23-26 FORD F250/350 4X4 RADIUS ARM DROP BRACKETS - 3.5" LIFT

Description

The 2023+ Super Duty introduced some new challenges, specifically pertaining to caster. The steering assist and Ford’s 1° – 3.6° allowable caster range seems to work alright for those equipped with stock, relatively low-mileage Super Duties but, once a lift or oversized tire enters the equation, the handling at this low caster specification leaves us wanting.

When lifting the front of the Super Duty 3 – 3.5″, the factory caster is reduced by approximately 1.5°. For the 2020-23 Super Duty, we provide a 2° caster shim which is enough to restore this caster and add a touch more – unfortunately, this “touch more” is rarely enough for proper tracking. This leaves us recommending our Adjustable Radius Arms proven to add an additional 2.5° of caster (when maxed). Combining the Carli Arms and 2° shims results in a Super Duty on 37″ tires that holds a lane, and returns to center after a turn, better than a stock truck.

Enter the 2024 Super Duty – Ford made ONE change to the platform… They added an outer axle-mounted guard to prevent debris from entering the outside axle tube (highlighted in RED for clarity). The issue is in the functionality of the ball-joint mounted caster shims we provide in our 05-23 Super Duty Systems to correct the caster. These shims don’t affect the axial position of the axle, but rotate the knuckle/upper ball joint position rearward relative to the axle’s outer “c” to increase caster.

Given the tight proximity of this debris shield to the axle tube, any caster shim over 1° will cause contact. Unfortunately, these trucks come with low caster from the factory compounded by the loss of caster from lifting the truck (radius arms tilt the axle forward – reducing caster – as the axle travels away from the frame); we had to figure out a solution.

Test 1 – Stock Radius Arms

The first test – throw our 3.5″ Coils on our shop 2023 Super Duty to see where the caster lands with no modification to the factory infrastructure. The 2023 is identical to the 2024 with the exception of the axle-shields that proved problematic so it was the perfect test bed to see how we could achieve the desired caster.

This is not a situation in which one should find themself; well, not a Carli customer… We’ve had the occasional customer call and say “the alignment shop gave me the caster shims back saying they’re not needed, do i need to install them?”  The answer is a resounded YES! The following is the result if no caster modifications are done.

• 2023 Ford F250 XLT 6.7 Powerstroke, 4×4
• 3.5″ Carli Pintop Installed
• NO Caster Correction
• Stock Radius Arms
• Stock Ball-Joint/Axle Caster Shims

Test 2 – Carli Radius Arms

Second Test – As we’re testing for the 2024 platform, caster shims are not an option. The 1° shims that would fit the 2024 wouldn’t provide nearly enough correction to rectify drivability. Instead, we skipped over caster shims and installed the Carli Adjustable Radius Arms with the MAX caster addition of our 4-notch shims.

In hind-sight, stacking the 1° shims with the Maxed Radius Arms would net a better result. That said, the numbers reflected here are with stock caster shims.

• 2023 Ford F250 XLT 6.7 Powerstroke, 4×4
• 3.5″ Carli Pintop Installed
• Carli Adjustable Radius Arms: Max caster correction, 4-Notch Caster Keys.
  
• Stock Ball-Joint/Axle Caster Shims

Achieving Proper Caster

With the above testing of available caster correction options, we were able to get the truck where Ford wants it, but is that where we want it? The factory Ford caster specification is outlined in the above printouts; it reads:

• 1.0°-3.6°: Driver
• 1.3°-3.9°: Passenger

These specs are for a stock Super Duty and, with smaller tires, the lower end of the range tracks and drives OK. Honestly, we’ve put a ton of time behind the wheel of 23+ Super Duties with this caster spec and they all drive fine without any signs of death wobble or instability. We’ve always preferred the tracking and handling of larger tires in the 3°-5° range. We’ve run up to nearly 7° with no ill effect (no wobble, tracking or driveshaft binding issues) aside from a “heavy” steering wheel – even this would only likely apply to an XL/XLT without the electric steering assist of the higher trims.

We set out to design a Radius Arm Drop Bracket solution that would be more cost-effective than (and stack-able with) the Adjustable Radius Arms and, hopefully, provide ample caster correction, even with stock arms.

The stock radius arm frame pivot is tricky as it’s a stamp-formed bracket with a deep lip around the perimeter. Normally, we design our drop brackets to bolt to the inside of the factory pivot, form along the bottom of the factory bracket, then shape to fit the factory arm exactly as our 5.5″ drops do. The issue… this is too much drop and would cause excessive caster for the lift height and an upward radius arm angle at ride height.

Back to the drawing board, our engineer thought outside the box (well, outside the factory bracket). Avoiding the above constraint all together, the Leveling Drop was designed to sandwich the factory bracket from the outside, allowing us to achieve the proper drop height.

To make this work, we pickup the same rear support as our 5.5″ drops, then our bracket sandwiches the factory bracket. To accommodate the “lip” on the factory bracket, we provide a thick spacer that keys into the Carli drop bracket taking up the gap on the outside, then a thinner spacer to take up the same slack on the inside and finally, a dual crush sleeve to provide inside support to the factory bracket. The exposed bolt shank represents the location of the two ears of the factory bracket when installed.

This color-coded picture is from the rear perspective. The bolt-heads represent the OUTSIDE of the frame rail. This would mimic the view of the driver’s side bracket installed from the perspective of the rear, driver tire.

Test 3 – Leveling Drops & Stock Radius Arms

We’re there! With just the Radius Arm Drops installed, we’re high-center of Fords recommended range and the truck drives fantastic. Combine these drops with a 1° caster shim on the ball joint and you’ll likely be sitting right a the top of Ford’s recommended caster range.

• 2023 Ford F250 XLT 6.7 Powerstroke, 4×4
• 3.5″ Carli Pintop Installed
• Carli Leveling Radius Arm Drops
• Stock Radius Arms
  
• Stock Ball-Joint/Axle Caster Shims

Test 4 – Leveling Drops & Carli Radius Arms

To confirm we could achieve the numbers we’re after, we combined the Leveling Radius Arms Drops with the Carli arms and installed the 4-notch shims and this was the result. Again, truck drove fantastic; arguable better than it did in Ford’s allowable range. This is where personal preference comes in. This higher caster spec tracked great, snapped the wheel back to center after turning and was extremely stable.

As the Carli Arms are maxed here, one could run the 1-4 notch shims to fine-tune the caster to their liking between 3.5° – 6°

• 2023 Ford F250 XLT 6.7 Powerstroke, 4×4
• 3.5″ Carli Pintop Installed
• Carli Leveling Radius Arm Drops
• Carli Adjustable Radius Arms with 4-Notch Keys
  
• Stock Ball-Joint/Axle Caster Shims

Although these were developed for the 2024 platform, Test #1 above tells us, even with the 2° shims, we would be at the low-end of Ford’s recommended caster spec on this 2023 we’re testing. Given we want to be at the top of the spec, if not slightly over (when running over-sized tires), we will be altering the kit build-outs to include these drops for ALL 23-24 applications once they’re available. If additional caster beyond what’s achieved in Test #3 is desired, Adjustable Radius Arms and Ball-Joint Caster Shims can be utilized (1° in the 23 and 24, 2° in the 23 only) to further dial in the caster to the user’s preference.