Progressive Rate Rear Coils

[old Jack]

Below is the calculated rear axle weights based on a linear rate of progressive spring rates for a given ride height EBH for King KCRR-35HD and the actual rear axle weights. We did a load test on Pajero 12's NW before a Simpson Crossing and it was these numbers actual test numbers that convinced him to change the HD coils over for EHD.

As you can see the actual kg are lower than the calculated under light loads but with 10mm of decrease in EBH the actual kgs are higher and the difference gets larger with every mm of coil compression.

EBH mm....Calculated kg....Actual kg
572mm..........1265kg..........1190kg
557mm..........1356kg..........1433kg
547mm..........1417kg..........1563kg
539mm......... 1464kg..........1691kg
535mm..........1495kg..........1747kg
522mm..........1574kg..........1905kg


OJ.

[Jasonmc73]

Below is the calculated rear axle weights based on a linear rate of progressive spring rates for a given ride height EBH for King KCRR-35HD and the actual rear axle weights. We did a load test on Pajero 12's NW before a Simpson Crossing and it was these numbers actual test numbers that convinced him to change the HD coils over for EHD.

As you can see the actual kg are lower than the calculated under light loads but with 10mm of decrease in EBH the actual kgs are higher and the difference gets larger with every mm of coil compression.

EBH mm....Calculated kg....Actual kg
572mm..........1265kg..........1190kg
557mm..........1356kg..........1433kg
547mm..........1417kg..........1563kg
539mm......... 1464kg..........1691kg
535mm..........1495kg..........1747kg
522mm..........1574kg..........1905kg

OJ.

Appreciated OJ,

So that would mean then after 1st stage of compression the load carrying capacity is more second stage than a slow progression looking at the two KG's given for KCRR35-HD 14.29 to 22.32kg's.
1st close together coils close up & then further apart are doing the work?
The chart there above would suggest i'm on rite track??
Between 572mm & 557mm = 15mm that spring KCRR35-HD is working soft 14kg's then stiffens 22kg's. Maybe not quite that fast but more like that?

& also what do these wights for springs mean? Is that amount of kg's to compress 1mm???

[old Jack]

Appreciated OJ,

So that would mean then after 1st stage of compression the load carrying capacity is more second stage than a slow progression looking at the two KG's given for KCRR35-HD 14.29 to 22.32kg's.
1st close together coils close up & then further apart are doing the work?
The chart there above would suggest i'm on rite track??
Between 572mm & 557mm = 15mm that spring KCRR35-HD is working soft 14kg's then stiffens 22kg's. Maybe not quite that fast but more like that?

& also what do these wights for springs mean? Is that amount of kg's to compress 1mm???

Hi Jason,

Not quite that simple, because there are 2 coils, the suspension geometry does not compress the coils evenly and there is the mechanical advantage of the IRS that changes as the coil compresses.

Even if the coil manufacturer supplied a compression vs load graph it would not translate 100% correct in real life.

I found the only way to know for sure is to do an actual load test of the vehicle with wheel scales.

OJ.

[Mundy55]

For any spring dummies out there like me this you may find this link below interesting.

I'm starting to think, Kings Springs might possibly be more the 1st graph example of progressive springs?

Quote

"This type of curve would be most likely on a spring with two very different rates – the stiff side of the spring is not compressing until the soft side has fully compressed."

If that was the case they get into higher spring rate within maybe the 1st 15 mm or 20mm of compression, which suits my thinking if it is the case in some ways.


http://automotivethinker.com/suspens...-rate-springs/

At the risk of being pedantic (again) this part of the quote: " the stiff side of the spring is not compressing until the soft side has fully compressed" is not correct. If you apply a load on the spring, both parts of the spring (ie soft rate part and stiff rate part) will compress, but the softer part will compress further than the stiff part, in the inverse of the ratio of the two spring rates. The initial effective spring rate is the combination of the two rates. Once the softer part has fully compressed, the spring rate will be that of the stiff part. So, diagram 1 should have only 2 slopes, not 3 as shown.

[Jasonmc73]

Yeah cheers Mundy

Agree with what you say & thanks for the pointers

Just observation of few have mentioned closely wound coils fairly compressed unladen static.

Like 2mm between coils

So i presume & it's only presumption after say 15mm to 20mm compression the tighter smaller wound coils have compressed, leaving no compression in that part of spring?
Therefore the higher rated coil section is doing the work is my thinking??

Noting Two Emms who has 9.46Kg to 14.5kgish springs fitted, he has 70kg's in the rear & reports ADD 100KG ball load that spring compresses further 17mmish.

So i gather it isn't the 9.46KG doing the work or anywhere near that

Noted his springs are new though.

[Two Emms]

Have been watching this thread grow with interest.

But after the last comment I had to stick my head under the back of my paj to see what the springs look like.

So in the same way that Jason has used the word "ish" a lot I can say that the top couple of coils on my springs (KCRR- 35HC) seem to be "pretty much" compressed. There may be a 1mm gap but not sure. Still about 70-80kgs on board. Looks like the "heavier" part of the spring is doing the work from here.

Still gives a nice ride though. Managed to get it out on some dirt yesterday and i'm happy. To those looking at my choice of spring, please note that i went for comfort not load carrying.Once loaded up with many kilos of camping gear it may be a very different story. I'm fine with that.

As to the comment that my springs are still new, I have done close to a thousand Ks on them so any initial sag should have occurred by now.

[Jasonmc73]

Have been watching this thread grow with interest.

But after the last comment I had to stick my head under the back of my paj to see what the springs look like.

So in the same way that Jason has used the word "ish" a lot I can say that the top couple of coils on my springs (KCRR- 35HC) seem to be "pretty much" compressed. There may be a 1mm gap but not sure. Still about 70-80kgs on board. Looks like the "heavier" part of the spring is doing the work from here.

Still gives a nice ride though. Managed to get it out on some dirt yesterday and i'm happy. To those looking at my choice of spring, please note that i went for comfort not load carrying.Once loaded up with many kilos of camping gear it may be a very different story. I'm fine with that.

As to the comment that my springs are still new, I have done close to a thousand Ks on them so any initial sag should have occurred by now.

Thanks Two Emms , watching how you get on with interest in coming months, once you've had some scope of use & k's.

[nj swb]

At the risk of being pedantic (again) this part of the quote: " the stiff side of the spring is not compressing until the soft side has fully compressed" is not correct. If you apply a load on the spring, both parts of the spring (ie soft rate part and stiff rate part) will compress, but the softer part will compress further than the stiff part, in the inverse of the ratio of the two spring rates. The initial effective spring rate is the combination of the two rates. Once the softer part has fully compressed, the spring rate will be that of the stiff part. So, diagram 1 should have only 2 slopes, not 3 as shown.

Saved me having to type it.

[Jasonmc73]

Yes i can understand what you mean, also logical, thanks for pointing that out & appreciated.

But looking at the progression of rate in these springs which is 50 to 60% give or take , I just wonder how much the second higher kg's has shifted before the lighter tighter wound 50 to 60% lighter section is compressed is all i am pondering, not exactly how accurate the graph is, just what it is suggesting representing.

I'm probably going to find out not in theory but in practise i imagine

I don't want to unhitch my camper & feel like i'm driving a tip dray at all other times, with the dash trying to land in my lap more than required & coins bouncing out of the coin slot hitting the roof when i'm not towing

I guess empty vehicle with my thinking only, example only the KCRR35-HD would be working at 14.29KG's maybe for 1st 20mmish of travel which is 25% higher than OEM then increases somewhat more suddenly than linear to a heavier 22kg's double 100%ish the original manufacturers spring thereafter in its travels.

A queston for kings, but I reckon this is possible, i'm not a clever man but along these lines.

Like bloody shoes need to try them on & see which one fits my likings the best

[old Jack]

I have had 5 different sets of rear coils in my Challenger, in order of fitting they have been;
1. Factory, linear rate, way to soft and wallowing, did not carry weight well.
2. King KCRS-23, progressive rate, great improvement over factory, carried weights to 250kg well but once at 300kg suffered too much lose of ride height.
3. Lovells CR69-HD, linear rate, disappointing did not carry weight above 300kg well but we're OK up to 300kg. Loss of ride height and bottomed out easily. KCRS-23 was better.
4. Lovells CR69-EHD this was a custom linear rate coil that rode too high and too hard, lacked flexibility so it would unseat from lower coil pad at full droop with long travel Bilstein shockers.
5. Lovells CR69-EHDVR, custom progressive rate coil, suited for minimum of 200kg minimum rear load and up to 500kg/600kg expedition loads. This coil that has been fitted for 120,000km of the 165,000kms travelled over the last 9 years. Bilstein shockers struggled to control the rebound of these coils so Dobinson MT/IMS shockers fitted 40,000kms ago and they can control this coil.

So having had both linear and progressive rate coils of different spring rates, I have been the happiest with progressive rate coils.

OJ.

[Jasonmc73]

Thanks Jack

I must say my interest which is quite high on the topic of springs due to it being something i eventually soon have to do far exceeds my knowledge in any way shape or form, but we all start somewhere

I would love Two Emms to fit the KCRR35-HD's for a lap & compare at lighter 80kg loads & no load throw in heavy load comparison as well

If the KCRR35-HC lighter 9.64kg coils were compressed & spring rate was now heading towards 15kg's spring rate & the KCRR35-HD's lighter rate of 14.29KG's was still capturung the job for longer not compressed unless major wooptie doo's he can let me know how the differing options feel

In easy going although obviously stiffer might be more the rebound strength & tougher spring to flog shocks much fatser , lighter spring 9kg being compressed most of its life under the vehicles weight or light loads, but less rebound from the overall spring

At axle capacity or above noted Kiwi1973 managed to snap his KCRR35-HD with airbag failure from memory

The KCRR35 PaulMcG mentions fealt firm be interesting to know how its progression in real life 11.7 to 17.86kg's actually feels to say a spring KCRR35-HD thats first rate is 14.26kg's which should hold unladen vehicle bit better in first rate progression/ first winds doing work for longer time in travel length

Reason i ponder that is PaulMcG has mentioned first few winds KCRR35 11.7kg's are pretty much compressed therefore possibly working towards 17.86Kgs in actual operation

One thing i have worked out is they'll all definately perform differently putting them through a range of applications in practice rather than just theory i have no doubts & some of the outcomes could leave me scratching my head if i had the chance to try a few against one in other

[Two Emms]

I would love Two Emms to fit the KCRR35-HD's for a lap & compare at lighter 80kg loads & no load throw in heavy load comparison as well

You are on the money here. Real world comparison is the only real way to determine what particular springs do. It's also near impossible. Honest, detailed reviews like folks post here, coupled with OJs data on ride heights (Thanks Jack ) do help with spring choices a LOT!

There's so many variables involved in spring selection. Spring rates, constant vehicle load, maximum loads, vehicle accessories, terrain, towball weights, passenger numbers etc etc.

Add to this the drivers perception of what constitutes a "comfortable" ride or "good handling" and accurate selection seems close to impossible

[Mundy55]

.......So i presume & it's only presumption after say 15mm to 20mm compression the tighter smaller wound coils have compressed, leaving no compression in that part of spring?
Therefore the higher rated coil section is doing the work is my thinking??......

The short answer is yes, but the amount it compresses before the soft part fully compresses depends on the coil separation distance and the number of coils. Theoretically (but not done in practice) you could design a spring with the stiff part fully compressing before the soft part if the length of the stiff part was short and the difference between the two rates was not great.

If there's only a mm or two between the coils in the soft part in normal static condition, I don't see why you'd bother with the progressive springs as you'd be hitting full compression over every bump, particularly with even a small extra load. If there's a reasonable space between the coils in the soft part, then when loaded the rear will drop much more with the soft rate before the stiffer rate becomes effective. That's why, for me, air bags are the answer if you have large varibility between day to day, touring and fully laden loading. You can achieve a different spring rate to match the loading before any compression.

But hey, you can't argue with success and OJ has tried lots of springs and has reached a compromise that suits his vehicle and loading differences.

[Jasonmc73]

Hi Mundy

Thanks mate cheers, i'm refering to Kings springs & the way members are reporting the compression travel of the progression & PaulMcG's opening post to thread regarding what Kings advised in convo.

Personally i have been researching airbags & they are about 90% required as far as i can see for my application.

The bulk weight is in the camper trailer.

The vehicle carry's 4 people, back seat 8 year old & 11 year old girls.

I may fit Ocam roof rack the only reason is to swing a decent awning off, trying to work out a way to avoid it though but i want something decent to anchor awning too.

I spent couple weeks in NSW recently, with ute, camping about, in the back of ute, rubbish to throw at next stop, pack of water bottles & box of beer + clothes bags go in there not in trailer.

The point being weight mostly at this stage of life i tow bulk weight, then I unhitch it.

So i have two requirements at this stage in life, hitched with weight to ball & unhitched.

Reading Airbag mans info as i have absolutley no idea they explain airbags as a helper in conjuction with the appropriate spring, airbag is the "helper".
To me that's what i need, i need the airbag to "help" the LIFTED spring i select when hitched & when i'm unhitched i require the spring not to be that harsh it's bouncing my coins up too the roof
& my dash is trying to land in my lap.

That's why I have an interest in TwoEmms choice, lifted, rebounds probably lighter it's a medium weight theory rebound unhitched yet 15kg spring rate under load.

But then it strikes me i just wonder how it actually performs compared to the HD version in real life with low loads as HD does have stiffer 14kg 1st progression & buggar fitting airbags

Hence my suggestion can TwoEmms try HD's & let me know

[Two Emms]

Hence my suggestion can TwoEmms try HD's & let me know

Sure, happy to.

Just post me a pair of HD springs, a loaded fuel card to allow a few thousand k's and get my boss to give me a couple of months off work

Seriously though, I fully intend posting a review in a few months. Hopefully I can include various heights and comfort/handling reports at assorted axle weights