Tech Tips

Rotor directional vanes.

Written by Site Admin.

Rotors/Discs may be unidirectional but for high performance many have directional vanes and slots.  Alcon rotors/discs will come with a Left and Right designation.  If you cannot find that or are using a different rotor, his should help you correctly install the disc on your car.

Internal vanes should lean towards the rear of the car.  This helps pump more cooling air through the disc.  Slots should lean towards the front of the car however the internal vanes take precedence and should drive the direction of the disc, even if that means the slots are not optimal.


Understanding brake balance

Written by Site Admin.

 

BRAKE BALANCE Safety regulations require that racing cars, other than veteran or vintage, must have two separate brake systems so that in the case of a hydraulic failure, one system will remain operative - giving the driver some chance of reducing the intensity of the impending impact! There is an additional advantage in this, as it allows the driver to adjust the front/rear brake balance to suit conditions and driving style.

For example, if the track becomes wet during an event, the driver can move the brake balance to the rear; thus reducing the braking on the front wheels which, due to lack of grip in the wet, will tend to lock since there will be reduced weight transfer. There is also the opportunity to adjust the brake balance to suit the driver's preference. It should be noted that, in dry conditions, although brake balance biased to the front tends to make the car feel stable under braking, brake balance should be set as far to the rear as the driver can tolerate as this will give the shortest stopping distance. This ensures that each tyre is giving the maximum braking effort that it can.

The balance bar system should be set up so that when the brake pedal is depressed to the position it adopts under heavy braking, it and the balance bar are at right angles to both push-rods - in both planes. This is achieved by adjusting the push-rod lengths - care is needed to ensure that adequate push-rod thread length remains in each clevis. This gives maximum efficiency of the mechanical operating system.

The fact that in this condition and with the brake released, the brake pedal in its 'off brake' position, the balance bar does not make right angles to the push-rods, is quite acceptable. This occurs because, generally speaking, the front calipers are larger than the rears and therefore more fluid is used to generate the required braking force, hence there is greater master cylinder travel at the front.

 

Inspecting your Alcon brakes

Written by Site Admin.

Racing brakes, unlike those fitted and used on Road Cars are subject to continually high temperatures and stress and therefore must be serviced correctly if they are to give continuing good performance.

The main items to be looked at very regularly are the discs and pads - both of which wear out. Inspection of these should be a regular part of car preparation - with worn items being replaced. Whilst inspecting calipers, it is advisable to look for any sign of moisture around the pistons - especially if the calipers have been very hot (see COOLING above) and the fluid connections.

If there is any sign of fluid leakage from calipers, they should be serviced and fitted with new seals. In long distance races it may be necessary to fit replacement pads - and possibly discs - during the event. This procedure should be properly practised (with HOT brakes) prior to the event to avoid risk, confusion and time wastage. It is important that replacement pads (and discs if being replaced) are pre-bedded so that the driver needs only to warm up the brakes prior to achieving an acceptable, but not at this stage, optimum, retardation. Discs should be regularly inspected for cracks and must be changed if necessary. During routine maintenance, clean calipers particularly the outside diameter of pistons - with clean soft cloth or paper towel - and inspect for any signs of damage or leakage, check fixing bolts for correct tightness.

Brake bleeding tips

Written by Site Admin.

 

Brake bleed procedure

1. Installation notes

1.1. Use a high performance ethylene glycol based fluid such as Castrol Racing Fluid or, for higher temperature use, Castrol SRF. Do not use silicone brake fluid. Brake fluid is hygroscopic and the boiling point will reduce if it contains any moisture. For optimum performance, fluid should be changed regularly.

1.2. Each Alcon brake caliper has an optimum mounting angle, normally within plus or minus 5° of vertical, to prevent air from being trapped in the piston bores. Check with Alcon’s technical department if the angular position is greater than 5° from vertical.

1.3. Ensure that the master cylinders are firmly fixed to a rigid bulkhead or cross member.

1.4. To avoid trapping air in the master cylinders, ensure that the fluid outlet port is uppermost. Preferably mount the cylinders level or with the push rod end slightly lower.

1.5. Avoid vertical loops in brake lines, which will trap air, particularly in the feed from the reservoir to the master cylinders.

1.6. To prevent a vacuum forming in the reservoir, there must be a breather hole in the cap.

 

How to bleed your brakes - Manual method

Written by Site Admin.

 

Let It Bleed

To properly bleed the brakes, start with a couple of 8-ounce cans of fresh brake fluid. An unopened can has a long shelf life. An opened can should be discarded within a few weeks. Get the vehicle up in the air and remove all four wheels. Well, okay, you might be able to do this with the wheels on if you can swing a wrench on the bleeder valves.

So, your next task is to make sure the bleeder valves can be loosened. You'll need a box wrench that fits the bleeder bolt. A crescent wrench or Vise-Grip probably will just round off the bolt's flats. A little penetrating oil drizzled on the bolts the day before will help. So will some judicious tapping with a hammer to break up any corrosion. Loosen the bolts, but leave them closed.

 

 

If you can't turn the bleeders without breaking them off, you'll need to replace the brake calipers or wheel cylinders. See the above notation about penetrating oil and light hammer taps before applying enough torque to break these minuscule, hollow bolts.

 

Sneak into the kitchen and appropriate the small turkey baster. Remove the top to the master cylinder reservoir and suck out as much of the old squid ink as you can. Clean any sediment out of the reservoir with a clean, lint-free rag. Do not spill any brake fluid on any painted surfaces -- it will remove the paint pretty much immediately.

 

Get a piece of clear plastic tubing (aquarium tubing is fine, and it's cheap). Push one end of the tube over the brake bleeder bolt at the right rear of the car. Put the other end of the tube into a small, clear bottle with an inch or two of clean brake fluid in it. (This will keep air from being sucked back into the brake cylinder or caliper.) Put a piece of 1 x 4 lumber or some other spacer under the pedal to prevent the pedal from traveling too far when line pressure is released. Top off the master cylinder reservoir with fresh fluid and put the cover back on the reservoir. Fluid will squirt out of an open reservoir every time the pedal is released.

 

 

Cue the Helper

Your helper needs to be someone who can follow instructions exactly. He or she won't get dirty hands so you don't need to pull one of your pals away from the ballgame. A teenager in a white dress will do fine. Have your helper sit in the driver's seat and await your orders. Here's the drill: You say "down." He or she depresses the brake pedal with about the same amount of force needed to keep the car from rolling forward at a traffic light. Then your helper says "down" and keeps the pressure on. When you hear the call, warn your helper that the brake pedal is about to sink underfoot and to keep the pressure on constantly. Then crack the bleeder bolt a quarter-turn.

 

bleeding brakes bleeding brakes

 

 

A bleeder bolt can become difficult to remove. Use a proper-fitting box wrench to keep from rounding it off.  Got ABS? You may need to use a scan tool during the bleeding process to cycle the pump and valves.

 

 

Some of the old, contaminated fluid will trickle down the tubing into your bottle. When the trickle stops, close the bleeder. Then you say "up." Your helper says "up," and removes his or her foot from the pedal.

 

Repeat this process until fresh, clear fluid comes from the bleeder. Any out-of-sequence moves can suck air into the caliper. Yes, the end of the tubing is submerged in fluid, but air can travel past the threads on the bleeder bolt into the caliper if there's ever any negative pressure in the system while the bleeder is cracked.

 

Every half-dozen or so iterations, top off the reservoir with fresh fluid. Do not allow the reservoir to get more than half empty -- air can be sucked into the master cylinder unless the fluid level remains well above the bottom of the reservoir that feeds the cylinder.

 

Once clean fluid is coming out of the brake, snug the bleeder bolt and move your operation to the left rear wheel and start all over again. Next repeat the process with the right front and finally with the left front. Follow that with a few strokes of fresh fluid from all four, again. Don't forget to keep the reservoir topped off.

 

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