Advice on Kings springs

[Ian H]

I'm getting new suspension fitted and going for Kings springs and Koni shocks.

I tow a medium size caravan using a WDH so no issue there but the camper trailer (Tvan) has a ball weight of around 160kg and obviously a WDH isn't practical for off road so the back sags a bit. I have air bags to help compensate in that instance.

I've also got the LRA fuel tank and a set of drawers in the back so I'm wondering what rating of springs would be best ?

The guys doing the job said there's not a huge range of Kings for the Paj and suggested the Raised HD (100-300kg) springs as a good compromise between support for towing and ride comfort.

Does that sound about right ?

[nj swb]

I'm getting new suspension fitted and going for Kings springs and Koni shocks.

I tow a medium size caravan using a WDH so no issue there but the camper trailer (Tvan) has a ball weight of around 160kg and obviously a WDH isn't practical for off road so the back sags a bit. I have air bags to help compensate in that instance.

I've also got the LRA fuel tank and a set of drawers in the back so I'm wondering what rating of springs would be best ?

The guys doing the job said there's not a huge range of Kings for the Paj and suggested the Raised HD (100-300kg) springs as a good compromise between support for towing and ride comfort.

Does that sound about right ?

As I'm sure you're aware, OJ is the man when it comes to this stuff. My 2c...

I think it comes down to how much you're carrying in the rear of your Paj vs how much you transfer into the Tvan.

I don't tow, so I'm carrying it all in my Paj - which also means I don't have the ball weight. I do have aux tank, a 70 litre water tank in the rear seat well, and a storage system that is rarely emptied - so I tend to have a significant load at the best of times, and it only gets larger.

I tried a couple of different "HD" springs and found I wasn't getting the height I wanted when fully loaded, so I now have Kings EHDs, and they're doing the job well. Last I measured, I was around +30 - 35mm "unloaded", and at normal factory ride height at my max load.

It sounds like you'd be a little lighter than me without your Tvan on the back, but have more load on the rear suspension with the Tvan on. HD springs and airbags might do what you need, depending on the amount of "lift" you're expecting when fully loaded. I'm confident the EHDs will give you the touring performance you need, but may be too stiff under normal circumstances.

[Ian H]

Thanks for that reply. I see on the Kings website that they only list the Paj up to the NW model. I assume the NX is the same.

[old Jack]

Hi Ian,
All coils are common across all Gen 3 and Gen 4 Pajero’s.
What is your current front ride height and are you happy with it or are you changing front suspension at the same time.
If you give me accurate front and rear axle weights then I can do some calculations.

OJ.

[Ian H]

Thanks OJ.

Current ride height with the aux tank empty but main tank at 3/4 is :

Front R 520
Front L 520

Rear R 530
Rear L 530

Weigh bridge, not hooked up to the caravan and with a full tank of fuel and the usual gear in the back as we'd have on a trip.

Front 1260 kg
Rear 1680 kg

Van
ball weight 200kg
ATM 2290

Cheers.

[old Jack]

Thanks for the accurate weights and details Ian.

Do you want an increase in empty and loaded ride heights?
Front 540mm +/- 10mm and Rear 565mm +/- 10mm is the safe maximum.

How many kms on the Odometer?
Chances are your lower rear coil insulators will be stuffed so will need replacing, tops insulators are still likely to be ok at 50K to 100K kms.

OJ.

[Ian H]

No further height increase is needed and in fact, any more and I'll be adjusting the garage opening. I just get in now.

Car has just clicked over 102,000

[old Jack]

Hi Ian,
By chance do you happen to have the part numbers of the Peddars coils that are installed?
Have you considered reusing the front coils if you are happy with the ride height and front axle spring rates?

OJ.

[Ian H]

Haven't got them OJ but the shockers are all making a noise so I'm just replacing the whole lot. They said can't put Konis on the sprigs that are there. Front and back.

The guy is reputable and sponsors our 4WD club so I'm happy to take him on his word.

[old Jack]

Hi Ian,
I find the mechanics statement that Peddars coils will not fit Koni struts is very interesting since the existing Peddars coils are fitted to EFS struts???
If Peddars coils were somehow different, then why will they fit EFS struts ???.

Reason I was asking was do I could compare spring rates and free lengths and see what King front coils are the closest to the existing Peddars coils.

OJ.

[Ian H]

Good point. I guess in the scheme of things if I'm replacing the rear springs and all the shocks, the extra for new front springs isn't that great.

There's no detail on the invoice from when they were installed, it just says Pedders suspension all round.

[old Jack]

Hi Ian,

I do not have technical specifications for King front coils but I suspect the KCRR-34 should give you a ride height of about 530mm +/- 10mm, but this is a best guess. This maybe too high considering you are looking for a rear height of 530mm and once you consider the weight transfer off the front axle when the Tvan is hooked up..
The KCRS-34 should give you a ride height of about 510mm +/-10mm based on the modest extra weight you have on the front.


Your normal rear axle weights are heavy at 1680kgs and this is not with full fuel, any extra load in the cargo area, back seat, any towball loads or front axle weight transfer.

Rear Axle load limit is 1780kg going from MMAL's brochure so this only gives you 100kg to play with.I believe the rear axle weight limits are based on the coils fitted and not on brakes because you can tow a 750kg unbraked trailer. Not based on engine power, gearbox or drive line strength because you can tow up to 3000kg with a GCM of 6030kg. Even the passenger construction tyres have more than enough theoretical load capacity!

With the caravan ball load with a correctly adjusted WDH is 200kg so that is 1880 kg rear axle weight.

With the Tvan 160kg ball load plus roughly 62kg of front axle weight transfer totals 242kg.

No wonder the Peddar rear coils are a bit saggy!

It would be worthwhile hooking either or both the Tvan and Caravan up(with WDH) and confirming the front and rear axle weights, measuring the ride heights front and rear, with only 5 psi in the airbags.

I am thinking that even the KCRR-35EHD rear coils alone may not be strong enough for your weights without any airbag assistance.
My calculations are;
Ride height 550mm +/-5mm with 1630kg rear axle weight

Ride height 540mm +/- 5mm with 1690kg rear axle weight.
Ride height 530mm +/- 5mm with 1760kgrear axle weight.
Ride height 520mm +/- 5mm with 1850kg rear axle weight.

My calculations are based on the spring manufacturers specifications that can vary by up to 7% and I cannot compensate for the uneven compression of the coils due to the radial/arc movement of the suspension arm but this is minimal since 50 mm change in ride height equals about 25mm to 30mm of spring compression so the coils normally work within a very small travel range. Also it assumes that the coil insulators are in good condition and not worn.

I have looked at all other rear coils from Kings, OME, Dobinson and Lovells and none of these are going to give you the conservative ride heights you desire for the weights you want to carry.

Chances are your lower coil insulators will be also stuffed so factor in a set of PolyTuff lower insulators.


OJ.

[Ian H]

Many thanks for the detailed response OJ. I'll factor that in and discuss with my mechanic.

I did a weigh bridge test with the WDH off and then on while the van was hooked up and the results were amazing.

With the van attached and no WDH, the rear was 1840, which is over the allowance. Attach the hitch and the rear went back to 1680, a reduction of 160kg which made it legal again. Of the 160kg reduction, 100kg went to the front axle and 60 the van axle, all well within the limits.

Since I did those measurements, I've taken out the heavy Titan drawers (70kg unloaded !) and put in a set from Drifta at half the weight. I also try not to carry too much fuel in the reserve tank unless I need it on a longer trip so another 50kg or so can be saved in most cases.

Interestingly, the measurements the mechanic uses are from the top of the guard to the bottom of the wheel rim, going past the central point of the hub. He reckons ride height for the spring he wants to use (KCRR-35HD) should be 775 on the reat for a 17"wheel. Mine are just slightly less than that at the moment.

I really appreciate the input.
Lots to consider and I don't want to get it wrong this time.

[Ian H]

Another option I've been considering is to remove the LRA aux tank (58L) and replace the main tank with the poly ARB version. It would reduce my fuel carrying capacity from 146L to 128L but it would remove the extra weight from behind the rear axle. I don't often need the full 146L and I could carry a 20L jerry of fuel if required.

Wouldn't be cheap to do but I could sell the LRA tank and defray some of the cost at least.

[old Jack]

Comments in "blue text" in your post below.


OJ

Many thanks for the detailed response OJ. I'll factor that in and discuss with my mechanic.

I did a weigh bridge test with the WDH off and then on while the van was hooked up and the results were amazing.
I am not surprised!

With the van attached and no WDH, the rear was 1840, which is over the allowance. Attach the hitch and the rear went back to 1680, a reduction of 160kg which made it legal again. Of the 160kg reduction, 100kg went to the front axle and 60 the van axle, all well within the limits.
I thought the van had a 200kg ball load, if so the rear axle load load should have increased to about 260-280kg? Not sure why you only got a 160kg rear axle weight increase???
Did you check the caravan ball weight on the weighbridge.

Since I did those measurements, I've taken out the heavy Titan drawers (70kg unloaded !) and put in a set from Drifta at half the weight. I also try not to carry too much fuel in the reserve tank unless I need it on a longer trip so another 50kg or so can be saved in most cases.
Every Kg counts particularly if it is rearwards of the rear axle.

Interestingly, the measurements the mechanic uses are from the top of the guard to the bottom of the wheel rim, going past the central point of the hub. He reckons ride height for the spring he wants to use (KCRR-35HD) should be 775 on the rear for a 17"wheel. Mine are just slightly less than that at the moment.
Yes, some people use the bottom of the rim but the correct method is centre of rim. A 17" rim is actually bigger than 17" when measures across the rim maximum diameter it is 18" or 460mm! So you need to minus 230mm off the under rim measurement to get a standard ride height measurement, therefore the 775mm is adjusted back to 545mm when measured from the centre of the rim.

The KCRR-35HD is a coil we had fitted and load tested in Pajero 12's NW

At ride height 540mm +/-5mm we weighed 1350kg and my calculations were 1430kg.
At ride height 520mm +/-5mm we weighed 1550kg and my calculations were 1490kg.
At ride height 520mm +/-5mm we weighed 1650kg and my calculations where 1555kg.

Reason for my calculations being out is I can only calculate the spring forces when the coils is evenly compressed and I have to assume the rate of spring rate change of the progressive design is lineal. Actual installed in vehicle load tests are the only to really know what results you will get.

Either way my concern is the 35HD are going to be too light for your application. If you are not happy with the results will your mechanic change them over free of charge, since he is so sure of the ride height outcome?
I really appreciate the input.
Lots to consider and I don't want to get it wrong this time.