Mupo Motorcycle Suspension: The What, Why, and How’s About It

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At Lemick Racing, we prefer to offer Mupo suspension to our riders. Why is that? What’s the difference between Mupo suspension and all the other suspension sold in the motorcycle industry today? It’s a long, complicated story that involves manufacturing efficiency, cost effectiveness, tooling, materials, coatings, experience, politics, and the willingness to innovate.

Suspension has been around for a long time, but the basic principal of how it works hasn’t changed much over the years. Although we are now entering an era of electronics and magnetic hydraulic fluids, which will have a huge impact on the ease and speed at which suspension damping (the controlled movement of fluid from a high pressure area to a low pressure area) can be altered, the principles behind the way damping is achieved remains the same.

Mupo Shock Internal View

Basic suspension works like this: when a shock absorber is compressed or rebounds, hydraulic fluid is forced through an orifice or valve, which restricts the flow of hydraulic fluid at a specific rate. The flow rate can vary depending on the type of valve, the orifice shape and diameter, and the viscosity of the hydraulic fluid. The thicker the hydraulic fluid, the slower the fluid will flow through the valve or orifice and vice versa. The faster the fluid flows through the valve or orifice, the faster a shock can rebound or be compressed. We can also change the flow rate of hydraulic fluid by either opening or closing the valve or orifice that it flows through.

For example, on a fork leg compression adjuster, most forks use a tapered needle in a round orifice. As you turn the needle in (clockwise), the orifice becomes smaller, which reduces the rate of flow by making it more difficult for the fluid to flow through the orifice, effectively slowing the rate at which a fork leg can be compressed. As you turn the needle out (counter-clockwise), the orifice opening becomes larger, which allows more fluid to flow and thus increases the rate at which a fork can be compressed. The suspension rebound is essentially the same, except that by turning in the rebound adjuster we are reducing the rate at which a fork leg rebounds or expands to its original, extended position, and vice versa. Needle adjusters are used primarily on slow speed adjustment, meaning they have more control over larger rolling bumps and dips. However, they don’t have total control over that damping aspect since the piston valving works in conjunction with the needle adjusters to control fluid rates.

 

For suspension piston valving, it gets a little more complicated. In this case, we have a rod that moves freely within a cartridge. Usually on the end of the rod, a piston is placed with several orifices of specific shape and diameter for optimum, unrestricted flow. The orifices on the piston are closed off by thin, flexible metal shims of varying diameter and thickness. The valve shims operate in one direction. When fluid pressure is built up within the cartridge, the valves are forced to flex and to allow fluid to flow through the piston. By changing the thickness, diameter, or number of shims (called a valve stack), we can further reduce the rate of flow and the optimum pressure at which they open. Because these valve stacks only open in one direction, a second piston or valve stack must be used to allow the shock absorber to move in the opposite direction. This is why most of today’s shock absorbers or forks have a compression and a rebound valve stack.

Mupo Piston kit with Shims

There are also other variables that effect suspension fluid flow rates and suspension damping, such as friction, heat, and fluid cavitation, which is when fluid mixes with air and creates bubbles. The best theoretical shock absorber in the world would be a shock that produces no heat, no friction and no fluid cavitation, so that all damping is controlled by only the piston valving, needle orifice, and fluid viscosity. However, currently this is impossible. Today’s suspension manufacturers must try and find ways to reduce the friction, fluid cavitation, and heat that is generated in a shock absorber in order to allow the valving to have the most consistent control over fluid flow and damping. This is just one area where Mupo suspension excels above many other manufacturers today.

When it comes to suspension, there are several manufacturers to choose from. One of the first things to consider is how well that manufacturer deals with the scourges of damping (heat, friction, and fluid cavitation). I’ll break it down a bit.

FRICTION AND HEAT

When a shock absorber is working, parts are constantly in motion and fluid is flowing through pistons and orifices under high pressure. Pressure and friction produce heat. As the fluid is put under pressure and flows, heat is generated and hydraulic fluid begins to change viscosity and cavitate. The change in viscosity means a change in damping because the fluid becomes thinner as it heats, which causes it to flow more freely and reduce the damping. This change in viscosity will begin to degrade the suspension damping to a point where it can become ineffective at controlling fluid flow rates, essentially allowing the shock absorber to compress and rebound uncontrollably.

In order to maintain a constant damping rate so that the shock absorber performs the same at the beginning of a race/ride all the way to the end of the session, it is imperative that heat and friction are reduced. Mupo suspension achieves this in two ways. First, it incorporates special anti-friction coatings within the damper itself where bushings slide back and forth. Second, it uses special computer-aided designed orifices and piston porting that allow smooth fluid flow with less unintended flow restrictions. With these innovations, Mupo is able to reduce friction to the absolute minimum. Unfortunately, many other manufacturers skip the use of special anti-friction coatings and optimal piston porting in order to reduce manufacturing costs; however, friction and the heat generated by it increase in the process, which causes the suspension to wear down more quickly. This is why some racers and riders that have chosen not to use Mupo suspension unfortunately notice a lack of stability and control after riding for an increased amount of time. It’s a common complaint with other suspension manufacturers: damping is good early on and after friction heats things up, damping drops off. But damping is what we need to keep the tires planted on the asphalt.

FLUID CAVITATION

As previously mentioned above, Mupo has put a huge amount of effort into reducing heat and friction in their suspension components, but they have also placed an equal amount of focus on reducing fluid cavitation. The reason is simple. Fluid cannot be compressed; therefore, it must be forced through a piston or orifice into an empty area. High pressure fluid seeks out and moves to low pressure areas. It is this process that produces suspension damping. When fluid cavitates though, it creates air bubbles, foam and pockets of air within the fluid itself. These pockets of air travel with the fluid through the same valves, pistons, and orifices, and therein lies the problem. Unlike fluid, air does compress. When the fluid with air pockets flows through valves and orifices, it causes an unstable fluttering effect. This fluttering effect can greatly reduce the shock absorbers damping ability since it weakens the shims by causing them to repeatedly and uncontrollably over flex and snap back into open and closed positions. Think of each air bubble passing through a valve as a tiny, microscopic explosion that occurs because of the repeated, quick switch from fluid to air and back, which causes instantaneous changes between high and low pressure.

Fluid cavitation results in excess heat, damage to internal valving, and uncontrollable weakened damping. If a shock absorber built for fluid damping had only air internally, the damping properties would be reduced to almost none. This is why it is vitally important to reduce fluid cavitation in suspension components and why Mupo has put so much effort into reducing it.

To reduce fluid cavitation, Mupo has developed specially formulated, anti-foaming hydraulic fluids that maintain a constant viscosity under greater temperatures. Furthermore, the suspension components themselves have been designed and tested to provide the smoothest flow possible, while the anti-friction coatings further help fluid to pass more freely without sticking to surface areas so it can glide unimpeded. As stated previously, many other manufacturers unfortunately skip these important details to save costs.

OTHER CONSIDERATIONS

Mupo’s main focus isn’t to reduce manufacturing costs, it is to produce a superior suspension damper. One that outperforms their competitors, is built extremely strong yet also extremely lightweight, continues to work well under demanding and punishing use, is easily adjustable, and most importantly, is custom built to suit a racer or rider’s needs.

Mupo offers varying degrees of performance to suit each individual rider’s needs while maintaining the highest level of performance within the needed range. If a specific rider is not concerned with weight, Mupo offers less costly shock absorbers that use more conventional materials, yet still maintain the same high degree of machining tolerances, special porting and anti-friction coatings along with their typical manufacturing excellence. At the same time, for riders interested in extra weight savings, Mupo offers suspension components CNC machined out of Aircraft Grade Billet 7075 aluminum and titanium wherever possible. None of Mupo’s suspension components are made of low quality forged or cast aluminum, which are commonly used by other manufacturers to cut costs.

Unlike most suspension manufacturers, Mupo custom builds their suspension on a per order basis to suit individual needs, guaranteeing the best possible configuration for each and every racer or rider by taking into consideration not just the rider’s weight, but also the tires they use, skill level, and many other specific requests such as stiffer or softer setups. Other manufacturers can produce a quality shock absorber, but does it always fit the rider? Usually not. Simply changing spring rates on a new shock does not make it a “custom-built” shock.

Mupo tests the custom-built suspension to verify that it performs as intended by placing the shock absorber on a dyno and running it through rigorous tests in order to make sure the damping curve is as smooth, linear, and consistent as possible.

Finally, while the pro level racing industry seems to be focused around a few manufacturers, don’t be deceived. Those manufacturers do not offer those products to the public, and the products they do offer are nowhere near the same quality, nor are they built to suit a specific rider and dialed in the same way their pro level products are. Unlike the others, Mupo’s mission from the beginning has been to offer pro level quality and performance to the public. Even though racing manufacturers tend to try to inhibit the ability of other manufacturers to enter pro level racing, Mupo, through their extensive racing experience, has still managed to enter and provide suspension to pro racers and has performed extremely well, proving Mupo can beat the competition when given the opportunity. Mupo suspension has won several championships and races worldwide and currently has racers in World Superbike, Moto 3, Italian Superbike, Brazilian Superbike, Australian Superbike and several other countries offering pro racing. Fighting off the opposition and politics, Mupo will only continue to get bigger and better.

If you are concerned about the ease of servicing Mupo suspension, parts are readily available and should a need arise, Lemick Racing and/or Mupo are always here to help. We can service or repair all Mupo shock absorbers, forks, cartridges, and steering dampers. We can also talk you through installation procedures and setup. If you have any questions or concerns, please be sure to contact us.

“Currently Based in Bologna, Italy, Mupo race suspension began in the Apennines between Bologna and Modena at the beginning of the 90s. It was originally created by a young man, Gian Luca Maselli, who established himself as a developer and tester of suspension systems for motorcycles at that time.

During that period, Maselli also worked as a race technician for many top race teams. In 2003, Maselli went into partnership with Sandro Cassanelli, and this was the starting point of a close collaboration still going on today that, over the years, has made Mupo grow and has helped the company to become one of the leading Italian brands in the racing industry.

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