Ten ply on caravans and campers

Submitted: Saturday, May 04, 2013 at 20:13
ThreadID: 102019 Views:4946 Replies:8 FollowUps:12
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Kimberley Karavans have put up a number of excellent mini E-Books on their website, which are free to download. They are well written and quite informative. I was just looking at their one on trailer stability and came across this on Page 9:


"Talking of Tyres, the author received an important lesson in 2006
when Kimberley had suspension arm issues with our Karavans and
engaged a professional engineer and ADR expert from Melbourne.
After spending the day evaluating the suspension design and look
-ing at the issue, he explained as follows:

"Your suspension is fine, probably one of the best I have seen.
Your problem is the tyres. You have allowed customers to use 10
Ply (equivalent) Tyres on your caravan and you have no control
over how they are used. These have much stiffer side-walls and
transfer corrugation vibration intensively on a towable trailer. In
virtually all the serious accident cases I am called upon as an
expert to testify, some aspect of the tyres are generally the prob-
lem and cause of the accident.

"With 30 years experience, I can
tell you there is good reason why 4WD manufacturers choose
the tyres they deliver their 4WD’s with as these are the ones that
legally have to meet ADR compliance. It is for this reason the
wheel size and tyre is specified on the VIN plate. The ADR rules
have limited regulation on suspension design other than for tan
-dem units. This is not the case with wheels and tyres where the
specified tyre by the manufacturer is crucial."

"He found that of the 10 cases with suspension issues, 8 of them
used 10 ply tyres and the other 2 had (narrow) split rims. Since we
changed our policy and educated customers on use of 10 ply tyres
and wider rims, we have had only one incident since. And guess
what they fitted to their camper trailer after delivery... 10 ply tyres!
We now offer a 5 year warranty on the suspension arms when the
wheels and tyres meet our policy."


This got me wondering - and not about knocking the Kimberley Karavan because I'd give my goolies to own one. My concern is this:

If you put 10 ply tyres, like Cooper SST Max, on your 4WD and the suspension broke as a result, you'd regard it as having pretty crappy suspension. Yet here we are with a company offering a premium off road product (and once again I'd love to own one) - where is it considered desirable to match tyres on the trailer and the tow - saying that ten ply tyres will break the suspension on the trailer.

Another manufacturer says that its of road Independent suspension should be pulled apart and inspected every 12 months - why?

Why do we buy an off road vehicle and demand high standards of engineering performance but, when it comes to buying an off road trailer or caravan (which can cost the same or a good deal more), we're happy to accept something less robust. Surely every camper or caravan that is sold as "off road" should be engineered to do anything the 4WD tow can do without breaking. Otherwise is just isn't an off road trailer.

Either it's an off road unit or it's not. Are the manufacturers pulling our leg and blinding us with polished chequer-plate?
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Reply By: Ross M - Saturday, May 04, 2013 at 21:34

Saturday, May 04, 2013 at 21:34
G'day Keith,

I agree with the above information and it is good to see one manufacturer actually taking into account, possibly they were forced to, the various factors involved in making a suspension successful.
There has, as you know, been robust discussion about the suitability of suspension fitted to off road caravans.ration

Unfortunately, many people only see the suspension as what is commonly called suspension and disregard the role tyres play in the overall quality of ride and the subsequent shocks and vibrations which are transferred to the wheel bearings and chassis.

One item not mentioned in the above comments is the role of shock absorbers and they too form an integral part of the suspension performance in both upward and downward travel of the suspension action.

Typically, a tyre which has 10 ply rating would be used to carry a significant load and in many situations will be inflated to a suitable pressure.
However, the speed at which the tyre is used will have a huge affect on the repetitive shock loading to the chassis as users travel at higher speeds than seen before and THAT bump has less time to be absorbed and equilibrium restored before the next hit it receives. Somethings got to give somewhere.

Possibly this is the reason why 10 ply and inappropriate use, causes failure rates on many vehicles. Most likely they don't have to be 10 ply, just too hard an inflation and too fast for the conditions.

Next time I see an "Off Road block of flats" being towed in rough country I will take more notice of the tyres they are using.

Ross M
AnswerID: 510330

Follow Up By: Member - Keith Berg - Saturday, May 04, 2013 at 22:59

Saturday, May 04, 2013 at 22:59

Good point. Well placed shockers should maybe help protect the suspension from bump loads by sharing some of the bump. To do that they have to work in the direction of the wheel travel, which is up and down.

I notice that all of the independent suspensions have their shock absorbers laid back at an angle. If the shocks are set at 45 degrees to the horizontal, only about 70% of the shocker's damping force goes in the direction of wheel travel and the rest just pushes forward horizontally and is wasted. If the angle is 30 degrees to the horizontal, only 50% of the shocker's work goes in the direction of travel. In the 30 degree case, the shock has to move 4 inches for every 2 inches of suspension travel. The wasted effort appears in the shocker as heat.

Now a single axle rated at 2,200 kg is going to need, I guess, at least two very good shocks. And with the laid back shocks working between 40% and 100% harder than they would have been had they been set vertical, it stands to reason that laid-back shocks are going to fade quicker over corrugations and put more load on the suspension.

Maybe that's why almost every heavy 4WD has vertical, or near vertical shocks. I suspect that laying shockers back at a silly angle might be cheaper. Or maybe the manufacturers haven't thought (or cared) about it. It's a good thing that most of the independent suspensions on trailers are very lightly loaded.
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Reply By: olcoolone - Saturday, May 04, 2013 at 21:55

Saturday, May 04, 2013 at 21:55
Could be possible but from a manufacturing perspective it is very poor engineering, they know their campers are going to be used off road and that people are going to fit different tyres to suit ones needs....... and nothing great about 10ply for strength.

Why would anyone in their right mind design and engineer something for 70% of their targeted market.

I think they need to find another engineer and learn to understand their market better.....

QUOTE""With 30 years experience, I can tell you there is good reason why 4WD manufacturers choose the tyres they deliver their 4WD’s with as these are the ones that legally have to meet ADR compliance."

What a load of dribble..... tyre manufactures choose tyres for a number of reasons including cost, wear, comfort, fuel economy, handling and YES to a degree to help the suspension work better (again for their target market).

I think they still think everyone still uses cross plys...

In other words they are blaming their shortfall and obviously poor suspension design and fabrication on tyres........ please.
AnswerID: 510333

Follow Up By: Ross M - Sunday, May 05, 2013 at 08:59

Sunday, May 05, 2013 at 08:59
I thought much the same as you did.
Anyone with a bit of knowledge and experience would have worked out possibly even more than the engineer has done.
I would expect the manufacturer of that product to know the relevant factors before they began building and not have to consult an engineer only after problems arose.

It is likely the one which had trouble used 10 ply tyres but what roads were they used on and HOW were they used may have more bearing on the issue.
How he could determine 10ply as a deciding factor is concerning.
With tyre pressures, shock absorbers and mass of suspension components not in his thinking as factors.

Manufacturers of vehicles usually choose tyres which are sufficient and cheap above all other factors.

Why pick on the tyres?

Ross M

FollowupID: 788439

Follow Up By: olcoolone - Sunday, May 05, 2013 at 09:27

Sunday, May 05, 2013 at 09:27
One thing you do in manufacturing and engineering is the find out first what caused the failure and the second thing is you re engineer the failed section.

When you have one constant and one variable in an engineering equation the only thing you can alter is the variable....... in this case the tyre if the constant fixed sum (10 ply tyre) and the suspension is the variable (re engineer)........ unfortunately they have made the tyre the variable sum and the suspension the fixed sum.

The most common thing to do is if something breaks is find out why it has fatigued and either increase/decrease the material thickness, change material type or increase/decrease bracing.

FollowupID: 788446

Reply By: The Bantam - Saturday, May 04, 2013 at 22:52

Saturday, May 04, 2013 at 22:52
I definitely think there is one fact that has to be faced.....in comparison the the vehicles towing them, caravans and all trailers even the best of them in every respect are crude, cheap and nasty.

look at what passes for suspension.

If you tried to sell a passenger car with that "top shelf independent suspension" offered on some caravans, you would be laughed out of the business.

Almost every motor vehicle offered for sale will have been designed and tested by a fully resourced team of professionals........most trailers including the majority of caravans have little or no input from anybody with qualifications better that a boilermaker.

AND..price is always an issue.....if not with the customer with the bulider.

AnswerID: 510336

Follow Up By: olcoolone - Sunday, May 05, 2013 at 09:15

Sunday, May 05, 2013 at 09:15
I think I would be hard pressed to damage our suspension on our Ultimate camper and I don't see anything wrong with the design...... most vehicle suspension is the same crude, cheap and nasty, what's the difference between a solid rear axle Landcruiser or Patrol and a solid axle trailer with shockers......
FollowupID: 788445

Follow Up By: AlanTH - Sunday, May 05, 2013 at 09:28

Sunday, May 05, 2013 at 09:28
"in every respect are crude, cheap and nasty." How true that remark is.
We've been having no end of trouble with our Goldstream, firstly it showed as bad scalloping on the nearside tyre which was instantly dismissed by the manu and retailer as "misalignment of suspension" who gave no assistance or advice at all in correcting it.
Van was approx 7 months old at the time and we'd deliberately gone for the Off Road pack with independent suspension and 16" wheels etc (extra 6 grand all up) as we knew we'd travel on some reasonably rough roads at some time.
After taking the retailer to the WA Consumer Protection lot we got new shocks and a new tyre out of them.
New tyre took about 2 months to arrive from the East as the maker got them cheap....bugger the owners, they can wait!
When I got the new tyre fitted the fitter showed me how far out of true the steel wheel was and advised it not be used except in an emergency and only then at low speeds. 240gr of weight used to try and balance it.
I had the other 2 wheels checked and they were both buckled but not quite as badly. There was no damage of any kind on any of the wheels apart from a bit of gravel rash.
It should be noted that at this time the van had only been on one dirt road and that was the GCR which can't really be called bad as all sorts of vehicles use it.
Back to the retailer for our complaint to be instantly dismised as "inappropriate use" this time so I gave them an ultimatum "2 weeks to come up with new wheels checked for being true, balanced and fitted plus recompense for the various other expences we've had".
No answer from either of the other parties so off to the small claims court and 10 days later the retailer advises that Goldstream will settle but that "they wouldn't have done"!
Still haven't got the money in the bank but as per court instructions we've given them reasonable time to pay which should be up at the end of this week, or the court will take action.
We hope the new balanced wheels are going to solve the problem of things like pelmets, above door head protector and an info sign on chassis falling off and drawer doors opening for no apparent reason.
I've read about peoples good experiences of GS when they've fronted them at their premises, but they have completely ignored us and why wouldn't they....they're in Melbourne and have our money, and we're in Perth.
At no time has any assistance been offered by them or the retailer (George Day) to find what the problem is, they couldn't care less.
But credit where it's due, the girls in GDs warranty section have been good but there's only so much their "technicians" can do with a tube of silicone:-)
Sorry this is long winded but the worst thing has been the attitude of the makers and retailer, but all the above has been carefully documented.
If nothing else, I reckon all wheels on vans/trailers should be checked and balanced as we've found during this whole saga that it's not unusual for steel wheels especially to be out of true.
This should be something done at manufacture but after checking in several yards could only see balance weights on second hand vans.
Vibrations can do serious damage to the whole of a van or tow vehicle not just stuff dropping off as we've suffered.

FollowupID: 788447

Follow Up By: The Bantam - Sunday, May 05, 2013 at 12:57

Sunday, May 05, 2013 at 12:57
Oldcoolone...mate where do I start.

lets look at simple beam axles on leaf springs.

the land cruser chassis is not a straight flat piece of steel, the front spring hangers are lower than the spring shackle attachment points allowing the spring to sit at the correct attitude and not inclined about 20deg.

It also allows the axle to travel further and the spring to work thu its entire reasonable acting travel.

The springs on the land cruser are very long in comparison to a trailer of similar capacity, thus making the ride softer and smoother for the same spring rate.
the springs are also flatter as well as being longer, thus reducing bump steer and forward and aft movement of the axle as the spring acts.

The springs of far better quality and the spring rate and progression has actually be designed for that vehicle and load rather than just being pulled out of a catalogue.

If you complain about the factory springs being poor in landcrusers .....hell there are aftermarket springs that have had more R&D and engineering attention for a single spring for a single model than goes into most entire caravan manufacturing plants ever.

The landcruser is fitted with bump stops, by far the majority of trailers are not.

because the chasis is not a straight beam it allows the shock absorbers to be fitted correctly and not as some obtuse angle.
The shock absorber rates have been designed for the springs and the load carried...
OH...there are shock absorbers..still the majority of trailers and caravans have none.

Now the axle....OK the landcruser axle is a driven axle...but if it was a 2wd machine of similar weight, the axle stubs would be heat treated and properly machined with fairly fine threads on the bearing adjustment....not a lump of cheap chineese steel that is one step better than mild steel, fairly roughly machined, not heat treated and with threads on the bearing adjustment that result in the bearing preload either being sloppy or over tight.

Most trailer axles they don't even scrub the mill scale off them before they slash a thin coat of black paint over everything under the thing

Then there are the bearings......most trailers even quite heavy ones run on bearings out of a 50 year old passenger car front end either an early holden or and early falcon...and then cheap chinese versions.

Mostly they would rather put two cheap axles with cheap 50 year old passenger car bearings on them that a single decent axle with ample modern bearings

Pull the bearings out of ya trailer and compere them to those out of the front of ya land cruser and tell me if there is a difference

and the same goes on....in every area.
There is no requirement for formal stability or crash testing in fact the whole required standards for light trailers in the ADRs less than 1/4 of the of the text devoted to headlights in passenger cars.

As for these jokes that they sell as independent suspension....OH HELL...you might not break it, but they have nowhere near the geometric sophistication that you would find in a 50 year old passenger car with independent suspension.
most of them is something that a bloke welded up in his back shed...if ya lucky he used a jig and is a competent welder

Then there are the wheels and tyres...a great many trailers especially caravans are pushing the envelope of not only the tyre fitted, but the load carrying capacity of the rim and the, load carrying capacity of tyres available to fit that size of rim.
Go check the load carrying capacity of the tyres factory fitted to ya landcruser and look at how much spare capacity is available in that tyre.

Even the very notion of light trailers as we know them has progressed little in 50 years.

In heavy transport, long heavy trailers with a high centre of gravity running on a single axle group are actively discouraged...because the format is fundamentally unstable......articulated vehicles and dog trailers with the loads supported at the ends are the norm because they are far more stable.
we see almost no dog trailers behind passenger cars and articulated only in the rediculoulsy large trailers.

I do not wonder why people have all sorts of problems with trailers.......almost without exception light trailers are very crude and as caravans most are fundamentally unstable.

because they are fundamentally unstable those who tow large trailers and caravans have to spend $$$ on suspension upgrades in the vehicles and on load distrubution and sway reduction devices.

FollowupID: 788468

Follow Up By: KevinE - Sunday, May 05, 2013 at 17:10

Sunday, May 05, 2013 at 17:10
Geez, I'm disappointed in my cheap Chinese camper! The jolly thing has done Maree - Oodndatta, the Flinders (3 times) including the gorges, Gawler Ranges, Dalhousie, Peake Ruins, Mt Dare, Old Ghan track, Chamber's pillar, Old South Rd into Alice, Lake Eyre, Palm Valley, Mereenie Loop, Painted desert, SA Riverland (twice), Yorke Peninsular & probably a few places I've forgotten about too since we bought it new in Jan 2012.

So you can see its been babied all its life, but the stinking Chinese wheel bearings & nasty Chinese stub axles & all the other crude Chinese bits on it just will not fail!

Its very, very disappointing to say the least! I keep reading expert comments on the internet about how these cheap, nasty, crude Chinese trailers fall to bits & mine just won't do it!

I think I may have to complain! ;)
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Follow Up By: The Bantam - Sunday, May 05, 2013 at 21:05

Sunday, May 05, 2013 at 21:05
Kev mate, I think we understand that you have baught cheap chinese crackers......but you have no illusion about the matter......lets fact it the Chinesse can do a fairly good job if you tell em to and slip em an extra half a bowl of rice a day.

But I am sure you would feel different if you had spent as much as a small house on a caravan and still ended up with the same level of sophistication....or even spent as much as a decent 4wd on an off road camper trailer.

There is quite a bit of difference between a fairly small fairly light box trailer with a tent screwed to it and having a pretty low centre of gravity and a 3 tonne rolling gin palace with hot and cold running satellite TV, or a supposedly funky off road trailer with all singing and dancing independent suspension......that falls to bits because someone put the wrong tyres on it.

FollowupID: 788493

Follow Up By: KevinE - Monday, May 06, 2013 at 18:41

Monday, May 06, 2013 at 18:41
Please give me a little leeway here mate, I'm not an expert like yourself Bantam!

They way I read it, up top you're saying the problems are caused by "crude, cheap and nasty" suspension bits.

But now, you seem to be saying tyres are the issue?

By the way; owning a camper trailer & a caravan are not mutually exclusive mate! Some of us own both ;)

"a 3 tonne rolling gin palace" what on earth were you thinking when you wrote that? Come on Bantam, you're better than that! I think we all know that racism has no place in the modern world. I used to supervise guys with an intellectual disability at work & that's the kind of nonsense that some of them might come out with!

FollowupID: 788537

Follow Up By: Member - David M (SA) - Monday, May 06, 2013 at 21:43

Monday, May 06, 2013 at 21:43
Beats me how you can find "a 3 tonne rolling gin palace" to be racist.
PS. Although it might just be your left way of thinking. :)
FollowupID: 788557

Follow Up By: The Bantam - Monday, May 06, 2013 at 22:51

Monday, May 06, 2013 at 22:51
The term "floating Gin palace" is a common term for a large fancy boat, typically found in Gold Coast waters.....it has nothing to do with race and everything to do with an alcaholic beverage.

As for the point I make.......the reasons a lot of people have problems with trailers of all types is the general crudity of them in every respect.

many of the trailer manufacturers make a big deal about how wonderfull their suspensions are.......but I am yet to see an independent suspension on any type of commercially manufactured light trailer ( that includes very expensive vans) that could be considered anything other than crude in comparison to what is found in towing vehicles.

In fact & I have posted this before......I doubt very much that any of the independent suspension systems offered on light trailers has any advantage over a properly designed beam axle and leaf spring set up.

But there is nothing to compare with because I doubt that you will find a properly designed beam axle and leaf spring suspension on a commercially sold trailer.

FollowupID: 788563

Reply By: The Rambler( W.A.) - Saturday, May 04, 2013 at 23:22

Saturday, May 04, 2013 at 23:22
I have read a lot of rubbish in my time but this so called engineer takes the cake especially as he claims to have 30years experience in this field.He states that 4wd manufacturers have good reason why they put specific wheels and tyres on their vehicles and then goes onto say that he has seen two cases of suspension failure with split rims.Tell me why all Toyota troop carriers which are designed for the harshest conditions all come new with split rims.I have been driving Troop carriers all over this country with split rims for over 30 years with no suspension issues and also using 10 ply tyres.I now have owned a Pioneer off road camper trailer for 6 years which has full independent suspension fitted with split rims and 10 ply tyres and Ican tell you it has seen more harsh conditions than most vans would see in a lifetime.So far I have done nothing to the suspension.All I can say Kimberly has been taken for a ride and Iwillcontinue using my 10 ply tyres and split rims which work very well for me.
AnswerID: 510338

Reply By: Member - J&R - Saturday, May 04, 2013 at 23:35

Saturday, May 04, 2013 at 23:35
So many experts....
AnswerID: 510340

Reply By: Member - Oldbaz. NSW. - Sunday, May 05, 2013 at 10:18

Sunday, May 05, 2013 at 10:18
I'm no engineer, or expert on anything much, but even I can see that response as
nothing more than a copout. If it breaks it is either poorly engineered, poorly
manufactured, or maybe subjected to extreme abuse.
To blame a stiff or overinflated tyre is laughable.
I thought the info on shock angle was very interesting & would welcome more
thought from the armchair engineers on that one.
We're about to cross the nation on dirt roads, & our little van has nothing flasher
than good old leaf springs....shocked..???. No , no shocks either. An extremely
risky intention, I hear the experts say...time will tell..stay tuned......oldbaz.

AnswerID: 510355

Follow Up By: bluefella - Monday, May 06, 2013 at 07:16

Monday, May 06, 2013 at 07:16
G'day Baz
In the early 60's my dad had a Viscount single axle, towed by a 59' vanguard. Where the old mate took that used to make my hair stand on end. Dad's opinion was drive to the conditions, it seemed to take along time to get somewhere but we got there.
FollowupID: 788501

Reply By: TTTSA - Sunday, May 05, 2013 at 14:40

Sunday, May 05, 2013 at 14:40
Been running 10 ply rating tyres on our T Van for the past 6 years, no problems so far. Only running about 28 psi though.
Sent my own Landcruiser rims and my own tyres to Track Trailer fitted from new.

AnswerID: 510368

Reply By: Member - Keith Berg - Monday, May 06, 2013 at 08:52

Monday, May 06, 2013 at 08:52
Maybe it's corrugations that damage caravans and campers more than anything else. Certainly a lot of gazetted "roads" around Australia would be classified as "off road" by any sensible person.

If Kimberley wants to place a condition on what tyres you can use before you buy its campers then that's fine - as long as the buyer knows. But if it won't take standard ten ply tyres, as used on many 4WDs, it's not an off road camper.

IMHO, Kimberley is a great brand with a premium product. It's unfair to single them out and I mentioned this tyre issue just by way of example.

If the caravan and camper manufacturers want to bandy around the term "off road' in their advertising, without putting the requisite engineering into the product, they should be called to account.

Bullet proof products are great. But how many would they sell if the price went up 20% to cover the extra cost? Maybe it's cheaper for them to wear the odd warranty claim that it is to get it right in the first place.

The issue is not about build quality on its own. It's about matching the product to the advertising claims and about customers getting what they are promised.

AnswerID: 510418

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