The Rear Brake's Performance is Critical
If you're unsure about replacing the rear brake pads or doing other brake work on a dirt bike, be assured that doing so is really not all that difficult, although should you be interested in more of the technicalities of a specific dirt bike's braking system than what this article covers, be sure to refer to a Factory Service Manual specific to the motorcycle being serviced.
Keeping the dirt bike's brake pads, brake rotors, brake pins and all the other parts that make up your braking system in check is a really good idea and can benefit you in more ways than you may initially realize and this is especially true if you're a competitive minded rider as being proficient in knowing what to look for on the brakes, as well as being able to change the dirt bike's rear brake pads can increase the braking performance and keep money in an enthusiasts or starving privateers pocket while maintaining the rear brake system.
Check this out... keeping your rear brake system in it's best possible condition can undoubtedly aid in out braking a competitor into the first turn (really any turn on a track) and this is true whether it be a motocross track, or after holding it wide open across a straight away before diving back into the woods on an off-road course with someone right beside you. Additionally, having a good rear brake is equally important if you're hitting the ramps since available stopping distances are usually pretty tight during competitions, so the following tips may prove very enlightening to some although if your braking performance is suffering due to a soft feeling pedal, you should check out our article on bleeding the brakes as fresh fluid can dramatically increase the rear brake's stopping and staying power.
What to Look for When Inspecting the Rear Brake
Often times, a quick visual inspection of the rear brake system components will be all you'll need to do after most moto's as or rides. You or the rider will likely already be aware of any failures or damage long before the return to the pits but knowing what to look for can be a great help as well so these steps below should keep you in the know.
Considering the conditions that the rear brake pads on a dirt bike are subjected to such as mud, sand and extreme heat, it really should be no surprise that the brake pads, hardware and brake rotor would and can frequently develop and show wear. This coupled with the fact that a lot of riders know that dragging the rear brake across rough terrain can make the motorcycle perform and handle better by settling the rear end but doing so causes accelerated wear of brake pads and the brake rotor among other parts so here's what to look for after each ride:
- Inspect the hydraulic system for adequate pressure or leaks:
This can be easily done by merely stepping on the rear brake pedal to check for adequate pressure while visually inspecting the remainder of the rear brake system extending from the master cylinder to the caliper for any signs of wetness or dirt accumulation. If the brake pressure doesn't feel adequate by a soft brake pedal or a pedal that goes bottoms out before any pressure is developed would indicate that the rear brake pads may either be worn way beyond their service limit or there is air trapped in the hydraulic system which can be addressed by bleeding the brakes and getting new, clean brake fluid into the rear brake master cylinder and caliper.
- Inspect the brake rotor for grooving, heat marks or other damage:
When checking the brake rotor, you also want to look closely for any heat cracking, discoloration, grooving or other unusual damage. Should any damage to the brake rotor become evident, the only remedy that should be considered is replacement of the brake rotor.
- Is the brake rotor bent?
Rear brake rotors do get bent occasionally such as when some whiskey throttling maniac behind you runs into you from behind or by other natural means such as rocks, stumps and the like. An effective means of checking the flatness of the rear brake rotor is to place the dirt bike on a stand with the rear wheel off the ground and spin the rear wheel lightly by hand while watching for any dragging spots when the brake rotor rotates through the brake pads. The brake rotor's flatness can also be checked by riding the bike in a smooth area and stepping on the brake pedal while feeling for any pulsation which may indicate a warped or bent brake rotor.
- Inspect the brake pad friction material every ride.
By far, the highest wear item on the dirt bike's rear brake system is the pads themselves, and depending on the compound you're running, and level of use, brake pads can be through dealing in no time depending on conditions such as mud or hard and aggressive use.
Anytime you inspect the brake pad's thickness you want to be looking for a wear indicator that is almost impossible to see or find most of the time.
A better way of checking a pad's thickness to determine the usability remaining in the brake pad is to take a close visual inspection and note the thickness of the friction material.
If the brake pad's friction material is equal to or less than the thickness of the pad's backing plate at any point on the pad, you can consider the rear brake pads to be done. So, to ensure the best performance and not boil the brake fluid or have any factors contributing to brake fade, the rear brake pads should be replaced.
If the brake pads are removed for other reasons, always inspect them for any glazing, cracking or other irregularities in the pad's friction material. If any glazing or other irregularities are noted, replacement of the brake pads as a set should be the only option considered.
- Ensure the rear brake caliper slides are not frozen
On most dirt bikes the caliper is intended to "float" while the rotor remains fixed and it's important to ensure that the caliper has very slight side to side movement (either of which may feel like slop to the inexperienced) Also, be sure to lubricate the caliper slides while checking them for wear the next time you have the caliper and caliper bracket off such as when changing a tire.
How to Replace the Rear Brake Pads on the Bike
Replacing the rear brake pads on a dirt bike is a common procedure that most anyone can do themselves and maintain a proper working rear brake capable of instant brake slides or to help slow a dirt bike down consistently so we wanted to hook you up with the quick rundown on how to do this like a pro, as well as what to look for so as to extract the maximum performance from the rear brakes.
- The first step to changing the rear brake pads on the bike is to ensure that the entire area is clean and the best time to do this is after washing the dirt bike. If you're going to be replacing the brake pads between moto's or while testing such as at the track and washing the dirt bike isn't really feasible, be sure to clean as much dried dirt or mud away as possible from the brake system with your fingers, a brush and / or compressed air.
- With the area clean around the rear brake caliper, place the box end of a wrench the appropriate size (most likely an 8mm) over the bleeder then a tube to a bleeder bottle as can be easily made with 1/8 inch clear tubing and an empty water bottle, then loosen the bleeder.
- With the bleeder open, use a pair of channel locks and very carefully squeeze the inner pad inwards pressing the caliper pistons back into their bores, forcing the brake fluid that's in the caliper out and into the bleeder bottle for disposal later. Continue working the pads into their bore by only squeezing the inner pad itself but do NOT start cramming screwdrivers between the pads & rotor.
- With the caliper pistons fully retracted, you'll need to remove the brake pin to allow the rear brake pads to be removed from the caliper, so you'll either have to carefully remove clips securing this pin, or remove the threaded plug on the side of the caliper near the rear as this enables access to the pin that the brake pad slides on, then remove the brake pin.
(Some bikes may have an external hex as either an aftermarket replacement part or it may have come this way from the motorcycle manufacturer. This style reduces this to one piece eliminating the plug.)
After removal of the brake pin, be sure to inspect the pin for any grooves, bending or wear. If any wear is evident on the brake pin which was just removed it's important to install a replacement brake pin,
otherwise the brake's performance will likely suffer.
With the pin removed, the brake pads should now come out the bottom of the caliper just be sure to not lose any shims that may be in place directly opposite of the pin as these may shift or fall out after removal of the brake pads.
- Should there be a piece fall from the end opposite of the brake pin, be sure to bend the tabs on this which keep it secure in the caliper or caliper bracket and reinstall these, as these prevent the aluminum bracket from developing grooves which may cause the brakes to stick and bind.
- With the old pads out, insert the new pads back into the caliper using the same orientation as what came out and ensuring the friction material is facing the rotor's surface. (you'd be surprised what some might do otherwise.)
- With a new brake pin, or using the existing pin provided it was in good shape when you removed it, place a small amount of anti-seize on the threads only (if threaded), then replace the pin ensuring it is securing both pads properly and either tighten the pin securely or install the retaining clips to secure the brake pin the way that the manufacturer recommends as be found in a factory service manual specific to the motorcycle being serviced.
Do NOT use any lubricants on the sliding part of the brake pin
New Brake Pads Do Require a "Bed In" Period.
Installing new pads often results in terrible performance from the rear brake's stopping abilities which can last for a mile or 3 until the "feel" comes back. This is because it takes time for the pads to become matched to the rotor.
(This is what is referred to as: "Bedded In").
How to Bed In New Brake Pads
To Bed In a set of brake pads is really no big deal. Here's how:
Ride the dirt bike around for a few minutes in a flat and smooth area holding the gas and brake simultaneously while gradually increasing the drag of the brake for 20-50 feet and releasing for a cool off then repeating.
Do this a few times and the feel on the pedal should immediately feel stronger. Once the pads are able to grip the rotor well enough to easily initiate a brake slide, the pads could be considered well "Bed In"