Before you move a 4-link bar or ladder bar, you need to know exactly where your car is right now. Otherwise you're not tuning, you're guessing. And here's the part most racers skip: a bar change isn't finished when the bar is bolted in. It's finished when the car is back at the same ride height, the same pinion angle, the same scale condition, and the same ARB condition along with everything documented. Skip that, and you'll swear the bar change "did something weird," when you really changed five other things by accident. 😮

The #1 rule: change one thing at a time.

Before the change

1. Set tire pressure and fuel level first. Both change ride height, rollout, and scale numbers, so lock them in before you measure anything else.
2. Confirm chassis ride height. Measure from repeatable chassis points (frame rails, rocker pinch welds, suspension brackets) but not body panels. The very bottom chassis hole is the "rule of thumb" for ride height!
3. Record current hole locations and bar lengths. Upper bar front and rear holes, lower bar front and rear holes, ladder bar holes, shock hole, ARB angle, all of it. Take pictures and write it down. Do not trust memory.
4. Check pinion angle and driveline angles. Record pinion angle specifically, plus transmission and driveshaft angles, so you know the actual working angles. Checkout this VIDEO of mine on driveline angles!
5. Confirm the rear housing is square and check wheelbase side to side. If the housing is already crooked, a bar change can make the car worse and you'll chase the wrong problem. A small side-to-side difference matters, especially on cars with a lot of adjustment history. Wheelbase measurements are to ensure you get back to current state. I have a detailed video on how to confirm if your chassis is square HERE.
6. Check shock installed height, available travel, and settings. Installed height is good, but available extension and compression travel matter more on a drag car. Record compression and rebound front and rear, plus any front strut limiter settings.
7. Check rod ends and bolt tightness. Loose rod ends, worn heims, bracket slop, or ovaled holes make a car inconsistent no matter where you put the bars.
8. Scale the car at race condition with the rear ARB connected, "race ready". Driver weight (or ballast) in the seat, race fuel level, tire pressure set, car bounced and settled. The 4 corner scale weights tells you the 4 corner numbers with the rear ARB in the mix.
9. Scale the car at race condition with the ARB disconnected on one side, "floating". Driver weight (or ballast) in the seat, race fuel level, tire pressure set, car bounced and settled, one ARB link disconnected. The disconnected number tells you what the chassis is doing without the ARB in the mix.
10. Write everything down and photograph it. The original setup is your insurance policy if the car hates the change.

Make the change
Move one bar/hole, and know what you expect it to do before you bolt it in. Note exactly which hole you moved and why.

After the change

1. Leave one ARB link disconnected, so the ARB doesn't lie to the scales. I call this "ARB is floating".
2. Reset race condition: same tire pressure, fuel level, ride height target, and driver weight, car settled.
3. Put pinion angle back where it was. On a 4-link, moving bars can change pinion angle. On a ladder bar car, changing the front hole can change attitude and the pinion relationship. This is one of the most-missed steps.
4. Verify rear-end square and wheelbase. Any change to bar length or preload can move the rear end slightly.
5. Recheck ride height before scaling. If it changed, your scale numbers aren't an apples-to-apples comparison.
6. Recheck shock installed height and travel. This should not have changed, but details matter!
7. Rescale with the ARB disconnected. This gives you the real chassis weight distribution.
8. Restore or adjust preload / cross-weight intentionally. On a 4-link, the upper right bar is commonly used to adjust preload; on a ladder bar car, it's usually the ladder bar adjuster or rod end. You're not randomly chasing scale numbers — you're restoring your baseline or intentionally adding/removing preload based on what the car needs.
9. Reconnect the ARB — neutral, or back to your previous known preload. With driver weight in and the suspension settled, the bolt should slide in free. No jacking, no fighting the link into place. If you had a known good preload before, put it back the same way.
10. Rescale, document, and make ONE test hit before changing anything else. If the numbers jumped when the ARB connected, the ARB is adding preload.

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The bottom line
A 4-link or ladder bar change isn't done when the bar(s) is bolted in. It's done when the car is back to the same ride height, pinion angle, scale condition, and ARB condition with everything is written down. Do that, and you'll actually know what the bar change did. Skip it, and you're guessing.

Download the printable Checklist

Want help plotting your 4-link or ladder bar, or building a baseline you can trust?
Start with my Suspension Tuning Questionnaire, then check out Remote and In-Shop tuning.