinematic point of view.

From a kinematic design point of view what Yeti have done is really clever. As we’ve seen so far, shorter linked bikes generally tend to create suspension curves with a bit more of a wild shape to them. Compare the curve shapes of the long-linked Norco Sight to the short-linked Ibis Ripmo and you’ll see. The Switch Infinity system then endeavours to have the effect of a really long linked bike but packaged into a small space. Trying to fit a meter-long link, let alone one infinitely long, into a bike would be impossible. Especially if you want a water bottle in there too.

Analyzing the Yeti can be done by substituting the slider mechanism for a very long link, to replicate that straight path of the slider, or analyzed with the link an infinitely long link to make sure the kinematic analysis is bang on.

On the SB140 the slider moves 4.9mm up from its starting position and then moves all the way back down to 0.9mm lower than where it started.

Moving more into the real world, though, the slider mechanism, with its pivot for the rear triangle, doesn’t take up too much space but does present its own challenges to manufacture and fix into the bike. There have been some reports of noisy Switch Infinity systems with the added connections between the front and rear triangle leading to a few more opportunities for creaks and squeaks.

Another packaging point with the Yeti comes when that water bottle clearance is added in. It’s always good to have your bottle out of the firing line of muck and so putting it inside the front triangle makes sense. With Yeti also having to make space for their Switch Infinity system this means the bike can have a bit of a pregnant look to it, with the down tube bend sticking out almost as much as the cranks.

0% Loaded prev 1/21 next

The instant center moves around in space as the links that define it move with the rear wheel. The yellow dots represent the pivots of the bike and the red the IC.





Behind the Numbers Yeti SB140 Leverage Ratio


Leverage Ratio

The SB140 has 15.1% progression with a constantly decreasing leverage ratio. It starts at 2.68 and finishes at 2.28. Over the whole range the average leverage ratio is 2.55.

The SB140 uses a 210 x 55mm shock and uses the Fox DPX2 as standard. There is a very good online shock setup guide that takes your weight, model and kit and outputs suggested pressures for the fork, shock and tires as well as suggested damper settings that should have you in a good starting point.

As is the case with the Ibis, it uses standard eyelets at either end and a really small shock extender to bridge the gap from the link to the shock. Yeti did another clever deign point, with the split extender using the same piece twice just flipped upside down.

The leverage ratio curve is about as straight a line as you can get from zero travel to around half way, after which there is a sharper drop in the leverage ratios. Despite the lower “link” being really long, the upper link still rotates quite a bit and does produce this flick in the curve at the end of travel.

When this is combined with a shock full of volume spacers it could pose the problem of running into a wall of progression rather than running into the end of travel. In extreme cases that wall can often feel like a bottom out despite you not actually getting to full travel.

But perhaps Yeti intended this difference between the start and end of travel, with the bike having a slightly more linear feel for the majority of travel with a good chunk of mechanical ramp for those times when you really get down to the end of travel. With Yeti suggesting slightly more sag, at 33% shock stroke, then this could well be the case and the bike did come with zero volume spacers in the shock.

The SB140 does have a good amount of progression, but a lot of that comes in the second half of travel where the ratio drops off faster. Extrapolating the very straight first half out to the end of travel would only yield around 8-9% progression, so that end drop is doing a lot of the heavy lifting.

Overall, the leverage ratios are low when comparing to the other bikes we’ve looked at with only the Unno having a lower average. Those lower leverage ratios move the shock shaft faster, and create more damping from the increased shaft speeds, when compared to a more highly leveraged ratio bike. Damping force is dependent on speed, with only a few suspension manufacturers including position sensitive elements that often work in conjunction with the naturally speed sensitive elements.

Sarah Moore reviewed the SB140 back in May and commented on its stability and control. With a bike being the sum of its parts some of that has to be contributed to the geometry. Although, to the annoyance of my bosses, geometry is not the be all and end all. The Yeti starts with good static geometry at sag but also benefits from having that good geometry continue to shine when the bike is dynamic. The overall progressive and straight leverage ratio curve and low ratios bringing predictability and support that keep you closer to that well-designed geometry that Yeti intended, rather than always riding too high or too low in the travel.

Sarah also commented that the bike didn’t blow through its travel too easily, again due to the lower leverage ratios offering a bit more hydraulic support overall, but also due to that second half of travel having ever increasing ramp up.

Higher speed, more man-made trails were said to yield better performance from the bike than slow speed technical ones. Perhaps due again to the amount of damping the bike generates but also possible down to the smaller wheels. Nevertheless, riding the bike in Whistler Bike Park sounded like a hoot and is testament to the capabilities of this trail bike.

At 33% shock shaft sag there is 34.3% rear wheel travel on the Yeti.





Behind the Numbers Yeti SB140 Anti-Squat


Anti-Squat

The SB140 comes specced with a 30T chainring, and by this point it might be a little easier for us to compare apples to oranges and bikes with different sized chainrings. We analysed the bike with the 30T ring to keep it true to what the bike is available with and the feedback from out on the trails.

Remember that if you were to up the chainring size you would drop the amount of anti-squat. Moving up to a 32T chain ring would drop the curves down by around 4% in the 50T cog, 8% in the 24T cog and 19% in the 10T cog.

The same curve shape found in the leverage ratio is also found in the anti-squat, with fairly constant percentages in the first half of travel and a drop off at the end. But in all gears the bike has more than 100% anti-squat at 33% shock sag.

The 50T gear actually has the lowest anti-squat of the whole cassette but is still at 109%. Going into harder gears the percentage increases to 123% in the 24T cog and 160% in the 10T cog. So, in all the gear associated with pedalling there is more than enough countering of the effects of load transfer and even enough left over to combat the other forces attempting to compress the suspension when pedalling. 100% might be seen by some as the magical number on paper, but in the real world often higher percentage yield better results and less reliance on the shock to add support when pedalling.

There is of course an upper limit too, where the forces would cause real world rise in the suspension when accelerating. But Yeti keep their percentages in a good range for the pedalling gears and this gives the SB140 the firm pedalling feeling that Sarah commented on in her review. On only the biggest slogs of road climbs did she need to use the lockout lever due to these high anti-squat percentages combined with some inherent support from the leverage ratio around the pedalling window of the bike’s curves.

When we compare to the other bikes we’ve looked at, and we’ll do that in more detail in our comparison article, we can see that as a trend all the bikes now tend to have around or above 100% anti-squat around sag and in their pedalling gears. The SB140 fits this trend nicely.

0% Loaded prev 1/21 next

The red IC dot is carried over and creates the blue IC - rear axle line. Intersecting that with the chain line we get the instant center of anti-squat, the green dot. The orange dot represents the 100% anti-squat mark. This is in the 30t chain ring and 24T cassette cog.





Behind the Numbers Yeti SB140 Pedal Kickback


Pedal Kickback

As we know, on bikes without an idler pulley to reroute the chain line we generally have more pedal kickback for bikes with higher anti-squat percentages. Years ago, engineers would focus more on the potential downsides of pedal kickback, looking to have low degrees of it. And as a result, there would be low anti-squat numbers. Over the years the advantages of higher anti-squat have become more of a priority in design.

The Yeti does have the highest ultimate kick back of any of the bikes we’ve looked, at 31.3° with a 32T chain ring and 50T cassette cog.

The same is almost true of the other gears, with them maintaining a higher degree of kickback until the very end of travel, where we once again see a drop off relating to the drop off in anti-squat.

Taking our example of going off a 1m drop that uses 75% of travel and being in the 24T cassette cog, how fast would the Yeti have to be travelling to never encounter the effects of pedal kickback? This example situation is based around a certain rear wheel compression time needed to get to 75% travel and then converting the pedal kickback to a speed at the cassette. As long as the bike travels above this cassette speed then the freehub would never catch up the hub body and pedal kickback couldn’t occur. For the SB140 it would have to be going at 11.7kph or 7.3mph.

Dropping down into the harder gears that critical speed would actually increase, as the drop in pedal kickback is outweighed by the gear ratio change in the 10T cog and you’d have to be going 15.1kph or 9.4mph.

In the 50T cog you could actually go a fraction slower than in the 24T cog, at 10.4kph or 6.5mph to negate the pedal kickback effects. The gear ratio once again having more of an effect on the critical speed than the increase in pedal kickback amount.

0% Loaded prev 1/21 next

Remember that pedal kickback is calculated with a fixed rear wheel and only looks at the influence on the crank. When we ride it can be a different matter. The blue line represents the bike at zero travel and the green shows how the cranks rotate backwards as the bike goes through its travel.





Behind the Numbers Yeti SB140 Anti-Rise


Anti-Rise

Tying in with the high level of anti-squat, the SB140 also exhibits a high level of anti-rise. So too is the flick towards the end of travel, but in the case of the anti-rise, to much less of a degree.

The anti-rise percentage remains pretty constant between 90-95% throughout the entire travel range, contributing to combating very nearly all the effects of load transfer from rear braking.

Depending on the other bike characteristics and setup, high levels of anti-rise can sometimes manifest themselves in a bit of harshness. In the case of the SB140, with its higher pedal kickback values too, this could well be contributing to what Sarah described as the bike not feeling quite as composed and supple in slow speed technical descents.

There’s always a balance to strike in all the factors of bike and what the Yeti gains in its incredibly mechanical support under acceleration and deceleration could mean that it’s a little firmer under foot in those situations.

Having never ridden in Colorado, where Yeti are based, it’s hard to comment if their surroundings play a commanding role in the style of bikes they develop. While high anti-rise isn’t necessarily a bad thing, Sarah comments that the SB140 did benefit more from being off the brakes and on the fast and open trails that she rode in Whistler, rather than the slow speed tech surrounding Squamish. It’s good to note that anti-rise doesn’t solely describe how a bike will brake. Instead it’s one part of the equation in explaining it.


0% Loaded prev 1/21 next

It's only the red IC dot we need to calculate anti-rise. The orange one again represents the 100% anti-rise mark.





Behind the Numbers Yeti SB140 Axle Path


Axle Path

The Yeti takes the most rearward axle path of all the bikes we’ve looked at with 3.6mm of rearward movement before moving 10.8mm forwards. The Yeti also moves the most rearward over the biggest travel amount, with it seeing it most rearward point at 39% shock stroke. Meaning that from your sag point you would actually have a fraction of rearward movement when encountering an impact before the axle would then want to move forwards.

It could be construed that the seemingly minute differences in axle path are insignificant. But even on bikes as long as you find from some of the extreme manufactures, they’re a study into fractions of millimeters and seemingly subtle changes can come together with other seemingly subtle movements to create something perceivable.

While yes, you might see a far more significant change comparing the Yeti to a high pivot Forbidden Druid the devil still lies in the details.






Assumptions in Analysis

All of the trail bikes that Behind the Numbers have looked at have been size mediums, and so we adjust our center of gravity (CoG) height to 1,100mm above the ground.

It’s good to remember that the analyses for anti-squat and anti-rise always assume a static CoG. In the real world, this is rarely the case, but needs to be done for analysis’ sake to allow it to be easily calculated and then compared to other designs and bikes. Once we have our analysis it’s then easy to add back in the real-world elements that are relevant to each of us and where we ride our bikes. For more chin-scratching about that, check out the Enginerding article on anti-squat.

There’s no industry standard for the fork in anti-squat and anti-rise analysis. We can either fix the fork travel to generate a single curve or we can adjust the fork travel as we go through the rear travel to create a window. For these analyses, we leave the fork at fixed at full travel. Again, as long as these assumptions about anti-squat and anti-rise are known and understood, it’s easier to analyze and compare bikes.





Final Thoughts


bigquotesThe SB140 is described as lots of fun, and some of you may solely attribute that to smaller wheels. While they do play a part, the bike shows us that predictability in suspension and efficiency in dealing with acceleration and deceleration help that too.

High levels of anti-squat and anti-rise keep the bike from, well, squatting and rising when you pedal forwards or brake. But in the case of the braking, and combined with the increased chain growth, it was a little harsher than some of the other bikes we’ve looked at in slower speed technical sections.

The SB140, along with Yeti’s take on a four-bar suspension system, keeps the world of mountain bike design interesting and diverse while not just doing it for diversity’s sake.







151 Comments

  • 147 10
 Let’s be honest here. We have no clue what all these numbers mean, we’re just here to find the cat
  • 6 1
 cat? What cat? :-)
  • 8 2
 did anybody else see the laser shooting cats in the background?
  • 4 2
 the picture at the top of page for clarification.
  • 3 2
 All those strange numbers on one side, a lot of meaningless vague adjectives and qualifiers on the other: "in the case of the braking, and combined with the increased chain growth, it was a little harsher than some of the other bikes we’ve looked at in slower speed technical sections". (increased, little harsher, some, slower)

But the cat IS cute ...
  • 6 0
 The wheels on my bike go round and round....
  • 4 0
 Cats are the IC´s for everything,place a Cat anywhere and watch the Magic happen:-D
  • 5 0
 I love how the top 10% of the comments just talk about how they don't understand anything and the bottom 40% is where they actually are arguing about this crap
  • 9 1
 They should include a 3 sentence tech summary for dumies:

- Antisquat = how much the pedalling force compresses/extends suspension: >= 100% good, 100% - bad
- Antirise = how much the braking force compresses/extends the suspension: 100% rear wheel gets traction but bike gets steeper , 100% neutral, > 100% bike gest slacker but rear wheel looses traction.
- Kickback = how much your crank would rotate when compressing the suspension when bike does not move. When rear wheel rotates faster than your crank rotates due to kickback is is effectively cancelled.
  • 1 0
 I scroll down to the comments and skip all the BS mumbo jumbo at the top....Smile
  • 3 1
 @Supergirl56: i find the picture disrespectful to cats and a misrepresentation of their powers and demand it be taken down immediately
  • 2 0
 @dirtbeard: The comic supergirl had a cat with kryptonian superpowers
  • 1 0
 @lkubica: I don’t understand, could you explain in simpler terms.
  • 2 0
 @lkubica: I think some might struggle understanding what 100% means do perhaps:

Antisquat - fully sik pedalling
Leverage Ratio - fully sik suspension effect
Anti-Rise - fully sick hunkered braking
Progression- fully sick shock action!

I think that might be easier to understand?
  • 83 13
 You guys are hilarious. This review was 100% written in layman's terms. I think some of you just don't like to read. Back to your angry birds.
  • 17 0
 I just let the comment section sum it up for me.
  • 8 0
 The top comment is always 'I don't know what any of that means...'
  • 4 16
flag kookseverywhere (Jun 19, 2020 at 8:35) (Below Threshold)
 Found the boomer
  • 4 9
flag DaFreerider44 (Jun 19, 2020 at 9:51) (Below Threshold)
 ok boomer ;D
  • 3 1
 What's a layman? I trust only Señor Banana
  • 61 5
 Everyone knows the most important number when it comes to a Yeti.
  • 35 2
 The first 7, 8 digits of your bank account balance? Or the number of your black Amex?
  • 2 1
 Beat me to it!
  • 34 4
 How many root canals you did last month
  • 9 1
 The number of rings on you auto maker's emblem?
  • 19 4
 Here are the only Yeti numbers that matter:

137 Dentists
180 Yeti's (can't have just one)
98 faulty triangles
2,000,000 PB trolls
  • 19 0
 @onlyDH: ok but seriously, am I the only one that comes across dentists with no sense of humor about riding dentist bikes?

Last summer on the BCBR I sat with a dentist at dinner who was riding a Yeti, and when I said something mild, like, “A dentist on a dentist bike!” He looked at me like I’d just kicked his puppy.

Then more recently I was giving one of my former classmates who’s now a dentist a hard time about how he should only be allowed to wear Rapha kit with his Cervelo, and he didn’t appreciate it at all.

Am I just running into dentists with poor senses of humor, or is it really offensive to tooth repair professionals to point out that they have nice bikes?
  • 11 0
 @atourgates: You've come across a dentist that has a sense of humor?

Much much higher likelihood of finding a humorous cardiothoracic surgeon!
  • 17 2
 @atourgates: I think that rich people probably don’t like poor people joking about their wealth
  • 27 0
 YOU ARE ALL RABID ANTI-DENTITES!
  • 3 1
 @onlyDH: nah.. More like how many engine rebuilds and head gaskets/tune ups... They arent unattainable..
  • 2 2
 @bohns1: plenty of money out there in this world. It’s just not as funny when people ask me how many software robotics roll outs I executed to make more than dentists
  • 1 0
 @mobilechernobyl: ima disagree with that one strongly. As a general rule cardiothoracic surgeons are some of the most miserable people on the planet. I've liked pretty much every dentist I've ever had.
  • 2 0
 @onlyDH: not a dentist.
but got some jokes about my Nicolai’s, as engineer bikes with deretisimas and bels/whistles.
and yeas I am engineer, i like it.
I just hate when people pointing on pinon asking where is battery on my emoped
When people asking about price honestly answering +- 1-5 overage monthly salary.
but its depends on what position and where you working
  • 3 0
 I don't know any dentists but all the Yeti riders I know are tradies. I think Santa Cruz might fill that niche around here.
  • 1 9
flag truehipster (Jun 19, 2020 at 22:42) (Below Threshold)
 @boozed: so America has population of your whole country in a state and your voice your opinion on who buys Yeti’s. Intelligent!
  • 33 0
 Don't blindly trust that software. Scans a blue bike, shows up in pink. Chances are these anti-squat numbers etc are negative too.
  • 9 1
 Yes it works with lasers and such. So what you see is a negative like with old cameras. Look the picture go to the right, but the results go to the left. Everything is upside down.
  • 26 0
 Can I request an analysis of Myles Rockwell’s 1993 Yeti ARC AS? Should be an interesting comparison to this SB140 =P
www.pinkbike.com/news/Myles-Rockwell-Bike-Check-Yeti-ARC-DH-2012.html
  • 10 0
 Such a great idea! @dan-roberts kinematic analysis of bikes from bygone eras would really drive home how much things have normalized in the last decade. Give people some perspective.
  • 5 0
 If you can get the old pro's who rode those bikes to also talk about their impressions of that bike that would also provide the on rider impressions like Sarah provided from her review. Get a pro rider interview and a sweet retro kinematic analysis in one.
  • 27 5
 Big thanks to Yeti for stepping up and keeping 27.5 wheels alive. They get it.
  • 10 4
 There are finally options for short travel play bikes again! Yeti, ibis, santa cruz, bird, guerilla gravity, and loads more! Not everyone needs to go full enduro...
  • 7 4
 For real!! Seems like some companies are trying to force 160+ travel 29ers on us. I'll take my 150/130 27.5 almost any day of the week.
  • 11 0
 Thanks for the analysis. Please have an executive summary of all "Behind the Numbers" bikes and results ready to go by Monday EOD and copy marketing and accounting, we want to make a decision by Tuesday EOD on which bike is best so we can move forward with finalizing this year's budgets.
  • 3 0
 This hits way too close to home...
  • 13 3
 STL stands for Standard Tessellation Language - not Stereolithography. Stereolithography is a specific additive manufacturing technique using lasers and light cured resin. I know all this because I majored in Philisophy in college.
  • 3 0
 Tesseract?
  • 8 0
 Dan knows what he is talking about, no need to get all syntax-y on him. The original .STL file format is derived from the term Stereolithography, which was developed by 3D Systems in the '80s. It has been in use for many decades in 3D interpolation software. Other acronyms, such as Standard (or Stereolithography) Triangle (or Tessellation) Language have subsequently come into use due to bored people finding convenient words that mean the same thing.
  • 2 1
 Yea, I'll take a grande caramel latte with nonfat milk - three pumps syrup, please!
  • 1 0
 @grizzlyatom: Sorry to get all syntaxy. Stereolothography equipment was developed by 3D Systems. The software that ran their machines and the .STL file format was developed with 3D systems by Materialise in Belgium.
  • 1 0
 @Endosch2: I'm not an authority on this subject by any means, but to my knowledge Materialise didn't exist when the software was developed in the mid 80's.
  • 11 2
 Props to the industrial designers doing the Yeti surfacing these days. Even reverse engineered, the surfaces look very good, flowing, continuous. Would be interested in their CAD process.
  • 8 0
 I have a niave question, as a certified non-engineer. Let's say, hypothetically, that a few different bike designers (Specialized FSR, Yeti Switch Infinity, Ibis DW and Santa Cruz VPP) were all to get together and design 4 bikes with identical geometry - then tuned their suspension design and compression/rebound settings to deliver identical suspension properties (i.e. anti-squat, leverage ratio, etc.). Would all of these bikes ride identically, achieving the same kinematics via different suspension design? What I am trying to get at is: is there something inherent to the "feel" of a given suspension design, or with the the right tuning, can you make just about any suspension design ride just like any other suspension design?
  • 5 0
 I think it would be possible to realize the same anti-squat etc for all these designs in a certain part of the suspension travel (for instance at the sag point) but probably not throughout the full travel.
  • 3 0
 You mean if different suspension designs can be tuned to have exactly the same characteristics? I reckon that's possible to a point but not entirely. Changing one thing on the suspension design (let's say link length or pivot placement) will always affect multiple characteristics and to tune all the characteristics the an exact specification might not be possible with a certain suspension design.

This is all speculation though as I am not a suspension engineer.
  • 1 1
 Do not think different manufacturers or suspension designer are would ever want their designs scientifically tested back to back! PLUS what would the point of having the same set up as different riders like different set ups any way All suspension set ups are a compromise to a certain extent!
  • 1 0
 Switch Infinity, DW and VPP are all technically short dual-link four-bar systems, with differences mainly in the direction the links rotate relative to each other, so I think they'd be pretty similar. In this case the packaging and "design language" that each company has chosen for its bikes might even have a greater effect than the choice of linkage if they allow it to limit their design flexibility.

Specialized FSR, as I understand it, is simply a long-link four-bar (i.e. Horst linkage) system so it would likely be somewhat different, depending on how much the other three exploit the greater ability of their systems to tune the anti-squat, anti-rise and leverage curves.

Disclaimer: Also not a suspension engineer...
  • 1 0
 And as if to prove it, I think I meant to say "dual short-link" rather than "short dual-link".
  • 1 2
 @aljoburr: so some bike company ((Kona) designs a 10 year old suspension On new bikes should not be called out? Explain?
  • 1 0
 @boozed: I'd say Switch Infinity would be more of a (infinitely) long four bar than a short four bar design. Not sure about that design Polygon and Marin use nowadays. It has a big slider too.
  • 1 0
 @vinay: Technically it emulates an infinitely long pivoting link but it connects to and acts on the rear triangle in the manner of other short link systems so, as I understand it, its kinematics are very similar. When it was introduced it also replaced a very similarly acting eccentric short link design.
  • 7 0
 Dan, have you thought about what happens if you have too much anti-squat. My theory is that it actually still results in pedal bob - but upwards pedal bob. It would be less obvious to the rider, but it would still waste energy. Wondering if you can look into that and maybe include some consideration in your reviews.
  • 3 0
 It absolutely does do that. I've had it on a Banshee Rune where it would bob in higher gears on the road, and you could damn near top-out the suspension on the older Norco Sight/Ranges by giving them a good stamp on the pedals.
  • 1 0
 That should be right. More than 100% makes the shock extend, which starts from sag towards full shock length. I am also curious why designing bike with anti squat that is way higher than 100%, such as 150%. Is the brand trying to let the shock extend to the full eye to eye length while pedaling with the same geometry on the paper?
  • 2 0
 So I just got an SB130 a few weeks ago and it has an oval chain ring (still 30 tooth just like this test bike here). No bob when I'm stomping or handling uneven terrain, but there is definitely a very rhythmic bob when I'm in the saddle on a steady cadence - say going up a fire road or other smooth, steady incline. At first I was confused because I know that shouldn't be the case with this particular frame, but I'm starting to put together that it may actually be the constant variation from the oval ring pulling the suspension up above the sag point. It's not enough to happen in most situations, but when I'm just riding at that very steady cadence, it starts to develop a bob after a few pedal strokes.

I'm trying to find a used round ring to test for comparison (don't really want to spend cash on one since I still really enjoy the ride on the oval ring) and trying to think of ways to zip-strip on a little jig to the shock so I can see if the bob is pulling the shock above the set sag point or down below it.
  • 1 0
 @big-red: , an affordable way, I just bought a funn nw ring for 30€.
  • 4 0
 Look up andrextr on youtube. He had a video recently addressing exactly this. His friend had a single speed downhill bike that resulted in 220% anti-squat. You could clearly see the suspension extending while pedaling.
  • 4 0
 @smokingblues: a value of 100% would perfectly cancel out the acceleration from pedaling. In reality our legs also supply additional force downward. If you pedaled perfectly (think a motor or drill just spinning the chainring) there would be no need for greater than 100%. If you apply any downward force at the bottom of your pedal stroke (pedaling a square vs pedaling a perfect circle) this would need to be canceled as well which is why we end up with something above 100%.
  • 3 0
 @big-red: I know that the SB130 felt like it had zero bob with a round ring when I rode it. Could be more subjective though.
It is interesting that the antisquat changes throughout each pedal stroke when using an oval chainring. A general article or video on that would be very interesting.
  • 4 0
 @LeoTProductions: If you look in the Pedal Kickback section of the article above, you can see the chain line between the leverage point of the chain ring and the leverage point of the cog. On a round cassette, that leverage point of the chain ring is always the same distance from the bottom bracket so the the force through the chain to the rear end is relatively constant as long as you pedal smoothly (and maybe use clipless pedals). But with an oval ring, that leverage point changes constantly as you pedal, with a high point and low point twice each per full pedal revolution. Just as the anti-squat changes depending on the gear you use (changing the leverage point relative to the rear axle), it changes once every quarter turn of the cranks on an oval chain ring because the leverage point is constantly changing as you pedal.
  • 1 1
 @big-red: Sounds weird that oval chain ring would have so much of a different affect, when you can run a oval chain ring on a single speed without a tensioner?
  • 1 0
 @LeoTProductions: I'll second this, I would like to see some type of analysis of the variation in antisquat with an oval chainring too - I was thinking the same thing just the other day. To be valuable though, you'd need to try to model an individual's actual pedal force vs. rotation curve, then plough this into the kinematics model with a round vs. oval chainring to see the differences on suspension travel.
  • 2 0
 @aljoburr: the issue is not variation in the length between the crank and the axle, but the angle of the chain from the top of the chain ring to the top of the cog at the axle. As that angle changes (aka the chainline changes relative to the pivot point), it can change the forces on the suspension without changing the length of chain between the points.
  • 1 0
 @big-red: Ok do sort of understand, but does sound like it would be something that riding the bike would make clear, but feel l am getting too old to get any benefit from, even if had access to ride one?
  • 1 0
 @big-red: My rigid fatbike with oval ring bobs too in this situation. Could it be the ring?
  • 1 0
 @hubertje-ryu: Interesting. I assume you mean bob as in the tires themselves are where the bobbing occurs?
  • 3 0
 why does anti-rise only apply to rear wheel braking (or am i misreading that) when braking the front wheel also results in a center of mass transfer from deceleration?

additionally, what is the hope with anti-rise? are we hoping to have a bike that extends during braking so that more travel is available in case of hitting a bump or landing off of a drop? or is something else the 'ideal' result of properly engineered anti-rise?
  • 2 0
 Higher rise equals increased squat. The increase should maintain more stable geometry as the fork dives under braking. IME the increase in geometry remaining static isn’t worth the suspension sensitivity loss when the brake is applied.

What these articles don’t really take into account is rider height and weight. A 65kg/1.75m rider is going to have a vastly different experience (and requirement) of suspension kinematics (and sizing, tire casing, suspension damping, wheel and frame stiffness etc) than a 95kg/2.10m rider.
  • 1 0
 @jclnv: OK, I think I had the definition switched in my mind. I was thinking higher % values of anti-rise meant that the bike was extending towards top-out, not squatting into the travel. So now I understand that if the fork is moving through its travel, you would want your rear suspension to be doing the same in order to keep the head angle from getting steeper and steeper. I think the author acknowledges that there are limitations about assumptions that need to be made for the sake of having a graph that makes sense, so your point about riders being different sizes (not to mention in different places at different times while actually riding) is well made.

Do you know why the assumption is that only rear braking affects anti-rise characteristics? it seems to me that grabbing a fingerload of front brake will cause some deceleration forces to act on the rear suspension of the bike as well. Also, does low anti-rise automatically mean that there is a loss of traction/sensitivity of the rear end? If so, what's happening there? I don't think we experience the same thing with our forks, do we?
  • 2 0
 @twonsarelli: Yes, when you apply front brake the riders centre of mass moves forward compressing the fork and unloading the rear suspension. Higher rise is used to counteract this effect by squatting the rear suspension to maintain the static geometry somewhat.

However, combined with the high rise/squat characteristics, the squat portion of the rear suspension travel is at a higher spring preload adding further to the effect. You can train yourself to not brake is areas where suspension sensitivity is required but IME, in real world use that isn’t always possible. Especially riding blind or during a race. It also asks more of the tire, meaning that you may have to run a heavier casing tire on the rear to compensate for the reduced travel while braking.

All IMO.
  • 1 0
 @jclnv: cool thanks
  • 5 0
 Excellent work, i enjoyed that. I can only imagine being a sales person and having all that memorized, and pitching the data lol
  • 2 0
 I too am curious how oval rings, and changing gearing in general effects AS and other suspension characteristics and how gearing can be used as a suspension tuning tool.
Is there an ideal AS number and does the ideal AS change depending on what speed you are riding and/ or terrain, which determines what gear you are in anyways?
  • 2 0
 From an experience of one, an oval chainring seems to have a notable negative effect on the anti-squat on my Canfield Riot. I had a 30T oval on it and replaced it with a 30T round which works way better.
  • 2 0
 @Alvey72: I can confirm that changing chainring sizes affects AS, both from my own experience and simulation software. It's noticable.
Also, it's not the fact that a given chainring is oval or not, it's the diameter/radius. For round chainrings it's obvious, but for ovals you need the somewhat "virtual" radius at the point where the biggest pedal force occurs. Which is right about at it's biggest diameter.
So for a good rule of thumb: An oval chainring with 32t should bring similar AS as a 34t round one, since a 32t oval has about the same radius at the critical point as a 34t round one always has.
To your example: The 30t oval pulled the chain from a higher point than your new 30t round chainring, which most likely resulted in less directional force against the squatting movement of the bike.

I hope I didn't mess up circumference/diameter/radius, I'm kinda tired and not so fond of the English lingo.
  • 2 0
 How much lateral flex travel and torsional twisting in the rear half of that bike? 25 mm on the 5.5 if I recall. Worked great except for the lack of high speed rebound damping tempering that lateral and torsional flex build up coming out the corners. Boomerang Technology?
  • 3 0
 @Dan-Roberts & @pinkbike - Thank you and please keep these articles coming for those of us with engineering minds. Unlike lots of the comments above, some of us understand and appreciate the analysis.
  • 4 1
 Oh gawd...flashback to physics class and realizing I’d rather be in the elevator plummeting 9.whatever meters per second per second than taking this test!
  • 3 1
 Would be interesting to see these analyses generated ahead if any real world review of these suspension systems. Performing an analysis of this nature, post test riding review just seems backwards.
  • 6 0
 I like the idea of doing this after the fact. If I were a reviewer I would be tempted to just repeat what the numbers say in order to be "right" or at least thats what biases tend to do.
  • 2 1
 I tend to agree with Sarah in what trail conditions the Yeti's suspension works best. I have a SB5 (I'm not a Dentist) and
when my son and I do epic George Washington National forest rides that include long steep ascents, long steep and knarly descents. The faster I go the better it feels, I call it my Colorado Sherman Tank cause that's where it feels like it belongs.
  • 1 0
 Does this bike go through a lot of chains?
Would like to know, not that I am going to buy one any time soon, but do own a 66 front end that may build a back end for!
Also would like to know if high anti squat would be good for pedal kicks?
  • 1 0
 Surely the IC should be calculated by mapping the centre of the radius of the axle path curve, along the axle path (single pivots would have a constant radius and IC, whereas bikes with ‘virtual pivots’ (that move) produce curves where the radius changes along the curve (hence a moving centre).
- a circle has a static centre; wherever you measure the radius on the circle it is the same and has the same centre, whereas with an ellipse, the centre of the (changing) radius moves around (along the wide axis of the ellipse).
I never got why they worked the IC the way they did, and now seeing the yeti IC red dot move in the way they suggest and I have to call it out...
  • 1 0
 Centre of curvature (CC) is not instant center IC).
Each point has his own centre of curvature, but all points of a rigid body share the same IC. IC "move" more than CC.
CC gives information about trajectory, but IC gives informations about dynamics (speed field, forces, ...)
  • 1 0
 @faul:
That’s a fair point but why use IC and not CC if CC is a better tool for comparing suspension?
Quote Dave Weagle:
_dw said:
07-15-2009
CC is the moving focus of the axle path curvature. IC is the rectified force center of the linkage system. Because the axle path is always perpendicular to the driving force vector, IC and CC both lie on the driving force vector. You need to know IC to determine anti-squat, but if you want to compare suspensions, CC is a much more useful parameter.
dw★link
Split Pivot
@daveweagle -Twitter
  • 1 1
 So doesn't pedal kick back help you boost abit out of berms under compression, if the pedal rises up as you compress the suspension, if you resist the kick back with your weight wount it transfer to the rear wheel causing abit of a boost??,, i had a ddg slammer with a consentric bb swing arm, and that old tank used to boost abit doing the compression kick back trick..
  • 1 0
 Sounds about right
  • 2 0
 At least with this bike you would need to be absolutely railing a berm at below 10mph in order to use 75% travel. Seems somewhat unlikely that you would experience this on an SB140.
  • 4 0
 I like the part where the rear wheel moves
  • 1 0
 i have a question. if a suspension design is tuned correctly, for example to counter pedal bob, will a basic shock (eg fox float dpx) function as well as a high end shock (like float x2)?
  • 1 0
 No matter what you're likely to pick up useful tuning capabilities with higher-end shocks like the X2. The ability to independently tune HSR, LSR, HSC, LSC is useful as you get more and more capable/particular about suspension performance. You're also going to get a different feel from your suspension based on the particular shock type (air spring DPX, larger air spring X2, coil spring DHX2) with the volume of the air spring correlating to more or less progession/linear feel - also tunable by adding and removing tokens. None of this means you cannot get terrific performance from a "lower-end" shock - but you can really fine tune and achieve more linear feeling from a higher end shock.
  • 1 0
 Low speed compression damping does affect pedal-bob quite a bit. I personally don't want to rely on the damping of a shock to counter this though, since more low speed compression also leads to a harsher feel.
  • 1 1
 The more I see these the less I want to know, haha. There's so much more to bikes than "science". No one does double blind testing on frames so brand vibe and intended purpose is gonna have an effect. Think how great bikes performed 10 years ago before you found out they were shit a few years later. Placebos are REAL. Hats off to those that put in the time, but if you let me know a bike pedals alright and maybe whether or not the suspension has a linear or progressive feel, that's pretty much all I need to know. Just don't have the maths in me.
  • 2 0
 How a bike rides is completely dictated by the science behind it, 100%. Every single mm and degree works together to change one another. You are right in that you may not be able to tell how a bike rides by looking at its numbers but that's only because there is infinite combinations of dimensions and movement. But rest assured they are completely responsible for how that bike rides.
  • 1 1
 "When this is combined with a shock full of volume spacers it could pose the problem of running into a wall of progression rather than running into the end of travel. In extreme cases that wall can often feel like a bottom out despite you not actually getting to full travel."

Why would you have that many spacers in it? A curve like that simply doesn't need a super small volume air spring to prevent harsh bottoming, thus won't need much in the way of spacers. What's the first solution to "not using all the travel"? Remove spacers!
  • 1 0
 now do same with G1 or saturn 14/ST

sb140 just proving what my 5-year-old carbine 29 is still good enough with it 160/140-125 AM/downcountry geo
  • 3 0
 That’s a lot of pedal kick
  • 3 1
 Do one of these write-ups on an Ibis so we can learn the secrets of how it does the job
  • 1 0
 Dan is there any chance you could make that background IMAGE available. I would love to make it my custom Teams background. Want to put of bunch of engineers off balance!
  • 1 0
 THe numbers?...I thought they are talking about the most important numbers..$$...the rest is pure theory...wayy to many variables to make those numbers sens-able.
  • 1 0
 I 3D scan frequently at work for various jobs using my Trimble station, this has to be the most impractical use of a scanner ever....
  • 1 0
 Surely the instant centre of Yeti’s switch infinity is the near vertically moving pivot? Infinitely (and impossibly) long 4 bar suspension, my bottom...
  • 4 1
 soooo out of my depth
  • 2 1
 The final thoughts sound a lot to me, that it is just for diversities sake.
  • 2 0
 Such rad kitten we have here...
  • 2 2
 There's few other bikes which I would care so little about. I don't know why exactly, but literally nothing about this excites me or makes me want to get a Yeti.
  • 3 0
 There are few other bikes that I am as excited about as a Yeti. Wink To each their own, I guess.
  • 3 2
 It's called Switch Infinity because you'll switch it out an infinite amount of times due to it failing.
  • 2 1
 I'm so confused, where are the Friday Fails? Is this taking place of Friday Fails?
  • 2 0
 I'm just wondering how the geometry is affected when the chainstays crack?
  • 1 0
 Weird it’s called an infinite link when it is the instant center that exists at infinity.
  • 2 0
 Oh man, is this a mini enduro?!
  • 1 0
 I thought this was going to be an article explaining/defending the price of these dentist wagons...
  • 2 1
 Long story short, go fast.
  • 4 3
 Reading the title, I thought it was the real number of broken frames!
  • 1 0
 Hey, can you guys do the spec enduro?
Cool articles, thanks
  • 1 0
 TrailPOV on youtube has done that one. His methodology is slightly different (he uses a continuous curve rather than separate curves for different sprockets, based on the assumption that if you're using more travel, you're moving more quickly and hence in a higher gear) so it's not directly comparable to what PB does here, but the mathematics is fundamentally the same.

www.youtube.com/watch?v=JYJxK1Dr_2s
  • 2 0
 Sports!
  • 1 0
 Norco Torrent says..... "hold my beer"
  • 1 0
 i thought it was sharks n laser beams not cats...
  • 1 0
 The simple joy of mountain biking....
  • 2 0
 27.5? Next!
  • 1 1
 I see they are sticking with pepto blue. At least we know the money is going for the tech and not the paintjob...
  • 1 0
 ok yeah this is cool but where are the friday fails...
  • 2 0
 Tacos and beer anyone?
  • 1 0
 This bike is lost in both translation and explanation!
  • 1 0
 Have you seen "Much Ado About Nothing" by William Shakespeare? Wink
  • 3 3
 Someone please give me a summary in one or two sentences.
  • 21 2
 its good, but not good because harsh
  • 24 5
 It's really expensive, you'll have fun riding it because you spent loads of money on it and it's a nice bike, you probably won't spend much time thinking about anti squat as you go over the bars at 5mph.
  • 6 2
 It's expensive AF. Tacoma sold separately.
  • 2 0
 With this bike you squat less. But you are getting kicked when going slow!
  • 1 1
 The important number here is the price of this bike
  • 1 0
 +- 1-5 overage monthly salary.
but its depends on what position and where you working
  • 1 0
 2 mooch moonie
  • 1 1
 Smaller wheels... pffff
Below threshold threads are hidden

Post a Comment



Copyright © 2000 - 2020. Pinkbike.com. All rights reserved.
dv65 0.029773
Mobile Version of Website