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IRONMAN 4X4 vs Bilstein
Two respected names in suspension. Where they separate is what arrives in the box, and whether the spring in it was chosen for the weight you carry.
Start Here
The Short Version
Five things that decide which suspension belongs under your vehicle.
- ✓Every suspension kit ships with its spring. Load ratings run from Light through Extra Heavy across Nitro Gas, Foam Cell Pro and IM2.5, and the ratings for your platform are chosen at the kit level.
- ✓The B8 5100 is sold as a shock, outside two Jeep kits. The Ride Height Adjustable version lifts the front by preloading the factory coil, which does not raise the spring rate, so it does not change what the vehicle can carry. Every Nitro Gas, Foam Cell Pro and IM2.5 kit replaces the spring, in a load rating chosen for the build.
- ✓On a leaf sprung truck, the rear leaf pack is in our kit. There is no Bilstein leaf pack for a 2005-2023 Tacoma, so with their shocks a rear lift comes from another brand. Ours arrives with the shocks, under the same part number.
- ✓Foam Cell Pro has no counterpart in the Bilstein range. Bilstein's off-road truck lines are gas pressure monotubes, and none of them use a foam cell.
- ✓Foam Cell Pro is built to be rebuilt. The B6 4600 and B8 5100 are sealed, and Bilstein recommend replacing them when they wear. Foam Cell Pro is designed to be resealed and go back on the truck, with a seal kit sold as a part for listed part numbers.
Four Series
What Type of Build Are You Planning?
Choose the series built for the toughest thing you ask of your vehicle, not the easiest.
Lift & Level
The Easiest Upgrade. Bigger Tires Start Here.
Daily driven trucks and SUVs. Includes all necessary spacers and brackets for lifting and leveling your truck without breaking the bank, allowing for bigger wheels and tires.
Shop Lift & Level
Nitro Gas
The Smart Upgrade. Better Than Stock in Every Way
Weekend warriors and daily driven trucks and SUVs. Durable twin tube shock design with nitrogen charge and increased shock diameter over stock, allowing better performance on and off road for little investment.
Shop Nitro Gas
Foam Cell Pro
The Workhorse Series. Outlasts Everything on the Trail
Overlanders, outdoor enthusiasts, heavily loaded trucks and SUVs, and daily driven trucks and SUVs. Increased oil capacity without needing a traditional nitrogen charge, so the Foam Cell shock is tough and requires little to no service.
Shop Foam Cell Pro
IM2.5
The Flagship Series. Unmatched Composure & Control
Performance enthusiasts, lightly and heavily loaded trucks and SUVs. Advanced monotube technology allows for precision performance and a planted, composed ride on and off road.
Shop IM2.5Lift & Level |
Nitro Gas |
Foam Cell Pro |
IM2.5 |
|
|---|---|---|---|---|
| Load Ratings: | ||||
| OEM | Light, Medium, Medium Plus, Heavy, Extra Heavy | Light, Medium, Medium Plus, Heavy, Extra Heavy | Light, Medium, Medium Plus, Heavy, Extra Heavy | |
| Shock Design: | ||||
| Twin-Tube, shocks included with certain kits only. | Twin-Tube | Twin-Tube | Monotube | |
| Shock Diameter: | ||||
| Up to 2.1" (53 mm) | Up to 2.1" (54 mm) | Up to 2.8" (71 mm) | Up to 2.5" (63.5 mm) | |
| Rebuildable: | ||||
| No | Serviceable | Fully rebuildable | Serviceable | |
| Warranty: | ||||
| 4 Year / Unlimited Mile | 4 Year / Unlimited Mile | 4 Year / Unlimited Mile | 4 Year / Unlimited Mile | |
| Every kit includes the parts listed for your platform. Check the kit page for anything your build also needs, such as longer CV axles on a 2022 or later Tundra lifted 2.5 inches or more at the front. Our warranty, like Bilstein's, carries its own conditions and exclusions, and both are worth reading in full. | ||||
Series By Series
Compared Spec For Spec
Every shock turns wheel movement into heat. How much oil it holds and how it handles that heat decides whether damping is still there at the end of a long day.
Largest published shock body diameter in each series, drawn to scale. Piston sizes are in the spec rows.
Lift & Level
Nitro Gas
Foam Cell Pro
IM2.5
Where this one lands
These two answer the same question, which is how to gain height without changing the spring. The 5100 Ride Height Adjustable sets its spring seat on snap ring grooves in the shock body, so the lift comes from preloading the vehicle's factory coil spring. It replaces the front shock with a Bilstein monotube as it does it, and Bilstein build a good one.
Preloading a coil does not raise its spring rate, and our Lift & Level keeps the factory coil as well, so neither of these changes what the vehicle can carry.
Add a bumper, a winch or a drawer system and you want a spring chosen for that weight. On our side that means Nitro Gas, Foam Cell Pro or IM2.5, in the load rating that matches the build.
Where this one lands
Different architectures. The 5100 is a gas pressure monotube with a larger 46 mm piston, and Bilstein build it well. Nitro Gas is a nitrogen charged twin tube built as a full suspension upgrade at our most accessible price point.
The difference that matters here is what you are buying. The 5100 is a shock. A Nitro Gas kit is a suspension: it is specified by load rating, from the ratings offered for your platform, so the spring is chosen for the winch, the bar, the drawers or the tow weight you actually run, and the damper is valved for the vehicle.
With 5100s, the spring is a separate decision. With Nitro Gas it is already made, in the box, at the rating you picked.
Where this one lands
There is nothing to put in the other column, and that is the point. Bilstein put a monotube gas pressure shock on a production Mercedes-Benz in 1957, and every Bilstein off-road truck shock on this page is built on that design. It is a proven architecture, executed as well as anyone builds it. Foam Cell Pro takes a different one.
Foam cell technology separates oil from gas with a closed cell foam insert instead of a pressurized nitrogen charge, so there is more room for oil inside the tube, and the top seal only sees pressure when the shock is working. That is what holds damping steady deep into a long, loaded, washboard day.
It also does that without a reservoir. We chose not to build one. Managing the heat inside a big bore body instead means there is no external hose or canister to route, protect or inspect.
And it is not only an overlanding shock. Foam Cell Pro is built for daily driven trucks and SUVs as much as for loaded overland rigs, so the same set that holds up on washboard is the set you commute on the rest of the week.
Where this one lands
Genuinely comparable hardware. Both are monotube coilovers, both replace the spring, and neither has a damping dial. The 6112 runs a larger 60 mm piston in a 2.65 inch body. Anyone telling you one is obviously better on the spec sheet is selling something.
Where they separate is the other end of the truck. The 6112 is a front kit. On a leaf sprung truck like the 2005-2023 Tacoma, the rear is a separate Bilstein shock and there is no Bilstein leaf pack to go with it. Our IM2.5 Tacoma kit covers both ends, with the rear leaf pack in the kit at the load rating you pick.
IM2.5 runs a CNC machined 57 mm billet aluminum piston in a 6061-T6 aluminum body, with an Acme threaded body for infinite ride height tuning. It is valved for your vehicle before it ships, so there is no damping to configure on install. Recheck the torque at 310 miles and after off road use.
Kit Contents
What's Actually In The Box
Two setups can deliver the same lift height and contain very different amounts of suspension.
Check which Bilstein line a setup uses before comparing. Most 5100 part numbers are a shock alone; the 6112 is a front kit with springs.
What You Get
One Part Number, Both Ends Of The Truck
To lift a 2005-2023 Tacoma at the front and the rear, count what each setup asks you to buy.
IRONMAN 4X4 TOY066KG |
Bilstein B8 5100 |
|
|---|---|---|
| Front shocks: | ||
| In the kit | 5100 Ride Height Adjustable | |
| Front springs: | ||
| In the kit, at the load rating you choose | Factory coil re-used | |
| Rear shocks: | ||
| In the kit | 5100, part number set by rear lift height | |
| Rear leaf springs: | ||
| In the kit, at the load rating you choose | Not in the Bilstein range | |
| Part numbers to buy: | ||
| One | Two, and the rear lift from another brand |
Both setups put a good shock at each corner. The difference is the spring.
Our Tacoma kit is one part number: new front coils and a new rear leaf pack at the load rating you picked, the shocks, and the rear U-bolt kit and spring bushings.
The 5100 Ride Height Adjustable is built to level the front of a truck like this, and it does that well, by preloading the factory coil. Lifting the rear as well means a leaf pack or a lift from another brand, because there is no Bilstein leaf spring for it.
What is in an IRONMAN 4X4 kit: a spring rated for the weight you actually carry, a damper valved for your vehicle, and the hardware to fit it, at one part number.
Load Ratings
Built For What You Actually Carry
A lift height tells you nothing about what a vehicle can carry. A spring rate does.
This matters at both ends of the vehicle. Bolt a steel bumper and a winch to the front and that weight sits over the front axle every day, so the front coil has to be rated for it or the vehicle sits nose down and works through less of its travel. Load drawers, a second battery, water and recovery gear in the back and the rear needs a spring rated for that constant weight. Our lift kit finder asks about your bumper, your winch, your drawers and your tow weight, and returns the load rating to match.
Long Term Value
Rebuilt, Not Replaced
Every shock wears eventually. What happens next depends on whether it was built to be opened.
The 4600 and 5100 are built to be replaced when they wear. Foam Cell Pro is built the other way. Order the seal kit listed for your part number, hand the shock to a suspension shop you already use, and the same shock goes back on the truck.
What It Means
What These Differences Change
Map your typical use across the full range, from the daily commute to the trails, and choose the option built for the toughest use you do regularly.
Proving Ground
Tested On The Australian Outback
We use the Australian continent as our proving ground. Our suspension is engineered and field tested in desert heat, on outback tracks and across the kind of distance that punishes equipment: sustained load, relentless washboard and a long way from the nearest shop. That is the environment Foam Cell Pro was built for, and it is why our range is organized by load rating and not by lift height alone.
IRONMAN 4X4 traces back to a Melbourne suspension manufacturer founded in 1958. Our products have been specified by fleet and military organizations and have completed the Dakar Rally.
By Platform
Kits Built For Your Vehicle
Both ranges are specified per platform, so make the comparison on the vehicle you actually drive.
On independent front suspension trucks, the Toyota Tacoma, 4Runner, Tundra, Ford F-150 and Lexus GX, a lift that keeps the factory coil leaves its load capacity untouched, whether that is a spacer or a shock built to re-use the stock spring. Every IRONMAN 4X4 suspension kit replaces the spring, and you choose the rating. Owners running a bumper and a winch on a Tacoma or a 4Runner are the clearest case for a load rated front coil, and heavily loaded overland Tundras and Land Cruisers are the clearest case for Foam Cell Pro.
Frequently Asked Questions on Lift Kits
Are Bilstein shocks worth it?
For a lifted truck, it depends on what you are buying. Bilstein build very good shocks, and the B8 5100, their shock for lifted trucks, is sold as a shock outside two Jeep kits: the Ride Height Adjustable version lifts the front by preloading the factory coil, which does not change what the truck can carry, and there is no Bilstein leaf spring for a leaf sprung rear. Every IRONMAN 4X4 suspension kit replaces the spring, in a load rating chosen for the build, as one part number.
Do Bilstein 5100s come with springs?
Not on their own. Outside two Jeep kits, the B8 5100 is sold as a shock. The Ride Height Adjustable version includes a spring seat and re-uses the vehicle's factory coil, lifting the front by preloading it, which does not raise the spring rate. Bilstein do sell springs: the B8 6112 is a front kit with new coil springs, the B8 5100 Lift Kit for the Jeep Wrangler JL includes all four, and the B8 5100 Leveling Kit for the Jeep Gladiator includes two front coils. Every IRONMAN 4X4 suspension kit includes the spring, rated for the weight you carry.
Is a leveling shock the same as a lift kit?
No. A leveling shock like the B8 5100 Ride Height Adjustable sets its spring seat higher on the shock body, so the factory coil is preloaded and the front sits taller. Preloading a coil does not raise its spring rate, so the truck can carry no more than it could before. A suspension kit that replaces the spring changes what the truck can carry as well as how high it sits, which is what every IRONMAN 4X4 suspension kit does, in a load rating chosen for the build.
Are Bilstein 5100s rebuildable?
No. The B6 4600 and B8 5100 are sealed, and Bilstein recommend replacing them when they wear. Their premium off-road lines are different: the B8 8100 and 8125 are owner rebuildable. Foam Cell Pro is rebuildable by design, with a seal kit sold as a part for listed part numbers, so when it wears a qualified suspension technician reseals it and the same shock goes back on the truck.
Which is better for overlanding?
It depends on what the truck carries, and overland builds carry weight that never comes off: a bumper, a winch, a rooftop tent, drawers, water. The B8 5100 is a capable shock, but on its own it does not change the spring. Foam Cell Pro kits are built for that weight: a big bore twin tube with a closed cell foam insert in place of a pressurized nitrogen charge, more room for oil than a gas charge leaves, no reservoir to route or protect, load ratings from Light through Extra Heavy, and a rebuildable design.
Am I downgrading from my factory suspension?
It depends on the lift. If a product raises the vehicle without replacing the spring, spring rate and load capacity stay exactly where they were while the tires get heavier and the geometry changes. Stock shocks are tuned for a near empty vehicle on smooth road. Add a bumper, a winch or a rooftop tent and that factory setup quickly loses control, composure and safety margin. Replacing the spring with one rated for your load, with a damper valved for the vehicle, is what makes it an upgrade.
Will the springs sag?
Our coils are CNC cold wound and bar peeled, shot blasted, preset to solid height and load tested to guard against sag. The other half of the answer is choosing the right load rating for the weight you carry, which is why every suspension series is offered in load ratings rather than one spring per part number. Expect around half an inch of settle on Foam Cell Pro front coilovers in the first miles, then check and reset ride height on the threaded body.
Do I need upper control arms?
There's no single lift height at which arms become mandatory. It depends on the vehicle, the height you run and the alignment you're trying to reach. We handle this by making arms a defined Stage 2 step rather than something you research separately after the kit arrives. Our Pro Forge upper control arms are drop forged with 4 degrees of caster correction to bring lifted geometry back toward factory specification.
Will I need an alignment?
Yes. A professional alignment is required after installing a suspension lift. Factor it into the total cost of the job rather than the price of the box.
Which IRONMAN 4X4 suspension series should I buy?
Lift & Level for height and bigger tires on a daily driven truck. Nitro Gas for weekend warriors who want a full suspension upgrade at our most accessible price point. Foam Cell Pro for overlanders and heavily loaded rigs that need load support, heat management and a rebuildable shock. IM2.5 for performance enthusiasts who want monotube precision and the most composed ride in our range, on and off road. Our lift kit finder picks the series and the load rating for your vehicle in about a minute.
Get The Kit Built For Your Load
Answer a few questions about your vehicle, your accessories and how you load it, and we will return the series and the load rating to match.