Brakes 101: What You Need to Know, Part 4

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Here’s our final look “at the braking point!” As you’ve no doubt noticed, we’ve shared a dozen or more tips with each week's segment. This time around we’ll wrap our series up with another dozen tips and two bonus tips. They’re all important, and they’re all practical. Check them out. We’re certain you can use them.

Tip 37 – PARKING PROBLEMS: If you have a car parked in storage, and the plan is to keep it there for a long period of time, pump the brake pedal occasionally to keep all cylinders (master and wheel) lubricated. This ensures the respective rubber cups don’t become unsealed from cylinder walls.

Tip 38 – THREAD LUBE: Never use anything to lubricate the threads on fasteners or bolts exposed to brake hydraulics except brake fluid (the only exception here might be bleeder screws). You can use anti-seize or other lubes on external brake parts (for example, drum brake adjusters). If you use anything other than brake fluid on fasteners that come in touch with brake hydraulics, you run the risk of contaminating the fluid. Then you’ll have nothing but trouble.

Take a look at the accompanying photo. It’s from an almost exact nut-and-bolt perfect Cobra replica from Kirkham Motorsports. There’s something here for anyone with a hot rod or other tube frame car. Vintage Cobras are essentially tube frame cars. They also use floor mount pedal assemblies, just like any number of purpose-built street rods and race cars. So what’s the difference?

First and foremost, the pedal box is completely removable. Think about that for a minute: The enclosure or box area around a master cylinder or two is usually hard to reach on any tube frame car. Put the car up on a hoist and fiddle with little parts over your head or remove the interior tin and work with the same stuff while standing on your head. If the complete pedal box is made removable, as is the case with these Cobra replicas (note the pair of bolt-in flanges on either end), you can work on the brake (master cylinders(s), pedals, linkage, etc.) on the workbench. It’s a whole bunch easier.

It’s a good habit to check your car’s brake fluid monthly. Use a clean cloth to wipe dirt from the brake fluid reservoir lid. Remove the lid and visually inspect the fluid level. If the fluid is low, add the approved type to the mark on the reservoir. Do not overfill. If the reservoir is low, you should check the system for leaks. Just remember, as brake lining materials wear, the fluid level goes down proportionally.

One cool part many old road racecars incorporated was a brake-cooling duct(s). If you decide to copy that theme, be sure to direct the air to the inside of the brake rotor. The rotation of the rotor will tend to draw the air from the inside to the outside. If you follow that route, your new ducting will help promote efficient brake cooling.

If you have an absolutely persistent squeak from disc brakes that refuses to be silenced (check out tip #6 in our first segment), try this on for size: Remove the pads and clean the back with brake cleaner to remove dirt and dust. Next, spray or brush a healthy coating of “Disc Brake Anti-Squeal Compound” on the backside of the pads (most auto parts stores sell a number of products that do this job). Allow to dry for half an hour or so, then reinstall the pads along with stock OEM anti-squeal shims (if used on your car). Consider the job done. The brakes should be quiet for a year or two at least.

Tip 43 – BEAT THE DRUM: If you’re in the middle of a brake job and you can’t pull off the drum, try this before renting a specialized puller or before wrecking something: Be certain the adjuster is fully released. Be sure the e-brake cable is slack. If your car has a drum retainer (not so common today, but used on some vintage combinations), be positive that the retainer screws are removed. Next, using a soft face hammer, whack the drum with a single hard blow to the face next to the axle flange. This usually breaks the brake drum free.

Tip 44: RUST IN PEACE: Brake bleeders always rust. That’s pretty much a well-known fact. If you’re lucky enough to get all four examples loose, spend a few bucks and replace them with new ones. In this case, you can use a small amount of Teflon tape on the threads. Be extra careful here – you don’t want to contaminate the hydraulic system. This will normally keep the bleeders from seizing when you need to use them next.

Tip 45: BUBBLICIOUS: Believe it or not, if you tap lightly on each caliper with a small soft-face hammer as your bleed it, you can loosen up air bubbles trapped within the hydraulic system. This allows the trapped bubbles to escape as you bleed the system.

If there is one key in the brake line puzzle, it's figuring out where the lines should be routed. Now, we can't give you a definitive blueprint on where and how the lines should be fabricated for your particular car. Each and every chassis is different. The idea is to get up close and personal with the bottom side of your car and figure out exactly where each segment of the line should go. What you have to consider is scrub line clearance ("scrub line" is the imaginary point where a piece of the chassis or a suspension component might contact Mother Earth if a tire was completely blown off a rim). The other thing you should consider is potential damage in the event a piece of the driveline or the engine decides to take a vacation. Some OEM cars (for example, 1982 and newer Camaros and Firebirds) have brake lines that are factory routed through the driveshaft tunnel. That's fine for Detroit, but for racers or rodders, it might be the wrong choice (consider a wayward driveshaft, for one thing). Potential heat and severe vibration sources should be next on your routing checklist. In simple terms, it's not smart to route the brake lines where they can become roasted by the headers or exhaust system. And it's also smart to mount the lines with a sufficient number of clamps to thwart vibration woes (where these clamps go can influence the location of the line). Finally, you have to consider the maintenance aspect of the entire car. If the lines are installed in a place that's vulnerable every time you roll a jack underneath or plant the car on axle stands, the lines aren't in the right spot. So where do you route them? It depends, but in most cases it's best to run the lines on the inside of the rocker panel or frame rail. On some cars, it is possible to route the brake lines right through the frame rail – but don’t forget about the maintenance factor. Eventually, you’ll need to access the brake line. If it’s completely encased in a frame rail, it will be impossible to fix (for example, if it springs a leak). In the end, don't take the planning part of routing lines too lightly.

A "spongy" brake pedal can be attributed to master cylinder deflection. Several experienced chassis builders with whom we spoke noted that in a modified car, the firewall sheet metal should not be used as the sole master cylinder mount (for example, if you decide to install a set of vintage Ansen-style hanging pedals in your street rod). Many experienced fabricators have found the cause of cracking in the area of the master cylinder on an OEM firewall has absolutely nothing to do with the structural integrity of the car or the chassis. Instead, it is the force of the driver's leg against the brake pedal that creates the cracking. Good examples of this include many vintage built-by-Detroit cars with manual (non-boosted) brakes that have never been modified: The sheet metal surrounding the master cylinder eventually fatigues in these cars, even though they were never modified (meanwhile, similar un-modified cars with power brakes seldom have evidence of firewall fatigue). That's why many experienced builders routinely brace the master cylinder mounting point to the dash structure when installing hanging pedal assemblies.

Tip 48 – GETTING HOSED: If you're going to use braided steel brake flex hoses, this is the stuff to use. It's Teflon core, braided stainless hose. Never use neoprene lined A-N hose for brakes. Under brake system pressure, a neoprene-lined hose will expand, which increases brake pedal travel. The stiffness of the Teflon liner combined with the tightly woven high tensile stainless steel outer braid eliminates excessive pedal travel. It also increases pedal firmness and feel by a significant margin. The stainless steel outer braid improves the abrasion resistance, and the design of this hose increases the temperature capacity as well. Instead of building your own hoses (and taking the chance you assembled them incorrectly), think about pre-assembled brake hose. With this type of brake hose, the hose ends are installed by one of two methods: The end is either swaged in place or it's crimped. In either case, the hose end attachment is permanent. Once the manufacturer attaches the ends, each hose is pressure checked. They use a hydrostatic pressure test that goes to 4,000 PSI on each hose. That pressure is far in excess of what any racer or hot rodder can test at home.

Tip 49 – LET IT BLEED: Bleeding brakes should be performed in this order:

1. RIGHT REAR
2. LEFT REAR
3. RIGHT FRONT
4. LEFT FRONT

The actual bleeding process works this way: Begin with the right rear caliper or wheel cylinder– it’s located the furthest distance from the master cylinder. Attach a clear 12-inch (or so) length of plastic hose to the bleed nipple. Place the free end into a jar containing an inch or two of clean brake fluid. By placing the free end in clean fluid, you’re able to prevent air from re-entering the system. Next, ask a helper (family member, friend, neighbor, etc.) to slowly press on the pedal to force fluid into and throughout the system. As this is done, open the bleed nipple by turning it counter-clockwise. As you open the bleeder, let the fluid start to escape. You should notice air bubbles in the plastic tube as it runs down into the jar. Once the bubbles stop, close the bleeder nipple. Check the appropriate brake fluid reservoir to see if you need to top it off. The last thing you need is to drain the reservoir. If that’s the case, you have to start from square one. So far so good, but you’re not quite done with the right rear caliper. At this point, have your assistant slowly push on the brake pedal as you open the bleeder. Before the pedal is released, close the bleeder valve. This prevents air from entering the system. Continue this procedure until there are no more air bubbles coming from that caliper. Recheck the fluid in the reservoir and top off as necessary. At this point, you can move to the next caliper (typically, the left rear) and begin the process again.

For some time, the Department of Transportation (DOT) has issued a set of stringent specifications for brake fluid types. The more common glycol-based or "conventional" fluids fall under DOT 3 and DOT 4 specifications. DOT 3 has a minimum dry boiling point of 401 degrees F while DOT 4 has a minimum dry boiling point of 446 degrees F. On the other hand, silicone fluids fall under DOT 5, which has a dry boiling point of 500 degrees F minimum. Something to watch for is this (and don’t get this confused with DOT 5): Another DOT fluid is 5.1. This is a Glycol based fluid that has a dry boiling point of 518 degrees F. In a typical passenger car, the conventional fluid boiling point diminishes with time. How long does it take for this to happen? In most passenger cars that operate under damp conditions, there can be a rapid deterioration of the brake fluid boiling point in as little as six months. Obviously, something like a show car isn't used in the rain, but it does go to show that brake fluid definitely is affected by time and weather. That's why some aftermarket brake manufacturers recommend you flush the system with fresh fluid on a regular basis (as an example, some road racers change fluid after each event!). So what's the big deal in regard to brake fluid boiling points? In reality, one of the most critical factors in regard to a hydraulic brake system is the dry and wet boiling point. If the fluid boils, small gas bubbles occur. These bubbles don't disappear. Instead, they're trapped in the system. Since gas bubbles are compressible, the brake pedal then becomes spongy. Generally speaking, a regularly driven car is further plagued by wet boiling points. Normally, the brake system will function with a percentage of moisture in the system. Over time, this moisture content increases and, as a result, brake performance decreases. That's why "wet boiling point" specifications are also provided by the Department of Transportation. These "wet boiling points" are outlined as follows:

• DOT 3: 284 degrees F
• DOT 4: 311 degrees F
• DOT 5: 356 degrees F
• DOT 5.1: 375 degrees F

As you can easily see, the wet boiling point of silicone brake fluid is significantly higher than its glycol-based counterparts. That's because silicone fluid does not absorb moisture, while glycol-based brake fluid does. When you take a look at a can of conventional glycol-based brake fluid, you'll almost always find a warning with regard to using the fluid immediately. The reason, of course, is moisture absorption. Once the seal is broken, moisture will attack the fluid in the can.