Investigating Aftermarket Parts Performance in Motorcycle Crash Incidents Expert Article

In this article, motorcycle expert Roland Hoover discusses aftermarket motorcycle parts and accessories. He examines the standard of care for vehicle manufacturers, part suppliers, mechanics, and motorcycle owners within the context of rider safety.

Motorcycle Part Failure Expert

Investigating Aftermarket Parts Performance in Motorcycle Crash Incidents

Motorcycle culture is interesting and ever evolving. For many riders, the motorcycle becomes an expression of their own unique identity and modifications utilizing aftermarket parts are common. A 2013 survey of motorcyclists1 conducted by the National Surface Transportation Safety Center for Excellence at Virginia Tech revealed that more than 70% of survey participants had modified their motorcycle with aftermarket parts or accessories.

Motorcycle modification ranges from moderate to extreme. Typical modifications include the replacement of minor components that do not drastically affect the handling or performance of the vehicle, such as grips, seats, engine covers, exhausts, lights, foot pegs or floorboards, and license plate brackets. Major component replacements that more drastically affect the performance profile of the motorcycle are also relatively common and include custom wheels, custom brakes and drive pulleys, upgraded suspension components, non-spec tires, hand controls, and handlebars. There are several hundred different styles of each of these components and new styles are continuously developed and made available to motorcyclists.

The proliferation of aftermarket parts has been a boon for the industry, but it has also created a considerable degree of complexity for vehicle manufacturers, parts suppliers, mechanics, and owners alike. The vast range of aftermarket parts, which are available in a broad range of quality, creates an assortment of potential issues as motorcycles are fitted with unique parts combinations that have not necessarily been designed to work together. The most common issues experienced with modified motorcycles involve individual parts failures, fitment and compatibility issues, and installation errors. We will examine these issues from various perspectives below.

Motorcycle Manufacturers

Motorcycle OEMs have a varied approach in regards to aftermarket parts installation on their motorcycles, some manufacturers design their motorcycles in a way that makes adding accessories difficult and un-profitable for aftermarket manufacturing, discouraging the use of aftermarket parts. On the other hand, Harley Davidson and BMW Motorad design their motorcycles to support the custom accessories culture and collaborate with Aftermarket Manufacturers to develop products.

OEMs will periodically rollout minor changes to their motorcycles to keep up with the changing tastes and emerging market trends. When motorcycle design changes are introduced to production, it is up to the Aftermarket Manufacturers to research and determine the changes and test fit their products to the updated motorcycle. Many Aftermarket Manufacturers have teams of engineers performing this function year-round. OEMs that compete in the Aftermarket Parts market are responsible for the design, function, testing, and fitment of their aftermarket parts in the same way as they are for their Original OEM parts.

The onus is on the manufacturer/distributor of the accessory part to confirm it fits and functions as intended on all years and models they claim it was designed for.

Aftermarket Parts Manufacturers

Trends in motorcycle accessories change rapidly and accessory manufacturers must respond quickly in order to stay competitive. This style-driven industry creates engineering challenges as manufacturers seek increasingly shorter product development cycles to bring their latest designs to market.

When designing new visual styles of critical components like wheels, brakes, suspension, and handlebars; manufactures must utilize computer finite element analysis and physical testing to ensure their designs are safe for the extremes of riding motorcycles and to ensure they meet applicable requirements. Some of the smaller design firms contract with the larger companies to perform their product testing; however, many do not have the tools or resources necessary to properly test their designs for strength and durability.

The accessory brands have the responsibility to produce quality components that can withstand the rigors of reasonably anticipated use and misuse. They are also responsible for providing installation manuals and user guides that can be used by people with varying levels of mechanical skills. Incomplete or confusing instructions can lead to parts and accessories being installed in a manner that can be prone to falling off, breakage, or failure resulting in a collision or injury.

Motorcycle Mechanics

When installing aftermarket components, the mechanic/technician is responsible for installation, proper fitment, and testing the operation of the component. Any discrepancies must be reported to their service manager and then depending on the issue to the customer and or the aftermarket manufacturer. Competent motorcycle mechanics perform a multi-point inspection every time they work on a motorcycle as a way to ensure their customers’ safety. These inspections can prevent collisions and other injuries from occurring by preventing or detecting mechanical and/or electrical failures.


Many customizations can be installed by the motorcycle owner with a few simple hand tools, and relatively little skill. The choice to perform the repair or modification themselves or use a mechanic is typically a financially based decision. According to the Virginia Tech Survey of Motorcyclists, nearly 60% of motorcycle owners will perform routine service and maintenance themselves up to a point before they will take the vehicle to a dealership.

When riding, significant vibration occurs from the road and engine, sufficient enough to cause fasteners to loosen and possibly introduce stress cracking or failure in aftermarket components. The Motorcycle Safety Foundation created the mnemonic “T-CLOCK” to help riders remember the items in a pre-ride safety check. Each letter represents a category of the motorcycle, as follows:

  • T – Tires and Wheels (Tire pressure and wear, wheel spokes and bearings, brakes, etc.)
  • C – Controls (brakes, shifters, hand levers, cables, hoses, throttle)
  • L – Lights and Electrical (headlight, taillight, brake and turn signal operation, horn, wiring)
  • O – Oil and other Fluids (levels, leaks, and condition)
  • C – Chassis (check for cracks, breaks, bearings, suspension, belt or chain, loose fasteners and components)
  • K – Kickstand (retracts firmly, no bending or damage, cut-out switch operates)

If riders/owners choose to perform their own installations, it is incumbent upon them to follow provided instructions and check to ensure that the installation does not interfere with other systems/components.

Forensic Investigations of Failed Motorcycle Components

The forensic experts at Robson Forensic regularly provide Expert Witness Investigations in incidents involving motorcycle crashes, fires, and other mishaps. Determining the cause of component failures, and subsequently liability, can be a complex process in cases involving modified motorcycles.

To discuss your case with an expert, submit an inquiry or contact the author of this article.



Featured Expert

Roland Hoover, Automotive Engineer, Motorcycle & Bicycle Expert

Roland Hoover

Automotive Engineer, Motorcycle & Bicycle Expert
Roland Hoover is a mechanical engineer with broad experience in automotive and motorcycle engineering. His career includes more than 20 years of engineering experience at OEM vehicle manufacturers,… read more.