Don't Overlook the Gearbox

Hi Samantha,

Knowing a motorcycle’s gear position can be valuable to a reconstruction, especially if you have a stuck tach needle. Here’s a video detailing the process I use when the motorcycle is still in gear at the time of my inspection.

Quick heads-up: the video is ~5 years old, which explains the COVID hair and Axiom apparel (my old firm, since acquired by JS Forensics).

A few caveats. First, it's possible for the gear lever to be actuated during the collision sequence, so know how the motorcycle moved throughout the impact and be ready to abandon or adjust your analysis accordingly.

Second, without a stuck tach, these analyses aren’t as helpful for big-engine bikes. A Yamaha R1 can go anywhere from 30 to 130 mph in 3rd gear.

Third, as with lots of motorcycle speed methodologies, a gearing analysis should be backed up by one or more independent analyses (rotational mechanics, simulation, wheelbase reduction, vault, EDR, etc.).

Establishing the gear position is a bit of an intimidating process at first, but after you practice it a bit, the fear of botching it subsides!

Keep exploring,

​Lou Peck
​Lightpoint | JS Forensics