Lock Resistant Brake System

Written by: Mike Ervin

Now you can use the same Lock Resistant Brake System winning Winston Cup cars use.

Stewart Brake Development has introduced the hottest thing in street and race car brakes since disc brakes!  LBS installs easily in the rear brake line and utilizes a unique dampening valve that acts as a shock absorber to sense and dampen the sharp spike in line pressure when the brakes are applied suddenly.  LBS improves the brake performance on any car or light truck, even ones with ABS.  ABS was designed for panic stops, not high performance driving.  LBS will prevent the application of  ABS under all but panic stops making the car much more driver friendly.  LBS works much better than a proportioning valve and dramatically improves the brake performance of older cars and light trucks that may or may not have one.  LBS also works well with disc brake conversions on street rods and 50s-60s cars.  Many people install an adjustable proportioning valve to try and balance the brake system and find they don't do the job.

LBS was originally developed for Winston Cup cars to prevent a loose or oversteer condition under heavy braking with lightening fuel loads and rear tire wear.  The same system will give you the same benefits on the street in a panic stop or on a slick road.  If the car is loose or oversteering, it means that the rear tires are slipping before the fronts when cornering and/or under heavy braking and can cause the driver to loose control or "spin out".  It is preferable to have the front tires slip first (called understeer) when braking because the driver has more control.  If you've ever had to slam on the brakes when someone pulled out in front of you in traffic and the rear end came around, you know what we mean!

Stewart LBS assures that the front tires slip first by dampening (not reducing) the pressure to the rear brakes.  With LBS, the rear tires will accept nearly twice as much braking force without locking up.  Leading Winston Cup teams us LBS to brake harder and drive deeper into the corners at tracks like Martinsville and Watkins Glen and you can use the same technology to stop shorter and safer on the street.

Why LBS works better than other brake balance systems

Passenger cars and trucks require about 70% of their total braking force on the front wheels.  This is due to weight transferring to the front of the car under braking.  Weight transfer is affected by the center of gravity of the vehicle- a taller vehicle like a pickup has more weight transfer than a Corvette.  The rear of the Vette doesn't go as light under braking, so it can use more rear brakes and stop harder.

The front/rear brake bias on a production car is usually achieved by using smaller calipers or wheel cylinders on the rear.  Race cars with two master cylinders sometimes use different bore sizes to reduce rear line pressure.  Dual master cylinder setups may also use an adjustable balance bar to change the pedal force applied to the front or rear master cylinders to achieve the proper front/rear bias.  The bar may also be driver adjustable during the race.

Each of these systems has the same problem, too much front brake and the car doesn't utilize the stopping potential of the rear tires, too little and the rear brakes will lock causing the car to spin.

Why proportioning valves don't work

Proportioning valves don't really prevent brake lock up because they maintain equal front and rear line pressure up to a point called the "knee point" which is controlled by a preset or adjustable spring.  After the knee point, rear pressure increases to only 36-57% of the front pressure, depending on how the valve is set.  Generally the knee point is higher than the pressure required to lock the rear brakes.  If the knee point is adjusted low enough to prevent rear wheel lockup, the rear brakes will be virtually useless.  If proportioning valves worked, ABS would never have been developed.

Why LBS does work

LBS doesn't reduce rear brake pressure, it just slightly dampens and delays it.  LBS prevents rear brake lock up without degrading rear brake performance and overloading the front brakes.

I am sure that like me, you have a story about a close call you had while driving, where you were nearly creamed by some idiot who made a left turn in front of you, or pulled out of a driveway, or wasn't paying attention as traffic slowed in front of him.

Whatever the circumstances, your reaction was to go into panic-stop mode.  You slammed on the brakes, the rear tires locked up, and the back end of your truck decided it wanted to pass the front wheels.  If you were quick to react and started counter-steering soon enough, you stood a chance of at least skidding in a straight line, but if you were tardy, you had to hang on for a spinout.

Trucks require about 70 percent of the total braking force to go to the front wheels.  When the brakes are applied in a sudden stop, there's a "spike" in the brake line pressure, where too much pressure is momentarily allowed to go to the rear brakes.  When that happens, because of the weight transfer to the front of the truck, the rear brake pressure is higher than necessary for sufficient braking.

Stewart Components of High Point, North Carolina, has solved this dilemma by engineering a Lock Resistant Brake System that eliminates the spike by damping and delaying the brake pressure so that excessive pressure to the rear brakes is controlled.

Originally designed for Winston Cup racing, the system has been made available to the public.  It's simple to install and improves the brake performance of any truck.  I have one of these on my 85 C-10 and can testify that it works great, and it works just as advertised.

This is a photo of the Lock Resistant Brake System (LBS) from Stewart Components.  The overall valve is small (about 1.75 inch in diameter and 1.25 inch in length), and the ports where the brake lines attach are 1/8 NPT.  The bracket assembly is included.

lbs.jpg (11106 bytes)

Installation Procedure:

1.  Locate the brake line fittings where the rear line meets with the frame line.  Loosen the fittings to allow the LBS to be mounted between the lines.  Make sure that any debris on the exterior of the fittings is cleaned prior to loosening to assure that contaminants won't enter the brake system.

2.  Install the 1/2- to 1/4-inch fitting into the valve.  The valve is made of aluminum, so be careful not to cross-thread the fitting into the valve.

3.  The bracket is attached to the valve.  This gives the valve a rigid mounting platform to attach to the framerail.

4.  Tighten the brake line to the valve.  Once the valve is installed, press on the brake pedal and check for any leaks in the system.  If there are on leaks, check the master cylinder to make sure the reservoir has the proper brake fluid levels.


Update!  Stewart Components has sold the LBS part of their business to DPI Racing Products.  For info on this product you will need to contact them.  They have contact information on their site.