How to: Build a better brake

Radio Control Car Action, Apr 2003 by Gonzalez, George M

5 tips for top stoppers

Almost all nitro-powered RC vehicles have some kind of cam-actuated disc-brake system that is reliable, adjustable and easy to maintain. RTR vehicles are built well at the factory, and most RC kits provide adequate instructions for proper brake assembly, but with a little extra effort when you set up your brakes, you'll shave seconds off your lap times. Here are the tips you need to build, adjust and maintain your disc-brake system like a pro.

Scuff the rotors

If your vehicle has a fiber or composite brake rotor and steel calipers, you can improve braking by lightly sanding the rotor's surface. Put a sheet of fine-grit sandpaper on your workbench, and then, with a circular motion, lightly rub the rotor over it to remove the high points and roughen it slightly.

Replace the brake spring with fuel tubing

For even smoother and more linear braking, replace the spring that tensions the brake lever with a piece of fuel tubing of the same length; slide the tubing over the brake linkage. To prevent the tubing from getting stuck inside the brake-lever eyelet when the brakes are applied, slide a washer or a pivot ball over the brake linkage between the fuel tubing and the brake-lever eyelet.

Glue the brake pads

If your brakes have metal rotors, the calipers probably have fiber, rubber or cork brake pads (linings). If these pads are not already securely laminated to the calipers, you must glue them to the calipers; most instructions suggest that you use with CA for this, but CA does not hold them for long. Instead, use a flexible adhesive such as DuraTrax's Shoe-Goo or Pacer's Zap-A-Dap-A-Goo. Put a dab of glue on your finger and then smooth it evenly over the brake pads. Press the brake pads firmly against the calipers, and wipe off any excess glue that is squeezed out. Install the mounting screws through the holes in the pads and calipers to ensure that the pieces bond correctly, and then allow the glue to dry for 24 hours. When you reinstall your brakes, you should find that they're more reliable and consistent than they were before.

Install tension springs or O-rings

If your brake rotor rubs against the calipers when you're accelerating or coasting, you're wearing out your brakes, and your braking will be inconsistent. To solve this problem, you could simply loosen the mounting screws that secure the calipers on the transmission or brake-cam housing, but you will lose valuable braking power in the process.

The best solution is to install small springs or O-rings between the calipers to push them apart when you release the brakes. You'll find small springs at most hardware and hobby shops, but the small, low-tension springs inside retractable ballpoint pens work best. The 0-rings used in RC shocks also work great; to work properly, they should be slightly wider than the brake rotor. Install the springs or O-rings between the calipers and use the tension-adjustment screws to keep them in place.

Setting brake bias

Most 1/8-scale 4WD buggies have separate front and rear disc brakes that allow brake bias to be adjusted. This feature allows you to set the force of the front and rear brakes independently. Since weight is transferred to the front of the car when you apply the brakes, they're typically set so that the front wheels are given more braking force than the rear wheels; in other words, the brakes are biased toward the front wheels-hence the term "brake bias." Setting brake bias correctly is a matter of trial and error, but it isn't hard to figure out what to do: just reduce the braking force on the wheels that lock up first under maximum braking.

To adjust the bias, reposition the linkage stops that put pressure on the front and rear brake levers; many buggies make the job easier by having thumbwheels on threaded brake rods. Some also have front and rear brake linkages joined on a yoke that can be adjusted using its own thumbwheel; this allows you to adjust total braking force without altering the bias settings.

PACER TECHNOLOGY (800) 538-3091; pacertechnology.com.

DURATRAX distributed by Great Planes (800) 682-8948; duratrax.com.