Q: Convert Front Drums to Disc
What do I need to convert my front drums to disc brakes?
A: 1st Gen bolt in brake swap — Mother of all Instructions.
1969-1972 (possibly 1968 too) A-body, including Chevelle/Malibu/Monte Carlo, Cutlass/442, Skylark,Tempest/LeMans/GTO/Grand Prix. Earlier cars are likely to have the 4 piston caliper, which is more expensive to rebuild. Later cars (’73 and up) have a redesigned spindle that won’t work on a 1st gen. F-body.
1968-74 X-body, Nova, Apollo, Ventura/GTO,Omega. Again, 1975 and later cars were fitted with an incompatible spindle. Don’t go there.
Forget Cadillacs or any of the big B-body cars like the Bonneville, Bel Air, Century, Olds 88/98, etc. Their spindles are too tall, and they are 5 lug on a 5 inch bolt circle most of the time.
Parts from the above qualified cars needed for the swap:
Brake booster (assuming you want power brakes)
Combination valve (proportioning & other valving function)
All of the above with the exception of the spindles, caliper bracket, and dust shield, can be used as trade-in cores for new or rebuilt parts from your favorite parts store. Tell the clerk the parts are for a 1969 Firebird, which is the brake system you are recreating here.
Drum brake spindles won’t accept the disk brake calipers without machining. Some aftermarket disk brakes, such as Wilwood, use the drum brake calipers for their setup. If you go that way, keep your drum spindles.
Check the spindles for any scoring or other damage on the bearing load areas. Bunged up threads are unacceptable as well. A number of restoration houses such as Classic Industries and National Parts Depot are selling new spindles just in case you can’t find anything affordable. They can also provide the caliper bracket, the other hard to find component. Dust shields are also being
Don’t pay too much for used parts as most everything will old and worn, and very likely only useful as a core exchange item. Some of the new GM conversion setups on eBay look reasonably priced, and the parts are all new. Just be sure that they are stock replacement parts and nothing kluged together from unnatural sources. For instance, some of the dropped spindle kits use 1978 and later G-body (Malibu/Monte Carlo/Grand Prix/etc) calipers and rotors. These may not perform as well as the earlier A-body stuff, and some of the rotors use metric lug nuts and other hardware.
Also be sure that the kit includes a master cylinder, booster (if needed), and the combination valve. You don’t have a complete brake swap kit without these parts.
Parts from your car to keep:
Steering arms (1st gen F-bodies are rear steer cars, as are the above x-body cars. A-body cars are front steer. This means that the center link and tie rods sit to the rear of the center axle line. Bolt your F-body steering arms to the A or X-body spindles, and you’re good to go.
New parts to buy:
Front flex hoses (from hard lines to the calipers). Do not, I repeat, do not use old, used, nasty, cracked, and spongy hoses. Always buy new hoses. Is your life or your car not worth the 20 extra bucks?
DOT 3 or better brake fluid (avoid silicone fluid as it is very difficult to avoid air bubbles and get a good firm pedal). Believe it or not, the Ford DOT 3 is considered about best non-race fluid around. Get it at your local Ford parts department, and take your Firebird when you go. It will improve the neighborhood.
Inner and outer wheel bearings, races, and seals. Get the Timken brand which are superior to anything else on the market. Most of the standard mainstream parts house brands like GMB are so lousy as to be considered junk. If the store doesn’t have Timken, then find someone who does. They are that good.
High temp bearing grease. Pick your favorite brand. Natural or synthetic. Avoid the cheap stuff.
Again, say that all of the above parts are for a 1969 Firebird with factory disk brakes when you go parts shopping. This will simplify things, and if you ever need replacement/service parts, they are easily found.
No modifications are needed here to the above parts. You may have to rework the flex hose brackets on your subframe, but not very much as I recall.
You may find that some (as in very few) 14″ wheels will rub on the brake calipers. I don’t know which particular codes will have a problem, so you’ll have to cross that bridge when you get there. You might be able to get away with a thin spacer, but you’ll have to experiment. All 15″ wheels should clear this setup. Disk brakes may push your wheels outward by as much as a quarter inch due to a slightly wider track. If your present tires are very close to rubbing on the outside, the disk brake conversion will make it worse. The stock narrow 205/80-14 or 15 inch tires are not an issue. It’s only an issue when you go to fairly wide tires and wheels that this comes up as an issue. Or if you use after- market wheels with a very deep dish.
Check the condition of your hard lines. If they are rusted, kinked, or the fittings are stripped, you are better off replacing them as well. Fine Lines and Inline Tube are very good at getting you the right parts if you think that your master cylinder or combination valve require unique fittings. Both of the above companies are known to bend up a custom set of lines for any special requirements. But you should find that 1969 Firebird disk brake hard lines should work without any difficulty.
Don’t forget to bench bleed your master cylinder before putting it in the car. This will make bleeding the entire system much quicker.
Upgrades to the above system:
Consider braided steel flex lines. Many are now DOT approved, and they reward you with an excellent firm pedal.
Performance pads. A good street compound from Hawk, EBC, or Performance Friction will give stopping performance, little dust, and excellent rotor life.
As usual, be careful when releasing the coil spring in the control arms when swapping spindles. There is a lot of energy in that spring and it’s easy to get hurt. And use proper flair or tubing wrenches on the brake fittings. Regular wrenches are sure to round off the fittings and create problems. Sears is a good source for reasonably priced quality tools. Consult your Pontiac shop manual for the details on removing and installing the brake parts. You do have a shop manual, right? They are readily available from any of the restoration parts houses or even eBay, and are essential to any Firebird owner.
By the way. While catching up on some of the recent postings regarding disk brakes compared to drum, some folks have said that drums aren’t all that bad. To be sure, on the first hard stop, you may get by with drum brakes. But repeated hard stops will soon teach you the meaning of fade. I remember a particularly exciting ride down a mountain pass in my buddy’s ’65 El Camino with drum brakes. After the 3rd big sweeping turn, the brakes rapidly began to fade, and each of the following turns involved a great deal of squealing tires and white knuckles.
It doesn’t take a high speed road course to push one’s brakes to their limit. Just a few hills, or heavy traffic on the way back from the car show. But if you must stick with drum brakes, check out Praise Dyno. They have some very good drum brake components that will really improve performance of the drum system. http://www.praisedynobrake.com/ I’ve been quite impressed with their products.
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Content last modified: January 22, 2014 at 11:58 pm