Correct Series 3 109 Springs

[Cchase]

What are the correct springs and shocks for a military spec framed 109" Series 3?

It came with parabolics that are well rusted, and from conversation with the previous owner, rather 'wafty' going down the road.

9 leaf or 11 leaf?

Cheers,

Colin

[Snagger]

The “waftiness” will be from bad dampers, not the springs.  Given your location, it’s a fair bet you have Rocky Mountain springs, which are a good brand.  Decent parabolics are better in almost every way than semi-elliptical springs, not rusting together, being more resistant to breaking leafs, having far better articulation off road and absorption of bumps on the road.  A little clean up and repaint would almost certainly be more beneficial with an replacement with old style springs unless you are looking for a completely original spec vehicle for classic status rather than practicality.

As for the dampers, avoid Pro Comp.  They are usually sold with parabolics as a kit but are woefully poor quality.

[steve b]

Have a look at the list of different OE leaf springs on Jones Springs here in UK , all the different types are listed and if you have queries they are very knowledgeable 

Check the bushes and U bolts on your set up for wear 

Steve 

[Cchase]

4 hours ago, Snagger said:

The “waftiness” will be from bad dampers, not the springs.  Given your location, it’s a fair bet you have Rocky Mountain springs, which are a good brand.  Decent parabolics are better in almost every way than semi-elliptical springs, not rusting together, being more resistant to breaking leafs, having far better articulation off road and absorption of bumps on the road.  A little clean up and repaint would almost certainly be more beneficial with an replacement with old style springs unless you are looking for a completely original spec vehicle for classic status rather than practicality.

As for the dampers, avoid Pro Comp.  They are usually sold with parabolics as a kit but are woefully poor quality.

Thanks for this. Would the one ton dampers be the dampers of choice, then?

C

[Cchase]

2 hours ago, steve b said:

Have a look at the list of different OE leaf springs on Jones Springs here in UK , all the different types are listed and if you have queries they are very knowledgeable 

Check the bushes and U bolts on your set up for wear 

Steve 

Yes, bushes will be replaced, as well as U bolts. The truck was in an accident - no brakes down a steep hill - before it came to me so I have yet to drive it.

C

[David Sparkes]

The 'wafetiness' of parabolic springs with a 109 is something mentioned, adversely, by TeriAnn Wakeman, although she is running a motorhome equipped vehicle, so always has more weight higher up than most people do.

This is due to the parabolic springs having little internal friction, so have less inbuilt anti-roll effect than multi-leaf springs. When the vehicle rolls the springs twist along their length, the parabolics twist more easily; the waftiness is the other side of the increased articulation coin.

You mentioned one ton dampers, this phrasing is generally used in relation to multi-leaf springs, where the increased weight limit is catered for by stiffer leaves, or more leaves. However it is achieved, the internal friction, of one leaf against the other is increased, especially as the spring is compressed in 'bump'.
Once the spring is compressed there is a lot more energy stored in the compressed spring (compared with a standard multi-leaf).
This means that one ton dampers need different settings; they are not just stiffer.
Due to the increased internal friction damping when in bump, the one ton dampers are softer than standard in compression, but due to the increased stored energy when the spring is compressed the one ton dampers are stiffer in rebound (than standard).

In the UK people often combine one-ton dampers with standard multi-leaf springs as this gives a softer ride, both in absorbing the initial bump and delaying the rebound response. Changing the dampers is cheaper than changing the springs and dampers. Many (most?) UK users do not expect to load their vehicles towards maximum weight, so retaining the standard load capacity is not a problem.

As you haven't driven the vehicle I would suggest leaving the springs as they are (cleaning and de-rusting is cosmetic, do as you please).

After you have driven it in your style of use (loading and speed), assess its waftey performance then consider changing the springs.

Regards.

[steve b]

The 1 ton dampers are also longer to allow for the spring chassis mount extension and the 6" shackles . 

As David and snagger says the parabolics have much less built in friction and behave more like a coil spring in terms of damping .

Steve 

[Cchase]

Sooo...

The front dampers were damaged in the accident, and were the Pro Comp units that Rocky Mountain sold with their parabolic springs.  I need to get something before I can drive the vehicle.

I have been in touch with RM and these dampers are no longer available. Summit Racing accepted the part number, but has none in stock

and in any case RM said that these are now made in Mexico and the quality had become suspect.

What do you recommend for a suitable damper for the truck at least for the front? I used the term 'One Ton' as it was a choice in the Paddock or John Craddock site. 

Thanks

[Snagger]

Pro Comp dampers were terrible when they were made in the US, so if they say they have worsened…😳

 

A lot of fuss is made about the dampers that are used for parabolics and how regular dampers will explode from the heat generated by the extra articulation.  That is a great example of internet rubbish.  Standard dampers on coil or air sprung models don’t tend to overheat or explode unless used in very arduous conditions.  The same would apply to this case.  I put some 1-ton standard dampers on the back of my 109 as it has a 1-ton suspension setup, and they have worked brilliantly for general use with the HD parabolics.  They replaced PC ES300s, which all sprung leaks, which in turn replaced PC ES900s which were far too hard and two of which leaked.

If you are going to drive an awful lot off road, then you could fit gas dampers of the correct dimensions, but standard SIII dampers will suit most parabolic sprung SIIs and SIIIs perfectly well.  We are not talking about a sports car, and the parabolics are not that soft or willowy compared to a good, greased set of semi-elliptical springs; it is the rusting and seizing of the semi-elliptical springs in very short time that sets them apart.

As for Terri-Ann’s advice, some of it is good, some I take issue with.  She has experience of a very heavy vehicle with extremely limited parts supply.  She has useful experience, but is no expert and has not experienced a great deal of alternative parts or mods, so read her comments and think well on them, but don’t treat that site as gospel - I write my own based on my own experiences too, and it doesn’t invalidate others’ experiences or solutions.

[Wytze]

On 1/15/2022 at 1:24 PM, Cchase said:

Thanks for this. Would the one ton dampers be the dampers of choice, then?

C

I use a set of Rocky Mountain  parabolics.  On the front i use a set of oil dampers, on the rear there are a set of gas dampers.  The difference is really noticeable.   The gas dampers make it a really smooth ride