Questions You Should Know about Single Leaf Spring

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Before getting into the characteristics of a worn/damaged set of leaf springs, let's first verify how they should look. 

Leaf springs are arranged into packs&#;a central leaf with eyelets at each end to house chassis-mount bushings and several supporting leaves that reduce in length as their positioning distances from the central leaf. All leaves in the spring pack are bound using a centering bolt and prevented from misaligning by a series of rebound clips. 

In proper working order, leaf spring packs should have a noticeable arch with the apex pointing downward, positioned just above the axle. Additionally, all individual leaves should be aligned and free from structural issues such as cracks or excessive corrosion.

You should also consider the condition of eyelet bushings. These integral bushings should be free from cracks, tears, dry rot, and other physical damage. The rubber should also be pliable, ensuring ample damping of vibrations and bumps.

What Do Bad Leaf Springs Look Like?

Now that we know what leaf springs should look like, what are the visual symptoms of a worn or damaged leaf spring? 

If you are looking for more details, kindly visit Single Leaf Spring.

The individual leaves are one of the first areas to inspect on a leaf spring. Due to excess corrosion or overloading, individual leaves may crack or shear completely, leaving a noticeable break in the steel. However, even if the damage is limited to a crack, you may see a line of rust running vertically through the width of the leaf. 

Another common breakage point is the centering pin, tasked with the vital job of centering the individual leaves together, as well as centering the axle under the leaf spring. If this pin breaks, you may notice one side of your vehicle's axle sitting too far forwards or rearwards in the wheel well. 

Lastly, check the two large bushings in the central leaf's eyelets and the bushings in the shackles. These components should be free from dry rot, tears, or excessive wear. If these symptoms are present, your leaf spring bushings are toast!

Post by zebedee » Jul 7th, '11, 20:29

gazwald wrote:...Galvanised or painted???

I was told by one bloke that the galvanising process causes issues with the heat treatment of the spring given they have to be dipped in molten metal to be galvanised.

I can believe that the reason that galvanised springs were not available for so long was that the galvanising process affected the heat treatment of the springs, but given galvanised springs are now relatively common practice, presumably someone has found a way around this.

How might this be so, I hear you ask, since you can't change the melting point of zinc or the phase transition temperatures of steel?

Zinc melts at 420degC. According to

I think it is fair to say that I and most of my classmates emerged from our engineering course, which included at least one subject largely about metallurgy, with a very good understanding that steel is bizarrely complicated stuff with a number of different possible crystal structures which give it different properties and which vary with alloying, and particularly with carbon content; and that we should consult a metallurgist, or at very least spend some quality time with technical references if in any doubt whatsoever... It's one of those areas where you come away with a clear understanding that you do not know very much!

Having said that, here's a basic plot of what steel gets up to:



The trick is not to get it warm enough for long enough to change state; and as you can see, not much happens below about 700degC.

Now, armed with the information above, alone, I certainly wouldn't commit to producing galvanised springs where no one had done it before, (I'd find me a good metallurgist first), but I'm quite prepared to believe that it is straightforward and that galvanised springs are fine.

gazwald wrote:The original springs don't appear to be galvanised and have lasted about 10 years but not without incident (2 broken leaves)

I am also looking to replace the double slipper set up with a roller rocker load sharing set up. Has anyone done the conversion? Did the load sharing make a big difference?

Load sharing would probably reduce spring breakages by reducing peak loads on each spring.

Load sharing certainly works.

I used to tow my 700kg boat with a Nissan Pulsar rated for 900kg with brakes. On a couple of occasions I also used the same car to tow a 400kg (empty) 8x5 tandem box trailer with brakes 300km to northern Victoria and back. It had camping gear, bicycles, that sort of stuff and was safely under 900kg.

The towbar height on my Nissan was rather lower than the Toyota Landcruiser it was normally behind, and the load sharing suspension was right at the end of its travel on the Nissan. It was pretty horrible, but by replacing the 14" front trailer wheels with my 13" low profile wheels and tyres off my boat (same stud pattern), we tipped the trailer forward a bit and got the load sharing working properly and it was much nicer to tow. It felt more stable and didn't jerk the car about on uneven road surfaces anywhere near as much.

I can believe that the reason that galvanised springs were not available for so long was that the galvanising process affected the heat treatment of the springs, but given galvanised springs are now relatively common practice, presumably someone has found a way around this.How might this be so, I hear you ask, since you can't change the melting point of zinc or the phase transition temperatures of steel?Zinc melts at 420degC. According to Wikipedia , hot dip galvanising is done at about 460degC.I think it is fair to say that I and most of my classmates emerged from our engineering course, which included at least one subject largely about metallurgy, with a very good understanding that steel is bizarrely complicated stuff with a number of different possible crystal structures which give it different properties and which vary with alloying, and particularly with carbon content; and that we should consult a metallurgist, or at very least spend some quality time with technical references if in any doubt whatsoever... It's one of those areas where you come away with a clear understanding that you do not know very much!Having said that, here's a basic plot of what steel gets up to:The trick is not to get it warm enough for long enough to change state; and as you can see, not much happens below about 700degC.Now, armed with the information above, alone, I certainly wouldn't commit to producing galvanised springs where no one had done it before, (I'd find me a good metallurgist first), but I'm quite prepared to believe that it is straightforward and that galvanised springs are fine.Load sharing would probably reduce spring breakages by reducing peak loads on each spring.Load sharing certainly works.I used to tow my 700kg boat with a Nissan Pulsar rated for 900kg with brakes. On a couple of occasions I also used the same car to tow a 400kg (empty) 8x5 tandem box trailer with brakes 300km to northern Victoria and back. It had camping gear, bicycles, that sort of stuff and was safely under 900kg.The towbar height on my Nissan was rather lower than the Toyota Landcruiser it was normally behind, and the load sharing suspension was right at the end of its travel on the Nissan. It was pretty horrible, but by replacing the 14" front trailer wheels with my 13" low profile wheels and tyres off my boat (same stud pattern), we tipped the trailer forward a bit and got the load sharing working properly and it was much nicer to tow. It felt more stable and didn't jerk the car about on uneven road surfaces anywhere near as much.

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