caravan independent suspension

Submitted: Saturday, Dec 27, 2014 at 22:45
ThreadID: 110537 Views:7346 Replies:14 FollowUps:12
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G,day : I was chatting to "old mate" .... who was worried about how his single axle c,van rolls around on the the main Rd , it has independent suspension with twin shocks both side . Is this the norm for this type of van ....
any experience wld b help
cheers
Cheers Nick b
VKS 737 ( 0915 )
Wish the missus was as dirty as the tailgate

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Reply By: taswegian - Sunday, Dec 28, 2014 at 09:41

Sunday, Dec 28, 2014 at 09:41
Suspension problems are often blamed the real problem being incorrect tyre choice.
AnswerID: 543441

Reply By: Peter_n_Margaret - Sunday, Dec 28, 2014 at 10:15

Sunday, Dec 28, 2014 at 10:15
What possible benefit can independent suspension have on a caravan?

Cheers,
Peter
OKA196 Motorhome
AnswerID: 543444

Follow Up By: Ron N - Sunday, Dec 28, 2014 at 15:13

Sunday, Dec 28, 2014 at 15:13
Well, Bushtracker seem to offer a perfectly satisfactory reason!
Quoted directly from their site ....

"The main reason for an Independent Suspension is that it breaks up harmonic motion; which is the biggest destroyer of caravans. It occurs in normal suspensions when the speed of the moving suspension coincides with the ruts in the road so that the bounces build on themselves creating a destructive force. The fully independent suspension cancels out this harmonic motion."

Cheers, Ron.
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Follow Up By: Peter_n_Margaret - Sunday, Dec 28, 2014 at 18:40

Sunday, Dec 28, 2014 at 18:40
Sales speak?
Does not seem to apply to the best off road vehicles in use in this country, most of which have solid rear axles and many with solid fronts too.
The OKA has solid axles front and rear and I would challenge any other 4WD in the business (with the exception of a Unimog) for lack of "harmonic motion".
Notwithstanding, a car DOES get benefit from independent suspension, but I see no value on a caravan.

I reckon it is about having a DECENT suspension, not about INDEPENDENT suspension on caravans.

Cheers,
Peter
OKA196 Motorhome
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Follow Up By: Bobjl - Sunday, Dec 28, 2014 at 23:25

Sunday, Dec 28, 2014 at 23:25
I followed a mate towing a van with dual beam axles on corrogations for hundreds of k's. My observations were that the axles and common style leaf springs were taking a hell of a pounding - it appeared that each axle/wheel was at odds with the other - one wanting to go up at a different time to the other whilst limited by the beam axle.

However on same trip whilst following a Van with a fully independent system on similar corrogations, each wheel appeared to absorb and manage the stress etc a lot better.

Maybe looks are deceiving?

Bob

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Reply By: TomH - Sunday, Dec 28, 2014 at 11:18

Sunday, Dec 28, 2014 at 11:18
Some more specific detail as to make of van, type of "independent" ,make and tyre choice would probably get more sensible and definitive answers.

Hard to comment when nothing specific is mentioned
AnswerID: 543448

Reply By: Ron N - Sunday, Dec 28, 2014 at 15:15

Sunday, Dec 28, 2014 at 15:15
A caravan that is reported to be "rolling around" excessively is more than likely fitted with incorrect tyres as 'taswegian' notes, and possibly even running incorrect tyre pressures.

Cheers, Ron.
AnswerID: 543458

Follow Up By: Ross M - Sunday, Dec 28, 2014 at 17:06

Sunday, Dec 28, 2014 at 17:06
Having 4 shocks per side is no good unless the shocks are actually working.
it is the shocks which dampen and attempt to eliminate roll movement so the springs can do their job.

Maybe, the shocks, 2 per side, are totally stuffed and just look like shock absorbers.
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Reply By: Member - Bruce and Di T (SA) - Sunday, Dec 28, 2014 at 15:48

Sunday, Dec 28, 2014 at 15:48
We have a single axle independent suspension caravan. It is Cruisemaster Independent with shocks and coils. It can certainly appear to move about at times but nothing moves inside the van. Because each wheel can move independently the roughness of roads seems to be absorbed and dealt with more efficiently, We have travelled over rough dirt roads and everything has stayed in place inside the van and the van has tracked well behind us. It is an offroad van.

Di
AnswerID: 543459

Reply By: Notso - Sunday, Dec 28, 2014 at 17:20

Sunday, Dec 28, 2014 at 17:20
Tyre pressures could be an issue. I've always had independent suspension and never had any "Rolling around" issues. But thinking about a vehicle of any type, low tyre pressure will cause it.
AnswerID: 543463

Reply By: Member - Sanantone - Monday, Dec 29, 2014 at 07:35

Monday, Dec 29, 2014 at 07:35
Jayco's reasoning for independent suspension:

Purpose designed to complement the Jayco Endurance Chassis,
JTECH Suspension replaces beam axles with individual stub axles,
allowing each wheel to react independently to the road surface,
while also lessening the chassis’ unsprung weight. Delivering
greater stability, a smoother ride, more precise handling and
increased ground clearance without increased ride height,
it makes towing easier and safer than ever before.
Precision manufactured using automotive processes to ensure
exact fitment, JTECH Suspension is the product of two years’
research and development at Jayco’s Melbourne headquarters,
and countless kilometres of real world testing across the best
and worst of Australian second class roads. Its features include:
— Electrocoated surfaces for optimum protection against
corrosion and stone chips
— AL-KO stub axles, bearings and brakes that are suitable
for fitment of AL-KO Electronic Stability Control
— Large diameter, heavy-duty Pedders off-road shock
absorbers and coil springs designed specifically for
Jayco RVs and Australian conditions
— Aeon rubber springs inside each coil spring, producing
a progressing rate when the suspension is compressed; and
— Toe-in and toe -out adjustment for wheel alignment
Tony
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AnswerID: 543477

Follow Up By: Bosun Broome - Monday, Dec 29, 2014 at 08:03

Monday, Dec 29, 2014 at 08:03
Anyone that has towed both over outback roads knows that it is a "no brainer".



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FollowupID: 830418

Reply By: Billion Star Camper - Monday, Dec 29, 2014 at 08:28

Monday, Dec 29, 2014 at 08:28
I agree independent suspension on vans and campers is a no brainer if you want to go really off main roads. I have a camper with a beam axle and will not take it off road where the road has a lot of corrugations, if the trip is for several days on those types of roads. If it was independent suspension I wouldn't hesitate.

Why are beam axle vehicles thought of as superior to 4 x 4's with independent suspension? Different situation altogether. 4 x 4's have to include a drive shaft and the suspension layout is completely different to a van with independent suspension. Beam axles are simpler on 4 x 4's and have less to go bang.

Its not about tires and pressures.
I am an apprentice retire. Its looking like my most successful career to date.

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AnswerID: 543478

Reply By: Member - nick b - Monday, Dec 29, 2014 at 09:12

Monday, Dec 29, 2014 at 09:12
Thanks all for your reply's some good points ....he has pumped tyre pressure up somewhat :( IMO.... and was better on there return trip .
but the Question was ...... Is this the norm for this type of van , to roll around (side2side) uneasy ride , on main Rd I.E hwy etc 100 ks hr ( Not about independent suspension in general ,missing the point)
Single axle coil independent twin shocks set on 45 angle , tyres maybe a consideration & most likely as full offroad type & may well replace them very soon .
My thoughts were , are the shocks doing there job ?? a high van , soft suspension , tyres , traveling to bloom'n FAST :( lol ....anyway whats your thoughts / experience ?
cheers
Cheers Nick b
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Wish the missus was as dirty as the tailgate

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Follow Up By: Frank P (NSW) - Monday, Dec 29, 2014 at 10:04

Monday, Dec 29, 2014 at 10:04
Nick,

Yes, your topic did get hijacked.

My hybrid van has soft, long-travel independent suspension.

When I first got it it did roll around a lot at highway speeds on the black, particularly if the road was a bit rough.

I had a wheel alignment done to correct abnormal tyre wear and after fiddling with tyre pressures have reduced the problem to nil. I have BFG All Terrains on the van, run them at 47PSI on the highway (as delivered, they were 32PSI).

Van is 100% stable at my towing speeds (up to 110kph, but mostly about 90 on the highway).

Based on my experience, check wheel alignment and, if the tyres will take them (look on the sidewall), try experimenting with higher tyre pressures.

Cheers

FrankP

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Follow Up By: Frank P (NSW) - Monday, Dec 29, 2014 at 10:33

Monday, Dec 29, 2014 at 10:33
And, as you suggest it could be stuffed shock absorbers, or shock absorbers mismatched for your mate's application. Try a suspension specialist for advice.

Consider getting a set of adjustable shocks and trying different settings.

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Reply By: awill4x4 - Monday, Dec 29, 2014 at 15:45

Monday, Dec 29, 2014 at 15:45
If it has Cruisemaster suspension I've always felt they are less than ideally sprung with a comparatively small coil that is located at a point forward of the stub axle.
The pics below give a comparison of the Cruisemaster and the SugarGlider suspension I had fitted to my van.
Note the position of the SugarGlider coils behind the axle line giving longer travel with less tendency to bind and a steeper angle on the shock absorbers.
When you think on a single axle van that may weigh up to 2500 kgs all that weight is supported by two coils.
I thing the sizing of my coils (note their size and thickness) to be more appropriate than the coil size supplied by vehicle components.
Regards Andrew.





AnswerID: 543491

Follow Up By: Roachie.kadina.sa.au - Monday, Dec 29, 2014 at 19:00

Monday, Dec 29, 2014 at 19:00
FWIW I fully agree with Andrew.....the geometry of the Sugar Glider unit is head and shoulders over the other type.....

I have a 1999 model Ultimate Off Road Camper with Sugar Glider suspension and I have always noticed that it seems to "sway" about on various road surfaces.

It is NOT a problem....it is, in fact, what the suspension is designed to do.

I wouldn't even consider a trailer/caravan for rough-road use (I purposely didn't say "off-road") as the correct type of independent suspension is the only set-up I would trust.

Roachie
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Reply By: awill4x4 - Monday, Dec 29, 2014 at 15:53

Monday, Dec 29, 2014 at 15:53
The pic below is Jayco's J Tech suspension and would be the most modern of all independant suspensions. (please note, Track and Vista owners are in a different league altogether)
Note their spring placement.
Maybe SugarGlider got it right 30 years ago.

AnswerID: 543492

Reply By: Member - KeithB - Tuesday, Dec 30, 2014 at 16:42

Tuesday, Dec 30, 2014 at 16:42
Shock absorbers laying back at an angle have to work a lot harder than they do when placed in line with the wheel movement.
Plus independent trailing arms have a much lower roll centre than leaf springs or rigid axle trailing arms with panhard rod. This, plus the fact that the springs are located inboard of the chassis, I think makes the independent trailing arm suspension exhibit a lot more body roll.
Colly Rivers has a lot to say about this type of suspension.
AnswerID: 543521

Follow Up By: Member - nick b - Thursday, Jan 01, 2015 at 19:25

Thursday, Jan 01, 2015 at 19:25
Quote "Shock absorbers laying back at an angle have to work a lot harder"
I would hav thought Shock absorbers laying back are only working at part pace as they are only moving part of the travel of the axle ,???

But wld agree with your body roll .
Cheers Nick b
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Follow Up By: Frank P (NSW) - Thursday, Jan 01, 2015 at 20:09

Thursday, Jan 01, 2015 at 20:09
Shocks that are not vertical will not work harder. They will work only as hard as they are valved to do. The angle off the vertical may make them less effective unless valving has been adjusted to compensate.

So a given shock, re-valved to accommodate its angle, will likely work about as hard as the same shock mounted vertically and valved to suit.

A shock not adjusted for its angle will work "less hard" than the same shock mounted vertically.

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FrankP

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Follow Up By: Frank P (NSW) - Thursday, Jan 01, 2015 at 22:41

Thursday, Jan 01, 2015 at 22:41
"So a given shock, re-valved to accommodate its angle, will likely work about as hard as the same shock mounted vertically and valved to suit."

On reflection, that is not quite right.

If the angled shock is valved to give the same results as a vertical shock, then the internal pressures and stresses would be greater. Simple geometry.

The shock need to be chosen to do the job correctly.

Perhaps that's why, in suspensions where the shocks are way off vertical as in some of the posted pics, there are often two of them.

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FrankP

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Follow Up By: awill4x4 - Friday, Jan 02, 2015 at 10:15

Friday, Jan 02, 2015 at 10:15
In my case with the SugarGlider suspension I decided to go with the 2 Koni shocks per wheel as mine is a single axle van with an uprated ATM of 2240kg.
To expect 2 shock absorbers (1 per wheel) to control that mass is unrealistic in my view, hence my dislike of the control rider suspensions similar to my SugarGlider but with a shock in coil is unable to go down the twin shocks route.
On a tandem van then possibly one shock per wheel may suffice but given the layback on some suspensions possibly not hence the vehicle components Cruisemaster using 2 shocks per wheel even on tandem setups.
Regards Andrew.
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FollowupID: 830591

Reply By: Member - KeithB - Friday, Jan 02, 2015 at 07:53

Friday, Jan 02, 2015 at 07:53
Just looking ay the Cruisemaster setup pictured earlier, is there a problem arising from the inability of dual axle caravans with trailing arm suspension to load share between the wheels?
Maybe air bag springs with a common air line between them on each side would work better for load sharing?
AnswerID: 543589

Reply By: swampfox - Thursday, Jan 08, 2015 at 12:11

Thursday, Jan 08, 2015 at 12:11
hi
Although springs and shockers can partially control sway . The only real answer is to have a sway bar .
This can be the conventional style . Warning this needs to be engineered properly otherwise it will restrict suspension movement .
Or a torsion bar mount between the 2 wishbones .
The alternate is a van with weight closer to the floor and not high in the air .
Or
Donot run your tow vehicle more than 2/3 of its tow capacity .
An example is the early rangers /bt50 The tow bar/vehicle is rated to 1800kgs without load leveler bars . Using load level bars is a very poor compromise for towing . Yes legally its ok but should not be your first option . A high capacity tow vehicle should be. A heavier tow vehicle will be less influenced by a van of given weight.


swamp fox
AnswerID: 543919

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