Tire guy in the next bay mounts four wheels on a Tacoma, hits every lug with a 1/2-inch impact until it stops, drops the truck, and sends it.

The impact gun over-torqued the lug nuts. A ½" impact can easily exceed 150+ ft-lbs, far beyond the Tacoma's spec of 85 ft-lbs (per Toyota service manual). Over-torquing distorts the brake rotor, creating lateral runout. This causes the brake pads to grab unevenly, inducing vibration felt as steering wheel shimmy under braking.

What happened:

1. Rotor distortion from excessive clamping force
2. Uneven pad contact creating thickness variation
3. Vibration transfer through the hub into the steering system

Fix:

• Remove wheels, inspect rotors for blue/discoloration
• Measure rotor runout with a dial indicator (spec: ≤0.002")
• Replace rotors if warped beyond spec
• Always torque lugs to spec with a calibrated torque wrench in a star pattern

Code reference: Tire Industry Association (TIA) recommends torque wrenches for final tightening. Many states require proper wheel installation per manufacturer specs.

Prevention: Impact guns for removal/initial threading only. Final torque always with a torque wrench.

Warped rotors from uneven lug torque.

What happened: The impact gun applied wildly inconsistent torque—likely 80–180+ ft-lb per lug. This uneven clamping force distorts the rotor hat and hub flange as the wheel heats/cools. Result: lateral runout (warpage) you feel as a shimmy under braking.

The fix:

1. Re-torque properly: Loosen all lugs, then torque in a star pattern to 83 ft-lb (2016+ Tacoma; check door jamb sticker for exact spec). Use a calibrated click-type torque wrench—not the impact.
2. Check runout: Mount a dial indicator on the rotor face. Spec is typically ≤0.002″ lateral runout. If over spec, rotors need resurfacing or replacement.
3. Clean mating surfaces: Wire-brush hub face and rotor hat—no rust, no anti-seize on the rotor hat.

Prevention:

• Use torque sticks only to get close (e.g., 80 ft-lb stick), then finish every lug by hand with a torque wrench.
• Post a torque-spec chart at each bay.
• Document final torque on the RO.

Code/Reference: Toyota TSB BR001-17 (brake judder from improper lug torque); SAE J2963 (wheel installation procedure).

Bottom line: Impacts are for removal only. Final torque is a hand operation—every lug, every time.