The following is the a distilled version of the Frequently Asked Questions and discussions (FAQ) about

Z car Brakes

as discussed on the Internet Z car club.

[The Internet Z car club is an international mailing list with over 125 members and

transmitted to a member's computer account over the internet.]

All information published here is the property of the original authors who are members of The IZCC and may not be reproduced for commercial purposes Everything stated here is based on the experiences and opinions of the original authors. The authors and editor accept no responsibility for any damages arising from use of this information. Always consult your workshop manual and take appropriate precautions when working on the car. If in doubt consult a specialist.

Are there any brake upgrades for the early Z-cars ?

Outside of pad/shoe material changes (semi-metallic), the most popular areas to upgrade are the rear drums to a disc setup, the upgrade of the stock calipers and rotors, and the use of stainless steel brake hoses at each wheel instead of the stock rubber ones.

The ZX stuff is probably adaptable at the front, but I don't believe that it will bolt-up. At the rear, 280zx calipers can be made to adapt. You need a special bracket however. I believe Jim Cook Racing now sells them. The front brakes off of a '79-? can be made to fit onto the older Z's. This entails taking the complete strut off a '79 Z, cut the strut tube below the spring perch, and grafting on the mating upper tube section of the earlier car. Before your get to that point you have a few choices; Will you use the same strut cartridge? You can weld the two tube section together with any length you want, so why not weld them together shorter and use the front cartridge off a VW Golf? It will increase the suspension travel in the upward direction (and lower it in the downward dir.). This mod is essential if you plan on lowering the car any decent amount (3" :-). The same can be done at the rear except using the strut cartridge from the front.

As far as using aftermarket caliper/disk upgrades, there are kits out there for both (Arizona Z-car used to sell a rear disc conversion package, maybe they still do ?). One list member uses Willwood 4-piston calipers and vented rotors, but they just barely fit inside 15" wheels.

The general benefit for stainless steel brake hoses is that they do not flex like the stock rubber ones, and should last alot longer. Whether they justify the cost is up to the individual owner.

Stainless steel lines don't give like the rubber ones. This means that the brakes will have less "feel" to them and can (if not used properly) lock up your brakes during a hard application of them. If you are aware of this limitation and don't lend your car out to others it shouldn't be a problem. The "soft pedal" phenomena, however, could be caliper-related. If you're generating enough line pressure to actually flex the hose, you're positively flexing the calipers and might consider larger ones (Nissan motorsports has them).

2 What are the pros and cons of silicone/DOT5 brake fluid ? Do I have to remove all traces of the original fluid? Do I have to change all internal rubber components (seals, etc.)?

A previous article in Skinned Knuckles (Sept 1993, vol 18, no 2) dealt with the whole silicone/DOT 5 issue. The following are excerpts from that article:


This article is a review of nearly all information we have published on this topic since 1980. Most commentaries have been favorable to the use of DOT 5 silicone brake fluid, but there have been a few detractors, some of whom have complained of "leakage," "fluid expansion," and "fluid compressibility." Few of the specific complaints have been capable of documentation, and at the present time I feel that the use of DOT 5 has been predominantly successful. Most of the problems that have been described are thought to be due to improper use of DOT 5 or improper rebuilding of brake components.

DOT 5 is not a panacea for a brake system that is defective, nor will it correct corrosion that has progressed to the point of incipient failure of the brake system. Simply bleeding out the old DOT 3 (glycol) fluid and replacing it with DOT 5 (as some have proposed) will not correct leakage or reverse corrosion that may have reached an advanced state. The best time to use DOT 5 is when the brake system is being completely rebuilt. Under these circumstances, DOT 5 will almost surely contribute to prolonged life of the system, and the evidence for this seems incontrovertible.

[A history of hydraulic brakes and brake fluids skipped]

[A description of DOT type fluids and their functional requirements skipped]

Table 1

Key requirements for DOT type fluids:

Requirement DOT 3 DOT 4 DOT 5

Dry boiling point (min) 401 F 446 F 500 F

Wet boiling point (min) 284 F 311 F 356 F -40F

Viscosity (max.) 1500 cS 1800 cS 900 cS

[Handling precautions skipped]

Outfitting your vehicle with silicone brake fluid - reprint of procedures recommended by Dow Chemical, producer of DOT 5 fluid. (Note instructions on avoiding entrainment of air bubbles and that Dow does not recommend the flush/fill method of converting to DOT 5 fluid.)

Maximum performance of Dow Corning Silicone Brake Fluid is best attained in a new rebuilt, clean brake system. Dow Corning Silicone Brake Fluid is compatible with SBR, EP, Neoprene, and natural rubber. There are two procedures for outfitting a vehicle. The first and recommended procedure involves reconditioning, including the replacement of worn or corroded parts. The second, a flush/fill procedure is applicable only for relatively new, corrosion-free braking systems. This procedure will give significant, but not complete corrosion protection and excellent low temperature performance. High temperature performance will depend on the amount of glycol remaining in the system.

[Directions for rebuilding brake system skipped]

Bleeding - Fill the master cylinder carefully, pouring the fluid down the side of the reservoirs to minimize air entrainment. Let stand until completely free of air bubbles. Bleed master cylinder if equipped with bleeder valves. Do not shake fluid containers. Avoid agitating the system while bleeding. Do not pump the pedal. Instead, depress and release slowly. Perform bleeding cycle twice to ensure that all air has been removed.

Silicone brake fluid field tests - [performed by Dow Corning]

Direct Mixing - Fifty brake systems were deliberately contaminated with silicone fluid. In each case, the master cylinder was emptied and topped off with silicone fluid, simulating and accidental mixing in service. These fifty vehicles were operated for thirty months without any incident of brake failure. (Editor's Note: Direct mixing is not a recommended procedure. Glycol and silicone fluids are not miscible.)

Flush/Fill tests - In spite of careful efforts to completely flush systems, subsequent teardowns revealed only partial success. From 10 to 30 percent of the original glycol fluid remained in the systems, even though bleeding was continued until only clear silicone emerged from the bleed ports. In spite of the failure to completely flush out old fluid, there were benefits of introducing silicone fluid, including reduced corrosion and improved low temperature pedal response because of the lower viscosity of silicones at low temperature. One of the vehicles put on test with the flush/fill method was a 1972 Olds Toronado. At the time of the filling, engineers did not fully appreciate the limitations of the flush/fill method in completely removing the residual fluid. The Toronado was run for six years and a total of 93,000 miles. Its brake system was then dismantled, at which time it was found that approximately 30 percent of the fluid in the system was old glycol fluid. Nevertheless, the teardown revealed no ill effects. All rubber parts were in excellent condition. Wear and scuffing of pistons were minimal. Some sludge from the original glycol fluid was noted, and some corrosion of metal parts was found in direct proportion to the amount of residual fluid at the site.

Pure silicone tests - (involved complete disassembly of all brake system components, cleaning of wheel cylinders and calipers and lines, and replacement of all seals.) One of the vehicles tested, a 1970 Chevelle, was driven 55,000 miles over a two year period. On teardown, system wear and corrosion were found to be non-existent. Water content of the silicone fluid was less than 0.01 percent and the physical properties of the silicone fluid were unchanged.

Conclusions of researchers

  1. Mixtures of silicone and glycol are possible with no adverse chemical or physical effects.

  2. Silicone flush/fills reduce corrosion and wear and improve brake performance. However, this technique will not give the equivalent of a pure silicone system.

  3. Full benefits of silicone fluids come only with original fills after complete removal of all residual glycol fluid.

US Army tests - In tests conducted under severe tropical conditions in Panama, brake systems of US Army test vehicles using silicone brake fluid performed far superior to systems equipped with conventional glycol fluids. It was not uncommon for glycol fluids to pick up as much as 10 percent water in a year under the extreme humid conditions. Excessive rust from water pickup was the cause of many failures during the test. In contrast, brake components from systems using silicone fluid were relatively free of any corrosion, and water pickup was virtually nil. Reference: U.S. Army Mobility Equipment Research and Development Command, Report 2164, January, 1976.

[Author's personal experiences lauding the benefits of DOT 5 fluid and bashing glycol fluids skipped]

Contrary to popular belief, being 'DOT-5' does not mean 'silicone.' The standards for brake fluids do not take into account what the fluid is made of, only of its properties. There are DOT-5 brake fluids that are conventional glycol-based.

As stated in the article, it is very important to prevent air bubbles in the system when changing over. One good way of doing this (aside from the "pour down the side of the master cylinder" approach mentioned in the article, is to take a very clean screwdriver blade and, when you pour the fluid into the resevoir, pour it down the blade. This should minimize splashing and, consequently, air bubbles.

As with anything, there is not a concensus about the merits of switching to silicone. Clearly, to effectively switching to silicone requires extensive procedures, but these may be worth it (especially with older cars) in preserving brake parts that may become scarce in coming years.