‘Horst Link’ Design

The ‘Horst Link’ was developed by Horst Leitner and Karl Nicolai and first patented(a) in 1993. Several of the patented ideas were bought by one of the mountain biking industry giants, Specialized, between 1998-1999. The concept behind the ‘Horst Link’ was to reduce the change in effective chainstay length and hence chain growth. This is achieved by placing a pivot below and in front of the rear axle (as seen in Figure (a)). As a result of this pivot location, the rear axle is mounted on the effective seatstay of the linkage, and is no longer arcing around the mainframe pivot point like single pivot designs.

When calculated correctly this design can achieve a number of positive attributes, such as eliminating pedal kickback and any form of braking induced suspension reaction which are detrimental characteristics. However to achieve this, the axle path becomes less desirable, and so a compromise has to be made to get an optimal design.

‘Lawwill’ Design

A less commonly used four bar linkage design is the ‘Lawwill’ linkage developed by Mert Lawwill in Germany between 1992 and 1994 and patented in 1996(b). The concept of this design is the most advantageous of the basic four bar linkage designs in terms of axle path manipulation and brake isolation. Once again the axle is mounted on the second bar of the linkage; however that link is now much shorter and actuates the shock via a long seat stay mounted rocker as seen in Figure (b). The problem with this design is that, in order to achieve the desired strength, the linkage inherently uses a lot of material to get the desired stiffness characteristics from the extended rocker, and so the weight increases.

‘Faux Bar’ Design

The most basic four bar linkage design is the ‘Faux Bar’ design as seen in Figure (c) above. This is the suspension linkage design Banshee Bikes currently use for its large travel bikes. This linkage still has the axle mounted on a chainstay which is directly mounted to the mainframe via a pivot, exactly the same as a single pivot design, and so will have the same axle path characteristics. However the two extra links that act as an interface between the chainstay and the shock via the seat tube, in this example, make this design much more laterally stiff than a single pivot bike due to there being two frame mounted pivots as opposed to one. The rocker plates that actuate the suspension can be orientated in a variety of geometries and can actuate the shock in a number of different ways (as seen in Figure 3) and can offer more adjustability in terms of leverage ratios experienced by the shock. 

Although the increased number of pivots provides the linkage with a better lateral stiffness, as well as more options for geometrical optimisation of the linkage and frame design, there can be maintenance problems if the bearings are not designed to take the dynamic and static loads demanded of them. This can prove costly for the consumer as well requiring time off the bike for the customer to replace them. This is a potential problem that must be considered when designing all multi pivot bikes; will the benefits outweigh the potential reliability issues associated with more complex designs?

‘Virtual Pivot Point’ (VPP)

The Virtual Pivot Point linkage design was developed by James Klassen of Outland Technologies and was patented(c) in 1995. The VPP linkage is essentially achieved by mounting the axle on a triangulated second link (that encompasses the rear wheel) of a four bar linkage design, (as shown in Figure 4). The VPP linkage directs the rear axle along a predetermined S-shape path as the suspension compresses. A result of this concept is that the suspension will not compress much when pedalling due to the inherent chain stretch designed into the system.  This results in good acceleration characteristics without the loss of small bump absorption. The main drawback of current VPP, other than the potential maintenance problems that are apparent in all multi pivot bikes, is that there is no brake isolation. This means that the suspension will become less reactive under braking unless a floating brake (which will add weight and complexity) is used.

This design has gained a very good reputation with mountain bikers worldwide, and so has become commonly used. Several variations of the design have been developed to make small improvements to the stiffness and suspension characteristics with care taken to avoid patent infringements.

• January 30, 2009 -- Single Pivot Suspension Design
• June 20, 2008 -- Magura Mountain Bike Brakes and Suspension

Although the concept is essentially very simplistic, consideration must be given when deciding the location of the pivot and the shock mounting points. For example an apparently insignificant change in pivot position will alter the axle path, and therefore dramatically change how efficiently the bike pedals and reacts to bumps.

Mountain bikes will experience lateral forces on the wheels when cornering, landing slightly sideways, or going through very rough terrain. It is difficult to make single pivot bikes as laterally stiff as multi pivot bikes due to the moments all being transferred through just one pivot. As a result of these thrust loadings on the bearings they tend to wear out faster. However this is not a big problem due to the fact that the bearings used are normally standard sizes, hence affordable, and easily purchased when requiring replacement.

• January 31, 2009 -- Four Bar Linkage
• June 20, 2008 -- Magura Mountain Bike Brakes and Suspension

While many companies offer great products, one of the best is Magura. Magura offers a wide range of products ranging from brake sets to rearshocks, and while these products kick butt, where Magura really kicks butt is in their offering of front forks. Somehow these guys manage to offer not only a couple of high quality forks, but they manage to offer forks for almost any riding style. If you are into going a little crazy freestyle, than you want to check out their 2008 Wotan suspension forks. If you are a just more of a functional rider than Odur style is something you want to look into. It really doesn’t matter what kind of riding style you have Magura bike parts certainly offer something for everyone. However their forks are really only the beginning.

Among the many offerings from Magura are some of the best brake sets you will find on the planet. With a combination of unique design and high quality materials, Magura has managed to create both disc and rim brakes. While true you can only do so much with a rim brake, going anywhere else but Magura for disc brakes is a waste of time. The disc brakes that Magura offer have two ideas in mind, that they work, and that they are easy to remove when you need to get to the tire. Overall they just plain rock.

So what is it that makes Magura so special? They have a passion that is almost unmatched in the field. The people at Magura want to make the best product not just for the sake of making a few bucks, but because they want the best ride they can get. This fierce dedication and passion to making bike parts has truly allowed Magura to rise above the rest of the crowd. If only all parts and bike manufacturers approached their craft in the same way.

• January 31, 2009 -- Four Bar Linkage
• January 30, 2009 -- Single Pivot Suspension Design
• January 19, 2009 -- Formula The One Brakes Review
• January 16, 2009 -- Proper Disc Brake Wear-In