Máy tính kích thước lốp xe
The detailed guide below is currently available in English.
Decoding the numbers on the sidewall
A marking like 225/55R16 packs three measurements: the tire is 225 mm across at its widest point, the sidewall stands at 55% of that width (123.75 mm), and it fits a 16-inch wheel. Add twice the sidewall to the wheel and you get the overall diameter — about 25.74 inches here — which is the number that must stay roughly constant when you change sizes so gearing, speed readings, and clearances all keep working.
Plus sizing without the surprises
Plus-one sizing (say 225/55R16 to 225/50R17) sharpens steering feel by shortening the sidewall while a bigger wheel fills the arches. The goal is a near-identical overall diameter; the calculator's comparison shows exactly how far off you are and what the speedometer will read at 60 mph. Stay within about 3% of the stock diameter, confirm the new tire clears the suspension and body at full lock and full compression, and match or exceed the load index.
Câu hỏi thường gặp
What does the speedometer error mean in practice?
If the new tire has a larger circumference, each revolution covers more ground, so the speedometer — which counts revolutions — reads low. At +3% error an indicated 60 mph is really 61.8 mph, and the odometer quietly logs fewer miles than you drive.
Why are revolutions per mile important?
Tire makers publish the figure for odometer accuracy, gearing choices, and oversized-truck fitment. It is simply 63,360 inches divided by the tire circumference in inches.
Can I change just the width and keep the same sidewall percentage?
You can, but a wider tire with the same aspect ratio has a taller sidewall and a larger overall diameter, which skews the speedometer. Wider plus-size fits usually pair with a lower aspect ratio to hold the diameter steady.