Step vs Flat Lips & Barrels Explained
Step vs Flat Lips & Barrels Explained
Why This Page Exists
One of the most common mistakes first-time wheel rebuilders make is ordering the wrong combination of lips and barrels. This page explains everything you need to know about step lips, flat (reverse) lips, and why matching them with the correct barrels is critical.
What Is a Step Lip?
A step lip is a type of outer lip profile where there is a noticeable drop or “step” from the face mounting surface to the outer edge of the lip.
Visual Appearance:
- A more classic, motorsport-inspired look.
- Creates the illusion of a deeper lip while maintaining strength.
Functional Advantage – Wheel Diameter Increase (Step-Up Conversion):
- Step lips are commonly used when increasing the overall diameter of a wheel:
- Single Step-Up: Convert a 17-inch wheel to 18-inch by replacing the lips and barrels with step-profile versions.
- Double Step-Up: Convert a 17-inch wheel to 19-inch by using a “double step” lip and barrel combination.
This is popular for giving older wheels a modern size while keeping the original center face design.
Assembly Difference:
- Mounting area is lowered relative to the edge, so the step inner barrel is required to meet flush with the lip’s step.
What Is a Flat / Reverse Lip?
A flat lip (also called a reverse lip) is an outer lip with no drop step – the surface flows smoothly and evenly outward from the face.
Visual Appearance:
- A clean, modern style with a sleek profile.
- Makes the wheel face appear larger and flatter.
Common Use:
- Modern aftermarket wheels and show builds.
- Typically paired with flat inner barrels (reverse barrels).
Assembly Difference:
- The mounting surface and outer edge are on the same level.
- Requires a flat inner barrel to ensure a flush fit.
Why Matching Is Critical (Step Lip + Step Barrel / Flat Lip + Flat Barrel)
- Mounting Plane Alignment: Step lips mount on a lowered plane, while flat lips mount on a flat plane.
- Bolt Hole Angles & Alignment: The bolt holes are drilled for specific angles depending on the profile.
- Structural Integrity: Wheels are designed as a matched system; mixing step lips with flat barrels (or vice versa) creates stress points, air leaks, and unsafe assembly.
- Aesthetic Quality: Even if bolted together, mismatched profiles will look incorrect, with uneven lip depth and poor face position.
How to Identify Which Lip You Have
-Visual Profile:
- Step Lip: Look for a drop or “ledge” before the edge of the lip.
- Flat/Reverse Lip: Smooth, continuous surface.
Barrel Compatibility:
- Step lips pair with step barrels.
- Flat (reverse) lips pair with flat barrels.
(Include diagrams showing correct & incorrect pairings.)
Pros & Cons
Step Lip (Pros)
- Can increase overall wheel diameter (step-up conversion).
- Creates deeper visual lip appearance.
- Classic, motorsport-inspired look.
- Often stronger due to stepped design.
Step Lip (Cons)
- Must use step barrels.
- Slightly heavier in some cases.
Flat / Reverse Lip (Pros)
- Clean, modern aesthetic.
- Easier to clean.
- Common availability of flat barrels.
Flat / Reverse Lip (Cons)
- Cannot increase wheel diameter using step-up method.
- Flatter appearance (less deep look).
Key Takeaways
- Step lip = Step barrel (for normal or step-up builds)
- Flat lip = Flat barrel
- Step-up conversions (e.g., 17 → 18, 17 → 19 double step) require step lips and step barrels designed for the increase.
Ready to Order or Upgrade?
- Use our Lips & Barrels Order Guide for accurate measurement instructions.
Consider adding:
- Rebuild Kit – all hardware and sealant for your build.
- Juju Wheels Wheel Roller – makes assembly easier and safer.