Thermal comparison of heavy vehicle wheel assemblies under alpine braking

Abstract

Overheating brakes cause brake fade, tyre blowouts and vehicle fires, but no study has investigated the influence of wheel configuration or rim material on these catastrophic failures. Laboratory measurements of the transient thermal response of heavy vehicle wheel assemblies to [Formula: see text] of alpine friction braking are presented; comparing brake and tyre temperature when using dual and single wheels with steel and aluminium rims. Under an averaged braking power of [Formula: see text], the final temperature increase of the brake was [Formula: see text] (3.7%) higher when using steel versus aluminium rims. The final increase in maximum tyre temperature was [Formula: see text] (16%) higher when using aluminium versus steel rims and [Formula: see text] (76%) higher when using single versus dual wheels. The greater thermal conductivity and cross-sectional area of the aluminium rims relative to the steel rims reduce the thermal resistance of braking heat flowing into the tyre; leading to higher tyre temperature when using aluminium rims. Dual rims and tyres have larger surface areas than singles which convect more heat to the air at lower temperatures; leading to cooler tyres when using dual wheels. The higher thermal diffusivity of aluminium and lower thermal capacities of single wheels also cause tyre temperature to rise more rapidly than when using steel rims or dual wheels. These results indicate that the risk of tyres overheating (which could lead to blowout) from extended use of the brakes is increased when using single wheels compared to dual wheels and further exacerbated by using aluminium rims compared to steel rims.