RC drift gear ratio (FDR) and rollout calculator

EzDrifts workshop deskUpdated September 2026Reference FDR bands attributed in Sources; the maths is shown step by step
Short answer

Final drive ratio is the internal ratio multiplied by the spur and pinion ratio. Rollout is the tyre circumference divided by the FDR. This calculator takes your own parts, returns both numbers, compares the FDR with the reference band for your surface, and tells you which pinion to buy.

Gearing is the one setup change you can make in five minutes with a single part, and it alters how the car feels more than most suspension tweaks. The catch is that spur and pinion teeth mean different things on different chassis, which is what the internal ratio corrects for.

Work out your final drive ratio and rollout

Use the tyre you actually run and count the teeth. The internal ratio comes from the ring gear and drive gear of your chassis, not from the spur and pinion.

Outer edge to outer edge, measured with a caliper
Count the teeth, do not trust the packet
The small gear on the motor shaft
Ring gear teeth divided by drive gear teeth. A Yokomo YD-2 is 2.6, which is 52 divided by 20
ArkEdge RC suggests 3500 to 5000KV for 1/24 drift

Every number above comes from the parts you typed in. Nothing is pre-set for a particular car, so a different tyre diameter changes the answer.

About this tool and its limits

Purpose: to support one decision, from numbers you supply.
Not suitable for: any medical, legal, safety or warranty decision.
Method type: arithmetic on your inputs, or an editorial rule stated below. It is not a validated model.
Accountable publisher: the editorial desk of this store.
Method version: 1.0. Last checked: 2026-09-14.

The calculation runs in your browser. This tool's own code does not save or transmit your answers. Separate site analytics and other services are described in our privacy policy.

Input What it means Accepted values
Tyre diameter (mm) Used directly in the calculation. any number, default 62
Spur gear teeth Used directly in the calculation. any number, default 84
Pinion gear teeth Used directly in the calculation. any number, default 20
Internal (transmission) ratio Used directly in the calculation. any number, default 2.6
Motor kV Used directly in the calculation. any number, default 4200
Battery nominal voltage Used directly in the calculation. 1S LiPo, 3.7 V, 2S LiPo, 7.4 V, 3S LiPo, 11.1 V
Surface you drive on Used directly in the calculation. Carpet, Asphalt, Polished concrete or P-tile

Worked example

With the pre-filled values shown above, it returns:

Headline result FDR - to 1
Spur to pinion ratio - to 1
Internal (transmission) ratio - to 1
Motor turns per wheel turn -
Rollout - mm travelled per motor revolution
Tyre circumference - mm

Calculation checks

Case Observed behaviour
Boundary input (highest accepted values) FDR 21.84 to 1
Invalid input (zero values) FDR - to 1

These checks show the tool behaves as documented. They do not establish medical or scientific validity.

What this result cannot tell you. It is an estimate derived entirely from the numbers you enter, using the relationships described on this page. It does not measure your situation, it does not account for anything not listed as an input, and it cannot establish which product you should buy. Where the result matters for your health, safety, money or a warranty, treat it as a starting point and check it against the primary source linked at the bottom of this page.

Products and commercial interest. This store sells the products these guides discuss. Product data never changes a calculation. To report a problem, use the contact page and include this page's URL, the inputs you used and the result you expected.

How the calculation works

  1. Spur to pinion ratio is spur teeth divided by pinion teeth. It is the visible gear math, and it is not comparable between cars on its own.
  2. Final drive ratio is that ratio multiplied by the internal ratio, so it describes motor turns per wheel turn. This is the number to compare between two chassis.
  3. Rollout is the tyre circumference, which is pi multiplied by diameter, divided by the FDR. It is the distance the car moves per motor revolution.
  4. Wheel rpm is motor rpm divided by the FDR, and motor rpm is roughly kV multiplied by pack voltage.
  5. The pinion suggestion reverses the FDR formula to hit the middle of the reference band for your surface, which is a better target than the edge of it.

Reference FDR bands by surface

Bands are the Yokomo-derived reference figures for 1/10 RWD drift published on the Marcus RWD RC Drift Blog. Compound names come from the tyre listings at Super-G R/C Drift Arena.

Surface Reference FDR band Motor turns it is written around Tyre compound that suits it
Carpet 7 to 9 10.5T to 8.5T brushless Hard HDPE carpet compound
Asphalt 8 to 10 13.5T to 10.5T brushless Asphalt-spec drift tyre
Polished concrete and P-tile 10 to 13 13.5T to 10.5T brushless Concrete compound, or a competition P-tile tyre
Which way is whichA higher FDR number is shorter gearing: more torque and acceleration, less top speed, more heat. A lower FDR is taller gearing: more top speed, less punch. A bigger pinion lowers the FDR. Because the pinion moves the number faster than the spur does, it is the gear you tune with, and the spur is the one you change when the pinion range runs out.

Worked examples from a documented chassis

These use the published figures for a Yokomo YD-2, whose internal ratio is 2.6, with a 62 mm tyre.

FDR values for the first two rows are the published Yokomo figures. Rollout is calculated from a 62 mm tyre. Two teeth on the pinion moved the FDR further than two teeth on the spur.

Spur Pinion FDR Rollout Where it lands
84 T 20 T 10.92 17.8 mm The stock combination, inside the tile and polished concrete band
84 T 22 T 9.93 19.6 mm Asphalt band, moving towards carpet
82 T 20 T 10.66 18.3 mm Shorter than the 22 T pinion, which shows how much the pinion moves
The limit of these bandsThe reference bands come from 1/10 RWD drift, tested with 8.5T to 13.5T brushless motors, and they assume a car of that size and weight. A 1/24 car with a 4200KV motor will not use the same FDR for the same result. What carries across is the outcome you are chasing: a wheel speed and a torque delivery that let the rear break away smoothly at part throttle. Use the bands as a start, then use the fact that a taller gear feels lazy and a shorter one feels snatchy to find the number for your floor.

Use it with these

Questions people ask

What is a good final drive ratio for RC drifting?
On 1/10 RWD drift the reference bands are 7 to 9 for carpet, 8 to 10 for asphalt, and 10 to 13 for polished concrete and P-tile. Those bands assume 8.5T to 13.5T brushless motors. A different motor or scale will want a different figure.
How do I calculate rollout?
Rollout is tyre circumference divided by the final drive ratio. Circumference is pi multiplied by the tyre diameter, so a 62 mm tyre is 194.8 mm around, and at an FDR of 10.92 the rollout is 17.8 mm per motor revolution.
How do I calculate the final drive ratio?
Multiply the internal ratio by the spur to pinion ratio. If the internal ratio is 2.6 and spur divided by pinion is 84 divided by 20, the FDR is 2.6 multiplied by 4.2, which is 10.92.
Does a bigger pinion give more speed?
Yes. A bigger pinion lowers the FDR, which raises top speed and reduces acceleration and run time, and adds heat to the motor and ESC. The pinion is the gear to change first because it is quicker to swap than the spur.
Why does the calculator ask for an internal ratio?
Because spur and pinion teeth are not comparable between chassis. The internal, or transmission, ratio is ring gear teeth divided by drive gear teeth, and it is what makes an FDR meaningful across two different cars. It is usually in the manual, and you can also count the gears.

Sources

  1. Marcus RWD RC Drift Blog. Final drive ratio (YD-2 multiplier 2.6, reference bands and the 10.92 and 9.93 examples) — ameblo.jp/marcus38060/entry-12350138594.html
  2. So Dialed. Rollout, final drive ratio and transmission ratio — sodialed.com/rc-setup-tips/rollout-final-drive-ratio-fdr-transmission-ratio
  3. RC Formula 1. A to Z of gearing: FDR and rollout defined — rcformula1.com.au/index.php/tech-tips/a-z-of-gearing-with-blinky-escs
  4. ArkEdge RC. 1/24 micro drift RC beginner setup guide — www.arkedgerc.com/blogs/articles/1-24-micro-drift-rc-complete-beginner-setup-guide
  5. Super-G R/C Drift Arena. Drift tyre listings by surface — supergdrift.com/collections/tires