Brake Hoses
I want to start this section out by stating that I am referring to the flexible brake hoses that connect the brake calipers to the metal brake lines. I normally refer to them as brake lines also but for the sake of this article I will refer to them as brake hoses. By definition they are hoses and not lines.
So why have a section under brake mods for something as simple as brake hoses? The job these flexible hoses do is pretty amazing and completely under appreciated for the most part. It is also a topic people have strong feelings and opinions on concerning what can be achieved by swapping out the factory brake hoses for aftermarket hoses.
The factory C4 Corvette comes equipped with flexible rubber brake hoses like most cars. When new these hoses did an excellent job of resistance ballooning or swelling under normal driving conditions. But even when new these lines could be pushed beyond their rated specifications. The extreme pressures that the brake system handles day in and day out will eventually wear out the lines.
The oem brake hoses are made up of layers of rubber and nylon webbing. You can see this in the picture below.
This setup works fairly well as mentioned when new. But as they age you end up with lines that look like this :
Needless to say this a disaster waiting to happen even if it didn’t start to effect the performance aspects of the brakes.
As for diagnosing bad brake hoses. There are only two possible symptoms that you are likely to run into.
The first has to do with the inner tubing breaking down. This can result in brake drag which is caused by the inner tubing collapsing or separating and acting like a one way valve. Fluid makes it into the caliper when you apply your brakes and then cannot return to the master cylinder when you release the brake pedal. This will cause that particular brake to drag.
The other symptom has to do with swelling of the hoses. This will cause a mushy feel to the pedal that will get progressively worse as the brake fluid gets hotter from driving.
But the main area that most are concerned with has to do with performance and that has to do with how well the hoses deal with pressure.
So how much pressure are we talking about?
Later models can reach line pressures of 1160 psi front and 680 psi rear with 100 pounds pedal pressure. This doesn’t take into account modifications you may make later on to the brake booster size or other areas.
These are definitely pressure levels that can stress the flexible hoses. Age and temperature can further effect the hoses ability to resist swelling as you can tell from the pictures earlier.
Aftermarket hoses combat these problems by using a different core and outer material. Most assume that the braided steel covered hoses perform better because of the steel covers. But that isn’t what makes them perform better. Its actually the inner core material which is usually Teflon.
So if the Teflon core is the secret then what makes the braided steel outer coating so great?
The braided steel coating protects the hoses from the environment and impact damage.
So the next question is do these new materials really make that much of a difference?
One of the world’s leading manufacturers of flexible brake hoses, with customers that include Formula 1, IRL, NASCAR and WRC teams and supplier to Alcon, AP Racing and Brembo for their brake kits is Goodridge.
Testing done by Goodridge found that standard OE-type rubber brake hose expanded by 0.136 cc/ft at 1,000 psi, 0.150 cc/ft at 1,500 psi, and 0.290 cc/ft at 2,900 psi, whereas the company’s PTFE(Telfon) braided stainless hoses expanded by only 0.0002932 cc/ft at 4,000 psi.
So almost zero expansion under pressure compared to the stock hoses. This means zero brake pedal give from hose expansion.
With the question of performance out of the way. Lets look at another area that is very important and often overlooked which is lifespan of the hoses and what happens if they fail.
The whip test standards require that “a hydraulic brake hose assembly shall not rupture when run continuously on a flexing machine for 35 hours.” When Goodridge conducted its testing, the company found that the OE rubber hoses from five different manufacturers failed in 15 to 27 hours, whereas six sets of tests carried out on PTFE braided hoses of various lengths resulted in 45 to 82 hours of flexing before rupturing. What this means is that even though the rubber hose manufacturers claim compliance with the FMVSS106 whip test standard, Goodridge’s internal testing showed failure of these hoses long before meeting the minimum 35-hour requirement, while its PTFE braided hoses far exceeded this standard.
Remember if a hose fails by rupturing you lose ALL braking from that section of the brake system. If it is on the rear you are not as likely to loose control other than some of your brake pedal action. But if its on the front its bad, verrrry bad.
Even if you choose not to upgrade your brake hoses you really should inspect them yearly to make sure there are no signs of cracking, swelling or leakage.
So the aftermarket hose have two distinct advantages. First they will resist swelling far better than the factory hoses and they are far more resistant to damage from the environment because of the braided steel covering.
So this one is a no brainer. If you have the money I recommend going with the braided steel hoses. Not only will they out perform the stock setup they just might save your life one day.
Next up : Brake Rotors
Back to my vette