4WD MODIFICATIONS - TYRES & WHEELS
We had been waiting for an opportunity to test Yokohama’s Geolandar A/T-S tyres in on and off road conditions and we’ve been evaluating a test set of six tyres in 265/75R16 size, with 10-ply rating and load-speed ratings of 123/120R.
The tyres were supplied by Yokohama, through Gold Coast-based Signature Tyres, who proved to be excellent people to deal with.
The Geolandars were fitted to our LandCruiser 75 Series and the part-worn BFG KO2s that were on it were transferred to another one of the OTA Team vehicles, a GU Patrol, for ongoing evaluation.
As with most A/T tyres Yokohama’s all-terrain tyre was developed to combine good off-road ability with capable on-road manners.
The Geolandar A/T-S uses a silica-enhanced tread compound moulded into a symmetric design that combines sculpted shoulder blocks, rounded-edge intermediate blocks and staggered centre blocks.
Dual interlocking pyramid sipes and multi-stepped grooves on the tread blocks are said to maintain block rigidity, to enhance wear and sharpen the tread’s biting edges to provide traction in loose dirt and gravel, as well as on wet and wintry road surfaces.
Protective sidewall mouldings on the shoulders increase loose-surface bite and help reduce sidewall cuts and abrasions from rocks and stumps, Yokohama says.
The tyre’s internal structure incorporates twin steel belts, reinforced by spirally wound nylon, for through-tread puncture resistance and polyester body plies for sidewall flexibility.
We drove the Geolandars mainly on secondary bitumen and on some dirt roads, with a few off-road excursions, for the first 12,000km and we headed for a gravel road and desert sand test in June/July 2017, followed by desert expeditions in 2018 and 2019.
Those tests took in some of the worst large-stone roads in Australia and plenty of mulga scrub pioneering work. We expected some tread cutting and chipping, as well as sidewall damage, but we didn’t get any visible wear and tear.
Original tread depth averaged 13mm when new and wore down to 12mm front and rear at the 12,000km point. After our further 11,500km of stony road testing the depth is 11mm front and 10mm rear.
The Geolandars look like they’d be good for around 100,000km life, barring accidents.
Our on-road impressions are that the Geolandars are quieter than the BFG KO2s and Bridgestone D697s we’ve tested previously, thanks to more closely spaced tread blocks. They’re also softer riding than these other 10-ply AT tyres.
We’ve found that they have sharper steering reaction, but whether that’s due to a tighter slip angle or a self-aligning tread pattern we’re not sure. Wet bitumen grip and handling are excellent.
They’re also very cool-running, building up little heat and pressure increase after an hour’s operation at our vehicle’s GVM of 3.5 tonnes (1.4t front axle and 2.1t rear). We’ve found that a starting pressure of 40psi in the fronts builds up to 43psi after an hour’s secondary road driving and the rears go from 56psi to 60psi. If we’re on freeways we up the front starting pressure to 40psi and the rears to 60psi.
The testing goes on!