Compare two wheel-and-tire setups and see how poke, offset, clearance, rolling diameter and speedometer error change — live.
Fender gap: horizontal distance from the outer lip of your current (old) rim to the fender edge. Strut gap: horizontal distance from the inner edge of your current rim to the nearest part of the strut or spring. Both drive the clearance figures. Fender height only changes the drawing.
Hub, rotor, axle, caliper and strut are generic illustrations for orientation only (the strut moves with the strut gap you enter). Wheel, tire and offset are drawn to scale.
All gaps are measured to the rim only. Tire dimensions vary a lot between brands and models (actual width, sidewall bulge), so check the real tire against the fender and strut separately.
| Measurement | Old | New | Δ |
|---|
Poke is how far the wheel's outer lip sticks out past the hub mounting face. More poke gives a more aggressive stance but raises the chance of the tire catching the fender. It's calculated as (rim width in inches × 25.4 ÷ 2) − offset (ET).
Offset, stamped "ET" on a wheel, is the distance in millimeters between the wheel's mounting face and its true centerline. A higher ET tucks the wheel further under the car; a lower or negative ET pushes it outward for more poke.
Your speedometer is calibrated to the original tire's rolling circumference. A larger-diameter tire covers more ground per revolution, so the car goes faster than the speedometer reads — and a smaller tire does the opposite.
Only overall rolling diameter changes ride height, not rim size on its own. Go up an inch in wheel but drop the tire profile to keep the same rolling diameter ("plus sizing") and the car sits at exactly the same height.
Estimates only. Real-world clearance also depends on bolt pattern, center bore, suspension and fender shape. Always confirm load rating before buying.