MyWheelOffsetCalculator
Guide
Complete Setup Analyzer

Wheel Fitment Comparison Tool

Compare complete wheel and tire packages side-by-side. Calculate rim poke, inner suspension strut room, tire sidewall bulge, and ride height deltas to build a perfect flush fitment without rubbing.

Complete Wheel & Tire Package Comparison
Setup A (Existing)18x8 ET45 • 225/40R18
Setup B (Proposed)19x9 ET35 • 255/35R19
Wheel Rim Poke
+23 mm
outer rim lip edge
Wheel Strut Room
-3 mm
inner rim room
Tire Tread Poke
+25 mm
tire outer sidewall
Ride Height Shift
+11.9 mm
ground clearance

The Holistic Approach to Automotive Fitment

When enthusiasts say their car has "perfect fitment," they are describing the delicate geometric harmony between four interrelated components: rim width, rim offset, tire section profile, and suspension ride height. Ignoring the tire when calculating wheel offset is one of the most common mistakes made by DIY builders.

Understanding Fitment Terminology: Poke, Tuck, and Flush

Tuck Fitment

The wheel and tire sit deeply recessed inside the fender arch (typical OEM factory look). Allows maximum suspension compression travel and zero risk of fender contact.

Flush Fitment

The outer edge of the wheel rim and tire sidewall align in a dead-straight vertical plane with the outer metal fender lip. The gold standard for modern aesthetic stance.

Poke Fitment

The rim lip or tire tread protrudes past the outer fender lip into the airstream. Popular on lifted 4x4 trucks and widebody builds, but can throw road debris against paint.

Tire Width on Rim Width: Square vs. Stretched vs. Donut (Bulge)

Every tire size has an approved rim width range published by the Tire and Rim Association (TRA):

  • Square / Standard Fitment: Mounting a 245 mm tire on an 8.5-inch rim (216 mm bead seat). The sidewall is nearly vertical, providing optimal rim protection and predictable cornering dynamics.
  • Mild Tire Stretch: Mounting a narrower tire (e.g. 215 mm) on a wider rim (e.g. 9.0-inch). The sidewall slants inward from the rim lip, which can give 5 to 8 mm of extra fender lip clearance on lowered cars.
  • Bulged / Meat Fitment: Mounting an extra-wide tire (e.g. 275 mm) on an 8.5-inch rim. Common on drag cars and off-road trucks, but generates greater sidewall deflection in fast transitions.

Wheel Fitment Frequently Asked Questions

Why should I compare wheels and tires together rather than just offset?

Wheel offset only accounts for the metal rim rim lip position. However, tires have sidewalls that bulge (or stretch) past the rim lip. An aggressive wheel might physically clear your fender, but mounting an excessively wide tire can cause severe sidewall rubbing on outer fender arches under suspension compression.

How much fender clearance is considered safe for daily driving?

On standard street suspensions, a clearance margin of at least 10 mm to 15 mm between the outer tire shoulder and the inner metal fender lip is recommended to prevent rubbing during high-load cornering or over road bumps.

How does negative camber help aggressive wheel fitments clear the fender?

Dialing in negative camber tilts the top of the wheel inward toward the vehicle center. As a practical rule of thumb, each additional degree of negative camber pulls the top of the tire approximately 4 to 5 mm inward away from the fender lip.

What is the difference between square and staggered wheel fitment?

A square setup uses identical wheel widths, offsets, and tire sizes on all four corners, allowing front-to-back tire rotations. A staggered setup uses wider wheels and tires on the rear drive axle (common on rear-wheel drive sports cars like Porsche 911, BMW M3, and Ford Mustang) for increased rear traction.

What does "fender rolling" do?

Most factory metal fenders feature an internal 90-degree horizontal metal pinch seam on the inside arch. Fender rolling uses a specialized mechanical roller bolted to the wheel hub to heat and fold this flat lip upward flush against the inner fender skin, gaining 10 mm to 15 mm of crucial outer tire clearance.