It’s simple. It’s different. It’s better.
You don't need a degree in rocket science to understand it, but in case you want one, we'll go through some of the high level math here. You won't see ambiguous anti-squat percentages or any complicated reasoning that obscures physics. We're not looking to sound smarter, were looking to make better bikes and sell them to you by telling you exactly how they work.
As Einstein famously said:
"Everything should be made as simple as possible, but no simpler."
The Parallel Axle Path™ was chosen for its constant cornering characteristics, but that isn't its only attribute. Every design problem is a tradeoff between opposing characteristics. Yin and Yang. Often times we want to achieve a balance between what would otherwise be mutually exclusive characteristics. Smooth and playful are examples. You want a smoother ride, give the bike more travel. You want a more playful bike. Give it less travel. The goal of the designer is to balance these to the greatest degree.
With the Parallel Axle Path™, we choose to balance 4 characteristics — cornering, traction, jumping, and smoothness.
Cornering is best when the bike keeps a constant wheelbase, so that it rides predictably -> enter the Parallel Axle Path™.
Traction is most useful when your front wheel does not wash out -> we want to make it easy to keep traction on the front wheel. The Parallel Axle Path™ automatically weights the front wheel when the suspension compresses and both tire contact patches move back. This generates traction when you push into the bike.
Jumping is best when the bike generates more pop force while expending less rider energy. This can easily be calculated based on the axle path. The pop force will always be normal to the contact patch, so we will refer to it as being vertical even though on an actual jump the bike is tilted backwards and so is the pop force. The result will not differ as the axle paths will tilt by the same amount as the normal pop force.
A perfectly vertical axle path will absorb 100% of the vertical pop force. A perfectly parallel axle path at 64° will absorb only cosine (90°-64°) = 90 % of the vertical pop force. Thus, the Parallel Axle Path™, transmits more of the pop force, and damps less of the pop energy. Exactly what we want to make a better jumping bike. Lets add a little bit of detail to show this better.
We want a ratio between pop force and rider energy consumed, and we want this ratio to be as high as possible. This is what determines the efficiency of jumping a full suspension bike. Let us start from first principles.
Change in energy is equal to force multiplied by a change in displacement in the direction of the applied force.
If we assume our axle paths are linear, we can simplify to.
But now we want to consider displacements that are not in the direction of the force. To do this we will find the component of force acting along the displacement direction (i.e axle path).
Where we now introduce vectors, and where t⃑ is now the vector carrying the amount of travel used in any given popping situation, and its direction is along the axle path. We can write this in terms of angle.
Where θ is the angle between pop force (vertical) and the axle path. Now we are ready to write the relation that we want -> the ratio of pop force to rider energy consumed.
Let us compare the F/E ratio of a vertical axle path and the Parallel Axle Path™.
Vertical axle path:
Parallel Axle Path™:
The Parallel Axle Path™ will pop 11% more efficiently than vertical axle paths for the same suspension preload.
Now, how about smoothness? Lots of people say high pivots are smooth, but how smooth, and why? These questions can again be answered at a high level by consideration of the force lines of action in relation to the axle path.
For this, we need to pick a bump size. Let's consider a medium sized, 3" bump. A bump of given size will exert a normal force on the tire if the brake is not engaged and there is no tangential friction. The angle of this force can be calculated by finding the normal to the tangent of the wheel circle at the point the tire contacts the bump. We will assume the tire does not deflect here, as the deflection will in reality be small compared to the wheel diameter. Otherwise, you will probably be ripping the tire off the bead since these bikes corner so well.
The equation of a 27.5" circle is given by:
For y=3", x=8.57"
The angle of the tangent at that point can be calculated as:
This is the bump force angle and comes out to 51.4° from the horizontal.
The relative absorption of this bump force by the suspension can now be calculated. This is simply the dot product of the two lines. In this case, we want to absorb more force for a smoother ride.
The force absorbed by the suspension is:
For the vertical axle path:
For the Parallel Axle Path™:
The Parallel Axle Path™ will absorb 20% more force than a vertical axle path for a 3" bump.
We have now described the simple physics behind cornering, jumping, and smoothness. We have shown how the Parallel Axle Path™ is better according to physics in each area. But is it better according to humans? We surveyed 21 demo riders to ask. Here is what they said:
- Cornering: 100% replied 'Yes' to 'Does it Corner Well?'
- Jumping: 90.5% replied 'Yes' to 'Does it Jump Well?' 9.5% did not hit jumps.
- Smoothness in Rough Terrain: 90.5% replied 'Yes' to 'Does it feel good in rough terrain?' 9.5% did not hit rough terrain.
- Traction: We forgot to ask this question explicitly, but it obviously contributes to cornering.
"Better is always different, but different is not always better."