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Front spring shackle reversal


bill van snorkle

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It has been several years now since I converted my series 2A to coil front suspension, but before that I had always meant to have a go at doing a front spring shackle reversal. About 30 years ago I owned two almost identical series 1 80 inch Land Rovers .One was a 1948 with front shackles, the other was a 1950 with rear shackles.Both vehicles were in good condition with near new springs and dampers. In various cross country comparison tests, ie steep rocky hill climbs and surmounting short vertical obstacles etc the 1948 was always superior and just got on with it ,whereas the 1951 model would hop up and down or the front end would rear up causing the truck to slew sideways to the slope in a single bound, which can be pretty scarey on any vehicle let alone one with such a short wheelbase and narrow wheel track.

Anyway, many years of offroad travelling in my series 2A in company with Toyota LandCruisers, Nissan Patrols, Jeeps etc has convinced me that for mountain goat type offroading, Landeys have got their front shackles at the wrong end of the spring. I'll give an example of what I have observed happens on a steep climb. When a leaf spring LandRover is climbing a steep difficult slope some of the front end weight is transferred to the rear axle by gravity so the front springs are unloaded slightly and the front of the vehicle sits higher on its springs. Due to torque reaction, the front diff pinion wants to rotate downwards causing the shackles to swing forward, lifting the front of the vehicle even higher. The spring now has alot of camber (arch) both for and aft of the axle assembly, so now the front axle is even less positively located to the chassis. Any forward thrust that the front axle assembly can develop merely cambers up the spring even more until the stored energy in the spring is greater than the thrust of the axle, then it releases this energy, sometimes so violently that the front end can leap into the air. I have witnessed a Stage one V8 front end literally leap sideways 6 feet due to the release of this pent up energy resuting in two broken springs, snapped propshaft and both expensive Koni dampers destroyed.

Now let me attempt to explain what happens when a Toyota Landcruiser with front shackles attempts the same climb. Gravity is gravity so weight transfer to the rear still occurs, so the tendency of the front end to sit higher is still the same,The front diff pinion due to torque reaction still wants to rotate downwards, but because the shackles are at the front of the spring, they swing forward and actually pull the sprung mass down, counteracting weight transfer. Because the spring is compressed, the spring is also relatively flat and straight giving the axle a more positive location to the frame to transmit forward thrust thus increasing traction, The more forward thrust the front axle can develop, the more the front end pulls down compared to vice versa with the LandRover setup. This makes the vehicle both more capable and safer to operate in steep

and offcamber terrain. Another advantage which I won't go into much detail about is that the front propshaft slip joints last a heck of alot longer.

Is anyone reading this convinced enough by my argument to give shackle reversal serious consideration ? By fabricating a few simple parts you can experiment with the principal without disturbing your chassis . If anyone is interested I will explain how in a later post.

Bill.

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the theory is doable, not particualrly goin to do it on mine though i wouldn't mind seein the results, sj's have it this way?

yeah sj's have the same set up. ive noticed it helps a bit on steep climbs but i ve also noticed that some times they start digging into the ground when ur in deep ruts or when trying to climb out of a hole with a very steep exit.

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How come the toyota guys are swapping their shakles to the back ?

There must be some good points with the LR setup..............

Some Toyota and Jeep guys in the US have swapped over believing that it improves the ride, but the trade off in offroad ability has seen quite a few of the serious players swap back.

Because LandRover front springs are so damn short, any possible improvement in ride that rear shackles might provide is lost due to the axle wanting to move back so far when striking a bump. Back far enough on occasion for the dampers to get bashed to death against the swivel housing bolt flange.In 4wd the front propshaft slip joint torque binds, pushing the transmission back on its mountings, applying the handbrake slightly each time, wearing out the linings. This undamped movement of the engine/transmission assembly also contributes to a less than smooth offroad ride.

If there are any good points about the LandRover setup that outweighed the bad points, I am unaware of them.Almost every 4wd suspension designer in the world is unaware of it either,and I think LandRover recognised this when they designed the RangeRover and put the front radius arms behind the axle instead of in front. It is dynamically similar to having the fixed end of the leaf spring behind the axle when you think about it.

Bill.

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Thinking cap on.

Would a tramp/wrap bar fix the problem?

(assuming it's even possible to fit one to a series front)

I did fit a single central tramp bar running back from the winch bar to the axle on the previously mentioned sideways leaping stage 1 V8, and it did improve the situation somewhat re smashing dampers, leaping about etc, but it still reared up on steep climbs due to antisquat characteristics of rear shackles so it wasn't a complete solution for serious mountain goat terrain.

Bill.

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Some Toyota and Jeep guys in the US have swapped over believing that it improves the ride, but the trade off in offroad ability has seen quite a few of the serious players swap back.

Because LandRover front springs are so damn short, any possible improvement in ride that rear shackles might provide is lost due to the axle wanting to move back so far when striking a bump. Back far enough on occasion for the dampers to get bashed to death against the swivel housing bolt flange.In 4wd the front propshaft slip joint torque binds, pushing the transmission back on its mountings, applying the handbrake slightly each time, wearing out the linings. This undamped movement of the engine/transmission assembly also contributes to a less than smooth offroad ride.

If there are any good points about the LandRover setup that outweighed the bad points, I am unaware of them.Almost every 4wd suspension designer in the world is unaware of it either,and I think LandRover recognised this when they designed the RangeRover and put the front radius arms behind the axle instead of in front. It is dynamically similar to having the fixed end of the leaf spring behind the axle when you think about it.

Bill.

I have a SOA project that is on the back burner for the moment, I'm very interested in your theories/conversions Bill, I was always under the assumption that trailing shackles would give a more stable on road ride, my theory being that the extra rubber bush would allow more movement, the same theory as a supermarket trolley wheel, didn't Jeep fit a panhard to some of there leafer's?

Of course the length of the springs has an effect on the amount of travel available, and with the amount of travel available from these longer springs fitted to Jeeps and toyotas then propshafts would indeed not last long in a trailing shackle set up. Perhaps the limited amount of travel available from LR front springs made trailing shackle possible and so the assumed on road stability from this set up was a benefit.

I've got a set of revolver shackles so the squatting geometry is of real interest to me, would'nt be too difficult to alter the mounts at this stage, I'm also using parabolic Jeep front springs because their longer,

I was going to fab a central anti-wrap bar of a design from one of the Jeep sites. Is there a good reason for the front leafs to be at the angle that LR use or can they be installed closer to hoizontal?

I knew Jeeps and zukis were leading shackle but but I didn't know Nisans and Toyotas were too, obviously not that much of a stability issue then, I thought the reason for most of the shackle reversal kits was for approach angles?

Always good to hear others experiences/designs, never stop learning.

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I have a SOA project that is on the back burner for the moment, I'm very interested in your theories/conversions Bill, I was always under the assumption that trailing shackles would give a more stable on road ride, my theory being that the extra rubber bush would allow more movement, the same theory as a supermarket trolley wheel, didn't Jeep fit a panhard to some of there leafer's?

Of course the length of the springs has an effect on the amount of travel available, and with the amount of travel available from these longer springs fitted to Jeeps and toyotas then propshafts would indeed not last long in a trailing shackle set up. Perhaps the limited amount of travel available from LR front springs made trailing shackle possible and so the assumed on road stability from this set up was a benefit.

I've got a set of revolver shackles so the squatting geometry is of real interest to me, would'nt be too difficult to alter the mounts at this stage, I'm also using parabolic Jeep front springs because their longer,

I was going to fab a central anti-wrap bar of a design from one of the Jeep sites. Is there a good reason for the front leafs to be at the angle that LR use or can they be installed closer to hoizontal?

I knew Jeeps and zukis were leading shackle but but I didn't know Nisans and Toyotas were too, obviously not that much of a stability issue then, I thought the reason for most of the shackle reversal kits was for approach angles?

Always good to hear others experiences/designs, never stop learning.

A couple of years ago I bought an old BJ40 Toyota for its deisel engine that I wanted to fit to my LandRover.

The vehicle still had a couple of months registration (tax) so I used it as a daily driver for that period. The truck had square shouldered 10.50x 15 31 inch tyres and knackered tie rod ends. Not a good combination for directional stability, but these things considered it drove quite well even at 120 kmh. The approach angle of the front springs was terrible, but there is no law that says it has to be that way.CJ 2,3,5 ,6,7 and 8'jeeps had short springs. Having the front of the spring higher than the back would also improve approach angles and should provide a softer ride as the base of the spring is aimed towards direction of travel.Short springs as on Landeys can still be used with front shackles. OffRoad on tricky rocky hill climbs that are pretty common over here the truck felt much more positively hooked up than any leaf sprung LandRover I have ever driven, save for the old 1948 model previously mentioned.

An example of the effects of antidive geometry of leading front shackles on climbing ability, is that I have found that even an unloaded leaf sprung Landey has so much more traction and climbing ability in reverse gear.. Due to the fragility of gearbox and front halfshaft universal joints this is not something I recommend experimenting too much with.

To do a proper experiment without upsetting the chassis, first you must lock the shackles to prevent them from swinging. this can be done quite easily my making a couple of boomerang shaped pieces of 2'' x 3/8'' flat plate steel with a 9/16'' hole on one end and a 7/16'' hole at the other end. Undo the lock nut on the bottom shackle bolt and remove the top shock absorber bolt on the chassis. Obviously the 9/16'' hole of the boomerang goes onto the bottom shackle bolt and secured with the lock nut, and the 7/16'' hole is fastened to the chassis through the shock absorber mounting hole with the bolt. The reason for the boomerang shape is to clear the engine mounting chassis brackets. The shackle is now locked in place and is now the spring hanger. Next thing to do is to free up the front of the spring. You can simply remove the spring hanger bolt and let the wrapper leaf sit on the bottom of the spring hanger. It then is the same as a shackleless slipper spring as used on the rear springs of some trucks and older TransitVans. To prevent the front of the spring from dropping out of the hanger altogether, from flat steel you can bend up a ''U'' shaped stirrup (catcher) that goes under the spring and attaches to the 3/8'' hole in the spring hanger that is about 3'' behind the spring eye bolt hole. To perform the experiment I would suggest finding a suitable abrubt bank or cutting on the side of an unsealed track. First, with the standard Landey shackle arrangement, attempt to climb the obstacle at an oblique angle (articulating) and square on in 4wd low range without any difflocks engaged if you have them. Experience has shown that it doesn't take a very severe or high obstacle to stop a leaf sprung Landey and start the front axle hopping, pig rooting. Next fit the boomerangs, spring stirrups and remove the front bolts. try the obstacle again. I think you would be surprised at the difference. And if you like it you can do a proper permanent shackle conversion. If you don't like it, what have you lost?

Bill.

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  • 1 year later...

Bill, as always you're a lifesaver.

Building a tramp rod assy is just not an option for me.

I am definitely doing the reversal. I had a set(X4) of solid steel bushings turned that match my (rubber/steel) chassis bushings id and od but a bit longer (width of the chassis at the reinforcing). I will knock 2 of them in as replacements for the chassis bushing. I have a set of military shackles that I will fit to them. The remaining 2 bushings will go as mid supports for the millitary shackles The shackle gets pushed back (swivels around the now steel chassis bush) and the lower bushings get welded to the bottom of the chassis. That is the now solid aft hanger. For the front I will simply cut the solid mounts off and weld the ends (plus at least 2-3 inhes) of a old leaf spring below the fornt end of the chassis and replace the probably melted rubber bushing.

Any further suggestions or concerns?

P.S. I have been scared a bit by some friends ideas on how road handling will be affected by this.

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Watching with interest, whilst contemplating reversing my front anti-wrap and thinking it'd be easier to reverse the spring shackles than weave the ARB through the steering links...

So what do you think of my method? Not too complicated. Just somewhat worried about the strength in the front. Hope the sideways forces don't tear the welding of the leaf to the chassis.

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this may have been said..

But... back when I was toyotaing..

And its been a while

The idea was.. and it was hotly argued, that it would give you better stability under braking and rough roads. being as your springs were now less inclined to be pushed back on hard impacts. I never did it. But I remember threads and garage discussions about it with everyone claiming the other was missing something.

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So what do you think of my method? Not too complicated. Just somewhat worried about the strength in the front. Hope the sideways forces don't tear the welding of the leaf to the chassis.

Sorry, Wrong quote Gareth.

Front shackles do give antidive characteristics under brakes, similar to the radius arms on a Defender. IMO this is a desirable quality to have. Toyota, Jeeps etc sometimes iffy handling IMO can be attributed to insufficient factory castor angle (only 1/4 degree on some builds)This becomes negative castor when the brakes are applied.Brake hard while making a turn and things feel a bit uncertain.The fact that the steering draglink plugs into the trackrod rather than directly onto a steering arm on the swivel housing as on a LandRover doesn't help the handling of these vehicles either.

Make sure if doing a shackle reversal that the propshaft slip joint has sufficient travel, because it will extend when the springs compress instead of getting shorter as on the standard arrangement.

Bill.

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Sorry, Wrong quote Gareth.

Front shackles do give antidive characteristics under brakes, similar to the radius arms on a Defender. IMO this is a desirable quality to have. Toyota, Jeeps etc sometimes iffy handling IMO can be attributed to insufficient factory castor angle (only 1/4 degree on some builds)This becomes negative castor when the brakes are applied.Brake hard while making a turn and things feel a bit uncertain.The fact that the steering draglink plugs into the trackrod rather than directly onto a steering arm on the swivel housing as on a LandRover doesn't help the handling of these vehicles either.

Make sure if doing a shackle reversal that the propshaft slip joint has sufficient travel, because it will extend when the springs compress instead of getting shorter as on the standard arrangement.

Bill.

Thanks.

"Make sure if doing a shackle reversal that the propshaft slip joint has sufficient travel, because it will extend when the springs compress instead of getting shorter as on the standard arrangement." - I will definitely keep that in mind.

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