Step 6: Front End
There are any number of different solutions to the type of front end that you install on your hot rod. Probably the first consideration is the style of rod you are building and this will then determine the type of suspension you use to match that style. From a practical independent system to a traditional tranverse mounted I beam to a Hi Tech independent setup up with coil overs or air bags.
I Beam or Tube Axle
As found in Fords from the 20's to the 40's. Original axles can be dropped or modified to provide for a lower ride height or you can buy aftermarket axles with the amount of drop you want. Available in either an original I beam style or with a tubular section. The basic difference in axles over the years is in the width. A 2" drop is considered normal, with a 4" drop almost impractical on Australian roads.
The original hot set up for traditional hot rods. But this configuration was prone to failure and premature wear due to incorrect geometry and or fitting. Ideally they should run as close to horizontal as possible.
Modern adaptation of the traditional wishbone. Provides for better suspension geometry and handling characteristics. Can be manufactured out of plain steel or show quality stainless.
Transverse Leaf Spring
As found on Fords from the 20's and 30's. The classic hot rod style. Mounted to the chassis at the top of the arch and to the axle via perch bolts. Leaves can be removed or added to improve ride height.
This configuration is not seen often as it was only every seen on GM products from the 20's and early 30's. Also not popular with hot rodders as it is difficult to get this setup low enough and still have sufficient suspension travel.
The ultimate front suspension. In it's budget form can be sourced from a donor vehicle like the HR or HT Holden where the crossmember is unbolted complete with suspension and relocated in the new chassis. Easy to convert to disc brakes and calipers (either HQ or VT Commodore) and most installations also feature the more precise rack and pinion steering. A modern alternative is the front end from a Mitzubishi L300. Can be sectioned to get desired ride height, alternative is to purchase dropped spindles which will retain full suspension travel. This suspension is popular for rods from the 20's right through to the late 40's. More suitable on full fendered rods as they are not really the prettiest things to look at.
A far more expensive version is the custom tubular or billet front ends constructed from scratch. However a word of warning, when purchasing your custom front end make sure you get an engineers certificate with it. Otherwise you will have to pay for the engineering computations on the front end as part of your engineers certificate for registration.
The front end graft can be a great way to update suspension, brakes and steering all in one go. Classic recipients are pickups and later model rods from the 50's which have a similar width chassis to the donor vehicle. A popular swap is the HZ Holden front end into a F100 or 55-6-7 Chev. The original chassis is cut off where the fit is best, so that the replacement front end will provide the original vehicle wheelbase.
Not used very often, but can be a trick way to get desired ride height and hide some of the suspension components.
Coil over shocks
Shock absorbers inclosed in coil springs are found in beam axle and independent suspensions. With the beam axle the are mounted vertically off the perch bolts. For independent suspensions they mount to the crossmember and lower control arm. Construction will vary from standard hydraulic shocks with fixed length springs right through to fully adjustable gas filled billet works of art.
A relatively new innovation. Air bags were originally used by the low rider set to not only get the minimal ride height they desired but also to display and jump their rides. Modern air bags can be adapted to most existing suspension systems, replacing the springs. For front ends they will usually require the relocation of shock absorbers. The ride and handling of an air bags system is different but comparable to a good conventional system, the added advantage is that the driver can choose the ride height to suit the conditions.
The original and conventional way of pointing your hot rod there are some standard configurations that have come to stand the test of time. Most commonly used for transverse leaf suspensions. For T-Buckets it is the Kombi, for Fords from the late 20's and 30's it's a late 70's box or HQ box. Can be hard to find a mounting point on some rods depending upon the engine and exhaust configuration. Often need a secondary shaft to connect to the steering column.
Rack and Pinion
Suitable for independent front ends, the R&P steering provides for less turns, tighter turning and a more direct feel. Can be mounted either in front of the front crossmember (L300) or behind (HR, HT) to provide adequate clearance of different engine types and mountings. Also easier to source and repair, the popular ones are from the Leyland front wheel drive 1800 series and more recently the VB-VC Commodore. They will usually require shortening. With the weight distribution of most hot rods a power rack is not required
Whilst not impossible to mount to a transverse leaf suspension, it is extremely difficult to retain the correct geometry and is definitely not recommended.
Steering Columns and wheels
There are a number of different columns that are suitable for installation into a hot rod, however there is one characteristic that they all must have to comply with Australian Design Rules. And this is they must be collapsible. Modern steering columns from Japanese and American vehicles have a tilt option which can give the correct angle to the steering wheel. A word of warning, before you spend what is a lot of money on that trick billet wheel, make sure that it will pass engineering. The big problem here is that there is to be nothing in front of the driver that will produce glare.