Thursday, May 30, 2013

Hub Stability

Hub Stability      
                Many people know that the hub geometry can make for a stiffer wheel. The wider apart the flanges are on a hub, the larger the bracing angle will be. This helps to create a stiffer wheel as the base of the triangle the spokes make as they enter the rim is wider. A wider base triangle is going to be a sturdier structure compared to a triangle with a narrow base. This illustration below demonstrates that and it’s easy to see which triangle (or hub) looks stiffer.

              But just moving the flanges outward isn’t the whole story; there is also the need for hub stability. You can have a very stiff hub, but if it’s not stable the wheel will not be as responsive, especially when climbing or sprinting. You can see from our hub designs that we have some of the widest hub flange spacing in the industry. In fact when riding the 11 speed Shimano version of the hub we decided to make the axle 131mm so we could cheat the flanges further out an extra millimeter. It may not seem like much, but it really does help with both stiffness and tension balance between drive and non-drive side spoke tensions.
                To add hub stability, you want the forces on the bearings to also be pushed out as far as possible. If the bearings were located in the middle of the hub the axle could have a pivot point in the middle. By moving the bearings to the very edge of the hub (right next to the drop outs in the frame and fork) the hub has the widest possible bearing stance which makes for the most stable option. Think back to that triangle again; if you had to support that triangle you are going to try and do so as far out as possible.

         Unstable supports under a triangle                         Stable supports under a triangle
This is where our new hub designs really shine. The non-drive side bearing has been moved out to the edge of the hub and is now supported by the hub shell. This makes for the widest possible hub stance and also eliminates the need for a long end cap system like many other hubs feature.  A pre-load is used to tighten the hub together on the axle and the small end caps locks into the pre-load and prevents it from unwinding when you ride. This pre-load system means no side pressure is placed on the bearings, greatly increasing the quality of the ride and prolonging the life of the bearings. 

     Hub stability is often overlooked as people want to make sure that the hub creates a very stiff wheel set (which we definitely have as well). However, many of us stand up to climb or sprint many times during our ride, and in those situations having the added stability in the hubs is very noticeabe. It will make for a more solid reacting wheel and one that inspires confidence. It’s just another way that we looked at the entire wheel system when designing the 2013 line up on our wheels.

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