Handy Hints Ė Doís and Dontís
1. Donít mix up calipers, left to right, bleeders always go to the top to get the air out (some older European and English cars were built to be bled backwards, making it hard to do at home). Modern cars always bleed air at the top.
2. When trouble shooting a soft pedal, clamp all hoses, taking the clamps off one at a time until you find where the softness is coming from. If you still have a problem with all lines clamped, then the master cylinder is the cause. If the pedal goes hard, it is fine. Sometimes the hose itself can be swelling.
3. New brake pads running on worn/tapered discs will cause softness until they wear to match and the springiness goes away. Machine discs when fitting new pads.
4. It is well proven that undersized discs do not cool well and warp quickly. Do not use when below minimum for safety and legal reasons.
5. Check master cylinders for residual valves when converting to discs. These valves are meant to stop air sucking past wheel cylinder cups but will make discs drag. Early American Corvette calipers can suck air and therefore need light pressure, special residual valves, all modern calipers are fine with none. If not sure, do the dripping bleeder test.
6. Never get any hydrocarbons, oil, kerosene, petrol etc. near brake parts Ė brakes use special rubbers which swell dramatically when contacted by hydrocarbons. Wash brake parts in Methylated Spirits or Brake Clean Fluid and lubricate with brake rubber lubricant (silicon based), or brake fluid during assembly.
7. Fitting new seals to used master and slave cylinders is not always successful. Bore wear, scratches and corrosion usually mean reduced life of rebuilds. Buy a new assembly or have yours stainless sleeved if necessary.
8. Cheap brake pads are a false economy; they wear quickly and do not stop as well.
9. A reaction disc is a small rubber disc which lives under the head of the booster output push rod. If this is lost, the brakes will be nearly uncontrollable with stopping proportional to pedal position, not pedal effort, sending you through the windscreen at the lightest touch.
10. With all modified systems, check everything for clearance, through all suspension travel and lock to lock, particularly brake hoses and calipers versus cross members and sway bars etc. on lock.
11. When converting a four-wheel drum type car to front discs (retaining original rear brakes), it is necessary to fit smaller rear wheel cylinders to reduce rear brake effort, as the front discs are not self-energising.
12. If not sure, seek the advice of an expert.