When the Rubber Hits the Trail

There are no set standards for the diameter and design of the mounting surface, the tire's bead. A few thousandths of an inch can mean the difference between de-beading a tire under low-pressure rock crawling, or ending up on your lid during high-speed cornering at medium pressure. Greg, our 4 Wheel Parts tire guy, said the M/T required a bit higher psi that other brands to seat the bead, reflecting tighter bead tolerances from the factory.

As much as we like to say we are Off-Roaders, the bottom line is that more often than not, we are pavement-pounders. Yep, it is sad but true. Whether we are heading to work or to the trail, our tires usually see more pavement than we would like. So when it comes to selecting a tire for our daily-driver/trail rig, there are both on and off road factors to consider; weight, road noise and etiquette and longevity are a few that come to mind for street use. Also, in all our vanity, we must admit, aesthetics play a role. But what about trail ability factors? For example: high-and low-pressure gription, carbon/rubber composition, sidewall strength, a traction-minded tread design, and last but not least, resilience to the brutal array of conditions we subject our tires to when we lock in the hubs. The perfect dual-purpose tire, that's what we want, right? These questions came to mind when we rolled into the Sacramento 4 Wheel Parts store last spring to pick up a set of Pro Comp's new 33x12.5x15 Xtreme M/Ts (XM/T).
Yes, by the time you read this, almost a year has passed since we mounted the XM/Ts on our test vehicle, the Two Week Taco. Instead of  jumping out and  ranting about how cool (or uncool) they are, we thought it would be prudent to get few miles under

Our own tread depth test showed 20/ 32ths vs. Pro Comp's stated 20.5/32ths: (this includes 2.5/32ths on the tread bar, the legal minimum). Two countries, four states and twelve thousand miles down the trail we still had 14/32ths, about two thirds of the available legal tread.  We'll let you know what the measurements are after the next 12,000 miles.

their steel belts, put the rubber to the trail - and the road so to speak. Thus is the impetus for this 12,000 mile tire test. It is a real test involving the things real people do with their rigs. We'll get to the details of the tire in a minute, but first let's talk about the 12k.
 
The 12,000-Mile Test
Immediately off the rack, we rolled south from Sacramento on a 2800-mile trek down the Baja Peninsula, which included eight hundred miles of high-speed dirt, whoop-de-doos, sand and rocks. Next was a long haul to Moab (2200 miles r/t) for the 2007 Easter Jeep Safari and a week of slickrock 'wheeling. For pure sand mania and dune running, (we call it testing.... or work), we made yet another haul across Nevada to the 124-square-mile sand mecca of Little Sahara State Recreation Area near Delta, Utah. This trip racked up another 1000+ miles. Back at the ranch, the M/Ts took on the mundane duties of stop-and-go traffic and the daily commute, hauled loads of crap to the dump, along with some granite wheeling in the Sierra Nevada, another quick trek to the Nevada desert and some mud running in the foothills.

The Extreme M/T's had no issues with bouncing back during more than a few unexpected Tacoma vs. Baja whoop-de-do airborne encounters

The XM/Ts even toted our cabover camper around for few weeks. Overall, a good sampling of what we think a multi-purpose tire might experience.

Baja Bashing, Slickrock and Sand Dunes
So what did we come up with? Our immediate impression was Ahhh, we love the feel, sound and smell of new rubber. It was like driving on butter compared to the aggressive and semi-worn XTerrains we replaced. But the real test began when we yanked the T-case lever into 4-Hi near San Felipe, Mexico and headed to Zoo Road, a high-speed, whoop-de-do laced section of the Baja 250 route. At 15-psi with us pushing them hard through high-speed corners, the XM/Ts enhanced sidewall tread was howling audibly as the sidewalls laid over and searched for traction against the hard pack sections. Kinda cool! It was also one of the few times we've blazed the Baja backcountry without shredding a tire on a wayward cacti or desiccated bovine femur.