What it does

Tire size compares a rear tire size with the one on the active bike and shows how road speed and the speedometer change.

1. Enter a size

1. Open Tire size from the hub. The current rear tire is shown at the top.
2. Enter width (80–360 mm), aspect (25–100) and rim (10–23 in). Results update as you type.

2. Read the result

• Current and new tire diameter in inches.
• Road speed change in percent at the same rpm.
• True speed at 100 indicated, for a speedometer that reads from the rear wheel.

Example

Going from a 190/55-17 to a 200/55-17 is +1.7%: about 101.7 mph true at 100 indicated.

Tips

Diameter is worked out from width × aspect plus the rim, so real tires vary by brand and wear. A taller tire raises road speed at the same rpm, much like a smaller rear sprocket. To keep the new size on the bike, change it in Edit bike.