Braking and Swerving Capabilities of Three-Wheeled Motorcycles

In my SAE paper titled “Braking and Swerving Capabilities of Three-Wheeled Motorcycles,” I report…you guessed it…on the braking and swerving capabilities of three-wheeled motorcycles. If you want to read the entire paper, here is a link where you can purchase it.

Here are some highlights:

Numerous studies have documented the braking capabilities of two-wheeled motorcycles with riders of varying skill levels and with a range of braking systems. Because motorcycles with conventional braking systems require the operator to independently control the front and rear brakes, most of these studies have examined differences in the deceleration achieved with the rear brake only, with the front brake only, and with combined use of the front and rear brakes. These studies have shown that the maximum deceleration for two-wheeled motorcycles with conventional braking systems is achieved with combined application of the front and rear brakes, although the decelerations achieved with the front brake alone are nearly as high as those generated with both brakes. Decelerations generated with use of the rear brake only are consistently lower than those generated with the front brake or with both brakes. This is the case because, during heavy braking, a significant portion of the weight of the motorcycle and rider shift to the front wheel of the motorcycle. This results in the available traction at the front wheel being significantly higher than the available traction at the rear wheel.

For a three-wheeled motorcycle with two wheels in the rear, a greater percentage of the motorcycle’s weight is carried by the rear wheels and the weight transfer to the front of the motorcycle during braking is less significant than for a two-wheeled motorcycle. This changes the characteristics of the deceleration when an operator uses only the front brake or only the rear brake. The testing in this paper explores the significance of these differences.

Here are some of the findings:

With the three-wheeled motorcycles in this study, the average decelerations for the tests that utilized both the front and rear brakes varied between 0.74 and 0.91 g. This range is situated in the upper half of the corresponding range for two-wheeled motorcycles (0.54 to 0.96 g). This is consistent with the fact that two-wheeled motorcycles require more skill for braking since there is more of a risk of capsizing if the rider locks up a wheel, particularly the front. For the three-wheeled motorcycles, less skill is required since the risk of capsizing is minimal, and the rider can lock up the wheels.

The average decelerations for the tests that utilized the front brake only varied between 0.36 and 0.42 g. This range falls within the range that is typical for rear brake only braking on two-wheeled motorcycles (0.31 to 0.52 g). The average decelerations for the tests that utilized the rear brake pedal only varied between 0.70 and 0.84 g. This range falls within the upper half of the range that is typical for front brake only braking on two-wheeled motorcycles (0.52 to 0.80 g).

The braking system on the motorcycles tested in this study is partially integrated in that application of the rear brake also applies some pressure to the front brake even if the operator does not apply the front brake lever. The logic behind this integration scheme seems to be a carry-over from the braking dynamics of two-wheeled motorcycles where a majority of the braking capability comes from the front brake. Based on the decelerations observed in this study, operators of three-wheeled motorcycles like the ones tested in this study could benefit from the logic of the integration being reversed, such that application of the front brake level applies pressure to both the front and rear brakes.