Rear dampeners (shock absorbers)

[Ent]

Followed up a lead from Oztech on a dampener tuning place. Assuming that the result is good the price is fair, but still not cheap. You are looking at around $400 a pair for re-valving, plus a re-build. Tempted to just buy new ones to avoid the hassle of removing the old ones, finding a temporary replacement, then re-installing the rebuilt ones.

The pricing of re-valving suggest why "one size fits all" valving is used. When you stop to think there is a huge difference in spring rate from the standard spring to the heavy duty one so what valving should the off the shelf dampener use? It by definition would have to be a compromise.

[Ent]

Rang King Shocks Australia. Price was not mentioned as if you had to ask you probably not going to buy. Ok, back to measurements, open, closed, and max diameter. OJ, time for you to shine

They normally build 2.5" dampeners, but even though they believe 2" dampeners are for motorbikes, they can do them for vehicles. I am almost certain that 2.5" will be too big in the diameter. Dam you Mitsubishi once again.

The only real issue is they may not have a good closed to open ratio due to design and construction. I think that the standard shock is 305mm closed which caused the engineer to blink as that is a very short length. I think maximum length will be only 485mm with their design. Yeap, this will be fun The reservoir can be mounted anywhere which is a bonus. But then where is the best place? Tasmania is a long way from them as well so not a case of dropping in the vehicle while they scratch their heads and see how things will work.

The biggest downside is they have not done a Challenger, so a crash test dummy again if I go this approach.

They have supreme confidence that their product is by far the best, but my experience with customised products is it is a hard and expensive road to go down. DooSo is an example IMHO of a very well sorted vehicle, but boy has this created some heart and headaches. It appears at every turn you wind up fighting some design decision made by a Mitsubishi engineer that cuts off numerous options forcing you down a narrow path.

So OJ, give me the numbers and lets start crunching them. Is the Bilstein B46 335 closed and 515mm open? The standard 305 closed and 495mm open? And is this centre to centre or absolute measurements.

So two options, use Bilstien B46-1333 valved for the heavier springs, or customised dampeners that supposedly make the Drummond ones look little underdone.

[Legs11]

2.5" will be too big in the diameter. Dam you Mitsubishi once again.

What exactly would a bigger bodied shock foul on? Is it possible to modify the car to fit your ideal damper?

[Ent]

From memory I think it is the sway bar. Though in general space is pretty tight in that area. I think this just a case of accepting that Mitsubishi rather have not considered big bore dampeners needed.

The Challenger has proven to be a challenging vehicle to develop. In many ways we are lucky a lot of quality bits can be had. But you have to hunt around. Definitely not a one shop fitout. You can put in a 112 litre tank plus 135 litre auxiliary tank and two spare tyres thanks to Kaymar. Thanks to Kings amoungst others you have a good range of springs to carry the load, or custom made ones. The front being a Triton means plenty of quality options there as well. But occasionally you strike an issue that without major works you can not upgrade. For most users the 50mm range of rear dampeners is acceptable. But for heavily laden vehicles doing things like the Simpson, Canning Stock route, etc they become marginal. But how many Challengers do these type of trips, maybe a hundred at most.

80,000kms out of a set of rear dampeners is not too bad so with a rebuild and re-valving the Bilsteins should be acceptable. Be nice to run Koni 90 series. Better still a racing quality dampener.

It would not surprise me that most Challengers over 100,000kms have degraded dampeners along with many other vehicles as dampeners tend not to be replaced. Very few people even on this forum would be running Drummond front end due to the cost despite the huge advantages it offers compared to fix spring solutions. So hard to expect some exotic rear dampener solution to have been developed. Had rather hope someone had done so.

in Tassie you just do not have easy access to drop a vehicle into a place like King or Drummond to have them figure out solutions. Kings Springs did a remarkable job developing custom springs by email. Had I been able to drop the vehicle into them it would have been a lot easier. Freighting rear springs to Queensland so they had a baseline confirmed very few people are after the level of precision that I aim for.

Most people may not know that the aftermarket springs they buy from most places were developed purely from paper based research. Heck, even the genuine ones are straight out of Mitsubishi's parts bin from earlier Pajeros. The common belief is lot of research and development went into suspension but the reality is the Challenger springs are no more unique to the vehicle than the headlamp globes.

No better example is the dampeners flog with springs. Ford with the BA had seventeen different setups with springs match to dampeners but we have dampeners being flogged that could go on the factory 14mm wire to 18mm plus heavy duty springs with zero change in tuning. Bilstein and Koni have the ability to be re-valved but at around $400 a pair this is rarely done. Handling and ride could be dramatically improved by correct tunning. But this takes skill, much easier to flog one standard setting and claim that the flaxen golden headed virgins putting them together are trained by the gods.

Familiar with suspension and the law I now recognise that an awful lot of 4x4 come out of tyre and suspensions places that could be yellow stickered. Annoyingly to me, a competent suspension specialist could turn out truely impressive results but such people appear rare. In a way we are to blame as often we chase price and fool ourselves that the brand name is king, instead of paying the large premiums to get true experts correctly tune the suspension. The difference between the indifferently handling HJ Holden Kingswood and nicely balanced HZ was one engineer that understood suspension.

[old Jack]

Hi Ent,

Notes I have on file are;
Factory shockers are 315mm compressed and 500mm extended centre eye to centre eye.
Bilsteins are 350mm compressed and 535mm extended, measured centre eye to centre eye.
If I was building a custom shocker then 525mm would be my target because at 535mm brake lines are firm and the angle of the lower spring pad is too great for positive coil retention especially if the coils have 17mm or 18mm wire diameter.

My rear Bilsteins have done over 80,000kms now, the firsts 12,000kms was at GVM+150kgs on a Kimberley trip with only HD Lovells coils. These coils where too soft and low so I ended up packing the void inside the coils with tennis balls to get us home and take the load off the shocker. Rear coils were replaced with custom EHDVR Lovells coils which carry the weight much better and the only time I feel the Bisteins are under dampened is on continuous whoopty doo's and the suspension is working at full travel for a continuos period. No problems with under dampening in the rebound on high speed corrugated roads.

From memory 46mm diameter is the comfortable max diameter but 50mm maybe possible if all bushes on shockers and sway bar are in good condition.

You could try Supashock, last I checked was about 12 months ago when they were developing their 4wd shockers.

OJ.

[Quinno]

The ones I know extended length, KYB and Tough Dog are 517mm extended, my old Ultimate Suspension was 525mm and, as above, Bilstein 535mm. I agree with OJ that 525mm is spot on, maybe 530 max. A lot of springs are 400mm free length, but for the longer shock of 525mm or more I believe 410mm free length spring is better. I don't really pay much attention to what they call +150kg or HD etc. as I want to know lb/sq in, of which my King Spring is progressive 170-225lb/sq in (from memory I think). Would like to know others because not many manufacturers will hand over technical data.

[old Jack]

Your on the money Quinno!
I have been collecting as much info as I can on Challenger springs and have been working on the math formula so if I have the spring rates, free heights, steel grade used and heat treatment, then I can calculate the expected ride height at given rear axle weights. Linear rate coils are easier to do the math on but progressive rate coils are a much more complex calculation. What we really need is spring makers to provide load to spring compression graphs but nobody does these. I have all the ARB specs and most of the King spring specs (ARB publish spring rates and free lengths in their export OME data and Kings have been really good at providing me with info by request.) Once I have it worked out I will contact Lovells, Dobinsons and other suppliers for specifications.

My formulas are very much work inprogress and I am almost ready with rear spring calculator on ARB and King linear rate rear coils, however the IFS on the front suspension and progressive rate on the rear adds further complications to the calculations.

OJ.

[Quinno]

Thanks OJ. I keep doing my research, because while I am happy with King Spring and KYB Skorched, it is still a bit harsh on fast small bumps on road (terrible roads are common in south west Victoria). At least it's better than the Lovell and Ultimate combo I did have. That was so hard it would jump the car sideways on bumps. Even ended in the ditch a few times at mere 20km/hr on gravel roads.

[old Jack]

Thanks OJ. I keep doing my research, because while I am happy with King Spring and KYB Skorched, it is still a bit harsh on fast small bumps on road (terrible roads are common in south west Victoria). At least it's better than the Lovell and Ultimate combo I did have. That was so hard it would jump the car sideways on bumps. Even ended in the ditch a few times at mere 20km/hr on gravel roads.

Hi Quinno, are you still running a Gen2 or a Challenger PA or PB/PC?
Either way the 3 link, coil, live axle rear suspension is the same but is the front coilover or torsion bar?

OJ.

[Quinno]

Still got NH Pajero and PB Challenger. The NH is torsion front and i haven't yet put rear springs across onto Challenger for trial and error. I can't recall part number of the Tough Dog spring on my NH but it's 420mm free length. At a guess it might be 200lb/sq in.

[Giddyup]

Thanks OJ. I keep doing my research, because while I am happy with King Spring and KYB Skorched, it is still a bit harsh on fast small bumps on road (terrible roads are common in south west Victoria). At least it's better than the Lovell and Ultimate combo I did have. That was so hard it would jump the car sideways on bumps. Even ended in the ditch a few times at mere 20km/hr on gravel roads.

Funny you mention that. I put in some dobinson mrr shocks about 20 000km ago and they feel exactly like you described. Really harsh on the small fast compression stuff. Hard to drive on dirt and corrugations without dropping tyre pressures. Particularly when the car is empty. I don't run a lot of weight even when loaded with gear, so maybe the valving is more suited to heavier cars. I don't think I'd recommend them to anyone.

[Ent]

Hi OJ

Thanks for that info.

Very happy with my extra heavy duty rear setup as far as springs go. Indeed, it is much more complaint with a lighter load than I could have ever hope for. The custom springs use the variable wire diameter to get good free height (around 420mm) and not be overly tall with a lighter load. Their scragged height is less than the bumpstops so they do not bind, hence very gentle impacts on a hard hit. They matched in with the Pedder 80 series rubber cones are near perfect for heavy loads. Indeed, the shock loadings would be likely a lot less than a lighter vehicle running standard suspension, or one where the springs bind out. I got no harsh thumps despite stuffing up my speeds a few times.

Chatted to Kings asking what spring rate I should valve for and the answer was very quick (as usual, indeed very impressed by Kings) as in the 250-300lb range. No wonder the standard valving in the Bilsteins feels underdone as it is likely in the 180-220 range.

On roughness of ride that is a factor of damper design. A great dampener should allow for the rapid compression of the shock and then controlled release. The ideal explained to be a multiple winner of Targa was the vehicle should feel that it is not increasing in height. Over control rebound will result in a vehicle getting lower after each bump in a series. Lack of control means the vehicle starts feeling taller and bouncing. Over controlled compression will give a harsh ride as the dampener, not the spring, is taking the impact.

Ok, course higher frequency corrugations are a different beast to long travel "whoopty doo's". On corrugations the Bilsteins fare much better than the latter. On the Simpson DooSo did not enjoy the triple humped dunes. Ok on the first "hollow" but by number three he was almost bouncing taking the rear wheels off the ground. After that treatment he lost the fine control when unloaded so he lurches a bit on cornering. Not excessively, but no where near refined as when the springs were lighter or newer. At 600mm rear EBH DooSo feels very tall and needs a good dampener to control that height.

When shelling out money for dampeners you are paying for their ability to resist heat and valving that attempts to workout what to do. The so called progressive dampening is designed to valve differently for smaller high frequency impacts to large slower impacts. Chatting to more than a few suspension experts and found Bilsteins are the leaders in progressive valving. Koni is better at looking after the oil to stop it frothing, reason dampeners fade.

Extreme aftermarket dampeners like DMS use high quality aluminium and remote oil reservoirs to dissipate the heat buildup. The bigger the bore (assuming the rod size does not increase) means greater oil capacity and is an approach used by the Koni 88/90 series and Tough Dog big bore dampeners. Trouble is clearance. A remote reservoir dampener can fit assuming it can find a place. Also, extreme dampeners can be adjusted, generally on rebound but some on compression. In many the two are linked, but in the ultra high end either can be adjusted independently. Only trouble with that is you need really to be a top class racing driver to quickly do this or a lot of kilometres of trial by error.

So looks like the Bilsteins did a reasonable job given they are 80,000kms old and dealing with a spring rate that unlikely was considered when valved.

Though I am tempted by the King approach as the DMS have demonstrated price is long forgotten and quality is remembered. They just do not fade out and feel as good now 80,000kms on as new. The trouble is i am just too far away to be a crash test dummy. If they had a pre-packed solution then I would go for it.

Cheers

[old Jack]

Hi Giddy,

What tyre pressures, what brand/model and size tyres are you running?

OJ.

[Ent]

I have to chuckle at times. Checked out if Dobinsons MRR were available for a Challenger. Was told no they are only intended for real 4x4s. Which strangely they consider a Triton to be a real 4x4, and the original Pajero as well.

What is a Challenger? Err? Triton chassis back to the rear door, then rear end following the design of the first coil sprung Pajeros to the point the springs are the same. Comes standard with rear diff lock might be a hint as well. Also, the PB/PC was targeted at countries like India, Russia, Africa and rather surprisingly made it to Australia. Yeap, definitely a shopping trolley to pick up the groceries in Siberia

Those pesky series one Landrovers must be shopping trolleys as well as they used the motor out of a a Rover car which we all know are luxury town cars. Yeap, Toyotas built the Snowy, err maybe one or two were used the vast bulk of 4x4s were Landrover. Heck, never let facts stand in the way of prejudice

[Giddyup]

Hi Giddy,

What tyre pressures, what brand/model and size tyres are you running?

OJ.

Lt265/70r16 toyo opat ii. Normally around 40psi. Light truck tyre and highish pressure isn't going to help the ride. Pretty sure the rear springs are made for more weight too. It's ok with ~150kg in the back, but empty is too firm. Though I think it's probably more about the valving, it has pretty good control on the larger dips with slower compression.