Guides
The thinking behind the numbers: what the markings and ratios mean, worked through with diagrams and examples you can check in the calculators.
- Tires How to read a tire sidewall: every marking explained A plain-English guide to the size, load index, speed rating, XL, M+S and DOT date code on a tire (tyre) sidewall, with an annotated diagram.
- Tires Plus sizing explained: bigger wheels without changing your gearing How plus-one and plus-two wheel upgrades keep overall tire diameter close to stock, what changes when they don’t, and how to check a size before you buy.
- Wheels Wheel offset vs backspacing: what they mean and how they move your wheels Offset and backspacing describe the same wheel from two directions. Learn the sign conventions, the conversion, and what a change does to inner and outer clearance.
- Fuel MPG vs L/100 km: why fuel economy numbers mislead, and how to compare them US and imperial gallons, the “MPG illusion”, and why consumption figures like L/100 km make fuel savings easier to compare.
- Drivetrain Gear ratios, tire size and RPM: how they fit together What gear and final-drive ratios mean, how tire diameter changes effective gearing, and how to work out cruising RPM and re-gearing after bigger tires.