Caravan independent suspension - what do you think?

Submitted: Monday, Oct 31, 2016 at 09:21
ThreadID: 133697 Views:5330 Replies:17 FollowUps:14
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Hi all
I have attached a few pictures showing different parts of the independent suspension on a small caravan I recently purchased new. I will not mention any names at this point but I would appreciate comment from any of you that have genuine experience in this area. The pictures show the trailing arms, the hangers that they attach to and the attachment of the shock absorbers. Do people think that what is shown look reasonable or should I be concerned. This van was bought new - it has travelled less than 1000km with about 10km on dirt.
thanks



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Reply By: Bobjl - Monday, Oct 31, 2016 at 09:31

Monday, Oct 31, 2016 at 09:31
Uuhhmmm, it gives the appearance of a previously used component having been re used - been sprayed [poorly]. I have had 3 vans built and not one of the suspension bits looked as yours does?
Some of the other construction areas give the impression of less than best quality workmanship.
I would be disappointed if it were mine and would be digging deeper. Maybe go back to where you bought it and look at a number of vans to satisfy yourself as to how they look, I would also go to other Van outlets and have a good look at suspension and there you will likely find the answer - how most new chasis and van suspension look from factory.
Bob
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Reply By: gbc - Monday, Oct 31, 2016 at 10:00

Monday, Oct 31, 2016 at 10:00
Not good.
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Reply By: Member - Phil G (SA) - Monday, Oct 31, 2016 at 10:09

Monday, Oct 31, 2016 at 10:09
Perhaps you can compare the welds and construction to this (note the lack of flat washers from Bunnings)

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Follow Up By: splits - Monday, Oct 31, 2016 at 21:50

Monday, Oct 31, 2016 at 21:50
There is an interesting comment here about a Vehicle Components suspension Cruisemaster

It is the second last post on the page. His other post two above it is also worth reading
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Follow Up By: Member - Phil G (SA) - Monday, Oct 31, 2016 at 23:00

Monday, Oct 31, 2016 at 23:00
Splits, did you post that? :-)
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Follow Up By: splits - Tuesday, Nov 01, 2016 at 10:56

Tuesday, Nov 01, 2016 at 10:56
Why? Is there something wrong with it?

I found it years ago and remembered the comment about weld quality. Some of the welds in the photos you posted did not look all that good to me.
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Follow Up By: Member - Phil G (SA) - Tuesday, Nov 01, 2016 at 12:02

Tuesday, Nov 01, 2016 at 12:02
Hi splits, sorry - poor attempt at humour hence the smiley. Wondered why you remembered it from 2012.

In the photo, The Vehicle Components welds look great to me, but the ones which weld the suspension to the chassis are from the chassis manufacturer and I agree with you they are not as good.

Cheers
Phil
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Follow Up By: splits - Tuesday, Nov 01, 2016 at 22:14

Tuesday, Nov 01, 2016 at 22:14
" but the ones which weld the suspension to the chassis are from the chassis manufacturer and I agree with you they are not as good."

They certainly are not as good. I would be doing them again if it was mine. It looks like they were done with a MIG with the welder lying in an awkward position under the van. Some of them appear to have air bubbles in them. That could have been caused by wind blowing the shielding gas away from the weld before it solidified.

I did a lot of welding back in the late 1970s and early 80s for a major structural steel company in Wagga Wagga NSW. One job was relocating some of the supports for a huge water slide for a park beside the river in town. The manufacturer, who was from out of town, put many of them in the wrong position. I spent two days hanging half upside down from a cheery picker about a mile above the ground while I tried to weld them back on with a big diesel powered DC arc welder. Every weld looked about 200 % better than those ones.

There is no excuse for that when the builders are supposed to be professionals.

The same could be said for a lot of suspension designs that you see under vans and trailers.
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Reply By: swampy - Monday, Oct 31, 2016 at 10:52

Monday, Oct 31, 2016 at 10:52
HI
Shockers need to match the spring rate , need the correct units .
Then again caravans and tuned suspension is unlikely .
shocker washers need to be larger diameter . Preferably use a hardened washer .

Bolts used on all photos ,the thread is to course .Need to be either UNF or metric 1.25 TPI . Course threads and nyloc can come loose . Use either double nuts or a captured nut .

Adjusting for wheel alignment
welded plate over either a worn out hole or what use to be an adjustment slot
I mentioned the bolts before .
Could also be the lazy end with no eccentric bolt /washer . The welded plate is to lock the wheel alignment in position

******Please please more photos of the trailing arm mounting points
both sides of both bolts on one of the trailing arms
Looking for more adjustment points
Are there no nylon/ eurathane/ rubber bushings in the mounting points or the trailing arm ????

The vehicle components photos clearly show they use an eccentric bolt system .
Used widely on cars also.
Even they are not perfect ,they have only used eccentric washers on one side . The nut end is not supported

This suspension has either /both been designed and/or repaired poorly
swamp
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Reply By: Member - Bookleaf - Monday, Oct 31, 2016 at 10:55

Monday, Oct 31, 2016 at 10:55
Is it just me or do the shockers slope inwards in Pic1?. My thoughts are that they would be vertical.
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Reply By: baznpud (tassie) - Monday, Oct 31, 2016 at 11:17

Monday, Oct 31, 2016 at 11:17
I am no expert in relation to suspension bits and pieces, but we do have a van with independent suspension that has traveled in excess of 70,000 ks, a lot of which was done on unsealed roads/tracks, and it doesn't look as bad as yours.
Yours looks to me as if it is a second hand one, i would be taking it a little further if it were me.
Cheers.
baz
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Reply By: Dean K3 - Monday, Oct 31, 2016 at 13:54

Monday, Oct 31, 2016 at 13:54
I would be getting this to a mechanical engineer to have a look at for compliance suspect it wouldn't pass period. use of washers as a gap filler isn't on period after awhile they simply twist and break or fall off when they fail.

welding looks like a cocky weld no penetration just sit ontop of the surface (ie cocky weld sits there like bird crap)

excess thread exposed think you could get a second nut on that thread section should be 2-3 thread exposed maximum on a nylock nut

if it was mine or folks I'd be getting it off to consumer protection as well
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Follow Up By: Shaker - Monday, Oct 31, 2016 at 17:52

Monday, Oct 31, 2016 at 17:52
What is the difference between a washer & a steel shim, also how & why can the washer twist?
I agree that it it is ridiculous to have that much excess thread exposed to be hammered by rocks, I would prefer to see the use of cone nuts & not nylocs in that situation, as vehicle manufactures do!

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Reply By: Member - Munji - Monday, Oct 31, 2016 at 15:22

Monday, Oct 31, 2016 at 15:22
Take it to a mechanical engineer, it's worth the time, money and piece of mind.
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Reply By: Member - Andrew & Jen - Monday, Oct 31, 2016 at 17:33

Monday, Oct 31, 2016 at 17:33
Are you a member of RACQ? If yes, they may be able to give you a first assessment as part of their member service. If they have concerns, their legal service might take it up on ypur behalf with the company that sold it to you.
Cheers
Andrew
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Reply By: swampy - Monday, Oct 31, 2016 at 18:57

Monday, Oct 31, 2016 at 18:57
hi
nothing wrong with shiming shocks just need to do it with
hardened washers of the correct size .

Fine thread bolts with captured /cone nuts / double nut everywhere

More photos of both ends of each trailing arm bolt
More photos of where bushes are suppose to be

swamp
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Reply By: Michael ( Moss Vale NSW) - Monday, Oct 31, 2016 at 19:11

Monday, Oct 31, 2016 at 19:11
I think it's fair to mention the brand, it is what it is! If the manufacturer reckons it's all good then everyone can judge their products for themselves. Michael
Patrol 4.2TDi 2003

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Follow Up By: Frank P (NSW) - Monday, Oct 31, 2016 at 20:50

Monday, Oct 31, 2016 at 20:50
Agree. Please post the brand
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Reply By: Member - RUK42 (QLD) - Monday, Oct 31, 2016 at 19:40

Monday, Oct 31, 2016 at 19:40
G'day again everyone
Thanks enormously for everyone who has replied - all good constructive replies. I feel I now have enough "ammunition" to go and have an indepth conversation with the manufacturer. I will not name them at this point because they haven't yet had the chance to reply - I haven't fronted them with this yet. I had not thought of using the RACQ for help - I may not need it but I'll keep it up my sleeve - as well as the concept of going to an engineer for an assessment.
I do believe that this problem may be an isolated case of someone rushing the job - I have since seen under other vans by the same manufacturer where rubber spacers and "bunnings" washers have not been used so mine may not be indicative of their normal work. The notes about fine thread bolts and double nuts I will certainly be taking up with them also.
Keep you posted - and thanks again
Kevin
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Follow Up By: Dean K3 - Monday, Oct 31, 2016 at 19:54

Monday, Oct 31, 2016 at 19:54
If you been under another similar unit might have been a Friday or early Monday job read between the lines.

Either way what you have there isn't right or sound looking at welds.

number of threads exposed is excessive this indicates a smaller length bolt in theory should have been used -might have been a engineering decision to use this length but doubt it

i have similar issue with shank on my tregg hitch has a long thread so two nuts fit onto it perfectly prefer it was shorter but way its manufactured to accommodate various hitch thicknesses

cone nuts relatively new item to me,only recently used one for a alko swivel jockey wheel always used nylocks as a single use item -called evolution as with everything

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Follow Up By: Frank P (NSW) - Monday, Oct 31, 2016 at 20:52

Monday, Oct 31, 2016 at 20:52
One reason for a longer bolt might be to get sufficient shank for the wearing surface of the bush to work on, instead of working on the threaded part of a shorter bolt. In which case excessive thread should have been cut off.
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Follow Up By: Michael ( Moss Vale NSW) - Monday, Oct 31, 2016 at 21:00

Monday, Oct 31, 2016 at 21:00
I was thinking the same Frank, a parallel shank for support, the whole thing is dodgy really. That suspension assembly has been on something else before that van for sure. Michael
Patrol 4.2TDi 2003

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Reply By: RMD - Monday, Oct 31, 2016 at 19:54

Monday, Oct 31, 2016 at 19:54
The swing arm has been previously used/loved and resprayed. Chipping clearly seen under the overcoated colour.
Nothing wrong with the washers being used like that. All they are doing is preventing sideways movement.
All the hardened washer rubbish is just that. Most vehicles do not have hardened washers on shocks.

The threaded end of the pivot bolts are a worry because there is little support with that thickness of plate and it appears the thread of the bolt is what is being supported and not bolt shank.
The welding is minimal for proper support with a thin plate like that.

Since the bolt is only a pivot the thread pitch should be OK. Many are coarse theaded as they don't have to clamp hard anyway.

Tvan suspension has bolts coarse threaded and they merely float and are not tightened against a face.
Engineering factors are not always seen by some.
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Reply By: TomH - Monday, Oct 31, 2016 at 20:18

Monday, Oct 31, 2016 at 20:18
To me it looks like a second hand suspension unit has been bolted in badly. I sold a van that had done about 20,000 with similar suspension and it was nowhere near as chipped as that. That looks like its several years only and just been oversprayed to make it look better. Welds are shocking and is very lttle to be holding a suspension arm straight.

Would be jumping up and down severely at the sellers.
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Reply By: Member - Phil G (SA) - Tuesday, Nov 01, 2016 at 11:15

Tuesday, Nov 01, 2016 at 11:15
I'm guessing the Bunnings washers are stacked where they are so the twin shocks don't hit one another! Looks like they are mounted too close together otherwise.
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Reply By: The Bantam - Tuesday, Nov 01, 2016 at 11:43

Tuesday, Nov 01, 2016 at 11:43
People need to understand and know from the very start, that, trailer suspensions are rough, crude and pretty much made to no standard whatsoever ......

Compared to Motor vehicles made by major manufacturers, even the best trailer suspensions are rough, crude and poorly engineered.

SO ...... look carefully at suspensions when you are considering any sort of trailer or caravan.

My personal view is that pretty much all of the independent trailer suspensions are so crude and technically flawed that they have no advantage over a properly designed leaf spring and beam axle suspension.

But their in lies the problem ..... BY FAR the majority of leaf spring suspensions on trailers and vans are equally crude and technically flawed and nowhere near the standard found on motor vehicles.

It leaves me gobsmacked, that people are paying $20G, $50G and $100G pluss for trailers and vans with POS suspensions that are not even equal in quality or design to a 40 year old utility design , like a Hilux or a 70 series.

Sorry but I call em like I see em.

cheers
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Follow Up By: Member - Phil G (SA) - Tuesday, Nov 01, 2016 at 19:36

Tuesday, Nov 01, 2016 at 19:36
I'd agree with everything, except for the MC2 suspension by Track Trailer as used on the Tvan and Topaz - but that's offroad suspension. Designed by an Engineer, the late Alan Mawson.
I'm guessing we could get you going next with caravan wheel bearings and then caravan brakes!!!
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Follow Up By: splits - Tuesday, Nov 01, 2016 at 23:04

Tuesday, Nov 01, 2016 at 23:04
" People need to understand and know from the very start, that, trailer suspensions are rough, crude and pretty much made to no standard whatsoever .."

Very true Bantam. Look at the trailing arm suspension under many vans for example. The mounting bushes for the arms are usually mounted in a straight line across the chassis and the arms slope down from the chassis. This means the wheels lean over with the van as it leans. There is also no axle steering assistance coming from this design and the tyre contact patch is being reduced.

Many cars have used the semi trailing arm design but that has been replaced by even better designs on many cars. The centre drawing at the top of this page explains how it works.axle steer

Then we have beam axles. A loaded spring should look like this
It will be flat and the front eye will be down low while the rear eye is much higher. The axle is moving up and down in an arc around the front eye of the spring. As the car leans into a corner the spring will compress even further while the one on the other side will have weight taken of fit. If you follow the path of the wheels it is easy to see that the whole axle is being skewed around in the direction the car is turning.

Now compare the path taken by a much shorter high cambered leaf spring like you see under caravans and trailers with the front and rear mounting points at the same height under a flat chassis. The axle can only be turned in the opposite direction to a car.

This means a swinging van can lean to the right for example and the axle is going to steer it further to the right. The pig trailer design of caravans is unstable enough as it is without that happening.

Does anyone know how you mane photos bigger?
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Follow Up By: Shaker - Tuesday, Nov 01, 2016 at 23:05

Tuesday, Nov 01, 2016 at 23:05
Or the MS suspension on the Vista RV Crossover.
Also designed by Alan Mawson, it is pretty much a refined version of his MC2 but with an extra link to eliminate the bump steer.

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Follow Up By: The Bantam - Tuesday, Nov 01, 2016 at 23:37

Tuesday, Nov 01, 2016 at 23:37
Oh hell PhillG ..... don't get me started about caravan wheel bearings, axles and brakes

So much of the problems with caravan trailers and suspension is that most of them continue to try to construct a suspension on a straight beam with little or no attention to the attitude of the spring and it's attachments.

So we have leaf springs that are too stiff, have poor articulation and short travel ...... but worse ... yes the whole of the travel is below the front spring attachment.

when coil spring independent is attempted it suffers the same problems but worse ...... very short trailing links with a savage arc, springs with rediculous attitudes ...... little or no improvement in travel or articulation ... still with overly stiff spring rates.
AND as has been mentioned bad tuck under positive camber on compression.

Sorry I have not seen one single independent suspension on a trailer that even comes close to what would be considered adequate or even competent on a passenger vehicle, commercial vehicle or truck.

When someone shows me a properly camber corrected, long trailing link suspension with a low front pivot point OR a dual wishbone suspension OR a crossover or center pivot axle independent suspension ..... all of which are viable in some form .... I may change my mind.

but in the mean time the easiest, competent suspension is to take the components from a leaf spring sprung vehicle with a similar rear axle loading to the trailer.
Install the springs in the same attitude as the donor vehicle and use the shock absorbers that belong with those springs.

cheers
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Reply By: Life Member TourBoy, Bundaberg - Tuesday, Nov 01, 2016 at 15:27

Tuesday, Nov 01, 2016 at 15:27
Something else that is of concern to me is that these components have done some lengthy off road trips, What condition fatigue wise are the stub axles in? have they been inspected properly for stress fractures?...I doubt it.
Cheers,
Dave
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2015 Fortuner
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