Tire Size Calculator & Visual Comparison
Compare two tire sizes side-by-side. Inspect 1:1 proportional scale drawings, speedometer drift, ride height delta, and wheel clearance in real time.
Current Tire (Original)
New Tire (Upgrade)
Scale Tire & Wheel Visualizer 1:1 Proportional
Accurate side profile & stance overlay with ground clearance indicator
Rubbing & Geometry Assessment
The new tire is 1.10" taller (+3.49%). Exceeds the standard 3% factory tolerance guideline. Verify suspension clearance and tire well clearance at full steering wheel lock.
⚠️ Ticket Risk: You are traveling 2.2 mph faster than indicated on your dashboard.
Effective Axle Ratio & Gearing
Full Engineering Specification Table
Precise dimensional delta side-by-side
| Measurement | Current (265/70R17) | New (285/70R17) | Difference | Variance (%) |
|---|
Closest Equivalent Tire Sizes
Calculated alternative sizes within ±3% of overall diameter
The 3% Fitment Rule Decoded
Why automotive engineers emphasize keeping tire diameter variance under three percent.
ABS & Traction Calibration
Modern Anti-lock Braking Systems (ABS) and Electronic Stability Control (ESC) rely on rotational wheel speed sensor data. When tire diameter deviates beyond 3%, sensor pulses can trigger false traction loss warnings or compromise emergency braking distance.
Transmission Shift Logic
Automatic transmissions and torque converters schedule gear shifts based on vehicle road speed and engine load. Taller tires effectively raise your final drive ratio, causing the transmission to hunt between gears on highway inclines.
Physical Clearance & Rub
Vehicle wheel wells are engineered with finite clearance around steering knuckles, front struts, and inner fender liners. Going wider or taller without a leveling kit or wheel spacers frequently causes rubbing at full steering lock or suspension compression.
How to Read a Tire Size Code
Anatomy of a standard metric tire designation: e.g. 265/70R17 115T
Width from outer sidewall to inner sidewall measured in millimeters (265 mm = 10.43 inches).
Sidewall profile height expressed as a percentage of width (70% of 265 mm = 185.5 mm / 7.30 inches).
Radial ply internal casing construction (the global automotive industry standard).
Diameter of the wheel rim in inches that the tire beads sit against.
Engineering Methodology & Mathematical Formulas ▼
1. Sidewall Height:
Sidewall (inches) = Sidewall (mm) / 25.4
2. Overall Diameter:
Diameter (mm) = Diameter (inches) × 25.4
3. Circumference & Revolutions per Mile:
Revs per Mile = 63,360 / Circumference (inches)
Revs per Km = 1,000,000 / Circumference (mm)
4. Speedometer Error:
Indicated Dash Speed = Actual Speed / Diameter Ratio
Actual Speed = Indicated Dash Speed × Diameter Ratio
Frequently Asked Questions
Everything you need to know about tire sizing, speedometer error, and fitment.
Will taller tires make my speedometer read slower? ▼
Yes. Because a taller tire has a larger rolling circumference, it travels farther with each revolution. Your vehicle's wheel speed sensors count revolutions calibrated to the factory tire diameter. Consequently, your speedometer will indicate a lower speed than you are actually traveling (e.g. reading 62.8 mph when you are actually doing 65.0 mph).
What is the 3% tire size rule? ▼
Automotive engineers and tire manufacturers generally recommend keeping tire diameter changes within ±3% of factory OEM specifications. Changes exceeding 3% can disrupt modern electronic stability control (ESC), anti-lock braking systems (ABS), automatic transmission shift points, and risk rubbing against suspension struts or fender liners at full wheel lock.
How do I calculate overall tire diameter in inches? ▼
Tire diameter = Rim Diameter + (2 × Sidewall Height). To find sidewall height from metric tire codes: multiply Width (mm) by the Aspect Ratio percentage, divide by 100, and convert to inches by dividing by 25.4. For a 265/70R17: Sidewall = (265 × 0.70) / 25.4 = 7.30 inches. Total Diameter = 17 + (2 × 7.30) = 31.61 inches.
What is 'Plus-Sizing' (+1, +2)? ▼
Plus-sizing is increasing wheel rim diameter (e.g. from 16" to 17" or 18") while proportionally reducing tire sidewall profile to keep the total rolling diameter identical to stock. This sharpens steering response and enhances cornering stability without throwing off speedometer calibration.
Does a wider tire change total tire diameter? ▼
Yes! Because the aspect ratio is a percentage of the section width, widening a tire while keeping the same aspect ratio produces a taller sidewall. For example, going from 265/70R17 to 285/70R17 increases overall diameter by 1.10 inches (3.49%) because 70% of 285 mm is taller than 70% of 265 mm.
Can I swap flotation truck tires (e.g. 35x12.50R17) onto my vehicle? ▼
Flotation sizes describe total diameter, section width, and rim diameter directly in inches. A 35x12.50R17 stands approximately 34.8 to 35.0 inches tall. Most stock pickup trucks require a 2.0 to 2.5-inch leveling or suspension lift kit, plus proper wheel offset, to clear 35" tires without rubbing on the front control arms or fender plastic.