HP, I thought it was the disc brake spindle was needed to use the 11.75 rotor & that is why the conversion kits that do not include spindles have a sleeve to add to the diameter of drum spindles.
It depends. The Viper conversion kits are somewhat different than other kits out there. The Viper to 11.75 kit needs drum spindles to allow the bracket to line up and bolt on, but also requires the large inner bearing to support the rotor, hence73-76 A body drum. There may be other spindles that interchange with that, but with looking it up in a Hollander, I dont know right now what would swap. If there are spacers out there that will allow you to use a large bearing rotor on a small bearing spindle, then that would also work.
You can still run the viper kit with a late b-body spindle, correct? I have 11 3/4" brakes on the front of my 'Cuda with cordoba spindles.
Again, it depends. In your case, it depends on which rotors you want to use. The ARE Viper brackets for 11.75 rotors only fit drum spindles. The ARE Viper brackets for use with disc spindles require the use of 13" rotors. With 17" wheels, you can easily fit the 13" kit in your wheels. For anyone with 15" wheels though, 11.75 is the biggest you can go with stock style parts. There are some mustange 2 kit and nascar spec parts that would fit a 12.12 rotor in a 15" wheel, but those would all be custom set up that I have no knowledge about.
As for the 74 Charger swap info, I'd love to have any that you are willing to throw at me. I've read somewhere about the change of geometry that in some cases can be a good thing. I do plan to lower the car some, so would it be ok for this application? Do you think the "B" swap would be a good option for me? Also, the Charger does not have a master cylinder or proportioning valve anymore, so would I need to source one for it or for a different car?
Most disc brake master cylinders are the same, with only manual or power assist being a differentiating factor. So a disc brake master cylinder for either your Challenger or the Charger would work. Same with the prop valve, although adding an adjustable rear brake bias valve may be helpful when mixing up different parts just to ensure maximum application of pressure to all four wheels.The light weight mopar performance master cylinders will work as well, so long as you use the 4 bolt to 2 bolt adapter. These also have the advantage of having a bias built into them which may change the need for a rear brake bias valve.
Suspenion geometry gets sticky. I'll give it a shot but I don't have any illustrations I can post up right now to help simplify it. Here goes...First some terms
Roll Center- this is the imaginary point where all the geometric lines of moving suspension parts converge and create a point around which the car pivots. There is one in front and one in back.
Roll axis-the line connecting the front and rear roll centers
Center of gravity-most people know this one, it is the point in the car at which everything above, below, in front and behind all are equally balanced.
Moment lever arm- the distance between the center of gravity point and the roll axis line. This arm is a lever and like most levers, the longer it is, the more leverage it creates.
On to the explanation. In stock form at stock ride height with stock height tires, most mopars have a front roll center that is 4 inches above the ground in front and 10-12 inches in back. This keeps the roll axis line somewhat high up in the car and close to the center of gravity. The result is that the moment lever arm is short and does not produce large amounts of body roll when cornering. Compared to other cars OF THEIR ERA, mopars were far ahead of the competition in this regard. Compared to modern cars they are somewhat lacking.
If you change the size of your tires, change the ride height of your car by lowering the torsion bars or swapping the springs, or drop a V8 onto /6 springs, then you alter these points. Typically lowering a car drops the center of gravity, which is good. However, lowering your car via torsion bars and springs is not a direct 1:1 ratio between suspension pivot points and the center of gravity. If you lower your car 4 inches, you COG may drop 4 inches, but your roll centers may drop 8 inches in the front and 2 inches in the rear. So you have created a bigger moment lever arm, so your car will produce greater roll forces, which will then require bigger torsion and sway bar rates to overcome, hence rougher ride, needs better shocks, cost more money, changes the ride characteristics, etc.
The later model B and F/J/M spindles are 3/8 of an inch taller than their predecessors that are found on all our favorite A, B, and E bodied cars. This 3/8" change obviously alters the way all those imaginary lines converge in the front end by raising the front roll center 2-3 inches. So, if you have a modified car that sits lower than stock, then this change will help restore some of that original geometry that provides a natural roll resistance.
If you have a car that sits at stock height to stock specs with tall spindles that raise the front roll center beyond stock, you can create a situation where the car does not create the excessive body roll that scares the average driver into slowing down. The car will loose traction and slide out of control before feedback tells the driver they are getting in trouble. Remember, Mopar had no ride height specs for the rear, only the front, and as leafs wear out and slowly dropped the rear roll center location, you could concievabley create a roll axis that is so close to the center of gravity that body roll is very negligible but the center of gravity is high.
So looking at this from the OEM manufacturers point of view, where they assume a certain amount of liability for the parts they install on a car, and the general public's safety for drivers that range from virtually no ability to near profession capability, you can then see why Chrysler chose to not use the newer spindle across all the product lines, especially those they knew were going away like A and E bodies.
So, remember this is a simplified, two dimensional presentation of items that work in a three dimensional world. There are many more factors at work in a suspension. Hopefully this was enough of an overview to explain the biggest difference about one of the most hotly debated topics in the mopar world.
