NHTSA Preliminary Evaluation PE21017

The Office of Defects Investigation (ODI) opened this Preliminary Evaluation (PE21017) on July 9, 2021 for model year (MY) 2016-2019 Triumph Thruxton and Speed Triple model motorcycles based on allegations of loss of front braking performance.Vehicle Owner Questionnaires (VOQ) indicated riders were experiencing a soft front brake lever that could result in an unexpected extended stopping distance. On July 28, 2021, ODI sent an Information Request letter to Triumph to learn more about the subject components and alleged defect.On September 24, 2021, Triumph submitted its response, which ODI analyzed.ODI learned that the majority of the VOQ incidents occurred two or more years after the motorcycle was manufactured. The manufacturer recommends changing the brake fluid every two years, regardless of mileage. As the manufacturer’s warranty lasts for two years from the date of sale, many dealers covered the complicated brake fluid replacement procedure under warranty. However, most of the motorcycles involved in these incidents were overdue to have their brake system serviced. Triumph conducted testing of the brake system to better quantify what riders were experiencing.Triumph found pulling the lever a second time immediately after an initial pull did result in less lever travel for the same force exerted on the lever.This reduction was two millimeters or less.Additional testing was conducted to ascertain the caliper force generated relative to various lever forces.Triumph found that the caliper force varied +/- 2% between the first and second pull of the front brake lever and any given applied force. Triumph claimed that the lack of proper maintenance was the cause of the soft brake lever.Triumph conducted additional testing to quantify this claim.The lever travel between the first and second pull increased 150% on an improperly maintained system versus a properly maintained system.However, the caliper force only decreased 2-3% on average with this increased lever travel