A typical master cylinder...
A typical master cylinder.
To say that brakes are important to your success in racing is a huge understatement, as brakes are vital at all levels of the sport. If you overlook brakes, you will find yourself fighting problems throughout the year. Master cylinders must also be looked at through the course of a season. If you have ever battled a soft pedal, the cause might have stemmed from your master cylinders.
The typical Late Model or Street Stock setup will have three master cylinders-one for the front brakes, one for the rear brakes and one for the clutch. One of the best things you can do to help preserve your master cylinders is to buy a rebuild kit and replace all of the seals that make up the unit.
The master cylinder is made up of a few basic parts. There is a reservoir on top, sealed by an O-ring and a wire clamp. But it gets a little more complicated inside. First, there is a rubber boot that, when removed, will reveal a snap ring that is holding the spring and the spring seat in place. Once you remove the snap ring, there will be a pushrod followed by the piston assembly, and then the spring and spring seat.
After the spring and pushrod...
After the spring and pushrod have been removed you can see the wear that has occurred on the inside of the cylinder wall.
Pay close attention to how everything comes out of the cylinder, because you will have to put everything back together.
There are three major steps to follow in the rebuild of the master cylinders. One is the replacement of the reservoir O-ring. When you replace it, make sure that you apply a small amount of grease on the new O-ring before installation. This will help protect the life of the O-ring. Also, when you are installing the reservoir back on the master cylinder, make sure that you don't over-tighten the wire clamp. Simply make sure it is snug.
A brake cylinder hone. This...
A brake cylinder hone. This tool can clean the inside wall of the master cylinder
The second step is to replace the rubber boot at least once a year. The rebuild kit will have the new rubber boot to replace the old one. If you don't replace it during the rebuild, you run the risk of it tearing, which will cause the soft pedal you might have experienced at some point.
And finally, replace the spring and spring bucket to ensure that your master cylinder will function properly throughout the year.
Again, there are a lot of small pieces that you will be pulling out of the master cylinder so watch closely how everything comes apart and make sure you put it back together exactly the way it came out.
Make sure you clean the inside...
Make sure you clean the inside of the master cylinder extremely well before and after you hone the cylinder wall.
One more important aspect of the master cylinder is the condition of the inside wall. Through the course of a race season, the cylinder will wear from the spring and the spring bucket sliding up against the inside of it. When you have everything removed from the master cylinder, make sure you clean it extremely well with a parts cleaner and then clean it out with brake cleaner afterward. Use a flashlight to see if you notice any scratches or wear inside the cylinder. You will need to hone the inside of the brake cylinder if you find any scarring.
(Note: If you have any deep scratches or gouges, you need to forget about the rebuild and buy a new master cylinder. Honing your cylinders can only do so much, and the deep cuts will cause a soft pedal and leaking of brake fluid. )
Honing will require a brake cylinder hone. By honing the inside of the master cylinder you will ensure that the rebuild will keep you running all year. Make sure that you don't make the same mistake I did and purchase the wrong size hone. Check the master cylinder to determine the size you are running.
To hone, simply take a standard drill and attach the brake hone to it. Then take a little WD-40, or other similar lubricant, and spray it on the hone and inside the cylinder wall. This will help the stones on the hone to clean the cylinder wall smoother and more efficiently. After you have used the hone in the cylinder wall, it is extremely important that you clean the cylinder wall again with brake cleaner. This will clear out every metal shaving and particle of dust.
The hone will clean any scratches...
The hone will clean any scratches and wear on the inside of the cylinder. If you notice any deep scratches or gouges, the best option is to buy a new master cylinder.
The finished product.
When you are putting everything back together, put some extra time into making sure everything is as clean as possible and that no dust or metal shavings are making their way into the cylinder. Leaving these inside the unit will only cause problems down the line.
Master cylinders are often overlooked, but if you ignore them repeatedly I can guarantee they will sideline you eventually. Some brake problems stem from having worn-out pads or drums, but many problems can be avoided by taking an hour of your time and simply rebuilding the master cylinders.