Suspension again

[GrayKnight]

Hi,


My auto PC Challenger has done just over 100,000km, a lot of that over some very rough and corrugated roads/tracks. It is fitted with factory alloy bull bar (no winch), factory towbar, long-range fuel tank, cargo barrier, storage system, fridge and second battery in rear, tools etc etc. I am now also towing a camper trailer which adds a ball weight of about 200kg. When travelling, there will be an extra 200kg (including driver and passenger) or so in the car .


The car was weighed with the above permanent load (ie excluding the camper and travel load) plus about half a tank of fuel.


Weights are front axle 1,135kg, rear axle 1,120kg and total 2,255kg. It seems as though I will just squeeze under the GVM when fully loaded with camper.


I measured the suspension with the permanent load but no driver or camper. The EBHs were front right 550, front left 550, rear right 515, rear left 515.


With the camper attached, the EBHs were front right 550, front left 550, rear right 490, rear left 490. I was surprised that the front EBHs didn't change - I did measure them twice.


Ideally I would like to get the suspension back close to factory specs, both with just the permanent load and also the camper attached. This may be difficult to achieve whilst keeping the ride reasonable. Increased ground clearance would be most welcome as the long-range tank hangs lower than the factory tank and I've already sprung one of its seams. And I wasn't travelling fast, just repeated thumps onto high central sandy humps on one of the nastier tracks. The towbar also bottoms out with regularity even without the camper attached.



I've gotten recommendations from four local suppliers (Central Coast NSW), only one of whom discussed my situation and possible solutions. One other asked a couple of questions, the others simply read from their catalogues. Two of them suggested near-identical OME gear. The recommendations are


1. King springs front KCFR-55H and rear KCRR-23. Bilstein shocks front BE5H842 and rear B461333CHALLRAIS. Plus airbags to handle the wide variance in load. Lift about 40mm front and back.



2. OME springs front 2605 or 2606 and rear 2938. OME shocks front 90008 and rear 60075. Lift 20mm front/35mm rear or 35mm front and rear.


3. Ironman springs front MITS040C and rear MITS042B. Ironman shocks front 24715FE and rear 24645FES. Lift not given.


The car is used mostly around town (with the permanent load), occasional day trips on dirt (no significant load increase) and one or two long trips each year outback (fully laden).



I've read all the posts on Challenger suspensions that I could find and realise that there is no "one size fits all" solution. I'm inclined to go with the King/Bilstein/airbag solution as this seems to give the flexibility that I need given the variance in loads between town driving and towing.


Any comments will be most welcome.


Cheers
Richard

[tpnkt]

Have you spoken to Australian Ultimate Suspension? They seem to be good with tailored solutions, I'm pretty happy with the results of the kit they put together for me.

Sent from my SM-A520F using Tapatalk

[GrayKnight]

Have you spoken to Australian Ultimate Suspension? They seem to be good with tailored solutions, I'm pretty happy with the results of the kit they put together for me.

Sent from my SM-A520F using Tapatalk

No I haven't. They're not close to where I live. Would prefer a local supplier.

Cheers

[old Jack]

Hi Richard,

I have put your numbers into my spring vs ride height calculator and I make the following comments.

Front Suspension.

1. Front Factory ride height is 542mm according to RVCS data. Factory coils have a spring rate of 680lbs/inch or 12.16mm/kg.
2. King coils KCRS-55, KCRR-55SP, KCRR-55H all have a spring rate of 750lbs/inch or 13.42kg/mm. So any of these coils will give you a firmer ride by about 10%.
3. To remain legal you need to retain 2/3's of the original suspension droop travel so if you use the 542mm standard ride height specification and from memory factory suspension droops to about 590mm to 600mm then you have about 60mm droop travel an since you must retain 2/3's then you can only lift to 560-565mm.

If you are happy with the ride height, the spring rate and the handling of the front coils then why change them? Why not just replace the struts?

The King KCFR-55H will be too high for your front axle load and this is likely to result in unwanted and unnecessary activation of the ABS, ASC and TC systems due to lack of suspension travel.

If you are happy to use a firmer spring then the KCFR-55SP will give you between 555mm and 565mm ride height and a 10% firmer spring rate.


Rear Suspension.

What you have reported does not surprise me, the factory coils are very light duty and are design for empty comfort and they do not carry weight well, they wallow through corners and bottom out easily on the internal rubber spring assist cones.

Forget airbags and replace the rubber cones with Peddars PN 5899 Aeon units these cost about $120 a pair and are a direct fit but they start coming into effect much early in the rear suspension travel, are much more progressive and handle deep compression loads infinitely better than the factory rubber cones. There are dozens of Challenger and Pajero Sport owners that have change over to these and I have not had on bad report!

Factory rear ride height when empty is 552mm according to the RVCS data.
Factory coil is a progressive rate coil that has a spring rate range of 90 to 160lbs /inch or 1.6kg/mm to 2.86kg/mm. These are way too soft as you already know. The minimum legal rear ride height for a Challenger is 512mm so even if you are not overloaded you can still be defected for being under the minimum ride height!

KCRR-23 is a progressive rate coil with a spring rate of 3.03 to 4.01mm per kg and with a 1120kg rear axle weight should give you a ride height of about 545mm +/-10mm so this coils will be too light for your application.

KCRR-23HD is a progressive rate coil with a spring rate of 3.66 to 5.17kg/mm and with 1120kg on the rear axle should give you a ride height of about 570mm at 1120kg and 545mm at 1320kg rear axle load. These would be the coil that I would suggest fitting.

King coils are very good, they also make OME and Tough Dog but you are not paying for the Big $$$ brand name!


Bilstein, theses are a great strut and shocker when on road but I found then too firm off road and after 3 strut failures in under 90,000kms, they are only covered by a 12 month 20,000km warranty they are an expensive strut to run from my experience.

Rear Bilsteins had much longer stroke and these where great in regards to wheel travel except for tight brake lines and they were way too hard on compression and way too soft on rebound for my custom Lovells EHDVR expedition coils. The back suspension would get up a pogo bounce when doing rough slow corrugated dune climbs. The rear Bilsteins lasted 100,000km of abuse but the current Dobinson Monotube are much more suited to my application but are more expensive than Bilstein! I have only 30,000kms on the Dobinson struts and shockers all ok at the moment so the jury is still out.

OME shockers and struts tend to be way too firm/hard on compression and too soft on rebound, they are made by Monroe and you are paying the ARB TAX for both coils and struts/shockers.

A good value medium to heavy duty strut and shocker is OzTec, with a 3 year/100,000km warranty. So unless you are doing a lot of expedition travel in remote areas at GVM+150kg weight the the OzTec are the choice. If you are interested in OzTec struts and shockers give Steve Sheppard a call at GSA in Queensland, tell him you are from the Pajero forum and he will look after you.


Summary, best recommendation I can make is;

Front either keep the factory coils or fit King KCFR-55SP with OzTec struts.
Rear, fit KCRR-23HD coils with OzTec shockers and Peddars 5899 cones.


OJ.

[GrayKnight]

Good morning Old Jack,


Thanks very much for your advice and your recommendation.

Summary, best recommendation I can make is;

Front either keep the factory coils or fit King KCFR-55SP with OzTec struts.
Rear, fit KCRR-23HD coils with OzTec shockers and Peddars 5899 cones.


OJ.

I'll probably keep the factory coils as the front end rides quite well, it's the rear end that wallows.


Just as an aside, I seem to remember from one of your posts you were going to do the Anne Beadell at GVM+. I did it myself in the Challenger a few years ago and I would have definitely been close to GVM - two people, long-range fuel tank, extra fuel in jerry cans, water, second spare, tent, food, storage system, fridge etc etc. I did remove the rear seats though.The car performed without any problems, though this is where I did spring the seam in the fuel tank - about half way across.


Thanks again, cheers
Richard

[old Jack]

Just as an aside, I seem to remember from one of your posts you were going to do the Anne Beadell at GVM+. I did it myself in the Challenger a few years ago and I would have definitely been close to GVM - two people, long-range fuel tank, extra fuel in jerry cans, water, second spare, tent, food, storage system, fridge etc etc. I did remove the rear seats though.The car performed without any problems, though this is where I did spring the seam in the fuel tank - about half way across.

Thanks again, cheers
Richard

No problem Richard,

Unfortunately my Beadell Tracks trip got postponed along with my CSR trip .
Combination of work and home commitments have meant extended trips are not possible for another year or so, 2 weeks off at any one time is about my limit. I did manage a 10 day Simpson Desert Innaminka and Arkaroola trip last year, GVM+150kg 4,200kms with only about 1000kms on the bitumen, no problems with tyres or suspension.


OJ.

[amec]

My 2 cents worth.

I am no expert, but this has worked for us on a recent 11k km trip to Cape York and home via Birdsville from the NSW Central Coast with our camper trailer in tow.
Bilstein shocks with HD springs resulting in around 40-50mm lift. Plus the addition of airbags in the rear with 22psi with our camper attached, ball weight approx 180kg. Airbag pressure dropped to 6 psi unladened to eliminate harshness.

Car travelled level and stable.

[GrayKnight]

Hi amec

I notice that you're on the Central Coast. So am I. Who did the suspension for you?

Cheers

[old Jack]

Hi Richard,

Any competent mechanic should be able to fit a suspension kit in 3 to 4 hours with reassembled front struts .Home mechanic can do this in about 5 to 6 hours.

Reusing your old springs will require the disassembly of your front struts and his is best done by someone that has the correct equipment and experience. With 100,000kms on your original suspension I would be fitting new top mounts to the front struts rather than reusing the old mounts. Allow about 4 to 5 hours labour for reuse of front coils, new struts, new rear coils, shockers and rubber cones.

You will also require a front wheel alignment check even though you are reusing the same coils.


OJ.

[amec]

Hi amec

I notice that you're on the Central Coast. So am I. Who did the suspension for you?

Cheers

Bushskinz at Cooranbong. I purchased from them and installed myself with the help of a friend.

http://www.bushskinz4x4.com.au/

[GrayKnight]

Hi OJ,

I'm just reviewing your recommendations for my suspension upgrade, and I think I may have mislead you slightly in my original post as to the extra weight added when travelling. The rear axle weight around town is 1120kg as I said, but when travelling the weight on the rear axle will be around 350kg more - ball weight plus food etc etc. This would make the axle weight then 1470kg rather than the 1320kg which you used to recommend the Kings KCRR-23HD. Will this change your recommendation at all? Thanks.

Cheers
Richard

[old Jack]

Hi OJ,

I'm just reviewing your recommendations for my suspension upgrade, and I think I may have mislead you slightly in my original post as to the extra weight added when travelling. The rear axle weight around town is 1120kg as I said, but when travelling the weight on the rear axle will be around 350kg more - ball weight plus food etc etc. This would make the axle weight then 1470kg rather than the 1320kg which you used to recommend the Kings KCRR-23HD. Will this change your recommendation at all? Thanks.

Cheers
Richard

Hi Richard,

Have you accounted for weight transfer off the front axle and onto the rear axle that occurs when you apply towball loads. Rough guide is 40kg of front axle weight transferred to the rear axle for every 100kg of towball download, so 100kg towball load equals 140kg of rear axle load.

OJ.

[GrayKnight]

Hi Richard,

Have you accounted for weight transfer off the front axle and onto the rear axle that occurs when you apply towball loads. Rough guide is 40kg of front axle weight transferred to the rear axle for every 100kg of towball download, so 100kg towball load equals 140kg of rear axle load.

OJ.

No, I hadn't accounted for the weight transfer so add another 80kg (the towball weight will be close to 200kg) making the rear axle weight 1550kg.


Cheers
Richard

[old Jack]

No, I hadn't accounted for the weight transfer so add another 80kg (the towball weight will be close to 200kg) making the rear axle weight 1550kg.


Cheers
Richard

Hi Richard,

At 1550kg rear axle load is near the 1600kg axle load limit so this will push the King KCRR-23HD and you will lose ride height. This may not be an issue if you are keeping the factory coils on the front but if you are changing front coils then the KCRR-23HD could be a bit on the low side once you are fully loaded and hitched up. My aim would go have your car sit level or no more than 10mm lower compared to the front suspension when fully loaded and hitched up and to have a rear ride height about 40mm higher at the rear than the front when unloaded.
I will check my spring tables tomorrow and advise of projected ride heights at your estimated rear axle loads.

OJ.

[old Jack]

Hi Richard,

I have checked my spring tables and at 1550kg the following springs have the following ride heights and spring rates.
Note ; these are all theoretical numbers and based on the manufacturers supplied free heights and spring rates, and assuming a single lineal rate of progression for the change in spring rate as these are all progressive coils.

KCRR-23HD EBH 515mm Spring Rate 4.84kg/mm.
Old Man Emu 2838 EBH532mm Spring Rate 4.69kg/mm.
Dobinson C43-045 EBH535mm Spring Rate 5.7kg per mm.

The above coils may still be suitable when combined with the replacement rubber cone springs as these start assisting from EBH535mm.

https://www2.pajeroclub.com.au/forum/showthread.php?t=45233

My Lovells CRR-69EHDVR have a non lineal rate of progression so they are multistage stage progressive rate coil and were designed to my requirements by Lovells. Compared to the coils listed above these coils can carry higher loads whilst maintaining excellent ride height without excessively high spring rates when fully loaded but still provide desirable ride heights when partially loaded.
The following figures are actual axle load weights with the coils installed in the Challenger whereas the above coils are based purely on the manufacturers information supplied and the math.

CRR-69EHDVR
1190kg EBH590mm Spring Rate 4.76kg/mm.
1289kg EBH580mm Spring Rate 4.76kg/mm.
1360kg EBH570mm Spring Rate 4.76kg/mm
1490kg EBH560mm Spring Rate 4.81kg/mm.
1585kg EBH550mm Spring Rate 4.81kg/mm.
1724kg EBH540mm Spring Rate 4.92kg/mm.
1875kg EBH530mm Spring Rate 5.07kg/mm. At EBH535mm there is also has 5mm of compression on the Peddars Aeon 5899 Rubber Cone Springs.

OJ.