Standard vs. Constant Load Springs: How to Buy Suspension Based on Your Gear Weight

The Most Common Suspension Mistake: Ignoring Your Gear Weight

Lifting a 4x4 vehicle isn’t just about fitting bigger tires, but properly supporting your vehicle. Many beginners will buy a basic lift kit, then bolt on heavy steel bumpers, a winch, a rooftop tent, and a fridge. This causes brand-new suspension to sag, leading to a terrible ride that can easily bottom out on a mild Tillamook State Forest trail. In order to help mitigate this issue, you should match your coil or leaf springs to your “sprung weight” by choosing between standard load and constant load springs.

Who Are Standard Load Springs Ideal For?

Standard load springs are engineered to provide a slight lift and improve ride quality for vehicles that remain close to their factory weight. These springs are best for those who use their rig as a daily commuter around Beaverton or Portland and only hit lighter trails on the weekend. It’s possible a vehicle with this setup might have upgraded tires or a lightweight aluminum roof rack, but they definitely won’t have heavy steel armor or a full-time camp kitchen in the back. Even so, these models can offer the most comfortable ride on pavement.

Constant Load Springs: Built for Heavy Armor and Overlanding

Constant load springs are designed with a thicker wire diameter and higher spring rate, hence why they’re known as the heavy duty option. They are specifically for carrying extra weight all the time. These springs are best for dedicated overlanders, those who regularly drive off the beaten path and require extra stability for their rigs. If you have a steel bull bar, a 10,000-pound winch, dual batteries, a rooftop tent, and a fridge slide, standard springs are bound to fail. 

Remember that these are for models under constant heavy weight, so installing these on an empty, stock-weight vehicle will cause the ride to be incredibly stiff and harsh, as the weight is required to make the suspension cycle correct and comfortable. Ironman 4x4 America offers multiple spring rates to pair perfectly with their Foam Cell Pro or Nitro Gas shocks.

What Happens if I Guess My Spring Rate Incorrectly?

Be sure to check which spring rate is the right fit for you instead of just guessing, as there can be dire consequences, such as:

• Sagging (The Carolina Squat):  Putting heavy gear on standard springs causes the rear end to sag, pointing the headlights into the sky and ruining steering geometry.
• Bottoming Out: Heavy rigs on soft springs will crash into the bump stops on rugged Oregon trails, risking damage to the frame and the shocks.
• Harsh Ride Quality: Conversely, putting heavy springs on a light vehicle means the suspension cannot absorb bumps, passing every single jolt directly into the cabin.

Doing the Math Before you Buy

Learn what your accessories weigh beforehand so you have a better idea of the type of springs you might need. The average weight of some common add-ons include:

• Steel Front Bumper and Winch (Approx. 150 to 200 lbs)
• Rear Bumper with Swing-Out Tire Carrier (Approx. 150 lbs)
• Hard Shell Rooftop Tent (Approx. 150 to 180 lbs)
• Fridge Slide + Loaded 50L Fridge (Approx. 100 lbs)

If your model has more than 200 pounds of permanent accessories bolted to the front or rear, it’s time to get some constant load springs.

Get Your Suspension Dialed in at Iron Rigs 4x4

Suspension geometry may be complicated, but there’s no need to go figure it out on your own! Our dedicated team at Iron Rigs 4x4 in Beaverton, OR can calculate your accessory weight and pair you with the exact spring rate you need. Contact us or stop by our shop to plan your build and receive a professional installation!

Frequently Asked Questions

Can I install constant load springs before I buy my steel bumpers and tent?

We do not recommend it. If you install heavy-duty springs on a lightweight, stock vehicle, the suspension won't have enough weight to compress the coils. This will result in a very harsh, stiff, and bouncy ride. It is best to upgrade your suspension at the same time you add your heavy gear, or wait until your build is complete.

Which suspension setup do Oregon overlanders usually choose?

It depends entirely on the build, but our most popular overlanding setups at Iron Rigs 4x4 usually involve pairing heavy-duty constant load springs in the rear (to support rooftop tents, drawer systems, and fridges) with medium or standard load springs in the front, depending on whether the driver has installed a heavy steel bull bar and winch.

Will upgrading my springs fix suspension sag?

Yes. If your vehicle’s rear end is sagging under the weight of your camping gear or towing setup, swapping out your factory or standard springs for constant load springs (designed for the specific weight you are carrying) will level the vehicle and restore your handling and steering geometry.