RC Tire Size Calculator
See how a different tire diameter changes theoretical speed and how to compensate with gearing.
Tire Change
Result
New theoretical speed
51.3km/h
(31.86 mph)
Diameter change
1.091×
Old speed
47.0km/h
Same wheel RPM assumed — theoretical comparison, not a measured speed.
Formula
- 1.
Speed Ratio = New Tire Diameter / Old Tire Diameter - 2.
New Speed = Old Speed × Speed Ratio
Worked example
- 1.Inputs: 110 mm → 120 mm tires, current speed 47 km/h.
- 2.Ratio = 120 / 110 = 1.091
- 3.New speed = 47 × 1.091 ≈ 51.3 km/h.
Assumptions and limits
- Keeping the same speed with larger tires needs an equivalent final-drive-ratio increase.
- Larger tires add rotational mass — expect more load and heat.
- Any gearing advice must be derived from a stated ratio definition.
Related tools
Guides and concepts
FAQ
Do bigger tires always mean more speed?
Only on paper at the same wheel RPM — extra load and slip can erase the gain.
Assumptions
- Wheel RPM is held constant between the two setups.
- A larger diameter raises theoretical speed by the same ratio.
- Tire deformation and load are not modeled.