Cooper Discoverer S/T Maxx


Cooper  Discoverer S/T Maxx; an aggressive all-terrain that works well in construction environments

by Bruce W. Smith

Work is nearly at a standstill with dozens of pieces of heavy equipment sitting idle at the entrance to RaCON’s $12 million Highway 82 bypass in Tuscaloosa, Alabama.

A spate of late spring rains have made the jobsite a muddy mess with only a few pieces of equipment working on erosion control tackling the soft, slippery conditions.

Of course rain doesn’t stop crew foremen and site supervisors like Mike Floyd from doing their job.

It just makes driving stock 4WD company pickups a lot more challenging in such conditions.

While revving engines, spinning tires and counter-steering for control is the game of the day for these guys, it’s not nearly as dramatic behind the wheel of Project Bedrock.

While everyone else’s pickups on the site are fighting for traction, my GMC Sierra 4×4 feels pretty well connected, considering the oily shale and clinging clay road surface.

I have two distinct traction advantages – a factory locking rear differential and more importantly, much better tires.

The latter are the new Cooper Discoverer S/T Maxx in an E-rated LT285/70R17. The Coopers, mounted on Vision Wheels V-Tec Warlord rims,  are what I deem an aggressive all-terrain with deep channels and big tread blocks.

“The S/T MAXX features Cooper’s 3-ply Armor-Tek3 carcass construction taken from the more aggressive mud tire,” says Cooper tire designers. “And it uses a new proprietary cut-and-chip-resistant tread compound with a progressive tread design.”

The tread design is well-suited for off-pavement use over rock, gravel, sand, dirt and light mud situations.

It’s also proving on this test it works decently in conditions where deeper mud with a high sand and shale content are prevalent.

All it takes for me to gain additional traction in this mess is a momentary stab of the throttle to clean the outer lugs. The tires pull the truck forward more than they dig down, which is exactly what’s needed in these situations.

Ride quality on the highway is slightly firmer than the all-terrains that came on the GMC from the factory. That’s to be expected from an E-rated tire designed to maintain a truck’s maximum load and trailering capacity.

You feel road irregularities with the S/T Maxx tires and the tread sets up a whine at about 30mph, akin to kicking a nest of yellowjackets. The faster you drive, the higher the pitch—and, the pitch stays constant over a variety of road surfaces.

But the sound isn’t really loud or annoying; it’s more background noise than intrusive at 65mph. In fact, our in-cab sound readings were only 2dB louder (68dB) than the stock tires.

I’ve now driven more than 1,500 miles on the Cooper’s Discoverer S/T Maxx, which we have mounted on 17×8.5-inch V-Tec Warlord 394 rims.

The Coopers do a commendable job of melding all-terrain and mud tire design into a “hybrid” that fits in well for those who need a tire that can stand up to roadbuilding and site prep work.

It performs well where rock, aggregate, sand and mud are the typical driving surface. It’s not too aggressive, not too loud, not too extreme for use on the typical fleet 4×4 pickup.

Cooper Discoverer S/T Maxx

  • Test vehicle: 2011 GMC Sierra 1500 CC 4Ă—4
  • Tire size: LT285/70R17 E
  • PSI as tested: 35
  • Noise: 68dBA @ 65mph
  • Mud traction: 7.5/10
  • Dry traction: 8/10
  • Ride: 7.5/10