The Physics of Power: A Rider's Guide to E-Bike AWD and Traction Management

There’s an intoxicating allure to the numbers seen on high-performance e-bikes: 3000W peak power, dual 1000W motors, 33 MPH. The promise is one of “lightning speed,” a machine that flattens hills and offers motorcycle-like acceleration. But as some new owners discover, there’s a disconnect between that promise and the pavement. One user review for a powerful dual-motor bike, the AMYET S8, captures it perfectly: “If you select both motors and throttle it hard… the front tire can spin which is pretty fun.”

Fun, perhaps. But it’s also a critical warning sign. That spinning front wheel is the laws of physics telling you that your bike’s power has just overwhelmed its grip.

This isn’t a design flaw. It’s the inherent trade-off of a “brute force” engineering approach, which puts immense power at your fingertips. Unlike sophisticated (and astronomically expensive) torque-vectoring systems in sports cars, most dual-motor e-bikes give you the full responsibility of managing that power.

Welcome to the professional’s guide to e-bike power. We’re going to move past the marketing and break down the physics of All-Wheel Drive (AWD), traction, and torque, so you can stop being a passenger and start being a pilot.

The Physics of AWD: A “Push” and “Pull” System

On a standard e-bike, a single rear motor pushes the bike forward. All the bike’s power, plus your weight, is channeled through that single, tiny patch of rubber at the back.

An AWD system, like the 2x 1000W setup on the S8, adds a second motor to the front hub. Now, you have a “push-pull” system. The rear motor pushes, and the front motor pulls. In a perfect world, this should double your grip. On a slippery surface like gravel or snow, the rear wheel might start to slip, but the front wheel, being on a different patch of ground, can still pull you through. This is how these bikes claim to climb astounding 35-degree slopes.

But this perfect scenario assumes the power is applied in a world without physics. And physics has a very strict budget.

The Core Principle: Your Traction “Budget”

Every tire has a “traction budget.” This budget is its total available grip, which is based on a principle called static friction—the “sticky” force that locks a non-moving tire to the ground.

Think of static friction as a strong, but brittle, bond. As you apply power, you “spend” your traction budget. If the torque from your motor exceeds this budget, the bond breaks. The tire instantly transitions from “gripping” (static friction) to “slipping” (kinetic friction).

The problem? Kinetic friction is significantly weaker than static friction.

This is why a spinning wheel is so hard to control. Once it “breaks loose,” it has far less grip than it did a millisecond before. It won’t stop spinning until you drastically cut the power, allowing that static friction “bond” to re-establish.

Case Study: Deconstructing the “Front Wheel Spin”

So, why does the front wheel spin so easily, as the user review noted? Two forces are working against you simultaneously.

1. Instantaneous Torque: The S8’s dual motors can unleash a massive amount of torque instantly. There’s no gentle ramp-up. When you hit that throttle, you are dumping hundreds of watts of power to a wheel that has very little weight on it.
2. Dynamic Weight Transfer: This is the real culprit. Think about what happens when you accelerate hard on a bike (or in a car). Your body is thrown backward. All the weight transfers off the front wheel and onto the rear wheel.

This creates a perfect storm: you are applying maximum power to the front wheel at the exact moment that wheel has the least amount of weight (and therefore the least grip). The result is inevitable: the torque overwhelms the tiny traction budget, the static friction bond breaks, and the wheel spins uselessly.

This isn’t a flaw. It’s the bike’s physics demanding respect. A Formula 1 car has the same “problem”—so much power that its traction is the limiting factor. The AMYET S8’s design, with its robust high-carbon steel frame and powerful motors, is built for capability, but it assumes a rider who understands this power.

The Pro-Rider’s AWD Management Handbook

Mastering a bike like this means shifting your thinking. The AWD switch isn’t a “go-fast” button; it’s a “terrain-management” tool. Here is a practical, scenario-based guide to using it.

• Scenario 1: Starting from a stop (Dry Pavement)

  • Rule: Start in Rear-Wheel Drive (RWD).
  • Why: You have maximum traction on the rear wheel due to your weight. AWD is unnecessary, wastes battery, and (as we’ve seen) will likely just spin the front wheel. Get the bike rolling to 5-10 MPH, then engage AWD if you need the extra acceleration.

• Scenario 2: High-Speed Cruising (Dry Pavement)

  • Rule: Use RWD for efficiency.
  • Why: Once at speed, traction is less of an issue than wind resistance. Running both motors is a massive drain on your battery (a topic for another day) and offers no real benefit. Save the power for when you need it.

• Scenario 3: Approaching a Steep, Loose Hill (Gravel, Dirt)

  • Rule: Switch to AWD before you hit the incline.
  • Why: This is what AWD was made for. Do not, however, throttle hard from a stop at the base of the hill. Approach with a bit of momentum, stay seated to keep weight on the rear wheel, and lean slightly forward to “plant” the front wheel. Apply power smoothly and let the “push-pull” system claw its way up.

• Scenario 4: Riding on Snow, Sand, or Wet Leaves

  • Rule: Use AWD and a low, steady throttle.
  • Why: On these surfaces, your traction budget is tiny. Any sudden spike in power will break the tires loose. The key here isn’t speed; it’s consistency. A steady, low-power application to both wheels is your best bet for maintaining forward momentum.

• Scenario 5: Sharp, Low-Speed Turns

  • Rule: Be in RWD.
  • Why: Your front wheel’s primary job is steering. Asking it to also provide propulsion while turning is a recipe for a “washout,” where the front tire slides out from under you.

Conclusion: Don’t Fear the Power, Master It

A dual-motor e-bike with 2000W of rated power is not a toy. It’s a serious machine that blurs the line between a bicycle and a motorcycle. The marketing sells the power, but the physics demands control.

That spinning front wheel isn’t a party trick; it’s a tachometer for your traction. It’s the bike’s way of telling you to be a smoother, smarter pilot. By understanding the simple physics of friction and weight transfer, you can graduate from simply using the power to truly mastering it. And in the end, that control is far more rewarding than speed itself.