ROTWILD bearing technology

The EIR ball bearings produced exclusively for ROTWILD differ from the predecessors in many attributes. The aim of redevelopment was to further extend the service life of the ball bearings on the highly strained rear swing arm and reduce the variety of parts along with the associated assembly and production errors.  

Five bearing sites

Five insertion points

The specially developed EIR ball bearings are put to use at five bearing sites:

  1. Main swing arm bearing (close to bottom bracket)    
  2. Horst link rear suspension at dropout    
  3. Pivot point on seat tube linkage    
  4. Mounting for spring element in the linkage    
  5. Linkage fastening on main frame

Different-sized EIR ball bearings

Differences to standard bearings


On the basis of our finite element analysis (FEA), the maximum forces occurring in the rear suspension are determined for the different load cases. These data have been used to develop three different-sized EIR ball bearings for the ROTWILD rear swing arm.      

  • EIR ball bearing Type I: Main swing arm bearing 15x28x9mm    
  • EIR ball bearing Type II: Horst link pivot point at dropout 8x19x6 mm    
  • EIR ball bearing Type III: Linkage 10x22x6 mm

Schematic illustration of inner bearing ring and spacer

Structure of the ball bearing

The special feature of the EIR bearings is the design of the inner spacer. It is wider than is the case in a conventional bearing this permits greater support for the entire bearing system and prevents small relative movements between the individual parts.

Schematic illustration of the full ball bearings

Advantages of EIR technology

EIR ball bearings are known as full ball bearings, i.e. the bearings are filled with the maximum number of balls. Whereas a standard ball bearing of dimensions 15x28x9 has a maximum of nine halls inside (known as rolling elements), EIR ball bearings are filled with 18 balls.  

The advantage of having a greater number of balls is the higher static load rating of the bearing. Every EIR ball bearing has no difficulty in withstanding the bearing forces arising during the ride. Wear on the bearing is therefore reduced significantly and the durability of the entire bearing is increased.  

EIR ball bearings use a stainless, wear-optimized steel alloy. They are also closed with a special seal on both sides and hence completely maintenance-free. This prevents dirt and water from entering the bearing. In addition, the bearing grease is not rinsed out and the bearing remains permanently lubricated.

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