Choosing wheels and tires has always been one of the most misunderstood parts of car setup.
Most online calculators give you numbers. Offset changes. Diameter differences. A vague poke value.
What they rarely show is what actually changes on the car.
GripDial’s free tire and wheel fitment calculator was built to solve that problem by turning abstract measurements into a physical, visual representation of fitment changes
Why Traditional Fitment Calculators Create Confusion
Most calculators assume the user already understands how wheel width, offset, tire width, and sidewall height interact.
For many drivers, especially in drifting and motorsport, that assumption breaks down quickly.
A number like “+18mm poke” does not explain where that change occurs, what it interferes with, or how it affects suspension clearance.
Fitment Is Geometry, Not Just Math
Wheel fitment is a three-dimensional problem.
Changing wheel width moves both inner and outer edges. Changing offset shifts the entire assembly. Changing tire width introduces sidewall bulge that most calculators ignore entirely.
GripDial models all of these relationships together.
Instead of isolating numbers, the system calculates the full tire and wheel cross-section relative to the hub mounting face.
Current Setup vs New Setup – Compared in Real Time
One of the most important differences in GripDial’s calculator is the side-by-side comparison model.
You define your current setup and your proposed setup simultaneously.
Every slider adjustment instantly updates:
- Overall tire diameter
- Sidewall height
- Poke and inset
- Ride height change
- Speedometer error
- True vehicle speed
Nothing is hidden behind a submit button or recalculation delay.
Visualizing What Actually Moves
The visual canvas is where most calculators stop and GripDial begins.
Instead of a table of values, the tool draws a scaled cross-section of both setups relative to the hub face and ground plane.
This makes it immediately clear whether clearance is gained or lost on the inside, outside, or vertically.
You can see which edge moves and by how much.
Tire Bulge Is Accounted For
Most calculators treat tire width and wheel width as interchangeable.
In reality, tire bulge can dramatically affect clearance even when wheel width remains unchanged.
GripDial calculates tire bulge based on the difference between wheel width and tire section width, incorporating it into poke and inset calculations automatically :contentReference[oaicite:2]{index=2}.
Speedometer Error and True Speed Matter More Than You Think
Changing tire diameter does more than alter stance.
It affects gearing, acceleration, and speedometer accuracy.
GripDial calculates true vehicle speed at a fixed reference speed, showing exactly how far off the speedometer becomes.
This is critical for track driving, competition rules, and data consistency.
Built for Drift and Motorsport Use
The calculator was designed with motorsport applications in mind.
Ride height changes, inner clearance to suspension components, and outer clearance to fenders are all treated as first-order concerns.
This makes it equally useful for drift cars, time attack builds, and track-focused street cars.
Why This Tool Is Free
GripDial believes understanding geometry should not be gated behind paywalls.
Better-informed drivers make better decisions, regardless of whether they are running full telemetry or just selecting wheels.
This calculator exists as a foundation for deeper vehicle understanding.
From Fitment to Full Vehicle Insight
Wheel and tire choices affect everything from suspension behavior to telemetry interpretation.
By making fitment transparent, GripDial removes one more layer of guesswork from car setup.
It is not about choosing the most aggressive setup.
It is about choosing the right one.
Conclusion – Seeing Fitment Changes Before They Happen
The difference between guessing and engineering is visualization.
GripDial’s tire and wheel fitment calculator allows drivers to see the consequences of their choices before turning a wrench.
When fitment stops being abstract, better decisions follow.