Car safety calculators
Small tools for the questions that otherwise end in a forum thread. Every result shows the formula behind it, and nothing you type leaves your browser.
Tire and wheel tools
Winter tire sizeFactory size in, every size that fits a smaller winter wheel out, with the wheel checklist.
Tire size and speedometerRead a full sidewall code, get diameter, load and speed, then compare two sizes for speedometer error.
Wheel offset and bolt patternHow far a new wheel moves in or out, its backspacing, and the bolt pattern from stud spacing.
Tire age from the DOT codeThe last four digits of the DOT code tell you when the tire was made. This says whether it is time to replace it.
Stopping distanceReaction distance plus braking distance by speed, road surface and tread depth, from real wet-braking tests.
Why a safety site publishes tire calculators
Tires are the only part of a car that touches the road, and tire failures killed 646 people in 2023. The most common reasons people change tire sizes, winter sets, replacement wheels and worn or aged tires, are also the moments a mistake gets built into the car. These tools exist so the geometry is right before the money is spent.
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