Free tools · Manufacturer data · No signup
Compare wheels & tires like an engineer
Bolt patterns, fitment specs, tire-size math, and side-by-side comparisons — based on manufacturer data. No fluff, no guesswork.
1,000+ size pairings · 550+ bolt patterns · UK & US pricing
Tire Size Calculator
Convert sizes, see overall diameter change, sidewall, and speedometer error. Plus-sizing made easy.
OpenBolt Pattern Database
Bolt pattern, hub bore, and thread pitch for popular cars — by make, model, and year.
OpenFitment Guides
Per-vehicle stock specs, bolt pattern, and plus-1/plus-2 sizing that keeps your speedo honest.
OpenTire Brands
Real tire lines from Michelin, Continental, Bridgestone and more — by season and segment, with price comparison.
OpenOffset & Backspacing Calculator
Convert offset to backspacing and see exactly how much a new wheel spec pokes out or tucks in vs. stock.
OpenWhy CompareWheels
Most wheel and tire sites are either thin affiliate stores or marketing pages dressed up as guides. We build the opposite: data first, opinions second. Every fitment row has a source, every wheel spec is traced to a manufacturer page or industry database, and the calculators are pure formulas you can verify with a calculator and a ruler.
Frequently asked questions
- What does tire size comparison show?
- A tire size comparison shows the difference in overall diameter, section width, sidewall height, and speedometer error between two tire sizes. For example, comparing 205/55R16 vs 225/45R17 reveals a 1.2% diameter change and a 4 km/h speedo offset at 100 km/h.
- Can I replace my tires with a different size?
- Yes, but the overall diameter should stay within ±3% of the original to avoid speedometer error and clearance issues. Use a tire size comparison tool to check the diameter difference before switching.
- How do I compare wheel sizes?
- Enter both tire sizes (e.g. 195/65R15 and 205/60R15) into a tire size comparison tool. It will calculate the change in diameter, sidewall height, and rolling circumference so you can see if the swap is safe.
- What is plus-sizing for wheels?
- Plus-sizing means fitting a larger-diameter wheel (e.g. going from 15" to 16") while using a lower-profile tire to keep the overall diameter the same. CompareWheels shows you the exact tire width and aspect ratio needed for each plus-size step.