Nothing on your hot rod takes on the storm like the front end setup. It’s the first to take on every pot hole and bump, and the most important piece of the hot rod as well. You may get by with a miscalculation on a rearend, interior or wiring, but a misjudgment on a front end means you are dead meat. For that reason, we feel that we need to take a little more time to see that we all get it right during the build.
Going Straight Or Not
This only leaves two options. One, you can go through a speed shop and order a straight axle. It will come bare so you will need spindles, backing plates and a brake setup. You will also need hubs and bearings and all the other bells and whistles. $3,000.00 later and you’ll be good to go with a cool front straight axle assembly. The only problem is, we’re building a hot rod on a cheap budget. So how is all that going to work out? Let me tell you, it won’t.
So what to do instead you ask? Good question. There are a multitude of old truck straight axles still out there. In the South region, they range from one to two hundred dollars, and the beauty is that most already have all the components still intact. Luckily for us, I invented a bracket that bolts to the spring pads and allows you to do a traverse spring set up like on every roadster or t-bucket that you see.
The brackets are $100.00, and with the cost of the axle, you’ll be set for about two to three hundred dollars instead of three thousand. You can go on Youtube and search transverse spring setup with Ringrods and see how it all works. Basically, the bracket attaches the radius rods, shocks, and spring perches, for one easy setup.
Going Into Detail
For those following along with the build, we will go into more detail. For starters, you will need tires and wheels on your axle to set it up at the height you intend to run. Next, bolt on a pair of RingRods’ brackets, or watch the video and you can make your own. Once the brackets are on, measure from bracket to bracket to get an idea of what your spring length needs to be. Ensure that you subtract the length of your shackles from the equation.
The shackles and leaf spring can be bought at Northern Tool, Harbor Freight, or Tractor Supply. The spring will be in the low twenty dollar price range. The shackles will bolt into the spring perches, which you can get through Speedway Motors or any speed shop of your choosing. They are listed at $6.99 each. Make sure you bolt everything together with grade-8 bolts.
The top hole on the bracket will be for the shock, and the second hole on top will be for the spring perch. The bottom two holes are for the radius rods, and we will get to them in a minute. Right now it’s time to roll the front axle up to the frame, which should be sitting on 2-inch x 8-inch wooden blocks. This will give you the proper ride height for this build.
The axle can sit directly under the front cross member of the frame if you wish to ride a little high, or it can sit up under a 6-inch tab welded to the front center of the frame, typically called a frame perch. This will allow you to sit a lot lower. You can also purchase U-bolts from the same vendors we previously mentioned. Once centered, the axle is ready to be bolted on. The spring shackle perches can be turned to allow the axle to have a backwards pitch on it.
Getting Positive With Caster
When you pitch your axle backwards it is called a positive caster. There is no camber on a straight axle unless you do it with a torch, which I don’t recommend. There is a company in Nashville that will do this, but they have been doing it since the 1940‘s, so don’t try this yourself.
Here’s how positive caster works. If the forks on your bike were straight up and down, you wouldn’t be able to control it very well. The forks are slanted (raked) backwards at the top, to make it easy to control. The same is true about your car. Six to ten degrees backwards allows you to steer easy, and your steering wheel returns straight when coming out of a curve. It also prevents what guys in the ’30s and ’40s called “roll over.” It was estimated that in a hard stop, the front end would roll forward six-degrees.
The positive caster also shifts weight more to the back. All of this, as well as the Ackerman angle play into the handling of your hot rod. The Ackermann angle was an imaginary set of V’s. The wide part of the V was the front axle and another at the rear end. The two V’s met in the middle of the car.
Ackermann Steering Geometry
Time and space would prevent getting deep here, but I can give you a quick simple example. When rodders now turn the axle around backwards, which is called suicide front end to get their hot rod to sit lower, it jacks with the Ackermann angle. Here’s how it plays out… In a curve, the right front tire scoots instead of turning. You can’t see it at any speed to speak of, but when turning tight in a parking lot, you will notice this to be true.
The wearing of one tire over the other is another negative thing about this setup. Now, back to our positive caster. The best way for a do-it-yourselfer to install the axle, is to place a degree finder on the top of the spindle, and when you’re between six and ten degrees, lock down your spring perch nuts. The second phase will be to hook up your radius rods. These will keep your axle straight from back to front. Measure from back tires to front to get it perfect.
The radius rods can be ordered for about $140.00, or you can make them yourself for around $25.00. You can cut four pieces of 3/4-inch pipe at 25-inches, and insert 1/2-inch clevis yokes in the fronts. A nut, welded in will give you adjustment with an additional jam nut added.
The two pipes will come together in the rear, and attach to a short piece of the same 3/4-inch pipe. The extreme rear of the short pipe will have a 1/2-inch heim joint mounted the same as the fronts. The traverse spring brackets will have two holes bored at 1/2-inch, and spaced 5 inches apart, which is what all radius rods will be.
The rear of the radius rods will attach to two braces welded to the frame. The clevis yokes and heim joints will allow you to keep your front axle always in line. The top center hole on your bracket will allow you to mount your front shocks. Quite a few of the steering arms on these old axles will not work well for your setup.
You can remove the top two spindle bolts and nuts and install a twenty dollar steering hoop from Speedway Motors. You can also fabricate one from a piece of 3/8-inch angle iron. One leg of the angle can be cut to fit over the king pin housing and bolt to the top two holes. The other leg can be shaped down and fitted with a heim joint bolted on.
In the next article we will get into the steering box and about the pieces it takes to make that hotrod go the direction you wish it to. Until then, keep on rodding!