The GMC Hummer EV was made official last week with incredible power figures – the most powerful of any General Motors production vehicle ever announced. At a staggering 1,000 horsepower and a titanic 11,500 lb-ft of torque, the new Hummer will deliver on its imposing reputation, and will also rocket from 0-60 in just three seconds.
However, that “official” torque rating is a bit misleading, and we’d like to take the time to explain why.
Torque is multiplied by the gear ratio, and while EVs usually don’t have “transmissions” in the conventional sense, there *is* at least one single gear set to reduce the rotating speed between the motor and the wheels.
Let’s take the 2020 Corvette with the Z51 Performance Pack, for example. its final drive ratio is 5.2:1, but it’s first gear ratio is 2.91:1. GM hasn’t shared this specific number, but the C8 Stingray should peak at around 7,100 lb-ft of torque at the rear wheels in first gear. That’s before drivetrain loss, and other variables.
To find the Hummer’s true torque figure, we need to know the drive ratio, as all vehicles have one. We don’t know it at this time, so it’s difficult to find the torque rating, but not impossible. Because with the 1,000 horsepower rating of the GMC Hummer EV, we can at least estimate a real world torque figure, which will still be incredible. Just not 11,500 lb-ft of what presumed to be wheel torque.
While we’re on the subject of wheel torque (or axle torque, if you prefer) it’s likely that the Hummer EV won’t even have axles. Take the Rivian R1T and R1S, for example. The electric truck and SUV siblings feature a battery “skateboard,” with four electric motors each fixated directly behind a respective wheel. Power is pushed directly to the wheels via a driveshaft – a simple, yet novel design. GM will likely apply independent rear (and front) suspension to its electric pickup trucks, allowing the the GMC Hummer EV and other BT1 platform trucks and SUVs to likely feature a similar design to the Rivian models. There’d be no live axles, and no driveshafts. Each motor could even have variable drive ratios depending on the situation. Hypothetically.
So how do we properly measure electric motor torque to the wheels?
For now, we can use an electric vehicle with a single drive ratio to help narrow down an estimate, as opposed an ICE vehicle with multiple gear ratios. If we consider the Chevy Bolt hp/lb-ft ratio, assuming the motors are similar, the Hummer might have somewhere around 1,300 lb-ft. Though, if we consider the torque-to-hp ratio of the Tesla P100D, the Hummer EV would roughly produce 1,550 lb-ft of torque. Plenty of output to take the fight to the Cybertruck.
Overall, the SAE torque rating is incalculable without knowing the gear ratio, but a number above 1,000 lb-ft is more than plausible. We’ll know for sure when the GMC Hummer EV is officially revealed on May 20, 2020.