OME rear leaf spring rate?

[superclarkey]

I just finished putting a BP-51 kit on my Hilux, I used the recommended lightest rear leaf kit in the rear, the EL106R which is rated to 0-300kg, there is a 300-600 and a 900+ version, so out of the 3 went for the lightest.

When I put the vehicle back on the floor it barely moved, looks proper jacked at the back so jumped up and down on it and put a stack of tyres in the back of the tub and once everything was removed, the actually suspension shock is only going down 12mm out of the 245mm travel.. seems to me like the rear spring rate is way too high?

I have nothing in the back of the tub, other than spare wheel, other than that it's empty with a full tank of fuel. (Oh actually I do have ARB summit rear tow step which is about 50kg?). So should be well within the 0-300kg range of the leaf pack?

(Can't drive the car around the block yet as I'm still doing work on it).

Thanks.

[dave g]

It will sofin up with use all new springs well be hard even though 200kg in the back to help it when you start to drive it around even run the shocks on the soft setting for a bit.

[superclarkey]

Hey thanks for your reply, are you saying it just likely to be sticktion between components that is holding the truck up this high? i.e like the plastic inserts between leafs and bushes that need time to wear and be able to slip?

I mean the metal springs are not going to change regardless of how much time is given (unless you go past the plastic deformation point and the springs no longer return to their original shape).

as it currently sits, it would be constantly topping the shock out and would be terrible.

[superclarkey]

Here is a shot for reference.



Tyres are 33x12.50R17 - see how the top of the tyre is below the chassis rail,

I have checked the rear shackles are the correct ones supplied by ARB/OME.

Problem is here in the UK, There is zero ARB support/Technical advice, so your on your own to deal with issues like this.

EDIT: should only be a 2" lift.

[superclarkey]

I think I might know the issue here, the shop that sold them to me considers the EL106R to be 0-300, when in fact looking at the ARB catalogue its listed as follows (And only info actually available)

Medium load
Constant 300kg
Constant 600kg

so my understanding would be

Medium load = <300kg
Constant 300kg = 300-600kg
Constant 600kg = >600kg

but that is still filling in the blanks, there could be allot of overlap and I'm sure there is..

so if my logic is correct this is the following..

Medium load = 0-300kg (EL105R)
Constant 300kg = 300-600kg (EL106R)
Constant 600kg = 600kg + (EL107R)

so... I have the wrong leaf springs for my vehicle.

[dave g]

Send a message to arb here in Australia and ask them directly

[dave g]

Just looked at the photos is it on the lift

[Bushwalker8]

You are correct, the OME EL106R is the Constant 300 kg and targeted at 300 to 600 kg. The light spring is indeed the EL105R at 0 to 300 kg.

Like most of the industry fixated with "lift" you can also expect the ride height to be little higher than standard at that specified load anyway. So if you are not carrying that load it's going to sit pretty high like your photo shows.

The spring part numbers changed a couple of years ago, when I got the mid range Constant 300kg the part number was EL090R and the spring rate was lbf/in: 220/389, N/mm: 39/68 and the current mid range EL106R lists similar rates of lbf/in: 220/384, N/mm: 38.5/67.2.

So as a rough rule of thumb with what you have there you can expect the first part of the ride height to vary something in the order of around 12mm for every 100 kg over the axle. I say rough as this can vary for a number of reasons, for example more effect if the weight is behind the axle, less if in front, as you get lower the second stage stiffer rate kicks in, and you would need to bounce it about and settle to overcome stiction etc. 

As a comparison the EL105R rates are listed as lbf/in: 169/305, N/mm: 29.6/53.5

[superclarkey]

Just looked at the photos is it on the lift

Yes it was on the lift but it had been put down and moved back and forwards and me and the mates jumped up and down in the back.. that was defo its resting place.

[superclarkey]

You are correct, the OME EL106R is the Constant 300 kg and targeted at 300 to 600 kg. The light spring is indeed the EL105R at 0 to 300 kg.

Like most of the industry fixated with "lift" you can also expect the ride height to be little higher than standard at that specified load anyway. So if you are not carrying that load it's going to sit pretty high like your photo shows.

The spring part numbers changed a couple of years ago, when I got the mid range Constant 300kg the part number was EL090R and the spring rate was lbf/in: 220/389, N/mm: 39/68 and the current mid range EL106R lists similar rates of lbf/in: 220/384, N/mm: 38.5/67.2.

So as a rough rule of thumb with what you have there you can expect the first part of the ride height to vary something in the order of around 12mm for every 100 kg over the axle. I say rough as this can vary for a number of reasons, for example more effect if the weight is behind the axle, less if in front, as you get lower the second stage stiffer rate kicks in, and you would need to bounce it about and settle to overcome stiction etc. 

As a comparison the EL105R rates are listed as lbf/in: 169/305, N/mm: 29.6/53.5

Yeah totally agree, I just took what they gave me as the right ones and didn't think anything more of it until I went to fit them.. I have spoke with my ARB Rep and they are happy to exchange them so hopefully that is problem solved.

Annoying I didn't really want a 2" lift, I just wanted better shocks that come with the GR Sport, so the BP-51's fitted the bill.. I will likely have the rear step on there which is around 50kg, and a spare 33 and rim which is another 45-50kg, so will have a constant 100kg on the back.

My goal is to get full articulation through full travel front and rear without any rubbing etc, so got a bit of cutting to do..

[superclarkey]

I've fitted the softest springs they can supply, but the rear still seems very high compared to the front.



I have followed the instructions, my vehicle is a 2.8D, with Automatic gearbox, so the front has 10mm of preload. (so reduced from the 20mm preload that comes on the front springs as standard).

Not sure if the back is still high or the front is low.. but it looks broken.

the back centre of hub to fender is 85mm more than the front.. That simply can't be right.

[Bushwalker8]

So confirming these are now the EL105R? Just visually without an extra 300kg (~36mm) this could be in the ballpark. Even with the extra weight they can sit a bit high.

Once bounced about and settled what are the hub center to bottom of fender heights at each corner?

[Rob_Wood]

Settling new springs is common practice. Have a look at some earlier posts in the various suspension sub-sections to get an idea of some different ways to achieve the ultimate goal.

[superclarkey]

So confirming these are now the EL105R? Just visually without an extra 300kg (~36mm) this could be in the ballpark. Even with the extra weight they can sit a bit high.

Once bounced about and settled what are the hub center to bottom of fender heights at each corner?

When I have had chance to move the vehicle about I will report back on heights. Annoyingly I wrote down the original heights but I lost the bit of paper so unsure how far away from standard I am.

[superclarkey]

Settling new springs is common practice. Have a look at some earlier posts in the various suspension sub-sections to get an idea of some different ways to achieve the ultimate goal.

Will have a look, thanks.

[Bushwalker8]

I will report back on heights.

I had a chance to re-measure mine so you can compare but I wouldn't hold your breath yours is going to change soon; you are on the right track re plastic deformation.

Since my springs were fitted they've clocked around 28,000 km mostly at or close to max rear load including about the Flinders Ranges and Cape York plus other stuff and they are still sitting about the same.

When they were fitted and at my base load the axle center to guard heights measured:
FL: 530 mm FR: 535 mm
RL: 582 mm RR: 593 mm

I've just measured them again at the same loading with the exception of roughly an extra 40L fuel in the tank:
FL: 525mm (-5mm) FR: 532mm (-3mm)
RL: 580mm (-2mm) RR: 589mm (-4mm)

The extra fuel weight between the axles in theory should account for somewhere around -2 to -3mm each end so it pretty much adds up and is negligible anyway.

As a general guide when I max out including the trailer ball weight there is roughly another 300kg spread around the rear plus 2 people center'ish and only then its sits level as I wanted. At that point the rear axle is pretty much at maximum load.

[superclarkey]

Thanks for sharing that info, really helpful

So your rear is about 50mm higher than your front.

I did some measurements but I measured from top of the tyre (as it's very flat and easy to get a repeatable measurement) and the guard (steel). I know I should measure to the centre of the axle but It wasn't easy and I just wanted a reference.

These are the raw numbers.

FL - 172 mm / FR - 175 mm
RL - 216 mm / RR - 213 mm

(I can correct these numbers but estimating the tyres size 32.6" divided by two and adding it to above number)

414 mm mm to be added.

FL - 586 mm / FR - 589 mm
RL - 630 mm / RR - 627 mm

But this doesn't make sense as it's pointing to my truck being 2inchs odd taller than yours.. so guess I need to measure this correctly in the near future.

So as you can see I have a really level truck from side to side, and more importantly I have about 40mm on the rear higher than the front.

So this reduces my worry a bit

[Bushwalker8]

The extra height in yours would be expected as mine is only used for long trips so it sits there patiently weighed down with a lot of extra' baggage geared up and ready to go. E.g. Bullbar (alloy), winch, side-steps, canopy, roof racks drawers, long range tank, spares, compressor, recovery gear, tools, etc etc.

The background is I picked and chose the springs so that when I was travelling it would sit flat near OE ride height. So my front coils are the next shorter free length than ARB recommended ones based on their fitted accessories guidelines but they were all the same spring rate so it was only a ride height matter and it worked out well.

[Myralga]

Something else of note for you is the BP-51 themselves.
Been a pressurized Shock assembly with the external Reservoir when compared to a standard shock or even a simpler yellow OME shock they take a lot more pressure/weight to get them to overcome that internal pressure and start to drop.
As a result they do help hold up the rear especially in a situation where you have very little weight on the rear of the car.
Furthermore they can be stiffer as all the internal seals are fresh and new etc.

So yeah it should come down with time to a degree and settle but adding some weight will help.

Also of note ARB state from memory that the increased lift is approximately 20mm front and 40mm rear (so not a true 50mm lift)
Add to this the original severe rake of the vehicle it had at new this makes it even more nose down doing the lift.


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