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Continuing on from the Specialized Stumpjumper EVO, we get to the Marin Mount Vision.
The Marin has an absolutely wild suspension system, with links everywhere and a slider thrown in for good measure too. It's actually a six-link bike, and takes a minute or two of brain cog turning to analyse.
Mount Vision Analysis Details
Travel Rear: 150mm
Travel Front: 150mm
Wheel Size: 27.5
Frame Size: M
COM Height: 1150mm
Chainring Size: 32T
Cassette Cog Sizes: 50T, 24T and 10T
Compared to the first version of this system, used on the Wolf Ridge, it seems Marin has beefed up the links, and added another link that's attached to the top tube to the equation in an attempt to up the stiffness. But there’s still plenty of connections between the rear wheel and main frame, and given that the slider isn’t keyed it’ll transmit lots of the twisting forces over to the links and pivots.
This layout is very complex, and with that, it must bring a lot of weight just to make the layout happen. There are lots of overlapping going on, with extra parts for the links and slider system, and the shock forces directed in the middle of tubes.
The layout also seems to limit them with the actual seat tube angle. They have to have clearance for the swingarm to tuck up in there, which is why its actual angle is quite slack. Unless you’re at the saddle height that Marin took for defining its geometry, you’re going to have quite a drastic change in TT and where your weight falls between the axles.
Most of the Marin’s suspension curves are actually pretty nice, so maybe it’s better to focus on them rather than the frame. Looks are subjective, but it's hard to please the eyes of an engineer with this layout, although it does make Marin and Polygon stand out from the crowd. It's possible that similar suspension curves could be re-created with simpler design, but that's a different topic altogether. For now, let's take a closer look at the numbers.
This video is of a different model than what's analyzed here, but it makes it a little easier to comprehend the Naild R3ACT suspension design. Leverage Ratio
The Marin Mount Vision has a 29.5% leverage ratio progression with an average ratio of 2.5. It's a regressive to linear to progressive curve.
Two things stand out here. Firstly, they go below a ratio of 2, which crosses under what some shock manufacturers state as their lower limit. This could mean that the suspension setup has to settle for some deep stroke hang up in the rebound department at ratios below 2 when the shock is moving fast enough to create big damping forces.
Secondly, there’s a big hump at the beginning of travel. Going from progressive to regressive and back and forth at high frequencies can create problems for the rebound. Looking at the shock shaft speed in the rebound stroke it will be slowing down constantly until the hump, and then need to speed back up again as the ratio drop on the other side.
The same can be said in the compression stroke, having slightly reducing damping before the progression kicks in to build damping pressure for the remainder of the stroke.
There’s a fair chunk of progression in there, which is calculated from the top of the hump to the end of travel. The average leverage ratio is on the lower side of things, potentially helping the damping have enough of a control over the shock movement.
Marin claim to be doing size specific kinematics, which is cool. It sounds like it has to do with the different center of mass heights between S/M riders and L/XL riders, but without analysing the different sizes it's hard to say how the changes in kinematic impact the leverage ratio and the balance of leverage ratio plus the weight transfer reactions. This is a nice feature though, and one that not many brands do.
The Mount Vision has bucket loads of anti-squat in every gear. The 50T climbing gear has a good amount of anti-squat all the way through travel, and enough there to even combat some of the cyclical mass of legs spinning, which in this gear could be at high cadences. This increase throughout travel is going to lead to quite an amount of pedal kickback that could easily be felt in this gear and at the slow climbing speeds that this gear dictates. Pedal kickback shouldn't really be a priority in design, but when it gets this high, it's worth pointing out.
Moving down the cassette the anti-squat increases quite a bit, and the progression of it as you go through the travel becomes steeper and steeper. Having a bit more than 100% anti-squat is good to combat the other forces that happen when you pedal that are trying to compress the suspension. But at some point, more becomes too much, and you’d be putting far too much force back into the suspension, enough to adversely affect your center of mass. For example, 200% would be pushing back at you with 2 times the force needed to keep your center of mass static. 100% is already a large force to resist the weight transfer, so adding it again would extend the suspension and push the center of mass forward. The Marin goes up to almost 300%.
These really high anti-squat figures are in the harder gears, and so the added anti-squat effects might be lost a touch in the head down shenanigans of sprinting. Also, the mass transfer inertia is lower at higher bike speeds. But still, the bike is going to be over fighting the mass transfer and be adversely affecting the suspension.
The slack seat angle is going to benefit from the bike's high overall anti-squat, and having at least progression and not mega high leverage ratios at the sag point and forward will help further to keep the bike up and keep that seat angle where it’s more effective.
The Marin's anti-rise numbers are really nice, with what should be a good amount to resist a good chunk of the mass transfer. Not too much to cause harshness from the suspension working too hard to combat the weight transfer, and not too little to have vagueness at the rear wheel.
The bike should react nicely when braking, due to the leverage ratio and anti-rise numbers. Maybe if the braking is done in some rowdy terrain, that is going to tweak and twist the bike, the lack of direct connections from the rear axle to main frame might come into play more. Some baguette wielding people might describe this as the bike finding its own line. But depending on the amount of twist there, it could introduce a bit of uncertainty when braking from all the loading and unloading on the structure.
Being really critical, it would be nicer to see the anti-rise increasing as you get further into travel. Not a huge amount, but enough to provide proportionately more support for the high energy hard braking situations that demand the most from the bike.
Compared to the Stumpjumper, which finishes at around 21mm farther forward from where it started, the Mount Vision's axle path only comes just over 4mm forwards. Having less forwards movement gives the wheel more room to get out of the way of the vector created from the wheel hitting bumps. But the fact that it doesn't travel very far forward comes back to the high anti-squat, and therefore, high pedal kickback values.
Until you really start to prioritise axle path over other characteristics, most of the bikes we analyse will have a touch of rearwards to their axle path, but will be biased towards the axle moving forwards as you go through your travel.
This more vertical axle path, combined with not too much progression and lower overall ratios, should mean that the suspension spends less time dealing with each impact before allowing the wheel to continue moving forwards with the bike. Final Thoughts
Previous Behind the Numbers Articles:Stumpjumper EVO Suspension AnalysisIntroducing Behind the Numbers - A New Suspension Analysis Series