Oztec suspension....tell me more

[ilikeachallenge]

Hi all,
After reading some positive comments by OJ and LR in another thread I have started looking at Oztec suspension as I've added quite a lot of weight to the PC and am still running oem suspension.Conveniently they have a local distributor and I will take the care in for them to assess soon.
The great suspension upgrade debate becomes more confusing the more you read.The vehicle is used as a tourer,tow rig for the camper trailer and wood trailer and also does quite a lot of local vic high country,steep greasy slippery type work.
Surprisingly it handles it all ok but could be sooo much better.
I need it to be well behaved on road and as supple as possible of road when climbing etc and not be lifting wheels.
So what is collectively known about the oztec product and what recommendations do people have given my set up as listed in my signature.
Steel TJM bar and winch,Full set of 3mm ARB bash plates,rasslar rock sliders plus basic storage system and constant rear load of approximately 40 kg in recovery gear etc
I don't carry the fridge or dual battery daily but they are on board for longer trips.

Cheers

[old Jack]

Yes the great suspension decision dilemma, what ever you do it will be an improvement on a worn factory suspension as long as you do not go cheap and nasty or too high.
Factory ride heights are 542mm front and 552mm rear, max lift on the front is 30mm to 35mm and max lift on the rear is 35mm to 40mm with an auto trans, and 40mm to 50mm with a manual trans.

A OzTec/King combo is very good value at around $1000 for parts then $400 to $500 to fit, this is a good upgrade for recreational 4wds that do not travel really heavy, tow heavy or travel for extended periods on badly corrugated roads at GVM or greater weights. Add a few hundred more to the budget and this will get you a Lovells/TJM /ARB/Ultimate/ Peddars/EFS/Dobinson etc etc but are these systems that much better and worth it or are you just paying for the brand name and national support and warranty? Add a few hundred more and you can get a Bistein/King combo this will give you a "performance suspension" this may or not be to an individual's liking in regards to comfort but the on road handing will be very responsive. If you are travelling very heavy and for extended periods on badly corrugated roads then if you add a few hundred more and you can upgrade shockers and struts to either Koni or Dobinson MT. Add a few hundred more and you can get Dobinson MRR or Drummond RR.

Regardless of which system you choose the best upgrade you can do is to replace the factory rubber spring assist cones with Peddars 5899, at $125 a pair these protect your rear coils and prevent harsh bottoming out of the rear coils no matter what coils you have fitted and are more reliable than airbags.

With your requirement to run almost empty and then loaded up and towing means you really need progressive rate rear coils.

There is no perfect one size fits all suspension upgrade and what I like and expect may well be different from the next person. You will find polarised opinions both for and against all brand. If you can drive other people's Challengers then this will give you an idea of what you like or dislike.

From my experience most suppliers tend to recommend front coils that are too high and too firm and rear coils that are too low and too soft. Struts and shockers that are too hard on compression and too soft on rebound. Make it very clear what ride heights you are prepared to accept, the level of comfort vs handling and the weight carrying capacity of the rear. Ask if there are any charges for changing the coils over if you are unhappy with the results and how many changes they will do for the included price.

OJ.

[littleriver]

x2 on the above ... pretty happy with our Oztecs front and rear with Kings ... (within GVM) ...

put another variable I just chanced upon - "EFS" $1156 + $200 to fit - 30mm lift HD front 95kg and HD rear 200kg

OJ" have you any info also on these ?

https://www.mccdandenong.com.au/index.php?route=product/product&product_id=19437&search=mitsubishi+challenger

...

[old Jack]

x2 on the above ... pretty happy with our Oztecs front and rear with Kings ... (within GVM) ...

put another variable I just chanced upon - "EFS" $1156 + $200 to fit - 30mm lift HD front 95kg and HD rear 200kg

OJ" have you any info also on these ?

https://www.mccdandenong.com.au/index.php?route=product/product&product_id=19437&search=mitsubishi+challenger

...

Sorry no info on EFS, mixed reports on Internet just like every other suspension kit, found this thread;

https://www2.pajeroclub.com.au/forum/showthread.php?t=50756&page=2

OJ

[littleriver]

geeze a quick search came up with these on special ...

https://www.ebay.com.au/itm/EFS-Lift-kit-Shocks-Coil-Springs-For-MITSUBISHI-CHALLENGER-2010-ON-30mm-Lift-/132021168223

All 4 Adventure still rave about them

...

[old Jack]

geeze a quick search came up with these on special ...

https://www.ebay.com.au/itm/EFS-Lift-kit-Shocks-Coil-Springs-For-MITSUBISHI-CHALLENGER-2010-ON-30mm-Lift-/132021168223

All 4 Adventure still rave about them

...

Or this,

http://vi.raptor.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=232038078464&category=33585&pm=1&ds=0&t=1521010323000&ver=0

Keep in mind these deals are for unassembled struts so there is extra labour involved swapping the top hat mounts over.
Trouble with All 4 Adventure endorsement is EFS is a sponsor and they are not driving Challengers!

OJ.

[littleriver]

Or this,

http://vi.raptor.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=232038078464&category=33585&pm=1&ds=0&t=1521010323000&ver=0

Keep in mind these deals are for unassembled struts so there is extra labour involved swapping the top hat mounts over.
Trouble with All 4 Adventure endorsement is EFS is a sponsor and they are not driving Challengers!

OJ.

well said ...



...

[ilikeachallenge]

Yes the great suspension decision dilemma, what ever you do it will be an improvement on a worn factory suspension as long as you do not go cheap and nasty or too high.
Factory ride heights are 542mm front and 552mm rear, max lift on the front is 30mm to 35mm and max lift on the rear is 35mm to 40mm with an auto trans and 40mm to 50mm with a manual trans.

A OzTec/King combo is very good value at around $1000 for parts then $400 to $500 to fit, this is a good upgrade for recreational 4wds that do not travel really heavy, tow heavy or travel for extended periods on badly corrugated roads at GVM or greater weights. Add a few hundred more to the budget and this will get you a Lovells/TJM /ARB/Ultimate/ Peddars/EFS/Dobinson etc etc but are these systems that much better and worth it or are you just paying for the brand name and national support and warranty? Add a few hundred more and you can get a Bistein/King combo this will give you a "performance suspension" this may or not be to an individual's liking in regards to comfort but the on road handing will be very responsive. If you are travelling very heavy and for extended periods on badly corrugated roads then if you add a few hundred more and you can upgrade shockers and struts to either Koni or Dobinson MT. Add a few hundred more and you can get Dobinson MRR or Drummond RR.

Regardless of which system you choose the best upgrade you can do is to replace the factory rubber spring assist cones with Peddars 5899, at $125 a pair these protect your rear coils and prevent harsh bottoming out of the rear coils not matter what coils you have fitted and are more reliable than airbags.

With your requirement to run almost empty and then loaded up and towing means you really need progressive rate rear coils.

There is no perfect one size fits all suspension upgrade and what I like and expect may well be different from the next person. You will find polarised opinions both for and against all brand. If you can drive other people's Challengers then this will give you an idea of what you like or dislike.

From my experience most suppliers tend to recommend front coils that are too high and too firm and rear coils that are too low and too soft. Struts and shockers that are too hard on compression and too soft on rebound. Make it very clear what ride heights you are prepared to accept, the level of comfort vs handling and the weight carrying capacity of the rear. Ask if there are any charges for changing the coils over if you are unhappy with the results and how many changes they will do for the included price.

OJ.

Hi all and thanks for the feedback.As always OJ to the rescue.its guys like you and a few other regulars who are invaluable to this forum and what the rest of get out of it.Thankyou.
Right so I finally had the time to get to my local Oztec supplier for an asssessment and quote for the PC.
For the Oztec front struts part number 54101,Kings front coils p/nKCFR-55H,rear shock p/n60090, and rear spring KCRS-23 supplied and fitted I was quoted $1510 incl gst
From your earlier feedback OJ this is in the ballpark.
I need this car to handle well on road in a variety of situations and loads but also be supple enough to do its thing when crawling in steep country.
If I'm not happy they will swap out the springs at their cost for a different spring rate.
Any feedback/thoughts are appreciated.

[old Jack]

Hi all and thanks for the feedback.As always OJ to the rescue.its guys like you and a few other regulars who are invaluable to this forum and what the rest of get out of it.Thankyou.
Right so I finally had the time to get to my local Oztec supplier for an asssessment and quote for the PC.
For the Oztec front struts part number 54101,Kings front coils p/nKCFR-55H,rear shock p/n60090, and rear spring KCRS-23 supplied and fitted I was quoted $1510 incl gst
From your earlier feedback OJ this is in the ballpark.
I need this car to handle well on road in a variety of situations and loads but also be supple enough to do its thing when crawling in steep country.
If I'm not happy they will swap out the springs at their cost for a different spring rate.
Any feedback/thoughts are appreciated.

Just looking at the spring part numbers I suspect that the fronts could be too hard and high and the rear too soft and low for the weight of your fitted accessories.

Front coils options;
KCFR-55H is a mid range coil that with 1202kg front axle load give about EBH 570mm, which is the maximum EBH you should be looking at to maintain legal wheel travel. At 1270kg (1260kg is max axle limit) for a EBH560mm.
KCFR-55 is a slightly lower coil that has the same spring rate as the 55H so 1136kg for EBH570mm and 1202kg for EBH560mm.

Rear coil options;
KCRS-23 is the lightest coil and for a rear axle weight of 780kg you could expect a EBH of 580mm and at 963kg EBH550mm.
KCRR-23 is the same spring rate but 15mm higher in free length so for a rear axle weight of 907kg you can expect a EBH of 580mm and at 1089kg EBH550mm and at 963kg EBH550mm.
KCRR-23HD is the same free length as the KCRR23 but a higher spring rate so for a rear axle weight of 1045kg you can expect a EBH of 580mm and at 1265kg EBH550mm.

Best if you can get to a weighbridge and measure your front and rear axle weights with full fuel and just the driver. This will give you a better idea of what coil to choose, also estimate the extra front seat, rear seat, rear cargo area and towball loads. This way you can see what your daily ride heights (EBH) and loaded ride heights are likely to be.

From my experience most resellers of suspensions go too high and hard on the front and too low and soft at the rear, then try to sell you airbags to fix the rear suspension.

Whichever coils you select, do yourself a big favour and fit Peddars 5899 rear cone assist springs whilst the rear coils are out, these protect the rear suspension from bottoming out when fully loaded and/or towing when you get deep coil compression. Dozens of Challenger and Pajero Sport owners have fitted these and I have not had a single negative feedback, only glowing reports.

All the above axle weights and EBH's are based on Manufacturers spring data and these can vary by 5% to 10% so there is still a degree of hit and miss with coil selection. All I can do is calculate the relative difference between coils and offer a comparison.

OJ.

[ilikeachallenge]

Thanks OJ How do you measure the front and rear axle loads individually on a weigh bridge and get an accurate outcome?There are a few public weigh bridges locally but they are all a full bridge that you drive the vehicle onto and get an overall weight.
Interested in your feedback re the method the local supplier used to calculate rear axle load.They lifted the rear of the PC with their forklift until the rear was off the ground and then lowered it until the tyres touched the ground and then checked the scales on the fork to get an unsprung weight of the rear.Your thoughts?For the front they just looked at what I have fitted and went with what the Oztec parts book recommend.I hate having to do things twice and don't want to balls this up.

[old Jack]

If you drive onto the weigh bridge so your front wheels are on it and the rear wheels are just off it, record the weight, drive onto the weigh bridge so all wheels are on it and record the weight, drive off the weigh bridge until your front wheels are just off it and record the weight. In theory the combined front and rear axle weights should be the same as the total weight but if not then you can calculate a percentage correction.

I measured unsprung weight by removing the suspension then with the body weight supported I weighed the unsprung weight. Not sure how accurate the forklift method is, did they tell you the unsprung weight?

Most suspension places will only list a few coil part number for each brand of coil but most times there are at least 3,4,5 or even 6 coils that are available from the spring manufacturer, different free lengths and spring rates determine the ride heights, weight carrying capacity and comfort level.

OJ.

[ilikeachallenge]

Thanks OJ
So obvious re the weighbridge now I feel a bit silly.I am hoping to get to this job this afternoon and will report back.Yes they did mention the weight which was 500kg measured with an anolouge forklift weight gauge which from industry experience I can tell you are not a precise or very accurate bit of kit.
I asked about his method of calculation when he was weighing the car and he said he lifts the rear until it is off the ground and then lowers it to a point where the wheels just touch the ground but springs are still at full extension and the forklift is taking the body weight and then takes his reading.Thoughts?
Update OK so I made it to the weighbridge this afternoon and came up with this.
There are 2 public weighbridges locally so I went to both and interestingly got the same readings.Front 1320kg Whole car and driver2380 kg Rear 1060 kg.
I also measured EBH and got front readings of 508 mm and rear of 530mm.
Any feedback you are able to give is appreciated.
Edit I just re read your previous feedback OJ and these weights are not with a full fuel load.The low fuel light came on just after doing these weights.

[old Jack]

Thanks OJ
So obvious re the weighbridge now I feel a bit silly.I am hoping to get to this job this afternoon and will report back.Yes they did mention the weight which was 500kg measured with an anolouge forklift weight gauge which from industry experience I can tell you are not a precise or very accurate bit of kit some times.
I asked about his method of calculation when he was weighing the car and he said he lifts the rear until it is off the ground and then lowers it to a point where the springs are still at full extension and the forklift is taking the weight and then takes his reading.Thoughts?

From my previuos post;


"Not sure how accurate the forklift method is, did they tell you the unsprung weight?"


A set of 4x wheel scales is only about $4K so it surprises me that most "Suspension Specialist" do not have them, to me it would be like using a mechanic that didn't have an electronic engine ECU computer!



OJ.

[old Jack]

Thanks OJ

Update OK so I made it to the weighbridge this afternoon and came up with this.
There are 2 public weighbridges locally so I went to both and interestingly got the same readings.Front 1320kg Whole car and driver2380 kg Rear 1060 kg.
I also measured EBH and got front readings of 508 mm and rear of 530mm.
Any feedback you are able to give is appreciated.
Edit I just re read your previous feedback OJ and these weights are not with a full fuel load.The low fuel light came on just after doing these weights.

Thanks for taking time to measure and post your EBH's and weights, these have been great as they have helped validate my formulas and confirm the calculations I had for factory suspension.


Your front axle weight at 1320 kg is heavy (max axle load is 1260kg), but this is due to the steel bar, winch, underbody plates and aux battery, a very common problem with the Challenger and Triton.
Your EBH of 508mm with factory coils is 34mm lower than factory spec and my numbers calculated an EBH of 517mm +/-10mm so by the time we put some spring sag due to overloading then my numbers are good.
KCFR-55H with 1320kg front axle load my numbers indicate an EBH of 552mm +/- 10mm so this is a nice EBH, going up to the KCFR-55HD should result in an EBH of 575mm +/- 10mm which is too high in my opinion, and could result in unwanted ASC/BS/TC activations and reduced droop travel effecting handling on and off road.


Your rear axle weight at 1060kg seems light since you have drawers and fridge listed in your signature so these could be empty and even the fridge removed (max axle load is 1600kg). Tank full of diesel is about 60 kg and this weight is mainly taken by the rear suspension.
Your EBH of 530mm with factory coils is 20mm lower than factory spec and is close to my calculations of 522mm +/- 15mm, these are a progressive rate coils and I can only calculate the transition of the spring rate change lineally where in most cases the spring rate change is not lineal but without actually doing physical compression tests it is the best I can do until I get enough feedback from those that have fitted aftermarket progressive rate coils and have done multiple weighs and EBH measures at different loads.

KCRS-23 with 1060kg rear axle load, my numbers indicate an EBH of 534mm +/-15mm, from reports I have been sent by other forum members is King coils tend to be on the high side of my numbers. I think the KCRS-23 will be too light and low especially once you put a few hundred kilios or so extra in the back when you load up. The difference between the front and rear EBH is the rake angle, factory rake angle is 10mm but I have seen up to 30mm. So with the KCFR-55H coils you should be looking at 560mm to 590mm. Note at 590mm rear EBH if you have an automatic you can get a very slight rear driveline vibration at 35-45 kph so 580-585mm is a sensible target.
KCRR-23 at 1060kg should be EBH 560mm +/- 15mm so this is the lightest and lowest coil to consider but it does not give you a lot of weight carrying capacity and minimal towball download capacity. If you travel light and do not tow then this could be the coil to use.

KCRR-23HD at 1060kg should be EBH 580mm+/- 15mm so this is right at the upper limit of the target EBH of 580-585mm if you have an automatic, manual trans can go to 600mm without driveline vibration. Driveline vibration can be fixed by fitting offset bushes to the trailing arms to change the diff to tail shaft angle. If you choose this coil then you really need to have an extra 100kg in the rear cargo area to reduce the rear EBH on a daily basis if you do not fit offset trailing arm bushes. This coil is ideal if you are towing and loaded in the rear cargo area.


All my calculations are based on data supplied by Kings and they tell me there is a 5-7% variance in spring rates as a normal manufacturing tolerance.



Please let me know what coil part numbers you end up fitting, your weights and EBH's so I can use these real life numbers to correct my calculations.


OJ.

[ilikeachallenge]

Hi OJ and thanks again for the feedback. Just to clarify some things for your ongoing calculations as my signature may have misled you a little.
Firstly my dual battery and fridge are only fitted to the car for longer trips away, the rest of their time they do duty in my work vehicle. I also do not have a fridge slide but a custom tray I made from black form ply that takes the place of the single seat behind the drivers seat and this is where the fridge is fitted when onboard. Also the dual battery is only fitted to the rear cargo area of the car on trips so these things may account for the light rear end weights you mentioned. Constant rear load consists of a false floor made from the same black 17mm form ply and covers the whole rear floor area and would weigh approx. 15-18 kgs.My storage unit is custom made from form ply also(are you seeing a theme here, I like form ply)and sits between the rear wheel arches over the axle and measures 350mmx350mmx1000mm.This carry's approximately 45 kg +- of recovery and emergency gear at all times.I estimate the empty box at 13-15 kg +-
If you think it worthwhile I can easily do another weigh in with a full fuel load to double check I recorded all the weights correctly as the weighbridge is nearby.
I would like to lift the car as much as possible within reason while still retaining reliable droop etc and on road manners.What sort of cost and potential issues may be expected fitting offset trailing arm bushes if required.Thanks again OJ and I look forward to your valued feedback.