4x4 Suspension & Weight Calculator — Find Your Spring Rate, Duty Tier & GVM Headroom

4x4 Weight & Suspension Calculator

Find your spring rate & duty tier.

A general estimator anyone can use to sanity-check front spring rate and rear leaf pack duty tier before buying a suspension kit. Pick your vehicle, tell us what's fitted (or planned), and we'll show you roughly where you land — front and rear.

i

This is a guide only, built from the same numbers we use to spec kits in-store. Always talk to us before ordering so we can confirm the exact spec fits your build.

Step 1 — Your Vehicle

Front axle formula is the same across all these vehicles — only stock/max axle weights differ.

Step 2 — Front Shock / Kit Type

This decides how we show your front result. Options update to match the vehicle you picked above.

Step 3 — Front-Mounted Accessories

Bull bar and winch hang off the front overhang, so essentially all of that weight loads the front axle.

Bull bar
Winch
Spot lights
LED bar or driving light pair mounted on the bar — about 100% loads the front axle.

Underbody & Chassis

Mounted between the axles, so only part of the weight transfers forward.

Rock sliders
~40kg total — about 35% of that reaches the front axle, 65% the rear.
Bash / skid plates
~15kg total — sit forward of centre, about 75% transfers to the front, 25% rear.
Dual / extra battery
~20kg total, ahead of the firewall — about 90% loads the front axle, 10% rear.
An extra/dual battery sits off to one side of the engine bay, so that side needs a touch of preload dialled in to correct the one-sided weight. Purely informational here — there's no purchase attached to this page, but worth knowing before you order.

Rear-Mounted Gear

Tray, canopy, boxes — mounted behind the cab, so this loads mostly onto the rear axle (roughly 20% front / 80% rear split).

Tray
Tool Box
Canopy
~233kg average, fitted over the tub.
Dog box
~90kg average.
Rear bar
~57kg average.
Long range fuel tank
~200kg loaded.
Drawers
~81kg unloaded.
Fridge + drop slide
~44kg average.

Towing

Tow ball weight loads almost straight onto the rear axle, on top of everything else above.

kg
Front Result

Recommended Front Spring Rate

Suggested rate
650lb
Est. front axle load
1185 kg
On the 6112, landing near a circlip notch is normal — each clip is 5mm of adjuster travel, worth roughly 10mm of ride height.
Rear Result

Recommended Leaf Pack Duty Tier

Suggested duty tier
LD
Light Duty
Est. rear axle load
970 kg
This load is over the Ford Ranger PX1/PX2's rated rear axle capacity (2015kg). Talk to us before ordering a pack — a GVM upgrade might be the better fix.
Running super light back there? A near-empty rear end can actually ride a touch rough — a bit of weight low down (an alloy tray, for example) isn't a bad thing and often settles the ride. Keeping your spare tyre in its original mounted position also has a benefit: that's usually factored into how the suspension is tuned. And weight kept low and central is genuinely good for stability — it lowers the centre of gravity, which helps guard against rollovers rather than just being something to avoid.

Rough averages for guidance only, built from the same figures we use to spec kits in-store. Every vehicle, load and driving style is a bit different — talk to us before ordering and we'll sanity-check the spec against your actual build.

Back to blog