Treg coupling and weight distribution systems

Submitted: Monday, Mar 23, 2009 at 23:07
ThreadID: 67132 Views:6605 Replies:8 FollowUps:17
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We have just acquired an offroad caravan (weight 1600kg) with a treg coupling. We have a 2002 Prado and have conflicting advice re need for weight distribution system. Rear door opening will not be possible with Hayman Reece system. Comments appreciated re need for weight distribution system and if so any recommendations for alternative workable systems.
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Reply By: Gone Bush (WA) - Monday, Mar 23, 2009 at 23:59

Monday, Mar 23, 2009 at 23:59
Try it without the WDH's. You'll get a feel for whether they are needed or not.

I tow our 16'6" Trakmaster (2500kg) without them.



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Reply By: Member - Alanc - Tuesday, Mar 24, 2009 at 01:03

Tuesday, Mar 24, 2009 at 01:03
Ditto above comments.
We have a 2001 Prado and tow a 15' offroad Coromal poptop (1600kg) fitted with a treg hitch and don't see the need for a wds (in our situation) although I did fit Polyair bags to rear springs. If I know we need to open the rear door when stopping I jack knife the van a fraction which allows us to open the door most of the way . Even when parked normally we still have good access to the back.
Regards, Alanc
AnswerID: 355804

Reply By: Baz&Pud (Tassie) - Tuesday, Mar 24, 2009 at 02:23

Tuesday, Mar 24, 2009 at 02:23
Hi Bernie
We tow a 2+ ton caravan with a treg fitting, have air bags in rear springs which keeps the whole rig nice and level. My understanding is that if you have a treg fitting you cant use a wds.
Cheers
Baz
PS not usually up at this time just can't sleep.
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Follow Up By: Member - Graham H (QLD) - Tuesday, Mar 24, 2009 at 08:47

Tuesday, Mar 24, 2009 at 08:47
Was in a van park a few weeks ago and there was a big Kedron with a treg hitch and they were using a WDH and said they had no trouble.
Incidentally Air bags are not a substitution for a WDH.

While they appear to level the vehicle, they dont and cant transfer the weight back onto the front axle that is lifted off by the action of putting the weight on the towball.



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Follow Up By: DIO - Tuesday, Mar 24, 2009 at 09:27

Tuesday, Mar 24, 2009 at 09:27
Why can't you use WDH with a Treg coupling ?
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Follow Up By: Keith_A (Qld) - Tuesday, Mar 24, 2009 at 10:37

Tuesday, Mar 24, 2009 at 10:37
My understanding is that while you can use a WDH with Tregg, but must uncouple it when offroad as the WDH limits the articulation (eg if you try to drive across a wash-out, or over a ridge).
We have towed a variety of off road rigs (latest is 2.4 ton) over the last 22 years and never used a WDH.

As the WDH transfers weight (from the ball) from rear wheels to front , perhaps a simpler solution is to have the correct weight on the ball ? (but then I have never used WDH, so there may be other reasons for them.)
.............Keith.
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Follow Up By: wendys - Tuesday, Mar 24, 2009 at 22:35

Tuesday, Mar 24, 2009 at 22:35
We have had offroad van with treg coupling since 1997. Van has been towed over 100,000km in that time. We've had a Hayman Reese WDH the whole time - think we got ours just as they started to make them to go with tregs. We do take it off if we are going on dirt roads, but always use it on the bitumen. We also have polyair bags inside the vehicle's rear coil springs, but that is to extend the life of same, in theory and improve our ride.
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Reply By: snailbait (Blue mntns) - Tuesday, Mar 24, 2009 at 09:53

Tuesday, Mar 24, 2009 at 09:53
et all
I have a wds with a treg part and a trig part the gold npart is modified to fit on the wds . and it is correct that it is the task of the wds to keep the coupling level and the front wheels on the ground when braking also it stops the hobby horse effect when moving
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AnswerID: 355832

Reply By: Olsen's 4WD Tours and Training - Tuesday, Mar 24, 2009 at 10:30

Tuesday, Mar 24, 2009 at 10:30
I would not fit one with a Treg hitch, but Treg hitch aside, according to Toyota and the RACQ Tow Mass Guide, the Prado requires WDS when towing max mass 2300kg with maximum tow ball mass (down-force) of 230 kg. No advice is given as to the minimum weight where WDS is required which would lead me to believe Toyota says it is only when towing maximum 2300kg.

The main reason for the WDS is to restore weight at the front wheels which normalizes steering geometry. When adjusting these hitches, measure the distance from bottom of front rim to bottom of wheel arch without trailer attached. Attach trailer and measure again. Adjust WDS until normal ride height is established at the front.

How much does your measurement change? Also, how much does your tow ball drop when you attach the trailer?

AnswerID: 355844

Follow Up By: Olsen's 4WD Tours and Training - Tuesday, Mar 24, 2009 at 10:37

Tuesday, Mar 24, 2009 at 10:37
Let me rephrase that last question- how much does the measurement at the front wheels change, and how far from the road surface is the centre of the towball when the trailer is attached. it must be between 350 and 460mm to be legal.
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Follow Up By: Jarse - Tuesday, Mar 24, 2009 at 12:06

Tuesday, Mar 24, 2009 at 12:06
Hi David,

I'm not sure of your source, but the centre of my towball is 480mm.

My tyres and suspension are standard, and the towbar/tongue/ball is genuine Toyota. Measurement taken with 0psi in the Poly's.

When towing a light trailer the drawbar does not compress the rear suspension at all.

Not discounting your claim on heights, but all my gear is OEM and therefore should be compliant.
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Follow Up By: Olsen's 4WD Tours and Training - Tuesday, Mar 24, 2009 at 12:18

Tuesday, Mar 24, 2009 at 12:18
I am a Tow-Ed Instructor, my reference is trailer laws. I will try to find a direct reference for you shortly.

Oh how I wish OEM stuff was compliant. 30% of the stuff I see is not.
I had a 4.5 tonne ATM trailer the other day, brand new with 3500 kg hitch, tyres with a total combined load rating of of 3600kg and numerous other issues.
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Follow Up By: Olsen's 4WD Tours and Training - Tuesday, Mar 24, 2009 at 12:26

Tuesday, Mar 24, 2009 at 12:26
"The National Code of Practice Building Small Trailers"
12.2.1 50mm Ball Couplings
Ball couplings used on trailers with an ATM of up to 3.5 tonnes must comply with Australian Standard AS 4177.3-1994 and be installed so that the height of the centre of the body of the ball coupling is between 350mm and 420mm from the ground when laden.
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Follow Up By: Olsen's 4WD Tours and Training - Tuesday, Mar 24, 2009 at 12:28

Tuesday, Mar 24, 2009 at 12:28
All of that aside, if the height does not change when loaded, you do not need a WDS as your front ride height and steering geometry is unaffected
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Follow Up By: Olsen's 4WD Tours and Training - Tuesday, Mar 24, 2009 at 12:38

Tuesday, Mar 24, 2009 at 12:38
Sorry I should read what I cut and paste, bit too busy sometimes. The law above changed recently and is now 350 to 460mm.
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Follow Up By: Gone Bush (WA) - Tuesday, Mar 24, 2009 at 12:52

Tuesday, Mar 24, 2009 at 12:52
This legal, not legal argument was done to death on a Caravan Forum and the end result was, I believe, that those regulations concerning towball height did not apply to off road trailers, caravans etc.

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Follow Up By: Olsen's 4WD Tours and Training - Tuesday, Mar 24, 2009 at 13:12

Tuesday, Mar 24, 2009 at 13:12
Hi Gone Bush,

I was not privy to those discussions on other fora, but you are correct re my use of the word legal, may be an overstepping of the mark.

I and others in the game take advice from various guides and standards and laws, and as I and others in the game see it, the Code is not itself enforceable as law, but should you depart from it, you may find yourself being found out on a legal limb.

The Guide is for Light Trailers and very light trailers which is by definition

A trailer with a ‘Gross Trailer Mass‘ not exceeding 3.5 tonnes
A single-axled trailer with a ‘Gross Trailer Mass‘ not exceeding 0.75 tonne.

So caravans and off-road trailers would seem to fit.

Anyhow, getting back to the original question. To determine if a WDS is required, you first must consult the vehicle manufacturer's specs, available from us at Tow-ED or from the RACQ in this state, then consult the trailer manufacturer, then check the actual ride height change. It is recommended you do this intially at the towball, with refernece to the National Code as above, then use the measure of front ride height to set your WDS. Never use a WDS to compensate for incorrect towball downforce. Tow ball downforce should be 8 to 12% of trailer mass (10% recommended) and should be within the vehcile and towbar manufacturers limits.
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Follow Up By: Lex M (Brisbane) - Tuesday, Mar 24, 2009 at 18:51

Tuesday, Mar 24, 2009 at 18:51
I believe the towball height as mentioned only applies to ball style couplings and not to tregs, AT35 etc
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Follow Up By: Lex M (Brisbane) - Tuesday, Mar 24, 2009 at 18:55

Tuesday, Mar 24, 2009 at 18:55
And this was discussed in detail in a previous post


65373
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Follow Up By: Jarse - Saturday, Mar 28, 2009 at 10:47

Saturday, Mar 28, 2009 at 10:47
Thanks for the information, David.

I've been away on a work trip for a few days, hence the slowness in my reply.

In your reference to 12.2.1, I suspect that is the standard for construction of the trailer, as opposed to the towing vehicle.

It would be commonsense, however, to set the height of the hitch on the towing vehicle to that of the coupling on the trailer (in a level attitude).

That's the good thing about the Reese WDH, it has a broad range of height and angular adjustments so you can do just that.

Thanks again.
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Reply By: Jarse - Tuesday, Mar 24, 2009 at 11:41

Tuesday, Mar 24, 2009 at 11:41
I used to tow a PC546 Coromal fitted with a Treg (about 1900kg loaded). My car is an 05 Prado, fitted with Polyairs.

I ALWAYS used the WDH (Reese) and found 15psi in the Polyairs worked well.

I tried towing once without the WDH and about 20-22psi in the bags, and although the setup appeared reasonably level, the overall stability of the rig was very poor when under way, with the steering/cornering not as positive, and front wheel braking somewhat reduced. A couple of times the "rocking horse" as somebody mentioned triggered the ABS on the front wheels with strong braking. That's where the WDH comes into its own (when braking forces increase the down force on the towbar, which in turn transfers some of the weight to the front wheels, somewhat eliminating the "rocking horse").

This is from many thousand k's of practical experience. Overall, with the WDH your work as a driver is easier (IMHO). Your results may be different, but I wouldn't be without the WDH now :)
AnswerID: 355851

Follow Up By: snailbait (Blue mntns) - Tuesday, Mar 24, 2009 at 15:04

Tuesday, Mar 24, 2009 at 15:04
hi Jarse
I Totally agree My 03 Prado does the same thing my Avan Liam adventure mk 11 is the same weight gvm 1990 kg TWO axles , the steering and corning are not as positive
Terry
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Reply By: ozjohn0 - Tuesday, Mar 24, 2009 at 15:52

Tuesday, Mar 24, 2009 at 15:52
Current Vehicle Tow Mass Guide stipulates that all model Prado's must use a WDH when towing.
Check Toyota handbook for minimum weight or check direct with Toyota Australia for minimum weight requirements. But certainly most vans or heavy trailers a WDH is required by them and so it becomes Law. That is it would be unlawful to tow without a WDH and may also effect any insurance cover.
ozjohn.
AnswerID: 355887

Follow Up By: Olsen's 4WD Tours and Training - Tuesday, Mar 24, 2009 at 19:41

Tuesday, Mar 24, 2009 at 19:41
Actually the guide has a #1 note (WDS required) on the 2300kg max limit but not on the 750 kg so my interpretation of that is that WDS is required for 2300 kg but not for 750kg

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Reply By: BernieM - Tuesday, Mar 24, 2009 at 22:46

Tuesday, Mar 24, 2009 at 22:46
Thanks all for your input. You have all given us enough information to understand the issues. We will check Prado requirements again and will probably see how we go without a wds initially if not specified as necessary by Toyota.
AnswerID: 355990

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