How rotational mass affects braking – Bendix explains

For many owners of new four-wheel-drives, especially those who want to tour or regularly hit the tracks, one of the first modifications they’ll make is increasing the tyre size of their vehicle, to give extra clearance beneath the diffs or lower control arms, and other underbody components.

Larger diameter tyres provide added clearance but also increase rotational mass, meaning greater braking force is needed to bring the vehicle to a safe standstill within an acceptable distance.

As is the case with most modification though, increasing performance in one area can often lead to compromises in others. In the case of larger diameter tyres, the extra clearance comes at the cost of reduced acceleration and braking performance, plus increased fuel consumption.

There are two main reasons for this drop-off in performance and they both go together. The first is extra weight – taller and wider tyres are heavier than what normally comes with a vehicle as OEM fit.

A move to a mud terrain tyre from an all-terrain or road biased tyre – which is usually stock fit on a new vehicle – also adds weight due to more robust carcass construction and chunky lugs. Depending on the size of tyre chosen, owners may also have to select a wider rim to accommodate tyre dimensions, again adding weight.

Owners who fit larger tyres such as these 35x12.5 mud terrains will know how heavy they are if they've ever had to handle one. The added weight adds to the rotational mass.

Weight as well as the diameter of a wheel and tyre package affects rotational mass. Rotational mass refers to any components that rotate with the wheel assembly: tyres, wheels and lug nuts etc. The further away the mass is from the axis of rotation, the larger the rotational mass, and the greater the force that’s needed to start and stop the assembly from rotating.

As a guide, if the radius of a wheel and tyre package is increased by 10 per cent, the amount of extra brake force needed to safely bring the vehicle to a stop will also be around 10 per cent, that’s roughly the diameter increase you’d get going from a 265/65 R17 to a 295/70 R17 tyre. And if changing from an all-terrain to a mud terrain pattern in this size, tyre mass would also increase considerably.

While Bendix can’t restore the factory acceleration and fuel consumption to what it was with stock tyres, it can certainly help reinstate and even exceed factory braking performance.

Bendix offers a number of braking solutions for vehicles running larger diameter tyres, that will restore (and even exceed) OE braking performance.

Bendix Ultimate 4WD™ Disc Brake Pads

Upgrading brake pads is the most cost-effective way to improve braking. Ultimate 4WD™ Disc Brake Pads are engineered for extreme conditions and hardworking 4WD applications; they also feature a high-tech ceramic formulation that provide low dust and noise and Bendix’s premium Mechanical Retention System (MRS) for improved pad attachment strength.

Braided brake lines

Another easy braking upgrade is to fit Bendix Ultimate 4WD™ Brake Hoses, featuring PTFE (Teflon®) tubing that’s wrapped in woven stainless steel 304 braid. This tough construction means they won’t expand under high pressure, ensuring a firm and responsive pedal feel.

Brake booster upgrade

Bendix also offers its ADR-approved Ultimate 4WD™ Brake Booster Upgrade, which can deliver up to 30 per cent greater stopping power, thanks to its dual diaphragm design which significantly reduces pedal effort.

Ultimate 4WD™ Disc Rotor / Drum upgrade

The next level in addressing the negative effects of rotational mass is to upgrade the disc brake rotors or drum brakes. Bendix’s Ultimate 4WD™ Brake Drum Upgrade Kit features High Carbon Metallurgy, SwiftFit protective zinc coating and Epoxy Coated Hub, leading to improved braking.

The Ultimate 4WD™ Sports & Performance Disc Brake Rotors feature four-wheel-drive specific metallurgy that increases rotor strength at elevated temperatures while also providing high wear resistance. Other benefits include high efficiency cooling pillars that channel cool air into the rotor, expelling hot air faster and increasing resistance to thermal cracks. Additional performance is achieved through Bendix’s Diamond Tip Slot technology which helps to expel gasses, dirt and water more efficiently from the rotor surface.

Bendix Big Brake Upgrade Kits provide all the components required to significantly enhance the braking performance of four-wheel drives fitted with big tyre and wheel packages.

Complete Bendix upgrade kits

Brake upgrade kits give buyers all the benefits of Bendix’s individual braking technologies in the convenience and cost effectiveness of kit form. Bendix offer several kit options including the Ultimate 4WD Brake Upgrade Kit (brake pads, rotors, brake hoses, brake fluid, Ceramasil lubricant, rotor wipes and more).

Then there are the Ultimate 4WD™ Big Brake Upgrade Kits, Bendix’s premium package with larger diamond tip slot front rotors, powerful 6-piston front calipers (front kit), a rear drum to disc conversion and all the associated parts required to complete the work (rear kit), along with Ultimate 4WD Brake Pads, Ultimate Brake Hoses and the ancillary products mentioned in the standard Ultimate 4WD Brake Upgrade Kit.