Thread: lifted springs for 2a 109?

Originally Posted by Warb

Pure logic suggests that if you make a leaf spring more flexible then you run the risk of over extending it. A normal leaf pack can be over extended, and will change its "set" if this happens. However a normal leaf pack is often so inflexible that in practice it cannot be over extended. A parabolic spring, on the other hand, is soft enough that over extending becomes a real possibility. To prevent damage it requires limits on it's movement. I do not see that as a failing. If a part is designed to work within given conditions, then using it outside those conditions always risks adverse results. If a parabolic spring (or leaf pack, coil spring etc.) is designed to provide (say) 10inches of vertical travel, removing the limits and expecting it to survive 18inches of movement is unrealistic.

If a normal leaf pack could be slimmed down to give the same degree of flexibility as a parabolic, it too would require limits - though of course by design it already has them, and RM are asking for no different limits than those designed by LR.

Spring travel is limited by the shock absorbers and bump stops. Springs should be able to flex within the limits of both without failing. Springs are in fact usually "scragged" (fully inverted) when manufactured, to make sure they return to their original set.

Parabolics are not softer than OEM springs, they are in fact (in the case of RM anyway) stiffer. So in terms of overall wheel travel, they are often quite poor. However they do have little/no interleaf friction, which gives them a smooth ride, and means that over small bumps they flex more like coils.

Because of the thick leaves, the stresses between the leaf faces on a parabolic are much higher, which means they could be expected to have a shorter life for the same deflection.

As far as axle tramp goes, surely that is a shock absorber issue? ....

No - it is largely a suspension design issue.

I wasn't specifically talking about "stiffer" from a spring rate perspective, I was talking "softer" from a usage viewpoint. The original spring rate of an old leaf pack has little to do with the movement of the axle under real world conditions, with the leaves rusted together most old leaf spring packs hardly move at all.

A well set up, lubricated leaf spring pack still has far more damping than a parabolic. Whilst a static load might cause less deflection on the higher rated parabolic, a shock load like hitting a bump will cause more deflection of the parabolic than of the lower rated leaf pack because there is less friction. This is why the ride is smoother, as you said.

So a well lubricated leaf pack may have a lower rate, but may still fail to reach its movement limiters whilst the same sudden load may bottom out the parabolic.

Equally the lower rated leaf spring may exhibit more flex under rock crawling conditions, the lower spring rate allows more compression/extension under the same (almost) static load.

Axle tramp may be a suspension design issue, but in this context the design is fixed in all but the type of spring (leaf or parabolic) so any increase in tramp is probably a result of a reduction in damping.

Even with the extra damping from interleaf friction that std springs give, plus good shocks the front axle still tramps badly.Tramp is when the axle housing rocks back and forth on the springs, twisting the springs length into a shallow S shape. The thicker section of the semi elliptic springs plus interleaf friction, plus shockers resists this force better than the long relatively slim profiled parabolics. Even so, take a look at the front shocker body of a landrover that gets a bit of real offroad work and you should notice it bashed up and dented from making contact with the swivel housing flange during axle tramp.
Bill.

Originally Posted by wagoo

Even with the extra damping from interleaf friction that std springs give, plus good shocks the front axle still tramps badly.Tramp is when the axle housing rocks back and forth on the springs, twisting the springs length into a shallow S shape. The thicker section of the semi elliptic springs plus interleaf friction, plus shockers resists this force better than the long relatively slim profiled parabolics. Even so, take a look at the front shocker body of a landrover that gets a bit of real offroad work and you should notice it bashed up and dented from making contact with the swivel housing flange during axle tramp.
Bill.

Exactly. My IIA ex-mil with reconditioned OEM shocks has bashed the hell out of the shocks from axle tramp.

Originally Posted by wagoo

Even with the extra damping from interleaf friction that std springs give, plus good shocks the front axle still tramps badly.Tramp is when the axle housing rocks back and forth on the springs, twisting the springs length into a shallow S shape. The thicker section of the semi elliptic springs plus interleaf friction, plus shockers resists this force better than the long relatively slim profiled parabolics. Even so, take a look at the front shocker body of a landrover that gets a bit of real offroad work and you should notice it bashed up and dented from making contact with the swivel housing flange during axle tramp.
Bill.

It does make some sense that the lack of internal damping in the parabolics results in more tramp, probably more so on the compression side (rear) of the springs, than the extension side because on extension I would imagine the leaf pack opens up anyway (at least as far as the pack clamps allow). But way back when I was young one of the standards in rally prep for the Escort was to fit anti-tramp bars. Given the nice hefty chassis to mount to in the Series Land Rover, is there not a similar solution available?

Originally Posted by Warb

It does make some sense that the lack of internal damping in the parabolics results in more tramp, probably more so on the compression side (rear) of the springs, than the extension side because on extension I would imagine the leaf pack opens up anyway (at least as far as the pack clamps allow). But way back when I was young one of the standards in rally prep for the Escort was to fit anti-tramp bars. Given the nice hefty chassis to mount to in the Series Land Rover, is there not a similar solution available?

Yes, that is a good option, and I have seen it done. Some non-LR vehicles come from the factory with control arms.

Originally Posted by isuzurover

Yes, that is a good option, and I have seen it done. Some non-LR vehicles come from the factory with control arms.

An old full leaf sprung 1964 LWB Austin Gipsey 4x4 I once owned and loved, which had a similar suspension to LandRovers was fitted standard with a tramp bar each side that ran from mounts on the axle tube above the springs, forward to mounts on the front spring hangers.The front end of that vehicle always felt better hooked up and more capable than the 109 Landy I owned concurrently.A similar modification to LandRovers was quite common among competitors in the UKs All Wheel Drive Club trials back in the day.
I once centrally mounted a single torque rod, made from a RangeRover rear trailing arm on a Stage One V8, mounted above centre of the axle tube, running forward and pivoting from just below the front bumper. This simple mod transformed what was a fairly hopeless vehicle even with difflocks, in steep, broken and rocky terrain ,into one of, if not the most capable leaf sprung 4wds I've ever seen, that even embarrased a few tricked up coil sprung 4wds.
Bill.