Editing 1937-1957 Buick Oldsmobile Pontiac suspension upgrade (section)
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==Brakes== The brakes on these cars definitely need improvement. The brakes should be handled first, because the decision you make on the brakes determines the spindles you'll need, and you must have your spindles before you can design your suspension. The information listed here is general in nature and varies from model to model and year to year. Earliest models had 1-3/8 inch by 11 inch brakes with 1 inch ID wheel cylinders. Postwar, they were 2-1/4" by 12”, with 1-1/8” wheel cylinders. The most basic upgrade would be to the later, larger, components. Control arms and spindles are unchanged for 20 years, so this is a basic bolt on. Even the shop manuals refer to this upgrade. The single reservoir master cylinder is located under the floor and bolted to the frame. A new split system master cylinder and power [[booster]] will be an amazing transformation of your stopping ability. Several aftermarket master cylinders and 7” boosters (with universal pedal mounts) are available. With a V8 engine swap, a 7” booster seems to be the most you can squeeze under the hood. The Geo Metro hanging pedal and 7 inch booster is one option, but the MC (master cylinder) is small. Didn't chase down a match, but the center hole and bolt pattern appear to be typical GM. Be sure to get one designed for a booster application, and pay attention to the pushrod length. Pulling the old pedals out was twice the work of putting the new one in. In this case, the unit was located just outboard of the steering column in order to clear the engine. Under the dash, the hanging pedal was slightly bent to the center, to get a good pedal position. And a new, larger pedal pad (more appropriate to a large car and automatic transmission) was welded on. ===Drum brake upgrade=== If you elect to do a power-only upgrade, and keep 4-wheel drums, be aware most master cylinders are designed for a disc/drum setup, and you will have to add 10 psi residual valves to the front lines. *The front drums and hubs come together, at about $130 each *Wheel cylinders are $32 each *Shoes are $25 plus cores *Hardware is $15, flex hoses are $25 each *The above mentioned wheel bearings are $200 So, a complete brake job will run around $600 just for the two front wheels, without the master cylinder or booster. ===Disc brake upgrade=== Aftermarket parts options: *[http://www.scarebird.com/6928.html Scarebird Classic Brakes] makes a setup for many General Motors makes and models. They supply the brackets for the calipers and the correct spacers for the spindles/rotors, and a tech list of parts to finish the job, for $100-$150, depending on application. For example, for a '58 Pontiac, they supply the brackets and spacers. From any source, new or used, you need a pair of '77 Bonneville 12-inch hubs/rotors, a pair of '88-'91 GM truck calipers, and 2 choices of flex hoses, depending on whether you want them 12 or 15 inches long. *[http://classicperform.com Classic Performance Parts] sells a tapered bearing conversion kit. If you are using all new parts, you can have disc brakes cheaper than rebuilding the original drum setup. ===Notes=== *Your original drum setup used 1/4" brake lines. 3/16" is recommended for disc brakes. *Many aftermarket master cylinders have metric fittings. You may find yourself putting different fittings on each end of your new lines to convert from metric to inch. There is a direct metric match to the 3/16" line size, so that is not a problem. *Master cylinder size is important, but slightly flexible. One option is the Corvette-style master cylinder, with ports located on either side. This makes installation easier, and they're fairly cheap. *The 1" bore will do the job, but expect the pedal travel to be a bit long. On the other hand, a 1-1/4" or larger master cylinder will move the fluid faster (shorter stroke), but the small 7-inch booster might not be up to the job, the result being a too-hard pedal effort. Your original master cylinder may push the discs fine as far as volume goes, but pressure could be another matter. *Virtually all cars will need an adjustable proportioning valve. Any change from the original setup – front or rear weight change, tire sizes, line sizes, rake or tail drag, disc conversion, etc., has the potential to throw your brake system out of balance. *Most disc conversions will require at least 15 inch wheels; check it out before you order. *The project in this tutorial used a Corvette 1" ID master cylinder, and a 7" single stage booster. This combination turned out to be "close enough". The brakes are a vast improvement over manual drums, but not perfect. Stopping power is great, until about the last 20% of pedal travel, as several test panic stops revealed. At the very bottom, you just can’t push hard enough to lock them up. The system probably needs a 9 or 10 inch booster to be perfect. There simply isn't enough power in a 7 inch booster to lock up a set of 215/75x15 tires on a 3500 pound car, on dry pavement. ====Improvements two years later==== Never really happy with the 7 inch booster. Moved some things under the hood to get more room and installed a 9 inch dual diaphragm booster from a mid 1990s Camaro. Now it stops like a new car. I'll never use a 7 inch booster again.
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