JK Forum Puts Geolandar Tires to the Ultimate Off-Road Test
Punishing Southern California course has met its match, as extreme mud terrain tires make a day of rock crawling seem like a cake walk.
Yokohama has been stepping in the right direction lately with their off-road tires, even getting the father-son team of Tony and Jordan Pellegrino of GenRight to use their Yokohama Geolandar X-MT tires in the Ultra4 series in the 4400 class. And earlier this month, it was a true test of traction and flex of the new Yokohama Geolandar X-MT tires at SoCal’s famous King of the Hammers course, where automotive journalists were invited to test out the tires. Of course, JK-Forum enthusiastically took on the challenge.
The Tires
The Yokohama Geolandar X-MT is billed as an extreme mud terrain tire focused squarely on the rock racer/crawler, overlander, and anyone who just wants to show off the biggest tire they can shove under their fenders. That’s why they are coming out with sizes that aren’t completely traditional for the crawler market.
The tread design is very aggressive and designed to work on rocks despite being an MT tire. The sipes cut into the tread blocks are mostly there for looks and will be worn away after 20-40% of tire life. Even so, the treads don’t exhibit terrible road noise.
The tread compound is a new proprietary blend of rubber, polymers and silica, but act like a softer compound while reportedly lasting longer than a Nitto Mud Grappler, Mickey Thompson Baja Claw, and even the legendary BF Goodrich Mud Terrain T/A KM2. The compound is also more cut- and chip-resistant than those tires. Under the compound are three nylon tread plies with a three-plus-two sidewall ply that wraps around the beads and crosses under the tread plies. Effectively, the X-MT is a six-ply tire because of the way the sidewall ply is done. Despite so many plies, the tires flex and still promote good road manners with a load range of E or D depending on tire sizing, but all tires will have a Q speed rating.
Currently, the only sizes available are 17- to 20-inch rims in 35- to 40-inch outer diameters, no 16 or under sizes. But if demand rises, the Japanese tire factory can produce them when and if the time comes. However, for tire extremists, a 42×14.50×20 will be arriving in mid-2019, following the debut of the Geolandar X-AT earlier in the year.
The Trail
The vehicle provided to us by GenRight was a bit of a surprise. It was a Jeep TJ Wrangler with a 2.5 liter I4 and AX5 five-speed manual backed by an Atlas with a 5.00:1 transfer case with 5.38:1 gears in the Currie Enterprises axles. The only real power additions were a pair of Venomaire 2XS forced air intake tubes. The gist is that it’s an electric axial compressor in the intake tube to force more air into the throttle body. The company explained that it is not a turbo nor a supercharger, but just a way to get more air into the engine. Cameron Harris, the owner of the TJ, stated it has made an impact, noting that the Wrangler used to suffer from stalling at high altitudes but now doesn’t since adding the system. As we drove it, it certainly didn’t struggle for power during the climb, but it wasn’t a V8-killer by any means.
The Yokohama Geolandar X-MTs installed for this test drive were a set of 40×13.50x17s, a much larger tire than what Harris normally runs, a 38×12.50×17. You could feel it, but the little 2.5 liter would just drive along without giving too much of a fit, as long as you ran it at high RPMs. Aired down, the little TJ with the X-MTs made crawling feel like a breeze. While it had to be shifted down a gear in some places, it was fine for up to third gear in high-range, and fourth and up for low range. Other than that, this little four-banger stayed right with the six and eight cylinder Jeeps of the rest of the GenRight crew…until we hit sand.
What was most impressive was seeing how much the sidewall flexed. After all, this is a three-ply tread with a three-plus-two sidewall ply on a brand-new tire.
Our first pass up a tall sand hill was done in high-range to second gear on the hard-packed stuff. Once the rest of the trucks went up and down the hill, the X-MTs dug like sand paddles — great for V8 trucks, not so much for a 2.5-liter. Once it dug in, it bogged down on us unless we clutch-kicked. Fortunately, all we had to do was turn back down the hill and allow gravity to assist us out of the rut.
After the sand hill, we allowed Harris to take over driving so we could get photos of it driven in true anger. It was also a delight to watch some of the Yokohama Japanese crew get taken up the rocks for the first time. Some of their expressions were pure amazement, some were a bit of terror. Even Fardad Niknam, Yokohama Senior Director of Consumer Product Planning and Marketing, took a ride in one of GenRight’s tube-chassis, four-wheel steering rigs and was quite surprised by his own tire’s capabilities.
What was most impressive was seeing how much the sidewall flexed. After all, this is a three-ply tread with a three-plus-two sidewall ply on a brand-new tire. But it would flex to provide the right amount of grip going up the rocks. Now, we couldn’t tell you how they will act long term because we were only allowed a brief time with them. However, looking at Jordan Pellegrino’s 4400 rig with its 40-inch DOT tires that has seen races at the King of the Hammers and The Mint 400, wear and tear most likely won’t be an issue if you have a proper alignment done.
Overall, the Yokohama Geolandar X-MT, which will be hitting stores around July, was an impressive tire in this debut run.
continued…