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.

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