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October 31, 2026 4 min read
In this video, I use my 1966 Chevrolet Impala SS to explain why uncontrolled burnouts can go wrong and how a line lock helps manage forward movement in a drag racing environment.
You'll also see examples of what happens when drivers lose control, along with an explanation of the difference between spinning the tires and managing the car's movement.
We've all seen it happen.
A car starts spinning its tires, the smoke starts rolling, and everything looks great. Then suddenly, the car hooks up, shoots sideways, or heads straight toward something the driver never intended to hit.
Sometimes it's a curb. Sometimes it's another car. And unfortunately, sometimes it's a crowd of spectators.
So why do burnouts go wrong, and what can you do to better understand what's happening?
A lot of it comes down to traction, throttle control, and managing forward movement.
That's where a line lock comes into the picture.
When you're spinning the rear tires of a rear-wheel-drive car, you're deliberately exceeding the available traction.
As long as the tires are spinning, they're producing less longitudinal grip than they could under normal driving conditions. But that doesn't mean the car can't move or change direction.
The trouble starts when the available traction changes or the driver makes an abrupt correction.
A few things can contribute to a burnout going wrong:
Sudden traction changes: The tires can regain grip as wheel speed, throttle input, or the pavement surface changes.
Uncontrolled forward movement: The car may accelerate farther or faster than the driver intended.
Loss of directional stability: Rear-wheel slip and steering corrections can cause the car to rotate or move sideways.
Driver overreaction: Abrupt throttle changes or steering inputs can make an already unstable situation worse.
That's why those Cars and Coffee burnout videos can turn ugly so quickly.
The driver may have plenty of horsepower, but horsepower doesn't automatically translate into vehicle control.
A line lock, sometimes called a roll control, is an electrically operated hydraulic valve installed in the vehicle's braking system.
Its purpose is to temporarily hold hydraulic pressure in a selected brake circuit.
On a typical rear-wheel-drive drag racing application, that means holding pressure on the front brakes while allowing the rear wheels to rotate.
The front brakes help limit the vehicle's forward movement while the rear tires spin.
It's a relatively simple concept that's been used in drag racing for decades.
And it's still useful today.
A line lock controls brake pressure. It does not control traction, steering, or the driver's throttle input.
That's an important distinction.
For a closer look at the hardware and how it works, read my earlier article:
What Is a Line Lock? How Roll Control Works
Here's something people don't always think about.
During a burnout, the rear tires are spinning faster than the vehicle is traveling. When the front brakes are released, the vehicle is no longer being restrained by the line lock.
What happens next depends on the throttle, available traction, vehicle balance, and driver inputs.
At a drag strip, drivers manage that transition as part of their burnout procedure, using the designated burnout area and appropriate track conditions.
The objective isn't simply to make as much smoke as possible.
It's to prepare the tires without creating unnecessary instability or damaging the equipment.
And even with a line lock, things can go wrong. The device doesn't prevent tire failure, unexpected traction changes, or loss of control.
Burnouts at the drag strip serve a purpose beyond entertaining spectators.
Depending on the tire construction and compound, a controlled burnout can help clean the tire surface and bring racing tires into an appropriate operating temperature range.
Drag slicks and other dedicated racing tires have different preparation requirements from ordinary street tires.
That's why a burnout procedure that makes sense for a purpose-built drag car isn't necessarily appropriate for a street-driven muscle car.
The tire manufacturer's recommendations and the track's rules should always take priority.
This is a subject we've already covered, but it's worth mentioning because the terminology still generates plenty of debate.
Line lock and roll control generally describe the same basic type of brake-pressure-holding system.
Hurst popularized the term Roll/Control, while line lock became the common generic description.
Different names, essentially the same principle.
If you want the complete explanation, check out:
Roll Control vs. Line Lock: What's the Difference?
If you're building a classic muscle car or a dedicated drag racing vehicle, a line lock may be worth considering.
Hurst's Roll/Control is one of the best-known systems in this category, and it's the type of old-school performance equipment that has remained popular for decades.
Featured product: Hurst Roll/Control Line Lock — Part #1745000
Shop the Hurst Roll/Control on Amazon
Shop the Hurst Roll/Control at Summit Racing
Before ordering, verify compatibility with your vehicle's brake system, hydraulic layout, and intended application.
A line lock is a brake-system modification. Proper installation, plumbing, electrical wiring, and testing are essential.
Affiliate disclosure: As an Amazon Associate, I earn from qualifying purchases. I may also earn commissions from other qualifying affiliate purchases at no additional cost to you.
I've spent more than 40 years working on cars, from collision repair and restoration to performance builds and classic muscle cars.
One thing I've learned is that understanding how a system works is just as important as knowing how to install it.
A line lock is a useful tool for managing brake pressure during a drag strip burnout.
But it isn't a substitute for driver judgment, proper tires, appropriate track conditions, or vehicle control.
And no burnout is completely risk-free.
Anybody can make tire smoke. Understanding what's happening underneath the car is what separates the smoke show from the mechanical knowledge.
Control the burn.
About the author: Troy Kane is an ASE Master Technician, ASE Collision Specialist, and I-CAR Gold-recognized automotive professional with more than 40 years of experience in automotive repair, collision repair, and classic vehicle restoration. He shares real-world automotive knowledge, shop projects, and technical demonstrations atV-Twins to V-8s.
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This site documents real builds, tools, and shop work from my own projects. Some pages are showcases. Some are how-tos and tool reviews. If you’re working on a project and want experienced guidance, I offer one-on-one coaching.