Rear Brake Line Upgrade – What Length Do I Need?

Have you spent some time recently studying how your rear brake lines are routed? Often it’s not something people consider. Fortunately for you, we’ve taken a look. This post will help you determine what length your new brake hoses should be.

OEM Solid Axle Brake Line Routing

Almost all solid rear axle vehicles have similar OEM brake line routing. It goes like this:

• A single solid brake line is run from the master cylinder to the rear of the vehicle.
• A single flexible rubber brake hose connects the solid line to a T fitting mounted on the axle.
• The T fitting has two solid lines attached to it. One runs towards the left wheel, and the other towards the right wheel. Those hard lines go all the way to the wheel cylinder in your drum brakes.

Rear Axle Disc Brake Conversion Brake Line Routing

Disc brakes are different than drum brakes in two ways that affect brake line routing:

1. Floating calipers move slightly when braking.
2. Servicing the brakes usually requires removing the caliper.

Because the caliper moves, a flexible brake line is mandatory. And, a flexible brake line makes it much easier to service the brakes. We provide flexible brake hoses with our disc brake conversion kits. To install the hose:

1. First cut the hard line on the axle. Use the hose we provided to determine where to make the cut. Hold one end about where it will bolt to the caliper, and the other end by the brake line on the axle.  The hose should have a slight S shape, and should not be taut. (It should have some slack in it.)
2. Use a flaring tool to re-flare the end of the brake line.
3. Connect the hose supplied with your kit to this hard line.

The hose included with our disc brake kit goes from the caliper to the axle, so the amount of lift doesn’t matter for hose length. No matter how much you lift your truck, the length of the outer flexible brake hoses will not need to change. It doesn’t matter if you are getting new rubber brake hoses or flexible braided stainless-steel brake hoses.

Front Axle Disc Brake Conversion Brake Line Routing

Some modifications create a situation where you should change your OEM front brake line routing. If you have:

1. Converted an independent front suspension vehicle to a solid axle (solid axle swapped).
2. And/or installed a lift and larger tires on a solid axle vehicle.

Both of these mods create more suspension travel than a frame to caliper brake hose can handle from a safety standpoint. Long frame to caliper hoses will have too much slack when the suspension is in a neutral position or compressed. The slack hose can either catch on the tire lugs and rip off suddenly, or be worn through slowly. This is obviously unsafe.

The safe solution is to set up your front brake lines just like the rear. This takes a little more effort, but it’s the only safe way to do it. OEM’s only run from the frame to the caliper because they know that suspension travel is limited.