Next on our to-do list was...
Next on our to-do list was to assemble an A-Body suspension with the two different spindles and compare the geometric differences. For this, we used Performance Trends' Suspension Analyzer, a great piece of software commonly used by circle track and road race teams. The next tool for maximum accuracy is this stand, which allows us to install a front clip from any car, at any angle, and directly measure pivot points, without any parts obscuring our vision. For this test, we set our '74 Dart clip to assume a 1.5-inch rake from front to rear-most cars of today have a slightly raised rear, which directly affects caster, and needs to be accounted for. We set the ride height approx. 1-inch lower than stock, which is also quite common. We set the "ground" level for a 26-inch front tire, and aligned it with a four-bubble camber/caster gauge. Toe-in was set to near 1/8-inch total (0.059-inch per wheel), camber was set to zero for ease of testing. Maximum caster attained with the A-Body spindle was 1.18 degrees.
Another interesting trend you'll find in the charts is caster change throughout travel. Negative caster is typically unstable and should be avoided if possible. Notice that both systems go into negative caster just slightly higher than ride height. You should try for as much static positive caster as possible to stay in positive caster through more wheel travel. It's worth the effort to correct these little problems for a more enjoyable ride.
The only word of warning we could come up with concerning this swap would be initial alignment. After installation, it's necessary to rotate the eccentric bolts a little further back to re-align it, and if your car is already at the inside edge of the adjustment range, you may have to use offset control arm bushings to increase the range. After 30 years of flexing, many of these cars are hard-pressed to achieve proper alignment specs with the original parts, so switching to these spindles may only make an existing alignment problem worse. The offset bushings (called Problem Solvers, Moog PN K7103) can be ordered through most local parts stores cheap, but few clerks know about them, so you have to specifically ask. The K7103 fits all A- and E-Bodies, and all B-Bodies from '62-'72. As with the balljoints, this number typically has to be crossed over to a different brand, depending on the store's supplier.
So now you have the facts, proceed to the nearest junkyard and get your disc brakes.
|Chassis Identification Chart|
|A||'60-'62 Valiant/Lancer, '64-'66(early)/'67-'72/'73-'76(late) Valiant, '64-'66(early)/'67-'69 Barracuda, '64-'66(early)/'67-'72/'73-'76(late), Dart, Duster, Demon, Scamp, Sport, Swinger|
|B||'62-'64 Savoy, '62-'64 Fury, '63-'64 330 and 440, '62-'64 Polara, '65-'76 Coronet, '65-'74 Satellite, '68-'75 Road Runner, '66-'78 Charger, '67-'74 GTX, '62-'70 Belvedere, '69-'71 Super Bee, Cordoba to '79 '75-'78 Fury, '77-'78 Monaco, '78-'79 Magnum, '75-'79 Cordoba, '79 300|
|C||'65 Dodge 880, '65-'73 Polara, '65-'74 Fury I,II,III, '65-'76 Monaco, '75-'77 Gran Fury, Newport, '65-'78 New Yorker, '65-'78 Newport, '65-'71 300, '74-'75 Imperial, '66-'69 VIP |
|F||'76-'80 Aspen, Volare, Road Runner, RT|
|J||'80-'83 Cordoba/Mirada, '81-'83 Imperial|
|M|| '77-'89 Diplomat, Caravelle, '77-'81 LeBaron, '82-'89 Gran Fury, '82-'87 New Yorker 5th Avenue, '88-'89 5th Avenue, '82 New Yorker |
|R|| '79-'81 New Yorker, St. Regis, Newport, New Yorker 5th Ave., '80-'81 Gran Fury |
String lines marking fore/aft...
String lines marking fore/aft centerline of car and spindle centerline left to right. Once the suspension was all set and aligned, lines were drawn on the Table to lay out centerline of the car and centerline of the spindles. From these two lines, and the simulated ground (our table), measurements are taken to each pivot point on the suspension. After all measurements are taken and entered into the software, it will create a three-dimensional model of the entire suspension, and analyze all angles throughout the specified range of motion. We chose to analyze 2.25-inch of travel in each direction from ride height, as this would be the average travel range for most cars considering this swap. The accompanying charts illustrate camber and caster change in degrees, and roll center and toe change in inches. Negative dive refers to the car rising up.
Measuring pivot points to...
Measuring pivot points to various lines. Dropping the points down with a plumb bob makes measuring easy and accurate.
Now that we understand these...
Now that we understand these terms, we can compare the two spindles. First, we found no binding of the balljoints with either spindle in their full range of travel, so that rumor is out. Next, we found no alignment issues with the B spindle. The factory eccentric bolts did provide enough adjustment for both of these spindles. If more is needed, offset control arm bushings can be used to get more adjustment out of the stock arms. We started with 1.18 degrees of caster and zero camber. After swapping spindles and readjusting to zero camber, we found 1.32 degrees of caster. Nearly the same, but a slight improvement.
Checking the range of motion,...
Checking the range of motion, we found the A-spindle provided us with 1.22 degrees of camber gain, while the B-spindle provided 1.69 degrees, another slight improvement. Roll center with the A-spindle was 6.73 inches above the ground, while the B-spindle was 8.14 inches above the ground. This is a step backwards from a racing standpoint, but will provide a little more roll resistance in a street car. And finally, toe-change did increase with the B-spindle. Toe change with the A-spindle remained (barely) within tolerances throughout the travel range. With the B-spindle, toe change is slightly excessive during extension, but well within range in compression, which is much more important. How often is your suspension fully extended on Main Street?