Checking the condition of the caliper guide is an essential step during any brake pad replacement. To assess it, detach the brake mechanism from the hub so the piston can glide along the guides with minimal resistance. A more dependable test is to separate the piston from the guides. When the system is free, the finger should react to the rubber boot’s elastic action and move accordingly.
If the finger feels stiff, old grease may have thickened or contaminants may have entered through a damaged guard. In any case, the system needs to be taken apart, cleaned thoroughly, and re-lubricated to restore smooth operation and reliable performance.
How to lubricate caliper guides?
The guide pins require a specialized grease that resists moisture and heat, tolerates temperatures from -40 to 200 degrees Celsius, provides wear resistance during small movements, and remains compatible with rubber components. The market offers a modest range of products, including both imported and domestic options. Examples include TRW PFG110, Niglube RM, Febi 31942, Molykote 31942, and PAG and MC 1630 manufactured by VMPAUTO.
Many brake lubricants exist, but most are formulated to lubricate the side surfaces of the brake pads so they glide smoothly along their guides. Some products are labeled anti-cracking lubricants. They are not the same as guide pin lubricants. Anti-squeak agents sometimes lubricate the rear of the brake pad that contacts the end surface of the caliper piston and must not be mistaken for guide pin lubrication.
To confirm that the fingers on the brake cylinder move away from the guide and return, press the finger and watch its return to the original position. A prompt return indicates proper mechanism operation.
Is it possible to lubricate brake calipers with graphite grease, lithol, and other improvised means?
Using improvised tools or common lubricants in place of the recommended specialized lubricant—such as lithol, copper-based grease, graphite grease, or even castor oil—can cause swelling of the rubber-plastic bushings of the guide pins. This reduces mobility and may cause the brakes to wedge. Protective rubber covers can also swell and detach from landing straps.
Additionally, missing the correct anti-seize additives in lubricants designed for small displacements speeds up wear on the working surfaces of the guide pins, leading to premature failure.
How to lubricate guide claws?
Before applying fresh grease, remove the old grease completely. An aerosol detergent effectively washes grease from the deep pits where the fingers move. A small amount of new grease is enough for lubrication. Some manufacturers supply lubricant in small sachets, around 5 grams each, which is adequate to lubricate two braking mechanisms.
Inspect the condition of the protective rubber boots. If cracks or cuts are found, replace the boots. Also check the finger for wear due to dirt ingress; if it is excessively worn, replace it. Before applying new grease, thoroughly clean the fingers and their pits to remove old grease and wear debris.
Fingers are typically sold as a complete unit with lids and grease. It is wise to purchase original parts or items from reputable manufacturers such as Frankit, a leading producer of brake system components for European, Japanese, and Korean models.
Attribution: Automotive Maintenance Manual, 2024 Update.