Pad Slapping and the Varying Levels of Brake Service and Repair
Pad Slapping what is it?
Pad slapping is slang for sole replacement of brake pads while not replacing or machining rotors of a disc brake system. Pad slapping is generally not advisable. At a minimum one really wants to have rotors machined or turned- this is a process where wearing brake rotors are cut to ensure a smooth uniform braking surface. To neglect replacing or machining rotors can result in undesirable effects. Most notably a shaking felt while braking in addition to screeching noises while braking. The appeal of pad slapping is understandable. By neglecting servicing the brake rotors one can save a great deal of money either from the cost of new rotors or the labor involved in machining. However aside from driver discomfort this activity can be potentially dangerous as pad slapping can accelerate wear of the new pads as the pads will not be in contact with a smooth uniform rotor surface. It can also be more expensive not to replace the rotors as customers will have to essentially pay for the same job twice should these aspects proove too unbearable. Ie they thought they could live with the vibrations or noise but it proved too irksome and the only remedy is to replace the pads and rotors.
Ok so the rotors need servicing too-how can I save $$
Depending on the application certain situations will dictate whether it is more cost effective to replace or to machine a rotor. For the vast majority of vehicles on the road today it is more cost effective to simply replace the rotors. Especially popular makes and models where parts are plentiful. However some older vehicles and a minimal amount of new vehicles rotor replacement can be rather laborious depending on how the rotors are fastened to the vehicle(rotors bolted to the rear of the hub-requires spindle removal)- an on car brake lathe would be ideal in these scenarios. Or the parts on older rarer vehicles may prove harder to come by (supply and demand-costly) where bench lathe machining would prove ideal.
Ways to save- Bring your own high quality parts (no parts markup), Find a local independent shop (less overhead than a dealer or franchise). Or utilize the likes of independents like Attentive Auto that source only high quality parts sold at cost to the customer.
The levels of brake service?
As prior discussed one should understand the difference between pad slapping and pad and rotor replacement or machining. Beyond servicing brake pads or rotors many garages might offer the following enhancement services.
Slide Pin Service Brake Fluid Flush Upgrade-Performance Parking Brake Adjustment
Slide Pin Service-The effectiveness of your brake pads are directly related to the proper smooth sliding operation of your Brake calipers-"the housing" of your brake pads. The slide pins ensure the caliper moves smoothly each time the brakes are applied. These slide pins are greased from the factory to ensure proper movement. Over time these slide lubricants loose their effectiveness causing the calipers not to move as freely which can lead to undesirable outcomes such as; uneven pad wear, sticking pins causing the pads to remain in contact with the rotor accelerating wear, reduced stopping ability as the brake pads wont be in full contact of the rotor. Further while there are protective boots over the slide pins over time these boots fail allowing moisture, brake dust, and rust to build up on the pins hindering efficiency.
The Remedy- Slide pins are removed from the calipers- the slides are polished, grease is added, and the boots and slide bushings replaced.
Brake Fluid Flush-Your brakes rely on hydraulic pressure amplified by the brake booster and master cylinder in order to move fluid to each brake component to provide the pressure necessary to stop a vehicle. This fluid is a critical component vital to stop a car. Without it the brakes will not operate and one will not stop.
The issue-Brake fluid is hygroscopic-meaning it absorbs moisture. Moisture will wreck havoc on a hydraulic brake system hampering the performance of the brake system. Seals can degrade and given enough time lines can rust out internally. In addition over time vapor commonly referred to as "air" can enter the hydraulic system. This is undesirable as inefficiencies develop as "air" can be compressed in a hydraulic system unlike brake fluid. This means should enough "air" enter the system input at the brake pedal translates to air in the lines compressing rather than a direct transfer of hydraulic pressure to each brake channel. This is commonly referred to as spongy brakes.
The Remedy- Your old brake fluid will be flushed out of the brake system and "air" bled from each channel restoring proper brake operation and preventative maintenance has been performed to protect against future system failures.
Upgrade/Performance- These are a series of measures undertaken to enhance braking performance in a variety of conditions. They can be as simple as adding cross drilled brakes and premium composite pads to reduce brake fade (this is particularly useful not only on sports vehicles but for those who tow ie your truck or van could benefit greatly from such enhancements). To adding steel braided lines in place of rubber to enhance pedal feel. To as extreme as upgrading to calipers with multiple pistons to upgrading master cylinder and or brake booster to optimize stopping ability.
Further in addition to the prior mentioned anyone can benefit from the simple addition of coated rotors. This special coating prevents rust build up around any surface the brake pads do not come into contact. What was once perceived as a gimmick has caught the attention of a variety of manufactures and offered as factory equipment. By preventing rust build up, brake pad longevity is enhanced as it prevents the build up of rust from seeping down to the pad contact area. Should this rust seep into the pad contact area grooves can form into the brake pad preventing uniform pad contact with the surface of the rotor. Further this special coating prevents the rotor vanes from rusting and reduces the vanes ability to retain brake dust greatly enhancing the rotors ability to dissipate heat-the culprit of brake fade.
Finally I feel it requires mention cross drilled or slotted and coated rotors simply look cool.
Parking Brake Adjustment- Dependent on design the parking brake shoes are cleaned and adjusted to allow easy engagement.
Clean and Adjust- When shops offer a clean and adjust service this generally refers to drum brakes. Factory equipped drum brakes when properly cleaned and adjusted offer adequate levels of stopping ability for most situations. The problem occurs over time as the shoes (think pads) of the drums wear the brake dust has nowhere to go causing a buildup in the drum assembly hampering performance and quite often creating noise. Further while drums are generally designed to be self adjusting it is real world experience that these brakes will require periodic adjustment.
The Remedy-The drums are removed, the interior assembly cleaned and properly adjusted. Properly clean and adjusted drum brakes tend to have a extremely long service when compared to disc brakes.
Brake Inspection- This is a inspection where the mechanic will briefly test drive the vehicle and assess brake function. Dependent on findings they will lift the vehicle and inspect brake components. If ABS or Traction/Stability is detected a code scan will be performed. An issue with brake systems is that components of both disc and drum brake systems are designed to wear and they do so very slowly. One should never solely rely on an audible or visual wear indicator to necessitate brake pad or shoe replacement as these indicators can fail or often be mistaken for other issues. Catching worn pads or shoes early can save great sums of money. Early detection of worn brake linings can save rotors, drums, calipers, wheel cylinders, and more.
Why is it often cheaper to replace rotors?
The cost of a rotor is generally cheaper than the labor required to machine the rotor. Aside from a cost benefit new rotors ensure true parallelism to the hub ensuring as much uniformity from the pad the rotor surface area as is possible allowing for optimum braking efficiency. Although slightly obvious it bears mention new rotors look better.