Link suspension calculator
Anti-squat, anti-dive, roll axis, roll steer and track bar geometry for a solid axle on links, front or rear. Pick your truck to see what a lift did to its factory links, or put in your own mount points for a custom build.
Pick your truck, or put in your mount points.
Sets the anti-squat range the numbers are judged against.
Numbers to aim for
Rear link suspensionThe anti-squat range follows what the truck is built for, from Crawlpedia's 4-link guide. Roll axis, triangulation, separation and pinion targets are the ones link builders on Pirate4x4 and in the 4-link calculator guides work to. Anti-squat is quoted with all the drive at the rear, the way builders compare it; the 4WD figure is in the stats above.
Your truck already has links
Adjustable links and bolt-on bracketsWhat's on your truck
Raise is from the factory bolt to the bottom hole, spacing is center to center. Makers rarely publish these, so measure yours.
Changes to try from here
| Change | Pinion | Anti-squat at stock height | Try it |
|---|
Each row shows your setup with that one part changed, so "Try it" adds it to what you already run. Set pinion angle first: a pinion rolled away from where the driveshaft wants it causes vibration and wears the joints. Then pick drop brackets for anti-squat. Until you measure your own mount points, the numbers show the size of each effect, not your truck's exact figures.
Estimate, worked out from sample mount points until you measure your own. Use at your own risk.
Every hole combination
| Frame holes | Anti-squat | Instant center | Lower angle | Use it |
|---|
Best first, at the lift you have set. Tap one to put the links there.
Where to weld the frame brackets
Leaf conversion or custom linksSet how many holes your frame brackets have, up in the form. This works out how far below the rail the first hole goes, so the truck stays in range from stock to 6 in of lift, and which hole to run at each height.
Measure the rail at your truck: bottom of the frame rail off the ground at ride height, and the stretch ahead of the axle that's free of the fuel tank, crossmembers and bump stops.
| Lift | Lower link | Upper link | Anti-squat |
|---|
Estimate. Measure your frame and mounts, mock it up and tack it before you weld anything. Use at your own risk.
Through the travel
Full droop to full stuffHow the numbers work
What is anti-squat?
How much the rear suspension pushes back against the truck squatting when you get on the throttle. Draw a line through each pair of links in side view; where they cross is the instant center. A line from the rear tire's contact patch through it, compared with a line to the center of gravity over the front axle, gives the percentage. 100% means the rear neither squats nor lifts.
What should mine be?
Rock crawlers usually run 70 to 100%, trail and overland rigs 60 to 90%, and desert trucks much lower, around 10 to 50%, so the rear soaks up whoops instead of kicking. Too low and the rear squats and feels soft climbing a ledge; too high and it lifts and hops under power.
What does a lift do to factory links?
It raises the frame mounts away from the axle, so the links angle up and anti-squat climbs. With fixed-length links the axle also swings forward and rolls, which changes pinion angle. That's why lifted trucks get adjustable upper links (to set pinion angle) and lower link drop brackets (to bring the link angles and anti-squat back).
What is the roll axis, and why does it steer the truck?
Seen from the side and the top, the links set the line the axle rotates about when the body rolls in a turn or the axle flexes over a rock. If that line tilts, the axle steers a little as it rolls. At either axle, a roll axis that runs downhill toward the middle of the truck steers it out of the turn (understeer, or tight); uphill steers it in (oversteer, or loose). Most builders aim for flat to slightly downhill.
Do I need a track bar?
Something has to stop the axle sliding sideways. Either a track bar (panhard) does it, or the links angle toward each other in the top view. Builders want about 40° of triangulation, upper and lower added together, before they leave the track bar off. A track bar also sets the roll center: the point where it crosses the middle of the truck in the rear view.
What about the front axle?
The same geometry gives anti-dive under braking (most run 25 to 75%) and anti-lift on throttle in 4WD. Axle rotation through travel becomes caster change, and the track bar should run within about a degree of the drag link, or the steering wheel turns as the axle moves.
Do adjustable links fix anti-squat?
Only a little. On factory mounts, lengthening or shortening a link moves the axle and rolls the pinion, which shifts anti-squat a few percent. Their real job is pinion angle and centering the axle. Moving a mount point, with drop brackets or a relocation bracket, is what changes anti-squat a lot.
Use at your own risk. These calculators are here to help you plan and to inform your decisions, not to sign off on a build. Many numbers are estimates worked out from factory figures, and some factory figures are not yet confirmed. Check every number against your own truck, its manuals and a qualified shop before you buy parts, cut, weld, lift, regear or drive on it. Long Range Desert Tools is not liable for anything you do based on these calculators or their results. The full terms are in our policies.