Our third bike in the trail category marks the halfway point and another change in suspension layout (and brand) to something a little less common.
Unno, by their description, offers limited-edition, hand-crafted frames. The limited-edition tag being very true, with only 50 of each frame made available every year. Technically speaking, almost all carbon frames are hand-made, but if you have followed the story of Unno then you know this is a little different
. It appears that blood, sweat, and tears went into taking Unno from an idea to an incredibly boutique brand that has done everything themselves. Literally everything. They are open about their quest to not take the “easy” road to make a bike by using the far east, choosing to do almost everything themselves instead, including design, engineering, manufacturing, and testing.
A tip of the cap should be given to any individual or team that takes the perilous plunge to start their own company in the bike industry. No matter the level of products that eventually emerge, or not in some cases, it takes guts to do that. Unno has five bikes on offer, ranging from XC hardtails all the way up to full-on downhill bikes. The Dash sits in the middle of their offerings in terms of intent, and it aims to offer the best incarnation of a trail bike from their point of view.Scanning
Again, a big thank you is extended to Thibaut and Bastien from The Factory
bike shop in Fribourg, Switzerland, for letting us borrow one of their most prized possessions. Thankfully, 3D scanning requires minimal contact with the subject; once we had the bike setup it was a completely noninvasive process to scan the bike, drastically reducing the risk of damage to it. One of the more difficult areas to scan on a bike are the fork and shock. Often, a high gloss black can be a difficult surface for the lasers and cameras to get a hold of the data.
The Unno's high gloss black finish is one of the trickier surfaces to scan, but the MetraSCAN 3D can see it well and can switch from a wide laser grid to a single line to help pick up the detail where needed.
For the Unno Dash, the whole frame is a high gloss black finish. And while it is a damn nice, some scanners could see it as a problem. However, the MetraSCAN 3D we used on the Dash lapped up the shiny black surface without issue. It’s a versatile scanning system and allowed the same level of detail to be grabbed as the other, often more brightly colored, bikes. The MetraSCAN also offered the ability to switch from a large grid of lasers to a single line to capture data in hard to reach areas, like deep pockets, and to help focus in on the details you want to capture.
And with the intricacy of the Unno design, and the short link layout and shared pivots, it's very compact in areas. The MetraSCAN was able to really get in there and extract the necessary data, though.
Using VXelemts, the reference points from the scan be picked out and turned into simpler geometry for then generating the kinematic.
The Unno Dash is a 29” wheeled, 130mm-travel trail bike with a 140mm travel fork.
Behind the scenes of Unno and Cero, Cesar Rojo’s other company, there is a hive of minds that have worked on motorcycle projects. There’s the potential that Unno frames include the learnings from this experience in the motorcycle industry, especially when it comes to engineered flex.
Unno Analysis Details
Travel Rear: 128.7mm
Travel Front: 140mm
Wheel Size: 29"
Frame Size: Medium
CoG Height: 1,100mm
Chainring Size: 32T
Cassette Cog Sizes: 50T, 24T and 10T
Motorcycle chassis development is years ahead of mountain bikes in terms of understanding, quantifying, and designing performance-enhancing flex, and Rojo has been quoted to say that many brands don’t understand the chassis flex concepts nor have the time or resources to properly test it out. While chassis flex could be perceived as negligible in comparison to the amount of suspension travel on offer, it’s a hugely important factor in a bike’s performance out on the trail, and the Dash might likely be benefiting from Unno’s experience in this field.
Continuing from last week, we still have a four-bar suspension system, but now with much shorter links connecting the rear triangle to the rest of the frame. Generally, as those links reduce in size, we see more movement in the curve shapes. The single pivot and long-link four-bar systems we’ve already analyzed having straighter lines, whereas the short link bikes have more pronounced curves to them.
As the link lengths shorten, the angles that they rotate through increase. And with the instant center being depicted by the intersection of those links, it can move around in a bigger window in space. For example, the upper link on the Dash moves through an angle of 58.5° whereas on the Commencal Meta TR 29 the upper link moves only 36.4°.
The Dash’s links rotate in the same way – co-rotating. This is opposite to brands link Santa Cruz and Intense that employ counter-rotating links. A small shock extender bridges the gap from the rear triangle to the shock while going around the seat tube, and it shares a pivot with the upper link.
Currently, only one size of Dash is available, with it being somewhat equivalent to many other brands' medium sizing. Unno is also very transparent with their suspension curves and geometry. Their suspension graphs show the full curves with values on the axes and specific values for their setup range between 30% and 40% shock sag.
Their geometry chart is one step ahead of a lot of manufacturers and shows seat angles for four different seat heights; as your seat gets further up, it angles back to the bottom bracket and gets slacker. Unno also uses an extremely short head tube, at just 85mm. If you prefer a more hands-down cross-country race setup, then this would be easy to achieve on the Dash. But if you run a tower of stem spacers to get your hands higher, then the 455mm static reach of the Dash will start to become a lot shorter.
Mike Levy reviewed
the Unno Dash last year and commented on the bike being an efficient climber yet one perhaps suiting a more precise and skilled rider that likes to move their bike around on the trail. He also commented that the Dash did have a bit more feel of hitting the bumps compared to other trail bikes. So, we can take a look at how the numbers and curves reflect those ride impressions.
The instant centre 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.
The Dash has 25.36% progression from the start of travel to its lowest leverage ratio at 63% shock stroke, or 64.5% (83mm) rear-wheel travel. After that inflexion point, it’s 10.5% regression until the end of travel. Regression being a leverage ratio curve that starts low and finishes high.
The Dash starts at 2.81 and then falls to 2.1 before rising back up to 2.32. Over the whole leverage ratio curve, there’s an average ratio of 2.26. This is considerably lower than the previous bikes we have seen in the trail category. Remember, lower leverage ratios see the force input at the rear wheel multiplied less when it gets to the shock. But as the ratio gets closer to 1:1 the rear wheel and shock would be moving the same distance. So, a lower leverage ratio system would be moving the shock shaft faster than a highly leveraged system.
But that end-stroke rise in leverage ratios would see the shock shaft then starting to slow down. And the inverse would be true when the bike was in rebound from bottom-out, with the shock speeding up as it reaches the lowest leverage ratio and then slowing down as it went back to zero travel. Sometimes these inflexions can be seen at the beginning of a leverage ratio curve, where the hump and its altering of the shock shaft speed can give a slightly harsh feeling. But as the Unno’s hump is at the very end of travel, the amount of time spent in this region is less than if it were at the beginning of travel.
The shape of the leverage ratio curve is parabolic, and when differentiating it we can see that it is pretty much exactly an x^2 curve.
Unno says that the Dash was designed with an air shock in mind, so this could explain that end-stroke regression, with the general shape of an air shock spring curve having a pronounced ramp at the end of travel. Unno does publish a rear axle load curve and shows the extent of running maximum or minimum spacers inside the shock. Unfortunately, there’s no mention of which air shock this is for, as each air shock has a different air spring curve and with options for OEM tuning for bike manufacturers.
At 35% shock stroke sag, which is what Unno recommends, there will be 38% rear-wheel travel. Still a little less deviation than an extremely progressive bike but a touch more than the Norco and Commencal that we looked at earlier.
The Dash actually runs a 200 x 57mm (imperial length) shock. Currently, this isn’t the biggest of problems with lots of manufacturers still making shocks in this length. Fox recently announced its new DHX2 and Float X2 with continued development in their imperial lengths.
With such lower leverage ratios than the Norco and Commencal, less air pressure would be needed to achieve the same sag and with the shock moving faster compared to a higher leveraged bike, the shock would then be able to generate more damping force. Mike commented that the Dash did transmit more feeling of hitting bumps than other trail bikes, and this could be down to those low leverage ratios combined with a shock that is already quite well damped. Perhaps the combination of the two brings the amount of feedback to the rider up a little, especially compared to something like the Norco with much higher ratios and a less damped shock. This could have been something that Unno designed-in to give the rider enough feedback to know what’s going on down at the wheels. As Mike said, this heavily damped feeling is liked by some riders and not by others.
One thing that this leverage ratio and shock combination does give is support, and as Mike commented, it makes the bike react very well to rider inputs for getting up and over obstacles on the trail. Less of the rider’s input would be taken up in the suspension and more going into finding those sniper takeoffs and landings that the Unno apparently loves.
The Unno Dash comes in two build options. The Race version gets a Shimano XTR drivetrain and a 34-tooth chainring, while the Elite model comes with a SRAM Eagle drivetrain and a 32-tooth chainring. We'll stick with the same 32-tooth chainring and 50T, 24, and 10T cassette gears for the analysis, although we can add in how the bigger 34T chainring would affect the bike on the Shimano build. That short link curve style is apparent in the anti-squat, with the extent of the change in the curves becoming more pronounced the harder into the gears you go.
In the easiest climbing gear, the Dash starts at 131% and drops 70% at the end of travel. There is a small lull before the end of the travel where it drops to 66% but it is really contained to the last third of travel. At 35% shock sag there is 83.5%. Compared to the Norco and Commencal, this is a touch lower around the bike’s sag point and would combat a little less of the bike’s load transfer from acceleration.
In the 24T cog, we see a bigger spread in percentages and a more pronounced dip in that final third of travel. Despite there being a higher starting percentage, at 35% sag there is a drop in anti-squat percentage, down to 77.6%.
In the 10T cog, we see the starting percentage way up at 228% and finishing at 47% with the most pronounced belly in the curve. At 35% sag, it sits at 66.8%. In the harder gears, the acceleration magnitude would generally be less than in the lighter gears, and so the follow-on effects of the load transfer-induced squat might be less notable.
Despite there being slightly less anti-squat on the Dash compared to the Commencal and Norco, the much lower leverage ratios would also come into play by providing some support when pedaling. Levy commented that the Dash is an efficient climber, and while we’re not up around or above 100% for the anti-squat, there is still a huge portion of the load transfer from acceleration combatted. And those lower leverage ratios would add support against the forces acting to compress the shock while pedaling.
For the Shimano equipped bike, with its 34-tooth chainring and 51-tooth biggest cassette cog, there is a drop in the amount of anti-squat. The curve shape follows the 32/50 we’ve already analyzed but is just shifted down by 3-4%. With the bigger 34-tooth chainring, and in the familiar 24 and 10-tooth cassette gears, the trend is the same and just sees a shift down of the anti-squat curve of 7.5% and 18% respectively.
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 centre of anti-squat, the green dot. The orange dot represents the 100% anti-squat mark.
The absolute maximum of pedal kickback comes with the smaller 32T chainring and 50T cassette, with 25°. There is a theme with the Dash to start off with a touch more pedal kickback than the Commencal up until halfway through travel, after which the pedal kickback reduces and finishes following a similar gradient as the Norco, if that were to finish at 130mm travel.
Comparing the Unno to the Commencal, which also has 130mm travel, the Dash has about 2° less pedal kickback in each gear. 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 Unno have to be traveling to never encounter the effects of pedal kickback? 8.7kph or 5.4mph. Slower than both the Commencal and Norco by a few kph. If we then dropped down to the hardest 10-tooth gear, where the pedal kickback is considerably less, then that critical speed drops right down to 8.3kph or 5.2mph.
To give some more real-world context, recent rides I’ve been doing around Champéry have shown average descending speeds between 20 to 26kph. If we take into account that for these very downhill-focussed trails, we would be further down in the cassette gears and closer to the lowest 5.2kph critical speed, we would easily never be encountering the effects of pedal kickback for that situation.
Looking at the Shimano specced Dash Race, with the 34-tooth chainring and 51-tooth biggest rear cog, the maximum pedal kickback drops when compared to the SRAM bike, following that trend in the drop of anti-squat. For the 34/51 we see a drop of 2°, for the 34/24 a drop of 1.7° and for the 34/10 a drop of 1.2°. Along with that drop in pedal kickback, we would also see a drop in the minimum speed needed to completely avoid pedal kickback, dropping to 7.9kph or 4.9mph.
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.
When we look at the anti-rise curve for the Dash, we can spot that short link curve shape again, but much less pronounced. In fact, the Dash has some of the least roller coaster-like curves for a such a short link bike that we’ve analyzed. The anti-rise starts at 80%, drops to a minimum of 66% at 66mm rear travel, and then back up to 74% at the end of travel. At 35% shock sag the anti-rise sits at 67%.
Overall, the Dash would be counteracting two-thirds to three-quarters of the load transfer from rear braking, depending on where you were in the travel. The remainder would then show itself in some suspension rise. This wouldn’t be as much rise as the Norco, but a bit more than the Commencal.
While we see more variation between bikes in the anti-squat, there is a much smaller window for the anti-rise curves. At our halfway point in the Behind the Numbers series, we have the Unno sitting right between the Norco and Commencal. Nowadays, more and more bikes follow this trend of being between 100% and 30% for the anti-rise, with few bikes going wildly outside that range, and the vast majority sitting under the 100% mark.
It's only the red IC dot we need to calculate anti-rise. The orange one again represents the 100% anti-rise mark.
The Dash sees the most rearward axle path so far, bearing in mind we’re looking at non-high pivot bikes. It starts off with 2.2mm rearward travel at 23% shock stroke, moving then 13.2mm forwards until the end of travel.
At 30% and 40% sag marks, the axle path would still be in its forward-moving phase for when it would encounter a bump. Despite that increase in rearward axle movement, the Dash finishes in just about the same axle position as the Commencal.
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.