in any orientation. This can cause the vehicle to suddenly move in the direction that the caster is pointed. At slower speeds, the caster’s ability to swivel can correct the direction and can continue travel in the desired direction. But at high speeds this can be dangerous as the wheel may not be able to swivel quickly enough and the vehicle may lurch in any direction. Electric and racing wheelchair designers are very concerned with flutter because the chair must be safe for riders. Increasing trailing distance can increase stability at higher speeds for wheelchair racing, but may create flutter at lower speeds for everyday use. Unfortunately, the more trail the caster has, the more space the caster requires to swivel. Therefore, in order to accommodate this extra swivel space, lengthening of frame or extending the footrests may be required. This tends to make the chair more cumbersome. Caster flutter can be controlled by adding dampers or increasing the friction of the swivel joints. This can be accomplished by adding washers to the swivel joint. The friction increases as the weight on the front of the chair increases. Anytime the caster begins to flutter, it slows the chair and shifts weight to the front wheels. There are several online anti-flutter kits for retrofitting wheelchair casters in this manner. Other methods of reducing caster flutter include increasing swivel lead, using heavier grease, reducing the mass of the wheel, or increasing friction with the ground by changing materials. Casters are also stopped completely using caster cups. Ergonomic designs Ergonomic casters are designed with consideration for the operating environment and the task to be performed so that any injurious effects on the operator are minimized. Long-term repetitive actions involving resisting casters can contribute to strain injuries. Improper specifications can also contribute to reduced service life of casters. Many parameters play a role in how well the caster performs. Parameters such as tire hardness, tread width and shape, the length of the trailing offset (the 'caster') and wheel diameter all affect the effort required to start the platform moving. Harder wheels will make the caster easier to roll by reducing deformation resistance. A less inflated tire offers more deformation resistance and thus more effort is required to move the attached platform. Turning effort is affected by the amount of caster and by the wheel diameter. Enhancements to traditional caster design include toe guards, track