CalculatorsDirect Drive Torque and Rig Strain
Direct Drive Torque and Rig Strain
Newton-metres at the shaft become a force at the rim and a moment the wheel deck has to react. The profile suggestion follows the torque bands rig builders actually shop with.
Inputs
Results
- Force at the rim
- 100 N
- Profile code
- 120
Related gear
- Direct-drive base in the torque you will actually run
Shop the sustained Newton-metres, not the peak number on the box, then match the profile.
$400–$1500
How the number is made
Rim force (N) = torque ÷ radius, and the radius is the wheel diameter in millimetres divided by 2000. Under 8 Nm suggests 40×40, from 8 up to but not including 15 Nm suggests 40×80, from 15 up to but not including 21 Nm suggests 40×120, and 21 Nm and above suggests 40×160.
A wheel stand can hold the low band for a short session. The codes are shopping bands, not a measured deflection. A long wheel-deck cantilever can need the next profile even when the torque sits in a lower band.
- Profile code. 40, 80, 120 or 160 — the second dimension of a 40-series profile.
Two moments, one cockpit
The wheel deck sees this torque. The pedal deck sees the brake moment. Size both, then cut the rails to the rider’s height.
Related calculators
- Aluminium Extrusion Cut List
The profile code picks the series. Height still picks the cut list.
- Wheelbase and Wheel Quick Release
A thicker upright does not make a foreign wheel bolt onto the base.
- Pedal Load Cell Rig Stiffness
The front of the rig can need a heavier profile than the wheel deck.
Questions
Why does 15 Nm jump to the 120 code?
The 80 code stops before 15. Fifteen is the start of the 40×120 band, not the top of 40×80.
Does a larger wheel raise the profile code?
No. The code follows torque only. A larger wheel lowers the force at the rim for the same torque, which is the other output.
Is this the same scale as the pedal tool?
No. Pedal moment uses 80 / 160 / 250 Nm steps because the lever is the pedal height, not a 5–32 Nm shaft.