Editing 1937-1957 Buick Oldsmobile Pontiac suspension upgrade

37 – 57 BOP (Buick, Olds, Pontiac) suspension and disc brake upgrade. For those of you who are newbies, or just new to BOP’s, we have the answer. As with all custom modifications, there are lots of variables and side issues. Since there is almost no Information or aftermarket parts for these cars, this will be as much Tutorial as Tech Article. I am going to divide this into sections, with more detail than most people want, so you can jump over The stuff you already know. Also I need to put a disclaimer here. Most of this info came from other Sources including members of this board, hence the “we”, I’m merely trying to put it all in one place. First, let’s look at what the problem is. With minor variation between models and years, all BOP share a common frame/front suspension setup. (Not Chevrolet – The other 3 GM’s that are referred to as the 3 ugly stepsisters). The front suspension is made up of unequal length upper and lower control arms and coil springs. The coils sit in a spring pocket on the lower control arm, and a spring perch built into the frame design on the upper end. Steering is thru a kingpin steering knuckle. Alignment is accomplished with an inner and outer concentric Screw adjustment in the upper steering knuckle mount. (accessible by removing the grease fitting and inserting An allen wrench into the hole). There are two types of shock arrangements. Roughly 37 – 49 (not all 3 changed the same year) have a lever action shock that is built into the upper control arm and serves as the upper control arm mount. 50’s models went to a separate tube type shock. Some internal to the spring, some external. The upper control arm is still a fixed frame mount, with caster/camber adjustment in the concentric sleeves. These cars actually drive reasonably well, and this basic technology was a mainstay for 50 years. So, let’s talk specific shortcomings. First, these cars came with zero to ½ negative caster. Negative caster makes the car easier to turn and gives greater control in deep muddy ruts and other Bad road conditions prevalent in the 40’s and 50’s. (Maximum speed limit nationwide in 1940 Was 45 MPH.). Generally speaking, positive camber will help the car Steer itself and stay centered and stable at todays highway speeds. High positive caster became more common as power steering became common. Conversely, Manual steering is fine at speeds, but parking lots will give you an upper body workout so you can drop your Golds Gym membership. Manual steering works best at about 2 ½ to 3 degrees of caster, which is a compromise between high speed stability and slow speed turning effort. Due to the up and down only rotation of the control arms and Cross rotation of the king pins, any attempt to add more caster is fraught with problems. Anti dive geometry is impossible in this setup. On the pre 50’s models the lever action shocks also present problems. (Aside from the fact they are hard to find And run about $200 each plus $100 core charge if yours aren’t rebuildable). Even in perfect working order they have shortcomings. They are basically a stock only application. Raising or lowering the vehicle puts them out of their designed operating range. Increasing or decreasing weight with engine/trans swaps alters their effectiveness. I should also note here that the hubs/drums run on ball bearings. While serviceable if properly maintained, it is generally agreed tapered roller bearings are stronger, more stable and stand up better to continuous high speed driving. (Ball bearings are now hard to find and cost about $200 for the full set. By comparison a full set of tapered bearings will run about $25). Brakes are non power 4 wheel drums with a single reservoir hydraulic system, enough said. With this basic understanding of the issues, we can start to discuss solutions. Most attempts to gather advice will result in 2 stock answers, Mustang II or GM sub frame. Personally I think the MII is a totally misguided answer. It may work well on Chevy’s, but they have a straight frame rail, so installation is straight forward and weight is within specifications. For BOP’s the frame rails is neither flat nor straight, plus there is that built in spring pocket, so modification of the frame rails would be required, and there is still a weight issue. The GM sub frame approach is definitely viable, and some would say, the best possible solution. If you have the tools, welding and fabrication skills, and your car is stripped to the frame, go for it. If your car is assembled with the engine in and fenders on, your fabrication skills are minimal, or you just don’t like the idea of hacking your frame, read on. This Buds for you. The next section will deal with the brakes. That is not only the worst part of these cars, it is the first decision that dictates the path you follow in later steps. [[image:41 frame bump good pic.jpeg]] The brakes on these cars definitely need improvement. [The information listed here is general in nature and varies from model to model and year to year.] I’m diverting to a brake discussion here, because a decision on brakes determines the spindles you need, and you must have your spindles before you can design your suspension. Earliest models had 1 ¾ by 11 inch brakes with 1 inch wheel cylinders. Post war they were 2 ¼ 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 system 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 MC’s and 7 inch boosters, with universal pedal mounts are available. (With a V8 engine swap a 7 inch booster seems to be the max you can squeeze under the hood). I like the Geo Metro hanging pedal and 7 inch booster, but the MC 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). I located the unit just outboard of the steering column to clear the engine. Under the dash I had to bend the hanging pedal slightly to the center to get a good pedal position. I also welded on a new larger pedal pad that seems more appropriate to a large car and automatic transmission. If you elect to do a power only upgrade and keep 4 wheel drums, be aware most MC’s are designed for a disc/drum setup and you will have to add 10# residual valves to the front lines. At this point I would like to comment on the cost of doing a brake job on the original brake setup. 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 and the above mentioned wheel bearings are $200. So, a complete brake job will run $600 just for the 2 front wheels, without the MC or booster. So let’s consider the next option, front disc brakes. There are several ways to go here, but personally, I like the Scarebird* setup. Basically 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 clarification purposes only, here is an example. On 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. Note: From CPP (Classic Performance Parts) you can get a tapered bearing conversion kit. Bottom line, if you are using all new parts, you can have disc brakes cheaper than rebuilding the original drum setup. Before you rush out and order parts, finish the tutorial. We will be discussing suspension upgrades that include changing spindles, which will change the Scarebird setup you need. Footnotes; Your original drum setup used ¼ inch brake lines. 3/16 is recommended for disc brakes. Many aftermarket MC’s have Metric fittings. You may find yourself putting different fittings on each end of your new lines to convert from Metric to Standard. There is a direct metric match to the American 3/16 line size, so that is not a problem. Master cylinder size is important, but slightly flexible. I like the corvette style MC, with ports out each side. Makes installation easier, and they are pretty cheap. The 1 inch bore will do the job, but expect the pedal travel to be a bit long. On the other hand, a 1 ¼ or larger MC will move the fluid faster (shorter stroke) but the small 7 inch booster will not be up to the job. Your original MC 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. 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. *I have no personal connection, or interest in, Scarebird Classic Brakes, in fact I didn’t even use them on my car, but that’s a whole different story we’ll get into in the next chapter. I recommend them because others have been very impressed with the product and they make a setup for Buick, Olds, Pontiac, Corvair, Dodge, Plymouth, Cadillac, Ford, Mustang, MGB, you name it. Plus I like the idea of knowing exactly what over the counter, inexpensive, parts will be needed later when you do a brake job. Update. I ended up with a corvette 1 inch master cylinder and a 7 in single stage booster. My opinion is: close enough. The brakes are a vast improvement over manual drums, but not perfect. Stopping power is great to about the last 20% of pedal travel. I made several panic stops to test the system. At the very bottom, you just can’t push hard enough to lock them up. Simply put, the system needs a 9 or 10 inch booster to be perfect. The tech man I spoke with at CPP felt the 7 inch dual diaphragm would have been better, but not much. There simply isn’t enough power in a 7in booster to lock up a set of 215x75 15s on a 3500 pound car, on dry pavement. The reason I say close enough; this would only be an issue in a total panic situation, to a full stop, on dry pavement. In that situation, do you want them to lock up? Front Suspension Here is where the fun starts. The original idea came from a magazine article that showed an upgrade for a 55 Pontiac. Reading this article, which has some decent pictures, will get you thinking in the right direction. . http://www.pontiacsafari.com/L1Garage/BallJointConversion.pdf With some research we figured this would work on all 37-57 BOP’s cause they all had the same basic set up. What we learned was, the 58 Pontiac Lower Control arms are the key. They are a direct bolt in, exactly the same as the originals, but with ball joints instead of king pins. 59 and later BOP’s went to a completely different control arm mount. 58 Buick lowers are not symmetrical, so they won’t work. (waiting for someone to confirm that 37-57 Buicks are the same as BOP’s, right now it is unconfirmed) Also we do not have a 58 Olds to check those lower control arms. What we do know is 57 is king pins, and 59 is all new. So 58 is it. We used the 58 Pontiac upper control arms simply because we got the whole front end. Make a note that several uppers will work. Looks like 58 to 60 BOP’s all had the same basic dimensions on their upper control arms. In fact, the 58 Buick uppers we used on one conversion had some built in twist that allowed us to add more anti dive than we could get with the Pontiac uppers. As you can see in the pics, the 58 control arms are more substantial than the 41. But all dimensions are the same. [[image:58 pontiac 41 pontiac lower control arm s.jpg]] The upper control arm mount is a fairly simple fabrication. If you have a pre 50’s car, the upper mount will differ from the article. The pre 50’s had the lever action shock, therefore no upper shock mount. On both of our conversions (41 Pontiac and 49 Olds) we fabricated the mounts out of angle iron. We used ¼ in. 3x3 angle iron on the Pontiac and added 2 gussets. On the Olds we had some 3/8 in. 4x6 angle iron, so only added one gusset. Note in the pictures how the front mount is higher than the rear mount. This sets up the anti dive angle. Up to 10 * is fine, as long as the upper ball joint is not in a bind. Be sure the frame is level side to side and has the correct front to rear angle that you want. (with 15 inch wheels, my spindle center was 12.5 inches off the ground. I blocked the frame, so that when the lower A was level, the spindle was 12.5 in up) Even a small error here will be costly. It takes ½ inch of shims to adjust 1 degree of camber. If you need to put additional shims on therear of the bracket, to increase caster, and can’t take enough out of the front to keep the camber static, you will have to cut it loose and start over. Unfortunately, you can’t do a full alignment until it is totally finished, basically driveable. So get this part right. If you have any doubts, shade towards the positive camber side, you can add more shims later to move it towards negative. Likewise, move the upper mount to a position about 3/4 inch behind the plumb line for the spindle, to set up at least 5 * of caster in the neutral position (neutral being the static position as mocked up, before final alignment). If you intend to add power steering, I would shoot for 6 * in the neutral position, but don’t get the uppers so far behind the lowers you put the ball joints in a bind. I drilled holes in the bottom plate of the angle iron and when I had it mocked up, I drilled thru the frame and bolted it up with 3/8 inch bolts. This was strong enough to allow me to assemble the entire front end, with springs, put the wheels and tires on it and set it on the ground. Since I had my engine in, I was basically in a final drive setup. I double checked everything, then tore it down and had it welded in place.

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