Yaris DPL 2011: Greater agility, improved steering feel and enhanced ride comfort

The new Yaris has been engineered to enhance every aspect of the driving experience, with a particular focus on urban agility and safe, predictable handling.

A new body structure offers improvements in both rigidity and aerodynamic efficiency. The new Yaris features a 15 mm wider front track than its predecessor, and particular focus on weight-saving measures have reduced the unsprung mass of the vehicle to promote greater agility.

The proven combination of MacPherson strut front and torsion beam rear suspension has been modified, the Electric Power Steering revised, and both the throttle characteristics and the transmission and differential gear ratios optimised.

In combination, these measures equip the new Yaris with sharper acceleration, greater agility and handling precision, improved stability and yaw response, and enhanced ride comfort.

Body structure — increased rigidity and enhanced aerodynamics

The extensive use of high-tensile steel within the new Yaris' construction not only saves weight, but also offers greater bodyshell rigidity for handling stability. Some 50% by weight of the new body is formed in high-tensile steel, allowing for a 5kg weight reduction with no loss of torsional stiffness.

Enhancements to the inherent aerodynamic efficiency of the new bodyshell include numerous underbody airflow rectification components which create a flat surface, smoothing the flow of air under the new Yaris. These include a front spoiler a full engine undercover front, centre and rear spats and a rear undercover which incorporates NACA-style vertical fins, creating a laminar flow effect to enhance stability.

Weight saving — lower unsprung mass to promote greater agility

Despite a small increase in length and an improved safety specification, the new Yaris is, in fact, 20 kg lighter than its predecessor.

The extensive use of high-tensile steel accounts for a 5 kg saving in bodyshell weight, and a new, lightweight rear seat design accounts for another 5 kg. The replacement of numerous steel suspension components with aluminium lowers vehicle weight by a further 3 kg.

Additional weight saving measures include the replacement of copper wiring with aluminium in 53 electrical circuits -effecting a 38% reduction in wiring loom mass, a 30% lighter starter motor, a smaller, lighter tailgate lock and striker mechanism, the adoption of a plastic fuel filler pipe, a plastic turbo air tube on the 1.4 D-4D turbodiesel engine, and a thinner instrument panel construction.

The reduced unsprung mass of the new Yaris promotes greater agility for ease of use in the urban environment.

Suspension — proven systems tuned for optimum performance

The new Yaris' front suspension is the independent, MacPherson strut system, which delivers high levels of ride comfort, driving safety, agility and grip, and a class-leading turning circle of just 4.7 metres.

In the interests of mass reduction, the revised system replaces the solid anti-roll bar, and steel strut bearing and stabiliser link of the current model with a hollow anti-roll bar, a plastic strut bearing and an aluminium stabiliser link. These weigh reduction measures improve the suspension's road tracking performance.

System performance has been enhanced through the adoption of a shock absorber 'initial valve' to improve damping force response, a rebound spring to reduce roll (in Sport grade models) and a change in lower arm bush characteristics. These revisions combine to reduce vibration and enhance ride smoothness while improving steering feel and yaw response.

To the rear, suspension mass reduction measures include a change of torsion beam inner tube from steel to aluminium and the adoption of a high-tensile material for the coil spring. A change in the torsion beam bush characteristics allied to an increase in spring rate lateral direction has improved the performance of the system, once again reducing vibration and enhancing ride comfort, while improving vehicle agility.

Improved steering feel and response

The new Yaris' Electric Power Steering (EPS) offers variable assistance for maximum urban manoeuvrability combined with optimum weight and feel during high speed driving.

For increased driver involvement, the steering column rake has been lowered by 3 degrees to 25 degrees to deliver a more engaging driving position. To improve steering feel and vehicle response, a quicker steering gear ratio has been adopted, increasing from 50 mm/rev to 56 mm/rev. The bearing rigidity of the rack and pinion gearing has also been improved to reduce friction and system play, further enhancing accuracy and feel.

To maintain ease of steering despite the adoption of a quicker gear ratio, the EPS motor power output has been increased from 55 A to 70 A.

Brakes and tyres

Incorporating Electronic Brakeforce distribution (EBD) and Brake Assist, Traction Control (TRC) and Vehicle Stability Control (VSC), the new Yaris is equipped with the latest braking and stability systems.

The vehicle is fitted with 258 mm x 22 mm ventilated disc brakes to the front, and solid 278 mm x 9 mm discs or 203 mm drums to the rear. The braking system benefits from the latest generation actuator, a 9" brake booster, stronger servo assistance and a lightweight, highly rigid brake pedal constructed from thin, plasma welded plates, giving an improvement in pedal feel.

Newly developed, fuel efficient tyres offer ultra-low rolling resistance and excellent levels of grip with no impact on stopping distance, while their reduced vertical stiffness further improves ride comfort.

14" wheels are fitted with 175/70R 14 tyres and 15" wheels with and 175/65R 15 tyres. The rolling resistance coefficient of both the 14" and 15" tyres has been reduced, contributing to lower fuel consumption, while the dry mu of the 14" tyre has been increased to improve grip.