When it comes to front suspension, the telescopic fork is pretty much the only game in town. Motion hail from France and are doing things rather differently, however. Their E18 fork is unconventional in pretty much every way, with a linkage system designed to prevent travel-robbing brake dive and using an innovative damper and leaf spring.
Motion's main party piece is the fact that the linkage design is said to almost eliminate brake dive, meaning that the amount of travel on offer to absorb bumps remains the same, whether you're braking heavily or not at all - an obvious advantage compared to a telescopic fork, which relies on low-speed compression damping to try and mitigate the effects of dive under braking and in other situations. Motion say that as dive isn't an issue, their fork requires much less low-speed compression damping and can, therefore, be more supple for better bump absorption and rider comfort.
A linkage design also offers a number of other potential benefits - Motion claim that minimal maintenance is needed for a start - but it's probably important to understand the pros and cons of a linkage fork versus the telescopic one you probably have on your bike before we get really stuck into what makes Motion's design special.
What are the advantages of a linkage fork?
We might as well start by saying that a 'traditional' telescopic suspension fork has a number of things going in its favour. They're easy to produce with precision, are relatively simple and can be made to be stiff in a number of directions for a low weight, plus it's easy to package a spring and damper into them. On the downside, as the fork bends under braking, they're prone to suffering from bind as friction increases between the two tubes that make up the fork and consequently reduces sensitivity. That means that minimising friction is crucial to high performance.
They also have another drawback. While it's possible to tune an awful lot of different characteristics of a suspension design that uses linkages, a telescopic fork can only ever move in one plane - up and down. That means that if you want to tweak how the front suspension responds to weight shift under braking (anti-rise/anti-dive) or tweak the axle path then you're out of luck, beyond altering static frame geometry.
Linkage forks offer another solution to this, but they've failed to catch on in the mountain bike world despite several efforts, such as the Lawmill Leader and AMP Research forks, Whyte's PRST-1 front end and the USE Sub fork, which also claimed anti-dive benefits. The motorbike world has a rich history of linkage forks, even in motocross, while many BMW bikes still use their Telever design.
Of course, because of the vast number of parameters you can adjust with linkage fork design, you really can't generalise about them too much, but there are some issues common to all. The first is that they're inherently more complex and therefore more costly to produce. Having a number of pivots and linkages also mean there's more potential for flex and play between each pivot - which is obviously multiplied by the number of pivots. Their inherent complexity also means it's possible to do some very bad things to the handling if you don't get it right. Whyte's PRST-1 fork was notorious for firing riders out the front of the bike thanks to an axle path that went backwards and then up.
The Motion anti-dive solution
When creating the Motion fork, designer Mathieu says that he didn't start with any preconceived ideas apart from wanting to solve the problem of brake dive. As a physicist by training and engineer by trade - in the nuclear industry no less - he did this by first writing out all the forces involved mathematically, then trying to balance them all while eliminating the forces that cause brake dive. After accounting for rider's centre of gravity and influence on weight transfer, braking torques and so on, he says he came to a solution that works to counteract brake dive independently of rider weight and centre of gravity, bike wheelbase and other variables, using brake torque to generate an anti-dive force.
Motion-E18-linkage-fork-first-ride-review-106.jpg, by Jon Woodhouse
With a set of pivot points defined by his equation, he then took a blank sheet of paper and designed a fork around those. Luckily, it was possible to get them in the right place and still make room for the wheel and to fit into a standard bike frame. In the simplest terms possible, the moment of torque produced by braking is countered by an opposing force, isolating dive from braking from the compression forces from bumps. As you brake harder, the braking torque and weight shift that wants to make the head tube drop and fork compress increases, but the geometry of the linkage creates an opposing force from the brake torque that acts to try and force the headtube of the bike back upwards. It's a cunning mathematical balancing act which teases out the dive due to braking from bump forces acting on the tyre.
As it happens, the fork doesn't eliminate dive entirely - there's apparently still a small amount engineered in as a touch of dive helps load up the tyre gently during braking, increasing grip and giving more feel so you can judge traction. They also say that the axle path is pretty much the same as a telescopic fork, only altering in the last third of the stroke to push the tip of the fork outwards to increase the wheelbase slightly.
Low maintenance priorities
Apart from combating fork dive, Motion's other design priority was to minimise the maintenance needs of the fork - often a bugbear of a linkage design. To that end, they use composite bushings in all the linkages that are then precision machined and pressed into the fork - a number of the linkages don't even use bolts and none need lubrication. They claim the ability to get many years of use from them with no maintenance needed in the interim.
The fork also does without the usual coil or air spring, using instead a bow-shaped carbon and glass fibre leaf spring on the drive side leg of the fork that's used in tension rather than compression. It requires no maintenance and the amount of progression is dictated by the shape of the spring - there's only one shape at the moment, but Mathieu says they can make pretty much any spring curve they fancy and in the future, it'd be very easy to switch out depending on what the rider wants.
Preload can be adjusted to give sag to suit different rider weights with the spring on the fork, and it's stated that it's able to cope with rider weights from 50-100kg. It's worth noting that this system doesn't change spring rate as well as preload/sag in the way adding air to an air spring would, so I'd suspect that this might cause some issues if you're at either end of that weight spectrum - again, that could be fixed with specific springs for heavier or lighter riders.
The damper lives on the other leg of the fork and it's a really very neat bit of kit. Motion's main aims were reliability and simplicity. For the former point, it's a low-pressure system that has a through-shaft damper rather than one that uses an internal floating piston, like pretty much every mountain bike shock. Through-shaft shocks are used in F1 and Moto GP suspension - as well as on Trek's latest full suspension machines - as they have very low damping lag. Lag is the amount of time it takes for oil to start flowing through the damping ports and generating damping force, so a faster and more controlled response is always better.
The fact that the oil isn't highly pressurised, as it would be in any normal system including a through-shaft shock, means that the seals can be lower friction and also less prone to leaking. How they achieve these low pressures without the oil in the shock cavitating is currently being patented so Motion isn't keen to publically share the details, but I've seen a schematic and it's a very, very neat architecture that gets around this issue, has a self-cooling effect and also compensates for any expansion in the oil due to heat.
It's possible to adjust the rebound setting on the shock by twisting a collar. Moving counter-clockwise speeds up the rebound while turning it clockwise past a certain point puts the fork into a firmer compression mode for greater support, for example when hitting big jumps at a bike park or so on. Although the shock has low-speed flow ports and shimmed high-speed circuits, they've chosen this setup for ease of use, though it'd be possible to have more conventional independently adjustable rebound and compression adjustment.
So how does it ride?
This really is the million dollar question. Lapierre kindly lent me a demo Zesty AM 527 Ultimate, which comes fitted with a 150mm travel RockShox Revelation fork with Motion Control damper. I headed up into the trails around Morzine and Les Gets to get a handle on how a 'normal' fork felt before switching to the Motion fork.
Sadly, this didn't work out quite as planned as it became apparent that the Revelation wasn't in the best of health, with the fork running extremely slow despite having the rebound open all the way, with extremely dry and tight bushings being the likely culprit. Even so, it gave me a bit of a feel for how the bike and stock suspension reacted over a variety of terrain.
With the E18 fork fitted, I headed back up to ride the same trails. It's quite an odd experience to look down and not see a fork crown beneath you, but apart from that cognitive dissonance, bouncing on the bike does pretty much what you expect and it's possible to see how much travel you're using and check sag by looking at the exposed shaft of the shock and has an O-ring on it for exactly that reason.
Motion says that because the fork doesn't dive, they spring it fairly softly initially and there's little compression damping. That was definitely noticeable within hitting the first few bumps as it's certainly super supple there. That said, I definitely prefer having a bit more support to push against in corners - especially the fast, banked berms that are plentiful in Morzine - so I switched it into the stiffer compression mode and left it there for the vast majority of the ride.
However, the fork really starts to come into its own when you hit braking bumps on the entry to a corner. Although your reflexes are primed to expect the front of the bike to sit down as you're on the brakes and you brace for a rough ride, the Motion fork simply doesn't squat under braking and it's noticeable that you're not riding in the last third or so of your travel, but in the softer start of the stroke.
It's a little odd to feel if you're used to feeling that hard weight shift as you turn in - which can often be useful in maximising traction - but despite this lack of feel, it became less odd feeling the longer I rode. It's really impressive that, even if you slap the brakes on halfway through some braking bumps like an absolute fool, the feel from the front suspension remains just the same.
However, fast and flowing bike-park type trails aren't really the best place to explore this fork as dragging brakes through a bermed corner is generally avoidable with technique, braking bumps feel pretty awful whether you're on the stoppers through them or not and you really shouldn't be using the brakes on the sort of hard compression take-off and landings that dominate jumpy trails.
The best place to find out what the Motion difference would be a rough trail where constant drag braking is almost unavoidable - so something steep and rough. Happily, this sort of thing is easy to find in the Portes du Soleil and it's here that the Motion fork definitely felt like it was sitting higher in the travel, leaving it more able to deal with the terrain. I'd hesitate to comment on overall performance and damping control with my only yardstick being a knackered fork with a low-end damper, but obviously the Motion E18 outshone that by some way - as you'd hope. A proper back to back test session would be the only way to see how it compares to a fully functioning, high-end fork so hopefully, that's something we can do soon.
I suspect that for my preferences, a different valving setup or spring to offer a bit more support in the mid-stroke would be ideal. I'd also prefer to be able to tweak my rebound and compression independently - ideally with separated high and low-speed compression - but I do get the sheer simplicity of this setup would appeal to many.
I'd also be extremely interested to see how those bushings - which did have the occasional creak when riding - would be looking after a full winter of British grit and mud. Again, I didn't get chance to weigh the fork myself, but at a claimed weight of 2,100g, it's on the higher side compared to telescopic rivals despite the carbon fibre lower legs. I didn't notice much more flex or twist than a conventional fork when riding, but bench testing would be the only way to know that for sure.
The Motion E18 is a really interesting departure from convention. The anti-dive properties definitely work as advertised and if it requires as little maintenance as they claim, it makes the £1,390 asking price look better value than it might otherwise. That said, the latest offerings from RockShox and Fox might still be susceptible to dive by their design, but they offer really excellent spring performance and damping control, with the former brand's Debonair air spring and the latter's new FIT GRIP 2 damper being particular highlights, as well as an overall weight advantage.
However, I really don't think the Motion fork should be dismissed as a novelty idea - quite the opposite. I simply didn't ride it long enough to come out as a complete convert or to be able to sing its praises without reservation but I'm cautiously optimistic about it and convinced of the benefits of the anti-dive - though I think there might be a touch more development needed in spring and/or damping support and adjustment for my tastes. Regardless, there's some serious engineering thought put into it and Motion seems very dedicated to bringing their philosophy and ideas to market properly, so I suspect they are more than able to work on these.
The Motion fork is available in two formats, with the 27.5" wheel E18 coming in 150mm, 160mm and 170mm travel with a maximum tyre of 2.5". For people on 29" wheels or running 27.5" plus tyres, the E18+ comes in 1450mm, 150mm and 160mm travel with a maximum tyre of 29x2.6" or 27.5x3". Axle to crown lengths are similar to conventional forks and a tapered steerer is used, with the ability to run Boost or non-Boost hubs with an adaptor.
There will be the first batch of 500 forks available to buy now for delivery in September, with a 20% discount available if you sign up to be a 'Motion ambassador' before the end of July and preach to the masses about the brand.
I'm really hoping we can get our hands on a fork for a much more extended test soon, so fingers crossed for that. You can find out anything else you might like to know on their website.
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