Compare your current and new tyre size: how much the wheel diameter, ground clearance and speedometer readings will change.
Checked by the editorial teamRates and formulas: September 2026
Diameter difference—
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New
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How to read a tyre marking
The size 205/55 R16 means: tread width 205 mm, sidewall height 55% of the width (112.75 mm), rim diameter 16 inches (406.4 mm). The letter R stands for radial construction, not radius.
Car and tyre manufacturers recommend that the diameter of the new wheel differs from the original by no more than 2–3%. Otherwise the speedometer and odometer will be noticeably off, ABS and ESP may not work correctly, and the wheel may rub against the arches and suspension.
If the new wheel is larger, the speedometer shows less than your real speed — you could get a speeding fine. If it's smaller, it shows more, and ground clearance decreases.
The permitted sizes for your car are listed on the sticker in the driver's door opening, on the fuel filler flap or in the owner's manual.
This information is for reference only and does not constitute financial, tax or legal advice. Prepared by our editorial team, last checked: September 2026. Found an error? Write to us.
Frequently asked questions
What happens if I fit tyres with a larger diameter?
The speedometer will under-read your speed and the odometer your mileage. Ground clearance increases, but handling may get worse and the tyres may touch the arches.
Can I fit R17 instead of R16?
Yes, if you choose a tyre with a lower profile so that the overall wheel diameter barely changes. For example, 205/55 R16 can be replaced with 205/50 R17.
What speedometer error is acceptable?
A difference in wheel diameter of up to 2–3% is considered safe. Speedometers usually over-read slightly anyway, so a small increase in wheel size often compensates for that.
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