At MotoGP speeds, air resistance is one of the largest forces holding a bike back on a straight. A rider who follows closely behind another bike can enter the lead bike's wake, where the air is already disturbed and moving differently. This is called slipstreaming, and it can reduce the following bike's aerodynamic drag.
Even a small drag reduction can help the rider gain speed, close a gap, or prepare an overtake before braking.
Understanding MotoGP The Slipstream and Tow
The wake is created because air cannot stay attached to every part of the bike and rider. It flows around the front fairing, helmet, shoulders, arms, legs, rear wheel, and exhaust area. Some of that flow separates from the surfaces, leaving swirling regions behind it.
These swirls mix with slower air and change the pressure pattern around the following bike. The rider in front is especially important because a human body is not a smooth aerodynamic shape. Small changes in elbow position, head height, or how tightly the rider tucks in can change the shape and strength of the wake.
A tow does not give the following bike extra engine power. It changes how much of the engine power is being spent pushing air away. If less power is needed for that job, more of the available power can increase speed.
This is why the effect becomes more useful near the end of a fast straight. At lower speeds, tyres, acceleration limits, and gearing can matter more. At very high speeds, the air becomes the main opponent.
A rider may begin several bike lengths back, then close rapidly once the speed difference builds. The pass is often timed so the following rider reaches the front just before the braking area rather than too early.
The wake is not a calm tunnel of air. It moves about, especially when the leading bike leans slightly, changes line, or meets a crosswind. The following rider may feel a less stable front end because the air reaching the fairing and aerodynamic wings is uneven.
Cooling can be affected too, since the radiator needs a strong flow of air through it. For a short straight this may not cause a major problem, but it becomes more relevant when bikes run close together for many laps. A rider usually moves out of the wake before a corner to get cleaner air, see the braking marker clearly, and place the bike on the chosen line.
When studying slipstreaming, separate the speed gain from the racing decision. A large tow is useful only if there is enough straight left to use it safely. Track layout matters.
A long straight followed by a heavy braking zone creates a strong overtaking chance. A short straight may give little time for the closing bike to complete the move. Notice how riders choose an offset position rather than sitting directly behind all the time.
That position can preserve some tow while improving visibility and preparing the next corner. Similar drafting happens in cycling, running, and road vehicles, but MotoGP adds rapid acceleration, strong braking, lean angles, and a rider whose body shape is part of the aerodynamics.
Key Facts
- Aerodynamic drag can be modeled as Fd = 0.5ρCdAv^2.
- Power needed to overcome drag is P = Fd v, so drag power rises roughly with v^3.
- A slipstream is the lower pressure, turbulent wake behind a moving bike and rider.
- A following rider in the wake can reduce effective CdA and accelerate more easily.
- The tow is strongest on long straights when bikes are aligned and close together.
- Riders must leave the tow before braking or turning because turbulent air can reduce stability and cooling.
Vocabulary
- Slipstream
- The region of disturbed airflow behind a moving vehicle where a following rider may experience less aerodynamic drag.
- Tow
- The speed advantage gained when a rider follows another bike closely in its slipstream.
- Aerodynamic drag
- The resistive force from air that acts opposite the motion of a bike and increases strongly with speed.
- Wake
- The turbulent, lower energy airflow left behind an object moving through air.
- CdA
- The product of drag coefficient and frontal area, used to describe how strongly a rider and bike resist airflow.
Common Mistakes to Avoid
- Thinking the following bike is being pulled forward, which is wrong because the main effect is reduced drag rather than a forward pulling force.
- Assuming slipstream works equally well at all speeds, which is wrong because aerodynamic drag grows with v^2 and the benefit is much larger at high racing speeds.
- Forgetting the cubic power effect, which is wrong because the power needed to overcome drag rises roughly with v^3, making small speed increases very costly.
- Staying in the tow too long before a corner, which is wrong because turbulent air, reduced visibility, and higher closing speed can make braking and turning less safe.
Practice Questions
- 1 A MotoGP bike has ρ = 1.2 kg/m^3, CdA = 0.32 m^2, and speed v = 80 m/s. Use Fd = 0.5ρCdAv^2 to estimate the aerodynamic drag force.
- 2 A rider in a slipstream reduces effective CdA from 0.32 m^2 to 0.27 m^2 at 80 m/s with ρ = 1.2 kg/m^3. Calculate the drag force before and after entering the tow, then find the reduction in drag.
- 3 Explain why a rider may move out of the slipstream near the end of a straight even though the tow is helping them gain speed.