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Introduction

Vehicle ownership cost is major influencing factor in process of buying a car. Fuel efficiency is one of the critical parameters impacting the ownership cost. Today all OEMs are very competitive in terms of fuel efficiency for their vehicle. To achieve better Fuel Efficiency, OEMs approach mainly depends on various factors as listed below
Factors That Affect Fuel Efficiency
In this blog, our focus will be to understand how tyre rolling resistance affects the fuel efficiency and how we can measure this impact. We will also see how tyres with low rolling resistance result in lower fuel consumption.

Rolling Resistance:

It is described as an energy required at tyre to keep your vehicle at consistent speed on road. In simple words it is an effort required to keep vehicle rolling. Values of rolling resistance depends on tyres used, surface on which it rolls, operating conditions, tyre pressure, load and speed. Impact of Tyre Rolling Resistance Crr  on traction and tread wear is predictable in most of the cases. Below graph gives a general relation between Crr, Traction and Tread Wear.

Graph Showing Relation Between Tyre Rolling Resistance, Traction And Tread Wear

Rolling Resistance And Fuel Economy- Test Methods

Majorly we can evaluate the impact of tyre rolling resistance Crr on vehicle fuel efficiency by following two test methods.
Tests On Test Track And Dyno Lab
Generally at ASI, for above explained test methods, one vehicle with different tyres is used. Fuel flow sensor with accuracy of ± 1 and 0.2 % of repeatability across measuring range is used for calculating fuel flow rate and total fuel consumed.

Relation between tyre rolling resistance and fuel economy

Below graph shows the relation between Crr Tyre Rolling Resistance and fuel economy as percentage of mean for various road conditions verses the percentage change in Crr from Mean Value. Overall trend is similar for different road conditions.
Graph Showing Realtion Between Fuel Economy And Tyre Rolling Resistance
From various tests it is understood that ~10% of decrease in Crr results in improvement of fuel efficiency by ~1-2 percent. For some cases, this relation linearly follows for 3 -5 % fuel saving for 30% reduction in Crr . Thus tyres with low rolling resistance saves fuel although this range is basically dependent on various test condition change like different roads, testing duration, weather conditions etc.

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Anuj Jha

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