Isuzu Dmax Suspension upgrades

Ok getting a bit more serious about doing an extended trip around NZ with the Dmax and towing a caravan, been looking at a few caravans and most of the ones we like are not only up in price ( funny that) but also weight so looking at upgrading the Dmax suspension to handle a bit more weight in the bum and at the same time give it a lift and remap to stop her dragging the bum during offroad work and a bit more poke for towing uphill.

Dmax is 2021 LS Auto, dual cab with canopy on back, 3500kg tow/350kg tow bar down weight and ~5700kgs CVM

So the plan is:

• 2" or just under lift front and back, no diff drop (happy to go a bit lower if I dont stress diffs)
• Upgrade to heavy duty rear leaf springs or put in a set of air bags (tow master or similar) - the airbags will require recertification
• remap upgrade?
• auto cooler ? is it worth it?

So any recommendations on what to install suspension wise and the other mods mentioned any recommendations on who to do it in CNI, performance mechanical in Taupo has been recommended.

Goal is to have a ute thats a bit better ground clearance for general offroad use, for example typical hunting and fishing access as in beach and South Island river work - nothing too extreme, keep good road handling ability when not towing as 90% of its use is lightly loaded road use. Suspension that can handle 3.3-3.5Te caravan on the back climbing up and down SI mountain passes. Avoid overloading diffs and drive shafts with too extreme lift.

If you go 50mm front and rear you will just achieve a slightly higher saggy bum. Controversial statement, but what you want over the factory leafs at the rear is more, more compliant individual leaf sections forming the leaf spring pack. Each leaf deflects under a set amount of weight, so for a greater range of loading before the overload plate at the bottom of the pack is in play you need more leaves. Once the overload plate is engaged, the next stop is just that, the rubber bump stop hitting the chassis. The danger there is creating a pogo stick at the back with many leaves loading and unloading and most factory oil filled nitrogen pressurized shocks won't like that work rate - buggers will fade young. It's not a fault of the product its the design of the suspension system is setup for urban soccer mums carting a bag of soccer balls and three kids to sports...

What you want at the back is a compliant multi-leaf spring pack with heavy duty foam cell shocks - rated to a stiff ride unloaded and then slightly baggy when fully loaded. That means you're at the extreme end of the load range when fully loaded or towing heavy, in the middle at your normal mid range load and then unloaded is stiff but not unmanageable. If your bump stops are engaging every bump when fully loaded, your springs are crud and aren't up to the task... I'm not a major fan of airbags, having been involved with one cracked chassis but that was due to the vehicle having quite a range from empty load to full load and the supplementary bags not getting adjusted according to recommendations.

Now the fronts - minimum lift to get the alignment and caster angles back into manufacturer's specs. Using the example of the ranger, with a 7-leaf high load pack and foam cell shocks in the arse, the fronts stayed on factory springs but foam cell struts. I needed a 20mm lift on the front wheels, with the Ranger's design 20mm of lift = 10mm extra compression on the factory springs. I achieved that by a foam cell strut with a removable floating lower spring cup and fitting a 10mm spacer ring under it. With the strut assembled on factory springs and dropped back into the vehicle this gave the required 20mm lift at the front end to get the adjustment range back into factory specs. Any higher than that, and the arse would have been drooping with a load on...

Hope that makes sense, but setting up a ute for towing with a 50mm lift all around will likely lead to disappointment - it's different if you are going for ground clearance or clearing wheel arches for bigger boots etc etc where you want the vehicle sitting flat but for towing you want the vehicle sitting flat with the trailer on which means that it needs to be up at the back when unloaded. Otherwise the stability goes to the pack when you have a heavy trailer on and the arse is dragging...

Only thing I could advise on is the auto cooler. Most defiantly yes. Any auto that tows often or heavy it's must have one, also can help out your brakes downhill by using the engine a bit more.

Sorted a d max a few years ago by buying 2 more factory rear main spring leaves

Cut the eyes off them and install one each side under the original main leaf
Taper the cut ends, then reassemble with the remaining original leaf pack, used original u bolts.

Slight lift and serious load carrying capability increase

Cheap performance mod

Having spent a fair few pennies on my 2020 dmax, the part numbers between the old shape and new ones are still the same for aftermarket kits.
My 2 cents, I currently have dobinson 3inch lift MRA in the front which is fantastic being able to adjust the rebound makes a smooth ride on the open road and then adjustable on rougher surfaces. Downside cert required. In the rear I have 2inch 300kg constant leaf springs with a 1inch extended shackle and the longest travelling shocks I could find.

In hindsight, the kit I had in it preciously from EFS would be preferred from a cost perspective. Give the guys at force4 a call in Auckland. They are extremely knowledgeable and with the weights you are looking at I'm picking would recommend the EFS xtr shocks (what I had).

I would strongly advise to stay away from ironman products. They are horrible from previous experience.

May pay to do a little research on wheel alignment specs with a lift kit. I went the 3inch cert route purely because with a 45mm lift kit I was chewing sets of tyres in 40,000kms as the wheel couldn't be adjusted properly due to the lift kit and chew the inners of the front tyres out excessively. Aftermarket Upper control arms, diff drop and 3inch suspension certed later finally getting wheel alignments right.

If you're going to be towing a caravan up around 3.5T you probably need to look at something a bit bigger, like a LC200.

Or get a lighter caravan.

Quote:

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Originally Posted by Savage1

If you're going to be towing a caravan up around 3.5T you probably need to look at something a bit bigger, like a LC200.

Or get a lighter caravan.

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Hate to sound like a stuck record, but as per @Savage1 s comments, go review John Cadogan's YT channel on towing 3.5T in Aussie: In essence DON"T!!

If your caravan actually weighs 3500kg, all full of goodies, you'd better have one skinny wife and no kids, otherwise you will be over your GCM. In Aussie the highway police will ream you for travelling like that, and sticker your wagon.

Quote:

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Originally Posted by JustAnotherSpearo

Having spent a fair few pennies on my 2020 dmax, the part numbers between the old shape and new ones are still the same for aftermarket kits.
My 2 cents, I currently have dobinson 3inch lift MRA in the front which is fantastic being able to adjust the rebound makes a smooth ride on the open road and then adjustable on rougher surfaces. Downside cert required. In the rear I have 2inch 300kg constant leaf springs with a 1inch extended shackle and the longest travelling shocks I could find.

In hindsight, the kit I had in it preciously from EFS would be preferred from a cost perspective. Give the guys at force4 a call in Auckland. They are extremely knowledgeable and with the weights you are looking at I'm picking would recommend the EFS xtr shocks (what I had).

I would strongly advise to stay away from ironman products. They are horrible from previous experience.

May pay to do a little research on wheel alignment specs with a lift kit. I went the 3inch cert route purely because with a 45mm lift kit I was chewing sets of tyres in 40,000kms as the wheel couldn't be adjusted properly due to the lift kit and chew the inners of the front tyres out excessively. Aftermarket Upper control arms, diff drop and 3inch suspension certed later finally getting wheel alignments right.

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Funny, I went with the Ironman on advice at the time and could not be happier. One of the reasons for that was they were one of the only local options where the lower spring cup on the struts was a floating design which allowed tuning of the preload in a non-adjustable way which meant no cert requirements. I'd suggest if you're having issues there is a component mismatch somewhere that meant things aren't working right. The factory shocks are fine in standard trim and are quite high quality, but change anything in the ride height or other setup features and they won't perform. Everything needs to work together...

Correct on chewing out the inners, wishbone macpherson strut suspension is not easy to stuff about with as the alignment adjustment range does not factor in changing the ride height setpoint with a lift kit. The problem with that is in extreme cases the tyres only run on the inner edge and on loose or metal roads the end result can be bloody dangerous.

I have standard old man emu suspension upgrade/lift in my hilux and very happy with it. Most of my driving is unladen so got the standard (medium) rear leaf springs and it has no issues when I do put our 20ft caravan on behind it for the big holiday load up and haul.