May 31, 2023 4 min read
35-inch tires on a mid-size truck you can buy from a showroom, with a warranty. Plus winch compatible bumpers, and real-deal underbody protection from AEV. If you read nothing else, you understand why the 2024 Chevy Colorado ZR2 Bison is different. Two years ago, this formula would have annihilated the competition, but in today's suddenly-competitive mid-size market, this may or may not be a silver bullet.
Big tires are the headline, but in addition to the LT315/70-17 Goodyear Territory MTs, the Bison adds steel bumpers, rock sliders, and skid plates made by ultra high quality aftermarket firm AEV to the already high-performance Colorado ZR2. There’s also some really impressive bump stops from Multimatic, and larger fenders designed to accommodate the increased tire size.
AEV makes the only off-road armor compliant with American crash and pedestrian safety standards. Coatings on those parts are made to factory automaker standards, which means they're also the only ones that won't start rusting after one winter in Montana.
What’s the point? 35-inch tires are a common goal for modification-minded owners seeking to boost the capability, and more often, the stance of their trucks. Big rubber pushes a truck’s body further away from the ground, and obviously changes the visual proportions of the vehicle. Bigger tires also roll over larger obstacles more easily, and have longer contact patches, increasing traction. That last point—traction—is something this Bison is then going to be very, very good at, thanks to front and rear locking diffs.
But what goes up, must come down. Bigger tires are also heavier tires, increasing both unsprung and rotational mass. The former impairs ride quality—the tire exerts more force on the suspension, and its momentum has a greater effect on the vehicle—while the latter requires more work from the engine and brakes to accelerate or slow the tire’s spin. Bigger tires also reduce the effective gear ratio, further limiting performance.
Owners seeking to get their Tacomas, Colorados, Rangers, or Gladiators onto 35s must then fit suspension or even body lifts, almost always need to trim parts of the body and frame, and if they’re hoping to retain performance, function-oriented builds also typically seek to increase the final drive ratio by re-gearing the vehicle’s diffs. And, like any other modification, those mods can cause as many problems as they solve, which is one of the unique selling points here—all this important work has been engineered and carried out at the automaker level, with help from the talent at AEV, not by some ex-cons working out of a lockup in Riverside.
Here you get a good look at the hydraulic bump stop—the prominent gold, blue, and silver tube hiding behind the Bison's non-disconnecting sway bar end link.
In a conference call with journalists, Chevy engineers explained that found room for 35s by, “raising the Bison’s stance,” and state that the Bison retains ZR2’s total 9.9 inches of front wheel travel. It remains unclear if they’re sacrificing droop travel in order to achieve the additional height.
In addition to the added suspension height, fitting 35s required Chevy to tune the damping rates in the chunky Multimatic shocks, which are otherwise identical to those found on the ZR2.
The new bump stops should help control the mass of the tires as the vehicle hits large obstacles, counteracting the tendency of big, heavy tires to abruptly achieve full suspension compression while operating at speed.
Those 35 inches also sacrifice the ability to fit a full-size spare in the standard location, under the bed. So, Chevy has grabbed a spare tire mount from AEV, and located that spare in the bed, eating up about 20 percent of its total volume in the process. You might want to consider a Rig'd Supply Ultraswing, which will move that tire out of the bed, behind the truck.
One thing Chevy has not done is regear the Bison. It retains the Colorado’s standard 3.42 final drive ratio. The Bison also continues to use the same 2.7-liter turbo four as the ZR2, which produces 310 horsepower and 430 pound-feet of torque, and which is mated to the same 8L90 8-speed auto as the last generation Colorado.
I asked Chevy’s engineers if they’d measured acceleration on the Bison. The response was that they don’t plan to release those numbers. The Ford Ranger Raptor's 3.0-liter twin-turbo V6 makes 405 horsepower and 430 pound-feet (on 91 octane). The 2024 Toyota Tacoma TRD Pro's hybrid powertrain makes a total of 326 horsepower and 465 pound-feet. Both rivals ride on 33s.
Then there’s the question of weight. All those steel protection parts add just over 300 pounds of additional weight to the regular ZR2. That reduces the Bison’s payload to just 1,050 pounds—the lowest figure on any truck currently on-sale, that I’m aware of.
That figure does already include all those really nice AEV protection parts, including a winch-ready bumper. But not a winch. Adding a 50 pound Warn M8000-S winch will take available payload to 1,000 pounds. Figure in a full tank of gas, and this Bison will only be able to carry 880 pounds. Remember that number needs to include people.
Chevy says it tested the Bison by running it through over 12,000 miles of desert races, including the Best of the Desert, Mint 400, and Legacy Racing Association. Cooling capacity and reliability should not be stressed by the larger tires.
With such a limited payload, there’s really only going to be one camper you an safely run on the Colorado ZR2 Bison. Weighing just 275 pounds when sized for a five-foot bed, the GFC Platform Camper will leave 580 pounds of capacity leftover on winch-equipped trucks. That should be just enough to safely carry two adults, some recovery equipment, tools, and outdoors gear. The GFC won’t impair your ability to carry or access that bed-mounted spare.
And if you plan to wheel your Bison hard, the GFC Platform is also going to do a good job of remaining securely attached to the bed, via the brand’s proprietary billet aluminum clamps. Just please don’t take advantage of the camper’s 800-pound dynamic roof load. Thanks to its fully triangulated, billet aluminum-reinforced space frame, the GFC really can carry nearly as much weight as the entire truck. — Wes Siler