How to Select the Right Length Coilovers for Your Build
Choosing the right length coilovers is one of the most important steps in setting up your suspension system, especially for custom off-road solid axle builds, whether a Jeep or a buggy. Getting it wrong can limit articulation, cause coil bind, or lead to bottoming out — all of which kill performance and comfort.
Here’s a step-by-step guide to make sure you select the perfect coilover length for your setup.
What You’ll Need
- Vehicle Jack and Jack stands
- Tape measure
- Pen and notepad
- Frame and axle bump stops in place (or at least planned)
- Tires on the axles(or at least a mock-up)
- A general idea of where you want your ride height set
Step 1: Get the Vehicle at Ride Height
Before you do any measuring, you need the vehicle at your intended ride height — where it’ll sit with all its gear, bumpers, winches, and so on.
- If the build isn’t complete yet, use jack stands to simulate the frame height.
- Make sure both axles are at ride height too (flat and level).
Why this matters: Coilover length is based around how much up-travel and down-travel you want from this ride height position.
Step 2: Measure Full Bump and Full Droop
Now it’s time to find your suspension limits:
- Full bump: Cycle the suspension up until the axle hits the bump stops (or where you plan to place them). Measure the distance between your upper and lower shock mounting tabs. Keep tire size in mind here – You will need to know how much room you have until your tire gets in the way.
Pro Tip: Subtract 1” from your full bump measurement. At full bump you want to have a little cushion for movement so your coilover doesn’t bottom itself out and slam the lower mount to the shock body or the shaft top out inside the body.
- Full droop: Let the axle hang as far as it can without overextending driveshafts or brake lines. Measure the shock mounts again in this position.
Pro Tip: It’s best to remove springs and disconnect the shocks during this step so you’re working with just the mechanical travel.
These two points give you the minimum (compressed) and maximum (extended) lengths you’ll need.
Step 3: Choose Coilovers Based on Travel Range
Compare your bump and droop measurements with available coilover sizes. Our Coilovers are labeled by travel (e.g., 10″, 11”, 12″, 14″), and each size has a specific compressed and extended length.
Here’s an example for our 12″ coilover:
- Compressed: ~19″
- Extended: ~31″
Fitment Rule:
Your full bump measurement must be greater than or equal to the coilover’s compressed length, and your full droop should be less than or equal to the coilover’s extended length. You never want your shocks to bottom out before your bump stops engage or top out before your limit straps do.
Step 4: Consider Mounting Room and Packaging
Now that you have a length in mind, confirm that the shock you’ve picked will physically fit in your mounting brackets. Coilovers are longer than just their travel length. Our 12” coilover will measure 31” extended, so make sure your mounts allow for that. Also, account for the overall body size with coils installed for coilover movement in the mount, as the axle “swings” in the suspension cycle, the coilover will move forward and backward in the mount.
Also factor in:
- Spring clearance from tires and chassis
- Mounting angles (ideally no more than 15-20° off vertical, inboard/outboard angles, or another general rule of thumb is to have your coilovers set at 90 degrees perpendicular to your lower links at full bump if this can be achieved)
- Space for tools to install and adjust them
Step 5: Prioritize Up-Travel vs. Down-Travel
Depending on your use (rock crawling vs. high-speed off-road), you’ll want a specific balance:
- Rock crawlers: More down-travel for articulation.
- Go-fast rigs: More up-travel to soak up bumps.
Most people shoot for about 50/50 up/down-travel at ride height, but some go 60/40 depending on needs. We don’t suggest this for everyone, but some rock crawlers will even set their coilovers up to ride 1-3” above bump to prioritize down travel, however, this will result in losing some handling characteristics.
Example:
If you have a 12″ travel shock:
- Up-travel: 6″
- Down-travel: 6″
So your ride height shock length should be 6″ above the compressed length of the shock.
Pro Tip: A general rule of thumb is that ⅓ to ⅔ of the shock should be up travel, depending on the application.
Step 6: Fully Articulate the Suspension to Check Clearances and Final Fitment
Once your up/down suspension cycling is confirmed, fully articulate the axle by flexing one side up while the other droops, simulating real-world off-road conditions. Rotate the tires lock-to-lock and observe clearances between tires, shocks, frame rails, fenders, bumpers, and any other nearby components. Carefully inspect for rubbing or potential contact points under extreme compression or articulation. Adjust shock mounting positions if needed or trim interfering bodywork. Allowing the shock to bottom out during articulation is acceptable if it helps limit over-flex that could cause damage. Always cycle both axles thoroughly, including with tires turned, to ensure smooth operation and anticipate future upgrades (like larger tires). This step is critical—be meticulous to avoid surprises after final assembly.
Step 7: Account for Coil Bind and Bottom-Out Clearance
You’ll also need to make sure:
- The spring doesn’t coil bind(completely collapse) before the shock bottoms out.
- The shock never bottoms out before your bump stop engages.
Use limit straps and/or properly placed bump stops to protect your coilovers.
Final Thoughts
Measuring for coilovers isn’t just about slapping on the biggest ones that fit. It’s about maximizing travel, maintaining reliability, and getting the ride and feel you want.
Take your time, cycle the suspension carefully, and measure twice. The right setup will let your rig work smarter, not harder, on the trail, rocks, or desert.
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