Originally Posted by
the evil twin
I am always somewhat perplexed about many points or solutions in discussions around mods and after market fixes to suspensions on heavily loaded vehicles of any description.
Pretty much the entire vehicle is engineered around the designed loads and then specified accordingly by the manuf. The braking system, transmission from clutch to wheel studs and every bit in between and of course the suspension.
The manuf then comes up with some figures such as GVM but is also very specific about loads on the particular axle groups.
Now, of course the engineers have put in a design factor (same concept but not the same magnitude as a rated shackle for example) BUT remember strength increases weight, is expensive, reduces performance and affects fuel and emmissiosn so you can be assured they don't build in all that much overhead.
So these numbers become an equivalent to the SWL and everyone here knows what the response would be to someone who suggested we fudge SWL on Snatch Blocks, Shackles or whatever.
If a Ute is dragging it's arse like a dog with worms then something is wrong. OK, it may just be worn out springs so get them reset or go after market or whatever.
If you need to exceed the max manuf specified inflation pressure of tyres then something is wrong. OK, you may just need to change the tyre size or load rating BUT if those tyres are spec'd by the vehicle manuf then something is absolutely wrong (not saying thats what you did Cuppa just using an example)
If you carry a load that exceeds the weight allowed for the axle group then something is wrong. OK, thats easy to point the finger at the cause , its the operator.
My first point is that you can easily be under GVM but overload a Tray and therefore the rear axle especially if you have load levelling devices.
Sure they make the vehicle steer a lot better and maybe even brake better but probably not by much and certainly not for long under repeated brake applications BUT the forces generated by the load still have to go somewhere and where they go is the spring hangers/towers, chassis rails, brake effort, increased torque loads in the diffs, axles etc, increased shear on the wheel studs etc just to rattle a few off.
In the last year I have had to deal with a Navara with a bent chassis (6 degrees) that never went anywhere near GVM loads but DID have very uneven loading practiced by the operators. I am still embroiled in a bitter dispute with another operator who cannot understand why you can't carry 11 people in a Troopy and an extra fuel tank and a steel winch bar and winch and 3 batteries and 200 KG on the roof and 150 KG under the troop seats and tow a trailer.
So... my second point. GVM upgrades are available. Some of the very modest ones require minimal engineering but still need attention regarding axle groups.
Others require very intensive engineering and modifications to chassis, braking systems, transmission components etc.
I believe that, for example, one figure is a minimum of 0.5 G braking at the new GVM
That may entail new tyres, rims, brakes, rotors, booster etc etc
Bottom line is IMHO, rafa, you may need to consider that the Patrol is possibly not the right vehicle and an LR/MR or F Truck or whatever is more appropriate.
I am a big fan of the Iveco Daily 4x4 Cab Chassis for example. I have been assisting in evaluation of these for Gov't here in WA and jeez, they are a very very capable bit of kit.
Chasing extra GVM out of a Patrol can be a very expensive exercise on a $ per KG ratio.