4WD MODIFICATIONS - SUSPENSION & BRAKES
The reason not a lot of effort is needed when braking is your vehicle’s brake booster that amplifies the force your foot applies to the brake pedal. A more powerful booster can improve braking performance.
Fitted to the engine-bay firewall, a vacuum-type booster contains a rubber diaphragm that divides the chamber in two, a return spring, an air valve and a push rod that passes through the booster and connects to the pedal.
The ‘boost’ comes from the engine’s manifold or vacuum pump system.
When the brake pedal is applied, the push rod that passes through the master cylinder opens the air valve within the brake booster. This allows air to enter the rear-facing side of the diaphragm within the booster, increasing pressure on that side. This forces the push rod even further into the piston within the master cylinder.
As more brake pedal pressure is applied, more air enters the booster’s rear chamber, multiplying the effect even further. Once the brakes are released, the return spring resets the diaphragm back to its original position.
Most OEM brake boosters use a single diaphragm, but the Bendix Ultimate 4WD Brake Booster has dual-diaphragm construction that effectively doubles the diaphragm surface area, without increasing the canister size.
The Bendix unit is said to be ADR compliant and to increase braking performance by up to 30 percent.
For added braking performance – particularly for all LandCruiser 70 Series models since the 1990s until today – Bendix’s Ultimate 4WD Brake Booster upgrade is a bolt-in replacement for original equipment. However, because the brake booster is an integral part of the braking system, this component should be installed by a braking professional.
Bendix’s Ultimate 4WD Brake Booster is currently available for a wide selection of Toyota LandCruiser models, with kits for additional vehicles under development.
We fitted a Bendix dual-chamber brake booster to our LandCruiser 75 Series, but discovered that the original master cylinder was four-bolt and the booster needed a two-bolt fitment. No problem, because it was time to replace the 30-year-old master cylinder anyway.
Our reinforced, braided brake lines are only a coupe of years old.
The new replacement master cylinder was designed for the contemporary 80 Series and was slightly larger internally. Without the Ultimate booster that upsize might have increased pedal pressure.
The new master cylinder and booster assembly was slightly longer than the original arrangement, but it squeezed into the 75 Series engine bay, with adequate clearance between the cylinder and our water-stop fuel pre-filter.
On consecutive days, with the same weather conditions, our brake mechanic checked out the performance of the new system, using a Brake Testa Millennium unit, version 2.7.
We know this unit is designed for pass-fail reporting during NSW registration tests, so it’s reasonably accurate.
The LC75 was fully loaded, with its slide-on camper in place and grossed just under 3.3 tonnes.
The successive testing showed that boosted brake pedal force went from 338N up to 439N and the maximum recorded deceleration went from 54%g to 78%g. Stopping time from around 50km/h was shortened from 2.9 seconds to 2.5 seconds.
Our subsequent traffic driving has shown that the new pedal ‘feel’ is more ‘modern’, with light, progressive travel replacing the previous ‘hard’ pedal. We feel much more secure, knowing that the loaded machine will slow and pull up when required, with minimal effort.
So far, we love the upgrade and will update this report in a month or two.