Submitted: Monday, May 07, 2012 at 12:25
ThreadID: 95411 Views:22222 Replies:8 FollowUps:28
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Does anyone know if its possible to upgrade the towing weights of a 120 Diesel Prado.the current weight of 2.5t is very much on the lenient side.Is a suspension upgrade possible????
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Reply By: olcoolone - Monday, May 07, 2012 at 17:44

Monday, May 07, 2012 at 17:44
Google is you friend.... give it a go.
AnswerID: 485217

Reply By: RobAck - Monday, May 07, 2012 at 18:40

Monday, May 07, 2012 at 18:40
I suspect you will find a GVM upgrade post registration will require as a minimum an engineers certificate as well as certification by your transport/registration authority and advice to your insurer to check that they will still cover you given that this is a vehicle modification and outside of its engineering specification

Our experience with Prado is 2500kg is the limit for the vehicle


AnswerID: 485225

Follow Up By: fisho64 - Tuesday, May 08, 2012 at 01:52

Tuesday, May 08, 2012 at 01:52
GVM is nothing at all to do with towing weight.
GVM is Gross Vehicle Mass.
Depending on state, but having spoken to the Engineering section at DOTWA, I was told that there is NO possibility in WA of increasing the tow weight of a vehicle that has already been supplied with a tow capacity by the manufacturer.
This is (I was told) due to there being too many variables and a lack of access to the manufacturers engineering calculations.
FollowupID: 760497

Follow Up By: RobAck - Tuesday, May 08, 2012 at 18:39

Tuesday, May 08, 2012 at 18:39
GVM is on part of the GCM calculation or Gross Combined Mass which is the combination of vehicle and combined mass of what it is towing. So GVM which is where the GCM or towing mass calculation is taken from is actually part of the process

I have a certified practising engineer who is qualified to deal with all vehicle modifications including GVM

I am also reassured by others comments supporting our view of the towing capacity


FollowupID: 760552

Follow Up By: fisho64 - Tuesday, May 08, 2012 at 20:55

Tuesday, May 08, 2012 at 20:55
GVM is part of the calculation, but doesnt relate to the tow capacity as specified by the manufacturer. An increase in a vehicles GVM as you mentioned above would have no bearing on an increased tow capacity, if anything it may be reduced to retain a similar GCM?
not sure what you mean by "I have a certified practising engineer" though? Do you employ one or have one in the family?

Fully agree on the tow capacity's, some of the dual cabs other than toyotas have a ludicrously high limit.
FollowupID: 760561

Reply By: Ross M - Monday, May 07, 2012 at 19:06

Monday, May 07, 2012 at 19:06
Towing 2.5 ton with a Prado is pushing it.
Just because the rating might be 2.5t this is an optimistic rating and while the vehicle might tow 2.5t it isn't really suited to doing so up hills and with a head wind etc, plus the fact the towed item is far heavier than the tug and in anything less than constant idea conditions you are asking a lot. You have no reserve of steering control/braking/collision avoidance etc.

Just upgrading the suspension doesn't improve the imbalance of the above mentioned items.
Unfortunately people are lulled into thinking eg a 3 ton towing capacity is the go for that particular vehicle and in most situations it should be towing no more than 2 ton so it has 1 ton in rated ability reserve for when things on the road aren't ideal.
Ross M
AnswerID: 485228

Reply By: GT Campers - Monday, May 07, 2012 at 19:29

Monday, May 07, 2012 at 19:29
Said with respect, you are looking at this situation the wrong way: this is not 'lenient' specification, you are expecting too much of the Prado design (competent as it is).

GVM upgrades do not assist with specified towing weights, you need to look at a bigger vehicle (eg: Cruiser) or a lighter caravan. Aim for no more than 2/3 of manufacturers' tow spec LADEN
AnswerID: 485232

Reply By: Member - Broodie H3 - Monday, May 07, 2012 at 21:33

Monday, May 07, 2012 at 21:33
Hi Brian, It was regret that I had to sell my Hilux because of the towing restrictions, I had asked around before doing so with the same questions that you are now asking,and the best I got was engineered specs for 2.5 tonnes, but the insurance company I was with put the kibosh on everyting by saying I would not be covered for such a modification.So we now own a Pathfinder ti55o. that is rated3.5 tonnes, but we will never tow that much 2.6 is about all I will tow, always need something in reserve, load in the back cargo area about 120kg. Hope this is of some Help.
Broodie H3
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AnswerID: 485245

Follow Up By: Member - Tony V (NSW) - Tuesday, May 08, 2012 at 10:37

Tuesday, May 08, 2012 at 10:37
Hey Broodie,

You sure that the Pathfinder TI550 is 3.5 tonnes? All indication suggest 3 tonnes braked towing.
FollowupID: 760519

Follow Up By: Member - Broodie H3 - Tuesday, May 08, 2012 at 13:04

Tuesday, May 08, 2012 at 13:04
Hi Tony, yes we are quite sure of the towing capacity, It was the only reason we went into a Nissan, I have always been in Toyota's before and believe me this is some vehicle to travel around in. As a tow vehicle could not ask for anything better. We put off buying it until the new Hilux came outand when we found out that the towing capacity had not been increased, we had to rethink our plans and came up with the Pathfinder, I even had a look at the new Landrover with the v6 Diesel motor but that was another 15 grand so we brought the Nissan it is the same motor and gear box that is in the Landrover which is a Renault motor, that Renault use in their four and five tonne trucks, so I was told.and the towing capacity is 3.5 tonne
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FollowupID: 760527

Follow Up By: Member - Tony V (NSW) - Tuesday, May 08, 2012 at 19:09

Tuesday, May 08, 2012 at 19:09
Thanks Broodie,

Just found the info,

"Ti 550
The Pathfinder Ti 550 includes all the features of the Pathfinder Ti shown above with the major addition to the range of a 3.0 litre V6 turbo-diesel engine, boasting 170kW of power and 550Nm of torque, mated to an advanced 7-speed automatic transmission and an increased 3,500kg braked towing capacity (up from 3,000kg on other Pathfinder models). A further performance enhancement includes upgraded larger front 320mm ventilated disc brakes (up from 296mm on other Pathfinder models). "

7 Speed auto and bigger brakes, looks like a lovely vehicle.

FollowupID: 760554

Follow Up By: Member - Broodie H3 - Wednesday, May 09, 2012 at 02:06

Wednesday, May 09, 2012 at 02:06
Hi Tony, It is a great vehicle and o easy to drive but the only concern I have at the moment is the thickness of the manual that comes with it. you need to be a rocket scientist to understand the book, let alone to operate all the features in it. It realy is a good compromise for a land cruiser V8 diesel. I currently get 12.1 km per hundred towing the van at a speed of 95klm's an hour go over that and I go to 12.5 per hundred klm at 105klm/hr, around the city I do 11.2per hundred klm' at viariable speeds, and it is comfortable to cruise in.
Broodie H3
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FollowupID: 760576

Reply By: nordi - Tuesday, May 08, 2012 at 01:14

Tuesday, May 08, 2012 at 01:14
Hi all

This is the towing weight for the Prado 150 D4D in Germany. The 120 was the same.

Anhängelast gebremst bis 12 % Steigung 3000 kg
Anhängelast ungebremst 750 kg

Manuel and automatic is the same.
I don't understand why there is 500 kg less for Australia

AnswerID: 485261

Follow Up By: fisho64 - Tuesday, May 08, 2012 at 01:55

Tuesday, May 08, 2012 at 01:55
"I don't understand why there is 500 kg less for Australia"
probably due to roads being of a lower standard here?
FollowupID: 760498

Follow Up By: GT Campers - Tuesday, May 08, 2012 at 08:41

Tuesday, May 08, 2012 at 08:41
Different markets/countries have different specs dueto factors such as road conditions, temperatures, gearing/transmissions tyre specifications, local laws.. etc etc that may all be different to Aus. Aus is generally a very tough environment
FollowupID: 760509

Reply By: The Bantam - Tuesday, May 08, 2012 at 13:10

Tuesday, May 08, 2012 at 13:10
I think others have given you the news on the Prado.

basicly you are stuck with the towing capacity, and even towing near capacity any further than the local dump, pony club or boat ramp is probably ill advised.

Towing weights most definitely do have relationship with both GVM and unladen weight...and the rules have changed in this country over the last few years.

In the past, manufacturers where only allowed to certify their passenger vehicles for a maximum braked towing weight of the unladen mass of the towing vehicle.
More recently there are more lienient allowances that seem to be bassed on a % of the GVM.

This accounts for the difference between very similar vehicles of differing ages.

There are many of us that view the current towing allownaces as simply rediculous and bordering on dangerous.

This is further borne out by the number of bent rear chasis stories ( supported by pictures) we are seeing on modern vehicles that have towing capacities 30% higher than very similar earlier models.

Note that toyota generally have a single towing capacity for a given vehicle model regardless of options........this indicates to me that toyota are engineering bassed on the capacity of their rolling chasis.
To me a sound engineering premiss.

Ya prado has a kerb weight of arround 2.3 tonnes, a GVM of arround 2.9 tonnes and a braked towing capacity of 2.5 tonnes.

That does not seem unreasoable to me...bassed on the towing capacities of other toyotas and other cars.....I am sure toyota could have recomended a higher twoing capacity under current regs....but they did not...there is a resaon for that.

Consider that the Prado is more or less a hilux station waggon ( people will argue that one) and is mechanicaly very similar.......the hilux has a stiffer and more rigid rear suspension, but in the year equavalent model the hilux has a considerably lower towing capacity.

I recon 2.5 tonnes is doing very well out of a prado...don't push it.

AnswerID: 485283

Follow Up By: GT Campers - Tuesday, May 08, 2012 at 13:37

Tuesday, May 08, 2012 at 13:37
Toyota is very conservative (sensible) with its towing ratings - the cars usually last soem time when towing heavier stuff.

Other manufacturers are... ummmm... not so sensible
FollowupID: 760534

Follow Up By: shylok - Tuesday, May 08, 2012 at 17:55

Tuesday, May 08, 2012 at 17:55
I find it very hard to understand why the 3 door prado has a towing capacity of 3 tonnes when it is smaller and 150kg lighter than the 5 door.
It has the same motor and transmission
FollowupID: 760547

Follow Up By: GT Campers - Tuesday, May 08, 2012 at 18:00

Tuesday, May 08, 2012 at 18:00
yep less kerb weight means it can tug more for the same fuel burn/heat load. But 500kg is a big difference compared to teh kerb weights of the vehicles
FollowupID: 760549

Follow Up By: The Bantam - Tuesday, May 08, 2012 at 22:53

Tuesday, May 08, 2012 at 22:53
The 3 door prado is a different vehicle, it has to be I have not looked close at it myself but.
If it is a 3 door it probably has less rear overhang...less towball leverage and less rear axe load.

Just reducing the tare weight by 150KG will increase the available towball down force which will increase the possible towing weight.

Remember there will be a minimum persentage of towing capacity that must be allowed as towball down force.

In toyota towing capacities calculations the engine capacity and transmission are not a factor, as the larger engined vehicles have the same towing capacity as the smaller.

toyota will be working mostly on
chasis strength
the maximum permissable load on partiularly the rear suspension.
braking capacity
the mass of the vehicle

If the GVm of the 3 door is 2.9 tonnes, then under the current rules 3 tonnes is probaly dooable

All those factors....but I would be laying my money on the maximum permissable towball down force as the pivotable issue.

FollowupID: 760568

Follow Up By: The Bantam - Tuesday, May 08, 2012 at 22:57

Tuesday, May 08, 2012 at 22:57
If you are looking at going anywhere near the towing must look at maximum permissable towball down force.

With lots of combinations that is where the limitation is going to be.

OH and you also have to watch the GCM gross combibation mass.

once the tow vehicle is loaded, you may not be able to tow maximum towing capacity.

FollowupID: 760570

Follow Up By: GT Campers - Wednesday, May 09, 2012 at 09:38

Wednesday, May 09, 2012 at 09:38
Towball downforce will not increase max towing weight - car manufacturers derive max allowable tow mass from coolng system ability...and just about nothing else. It's all about keeping the engine and trans cool until the warranty runs out ;)

But rules are rules and regs are regs.. so for Prado wagon, 2500 is the number
FollowupID: 760588

Follow Up By: The Bantam - Wednesday, May 09, 2012 at 10:48

Wednesday, May 09, 2012 at 10:48
I think that is a bit dismissive.

Ford and Holden may because of their crappy underspecified transmissions change their towing capacities with engine and transmission options ........

Hell, Ford typicaly even require additional auto transmission cooling for towing anything more than a domestic box trailer

Toyota do not

Ford and holden may change their towing capacity with suspension options.....

Toyota do not.

Again in general Toyota do not change their towing capacity with engine or transmission options or any other options for that matter.

There are many things that come into satisfying the requirements.

vehicle mass is clearly a major and predominating issue.

rear axle loading is also

If the towball down force and therefore rear axle loading, just happens to be a limiting factor for that vehicle it WILL most certainly change the towing capacity.

Look at the towball down force compared to braked towing capacity for a number of vehicles, it is far from generous and if you subscribe to having more than 10% of your trailer mass on your will in many cases find the down force IS the limiting factor and not the braked towing capacity.

OH....and cheater bars or a "load sharing hitch" will not reduce towball down force.

FollowupID: 760596

Follow Up By: GT Campers - Wednesday, May 09, 2012 at 11:11

Wednesday, May 09, 2012 at 11:11
It's not dismissove - it's fact, and I include this info to the priginal poster about why a GVM upgrade or a letter to the editor won't allow the Prado to tow anything heavier.

Max tow mass is a derived engineering figure based on the vehicle's cooling system's ability to shed heat produced by engine/driveline when developing the power required to tug XXXkg along a road at, say, 80km/h.

Please realise this has nothing to do with towball weights/downforce or axle loads or the angle of the dangle. It is simply a case of: 'this engine will get this hot, pulling this weight, along this road, so will need to shed this much waste heat through this radiator aperture"'

Thsi figure may (not always) then be tested/validated with on-road testing during a vehicle development program to test hardware such as exhaust hanger rubber etc and cooling system compromise with bull bars etc installed


FollowupID: 760598

Follow Up By: fisho64 - Wednesday, May 09, 2012 at 17:28

Wednesday, May 09, 2012 at 17:28
sorry but that is a little rediculous.
Are you saying that the manufacturer doesnt take into account brakes, chassis strength etc when calculating max tow capacity?
Besides the fact that no manufacturer I know of releases any of these sort of calculations (so you and I would have no idea what is the limiting factor) it should be obvious to anyone that these sort of engineering calculations are based on a wide selection of the limiting factors, cooling systems being only one of them.
FollowupID: 760618

Follow Up By: GT Campers - Wednesday, May 09, 2012 at 21:55

Wednesday, May 09, 2012 at 21:55
FollowupID: 760657

Follow Up By: fisho64 - Wednesday, May 09, 2012 at 22:22

Wednesday, May 09, 2012 at 22:22
Im assuming thats a "yep" to my first sentence!
FollowupID: 760660

Follow Up By: GT Campers - Thursday, May 10, 2012 at 09:36

Thursday, May 10, 2012 at 09:36
Fisho.. you can't answer a sentence so my 'yes' is the response to your one and only question..

I will try explian/clarify things further: rear body/chassis/suspension strength and rear axle capacity determine drawbar weight. This has nothing to do with MAXIMUM tow rating specification of the vehicle The MAXIMUM tow rating is detemined by driveline durability, the biggest factor being the ability of the cooling system to keep up with shedding the heat required to power a vehicle combination of XXXXkg along a road.

From a vehicle manufacturer's standpoint, little else matters

Anything over 750kg being towed does its own braking so the tow car brakes aren't considered to any great extent.

All that may surprise you but , that's how it's done!
FollowupID: 760686

Follow Up By: fisho64 - Thursday, May 10, 2012 at 09:58

Thursday, May 10, 2012 at 09:58
Thats a huge over simplification.
Rear chassis strength in some cases may be the limitation. But your last answer is a little more in line with what Bantam is saying, and I reckon he nailed it pretty much.
FollowupID: 760688

Follow Up By: The Bantam - Thursday, May 10, 2012 at 11:53

Thursday, May 10, 2012 at 11:53
sorry GT.....still an over simplifcation and a biasing of the argument toward one particular engineering consideration.

You simply can not say this or that factor has nothing to do with another.

In the not too distant past there was one single peramiter that determined towing capacity of pasenger cars in most states and that was vehicle mass, you could not tow more than the towing vehicle weighed.

Things have changed.

We live at a time when many of the manufacturers are pushing the limits of the vehicle formats. It is very reasonable to see that as they push the envleope any the various engineering factors can become a limitation.

It is a fact that IF a manufacturer wishes to nominate a specific maximum towing capacity, that vehicle MUST be capable of supporting a certain persentage of that capacity as drawbar down force.
IF the vehicle cant support that persentage of down force they can not mominate the higher towing capacity.

Look at the latest crop of 4 cylinder utes, the manufacturers are nominating towing capaicities nealy twice that of the precceding generation, on a format that remains largly unchnaged on vehicles that do not weigh too much more.

Also note that after 30 years of sticking with the same nominated tyre size more or less across the brands, it has become necessary to increase the tyre size on 4 cylinder utes to permit the increased rear axle loads.

Be asured that these very high permissable towing capacities are pushing the envelope in every peramiter.

On one vehicle it may be cooling, on another it may be the strength of the gearbox ( typical of US manufacturers) on another it may be rear axle strength or chasis strenght ( as we are seeing from the reports) or even vehicle stability.

It is simply unrealistic and nonsensical to say that all manufacturers base their towing limits on one single peramiter.

AND experience shows that to be the case, testified to by the types of "in use failures" that we are seeing when people push the bleeding edge of the towing capacities.

Further manufacturers such as Toyota standardise engines and transmissions across a very wide range of vehicles...a very wide range of vehicles that have significantly differing towing capacities.

The biggest example is the hilux V the hiace, two vehicles with very similar uses, load carrying capacities and GVM and in the 2wd base model very similar if not identical engines and trasmissions.
BUT over the decades and several incarnations, the van has always had arround half the towing capacity of the utility.
There is definitely something other than engine capacity, transmission and cooling being considered here.


FollowupID: 760694

Follow Up By: GT Campers - Thursday, May 10, 2012 at 12:49

Thursday, May 10, 2012 at 12:49
Lads, all I have done here is to simply explain how it is *actually* done during vehicle development phase of passenger-type vehicles. Keeping it COOL - engine, trans, diff - is what determines *maximum* towable weight.

I am not saying I agree with this...but that is what is done when the dudes in white coats park a mule car in the sun all day near Katherine then take off at full-throttle with a 2000kg dead weight on a rigged-up trailer.

Once again I iterate this has nothing to do with rear axle weight or drawbar download; yes these figures are specified by the manuafcturer but these figures are not actual machine weights towed by the engine - they are weights carried by the suspension/chassis so do not tax the cooling system. 100kg vs 200kg vs 500kg on the drawbar has nithing to do with MAXIMUM permitted tow weight.

Think of it this way: A Prado flat-towing a 2000kg vehicle with a tow rope will have the same fuel burn as a Prado towing a 2000kg caravan even if there is 250kg into the drawbar. Its gearbox/diff is working just as hard and it will generate the same heat and need the same amount of radiator to expel that heat.

And that, kwazy kids, is what determines max tow weight.

The Hiace vs Hilux is an awesome example: Similar drioveline, weight etc but the Hiace has totally different aero and has around half the aperture for radiator...

Ha! I feel like that dude with the moustache on the ABC's old The Science Show...remember that?
FollowupID: 760699

Follow Up By: The Bantam - Thursday, May 10, 2012 at 14:28

Thursday, May 10, 2012 at 14:28
What you have done here is insisted that only one of the many factors actually considered determines the towing capacity of all vehicles.

so you have spoken directly with the head office engineers and designers from all the various different manufacturers.

As far the highace having half the apiture.....sorry have you laid on you back under one recently...there is a huge unobstructed hole the full width and height infront of the radiator of a hiace. its not even obstructed by the bumper...all the modern vans do not pull air thru the grill

The single biggest difference is that the hiace has much softer suspension than the hilux.

No doubt there will be thermal testing.....but there is far more to it than that.

If what you say was true, a vehicle with a bigger engine and radiator would have a higher towing capacity.........not if it is a toyota it will have the same towing capacity as the base model that has a smaller less powerfull engine and radiator.

FollowupID: 760706

Follow Up By: GT Campers - Thursday, May 10, 2012 at 16:08

Thursday, May 10, 2012 at 16:08
Hi, I am not insisting anything...,this is not MY opinion, it is simply how it's done...Okay?

Yes, yes, and yes

Suspension/chassis has nothing to do with maximum tow rating; it does however help detemine drawbar weight

once again: Maximun tow rating is detemined by engine cooling. Toyota will specify one figure per series as they all have the same size hole in the front of the car
FollowupID: 760718

Follow Up By: The Bantam - Thursday, May 10, 2012 at 16:27

Thursday, May 10, 2012 at 16:27
Keep digging chum, you are the one with ya company brand at he head of each post.

so explain why a 2 door prado has a higher tow rating than a 4 door, same engine, same transmission, same cooling system same hole in the front.

FollowupID: 760722

Follow Up By: GT Campers - Thursday, May 10, 2012 at 17:03

Thursday, May 10, 2012 at 17:03
I think I'm picking up a bad vibe there... chum... but if you don't like the way car designers do things... take it up with them, not me - all I've done is explain how it's done!
FollowupID: 760726

Reply By: The Bantam - Wednesday, May 09, 2012 at 12:28

Wednesday, May 09, 2012 at 12:28
It does not matter how big the engine, transmission or radiator is.

If the chasis is not strong enough, or the rear axle and suspension will not support it, or the vehicle mass is not sufficient,

That will limit the towing capacity, just as surely as the vehicles ability to pull the load without boiling its head off.

If towball down force was not a significant engineering issue it would not be stated....but it is.

If we are discussing the difference between two similar vehicles that have the same engine, transmission, running gear and a very similar chasis as in the 2 door V 4 door Prado instance

The decrease in kerb weight and thus the increase in available rear axle load may account for an increase in towing capacity.

Particularly when many of these modern cars with high rated towing capacities have very powerfull engines compared to the past BUT may be pushing all the other various engineering limits.

I can tell you that a 2.4 litre hiace van will happily tow more than twice its rated towing capacity at highway speeds and up the cunningsham gap range with out running out of schnaps, crapping the tranny or boiling its head off.
I know a couple of blokes who used to do it regularly.
NOT a good idea, in my opinion dangereous, but the engine and tranny are certainly not the limitation in this case.

Try towing my small boat under 750kg with my 4.1 litre XF of the past and its tranny is smelling hot after a 20 minute slow ride back from the boat ramp.

In this case the trannies ability to cool its self is the limitation.


AnswerID: 485348

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