Ladder Bars and Hair pin radius rods can be installed straight along the chassis rails or angled towards the centre of the chassis to allow for the differential to ride up over bumps in the road with out binding up the rear suspension arm bushes.
However one of the problems when installing a ladder bar supported rear end is that not all of us can cut out the floor pan like a tubbed drag car. Add to this the array of different chassis and floor pans with a different height step up for diff clearance, from early hot rods to mono construction muscle cars to pick up trucks and 50’s lead sleds and 60’s yank tanks, of which dimensions can lead to some hair pulling and much garage swearing late at night when a mass produced ladder bar kit just does not fit.
The problem is more in trying to get the ladder bar or hair pin radius rod to sit level at ride height and attach to the diff and to the car in a clean and functional way. All chassis shapes are different and the chassis step up dimension at the rear is relative to how far the cabin floor steps down in the middle. Some chassis are relatively flat like a pick up truck or an A’ model chassis and others are really stepped up like an AC Cobra.
The above pics shows a rod under contruction fitted with hair pin radius rods to locate the rear axle and a perpendicular to the chassis pan hard bar.
What brackets you choose will depend on how you are going to brace the chassis to attach the front of the hair pins or ladder bars to the frame. The diameter of the tyre you are going to run will determine the axle centre line height, then you will have to determine the ride height relative to the body that you are going to run. So please don’t ask us for a standard kit to suit your vehicle …… are you building a custom car or what? . We have a range of custom brackets so you can sort it out properly and if you do not see what you want, send us a sketch and we can make it for you.
We have identical paired brackets that allow you to angle the hair pin or ladder bar towards the centre of the chassis for both the chassis mount and the diff mounts. We also have a range of pan hard bar brackets and we can custom make street legal bushed rod end pan hard bars for the street.
The picture below illustrates the subtle differences between body styles
The critical dimensions of each bracket are shown in a picture under each component listed here in the Kustom Bitz shopping cart. Our standard diff brackets have 150mm hole centres for the bars and we have diff tube diameters in 64mm, 71mm, 76mm and 84mm which will cover 90% of all Borg Warner, Falcons, Fairlane, Mustang, Holden, Ford 8 ¾ diffs and the popular Ford 9 inch diffs from tank Fairlane, GT Falcon, to big bearing aftermarket diff housings. The important thing to note is measure your diff, because all models are different. The steps we have chosen for our sizes means that there is not much to linish or file off if your diff tube size is close to one of our standard sizes.
The other important dimension to know is the brackets are set to get either the bottom bar of a typical drag racing ladder bar parallel with the ground OR a typical hair pin radius rod of which should be symmetrical in its installation which typically means the front rod end will be in the centre of height ~ relative to the diff end rod ends. i.e. The front mount position is usually different to a drag racing style ladder bar, because they are different shapes. See diagram on main info sheet above and below.
As we stated above the rear diff bracket holes are 150mm apart and the top hole is used as a reference to the diff axle centre line to identify our three sizes. Shape 1 the top hole is 45mm above the axle centre line, Shape 2 the top hole is 20mm above the axle centre and Shape 3 the top hole is 5mm below the axle centre. This give you a 50mm window to play with which will cover most variations, in any case Size 3 places the bars pretty low relative to the diff and it is about as low as you can go with a 15inch diameter rim. NOTE that in the diagram above and below size 3 is shown on the left then size 2 and then size 1 far right. Note that the bottom bracket hole is in the same height position on the drawing and you can see the obvious different positions of the axle centre line. So size 3 places the wheel further up into the wheel well for deep stepped chassis and size 1 is for not so deep wheel wells. The rest is up to you .
If you are installing the bars inline with the chassis rail then use a pair of “SHORT” brackets per side. However if you wish to angle the bars toward the centre of the chassis to meet street registration requirements then you will need one “SHORT” and one “LONG” bracket per side to provide enough angle for you to play with positioning of the bars.
Ladder Bars and Hair Pins
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You would think a supercharger kit install would be pretty simple .... well no, is the short answer.
A wise man once told me a 'kit' is not a solution. And having worked on a few of these set ups now these words keep ringing in my head and I remember this old man who at the time I didn't think was that wise at all .... now I am older and I see.
In this install I had to port match the heads to the intake as there was a substantial lip into the head port because of the large intake manifold ports. If not corrected would have led to fuel puddling and fouled plugs and drivability problems that would have been hard to diagnose once assembled. Also the distributor hole at the back of the manifold was off centre and way too big for a standard chevy dizzy and any aftermarket dizzy too. So I had to make a boss to take up the slack and provide a stable boss for the dizzy clamp to work properly.
To add to the woes, the engine assembler failed to pick up that it was a tall deck block and required a longer oil pump drive shaft .... that was hard to diagnose when a new engine loses oil pressure for no reason.
I got there in the end with modded accelerator links, better fuel line route, boost referenced carburettors and a proper harmonic balancer for a blower application. The install was challenging on this one but the end result was a sweet running engine with monster amounts of torque to hall this heavy full size sedan around the hills .... and cool looks of course.
41 Willy Coupe chassis fabricated to original dimensions yet extra strength provided in the depth of the chassis and via tubular centre X member and many tubular cross members to take the weight and torque of a big block Ford drive line. This chassis will have an original steel body fitted to it and the owner wants the whole car to resemble an early 60s drag car, right down to the rear radius rods that look like ladder bars, however it has to have nice street manners and pass ASRF construction guidelines for safe street rod engineering. Now many may argue a leaf sprung front end and rear end is not the best handling street car and I would agree, but there are always trade offs for the look you want and the right combination of parts installed with the correct geometry can still yield a very nice driver with a really cool look. When driven responsibly this 41 Willys will provide hours of enjoyment for the owner cruising around.
Chassis by Kustom Bitz [our custom designed rails], Engine Ford Hemi V8, T400 auto, 9" diff installed on leaf springs with diff housing floaters designed by Kustom Bitz for street use [so we have flexibility and suspension give], Super Bell front I beam with disc brakes cleverly mounted to parallel leaf springs without any mods to I beam and not relying on welded parts.
See our section on Hot Rod Chassis construction for more images of our various Willys Coupe chassis that Kustom Bitz has built.
The Toyota Crown ute is progressing along, the body is fitting the modified original chassis and this is how it will look when it's dropped ... I think it has the right stance ... The framing you can see is holding the upper body together as the floor and lower sections are rusted away and have been cut out, then to be completely refabbed by us. The frame allows us to lift the body on and off as we please during this stage.
Kustom Bitz just completed a 35-41 chassis, stepped up at the rear and a reversed centre X member allow this chassis to sit 40mm off the deck. It runs a Rod Tech IFS, big block chevy and L80E auto, a 9 inch diff with floating hubs, all on modified original rails. Kustom Bitz has developed our own boxing plates that suit the original rails near on perfectly. Original Ford rails are curved from front to back there are no straight sections, so to get something that fits right we had to jig the chassis up and map them out. This is what we do, when it just needs to be done right to make it a well engineered car. This allowed us to make a nice transistion for a high step at the rear. We have designed in 6 inches of travel at the back, so this car can have a normal, almost stock ride height then dumped to the max when parked.
'67 Toyota Crown ute chassis build is going well. Got the LS engine and 6 speed manual box in place and we can use all the orginal serpentine pulleys, brackets etc. The narrow wheel track on the Toyota called for a tailored solution when it came to the front end. These old Toyotas dont have service parts available any more so the front end had to be changed, so that made a brake upgrade alot easier too. We run R6 air bags from Air Ride sitting at a ride height of 6" for the air bag so got plenty of air volume in them for a good ride quality and a full length travel shock absorber so we get proper rebound tuning, along with a power steering rack. So at the sill [belly of the car] we get a 5" ride hieght with a 4 inch drop, this thing will look great.
Recently in Victoria some engineers have called for the upper and lower mounts for the rear coil over shockers to be a double shear bracket. The thoery is that the bolt has too much twisting force on it and it will break. Well thats why on Hot Rods we use a 5/8" grade 8 bolt in a single shear bracket application to over engineer it so it does not break. A typical OEM application uses a 1/2" bolt in a double shear bracket. However to please the engineer we have thought out a simple plate kit that can be welded in on the upper mounts as you see here to satisfy their requirements and should fit into most applications without too much effort or rework. We have a lower mount bracket nutted out as well.
So many hot rod shops don't install proper bump stops. In this instance we had to rebuild the shocker mounts on the diff as the rear end was bottoming out on the shocker travel becasue it had no properly designed bump stops in place. So the shock absorber mounting bracket was absorbing every bump when the suspension bottomed out, easy to see why both mounts broke.
While we were repairing the diff I made a simple yet effective progressive bump stop that is held in place via the U bolts that hold the diff to the leaf springs. It turned out a very successful set up.
This is yet another example how Kustom Bitz can sort out problems on your custom car or hot rod, its what we do.
Back in the day Group C racing one of the tricks to get the Holden Torana to handle nice and be more predictable in corners was to fit a rear pan hard bar to give much better diff locating than the OEM triangulated 4 bars offered. However the body, subframe and floor pan at the rear is no where near strong enoungh to concentrate the loads of pan hard bar in any one spot, so it has to be carefully planned and constructed, especially so in a street car like this that we cannot put a full roll cage in. You see in a race car I can place the roll cage in a position to pick up such loads placed on the pan hard bar brackets, but in this situaton we couldn't.
The picture above is with the unit installed, keep in mind the car was just a shell so no weight was in it and the rear is sitting high. Once the full wieght of the car is on, it will sit fairly level. It retains the original triangulated 4 bars however we run PU bushes in the bottom arms and ordinary rubber in the top arms. So the lower arms and pan hard bar do the locating and the top arms have some give so they don't bind with the pan hard bar.
We have put a lot of time and effort into this 38 Plymouth. The whole rear lower panel and floor right through to under the seat has been completely hand fabricated and replaced. The front and rear mud guards have been widened and the shape reworked for cleaner lines, the guard edge now follows the wheel's shape and shall feature a straight edge running board.to clean up those ugly Plymouth bits but still retain some typically Plymouth features like the swage lines. We have basically just fattened it up and made it more curvey.
First pass for the day in Q1 in Vintage Gas [V/Gas] and we did our first wheels up launch in "Angas" and later in the day ran our best time so far with this combo with an 8.80s for the 1/8th mile track with an ET of 79mph.
The venue was Sunset Dragway which is just outside Mildura in country VIC. It was a 20deg sunny spring day with little wind, an all but perfect day for this time of year. Great facilities at this venue for grass roots racers like us and they really looked after all of us racers, so its well worth the trip we had a blast.
As far as our little 105e Anglia Gasser goes there is still heaps in it yet when a few tech issues get sorted out, but totally stoked at the moment. woo whooo .....
. We have a range of custom brackets so you can sort it out properly and if you do not see what you want, send us a sketch and we can make it for you.
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