TWR ACR

Q&A, gearing, manual, and guides

On-road•Touring/GT•1/12 scale•2WD

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Gearing

Stock gearing for the TWR ACR, with common pinions and their ratios.

Stock spur

48T

Internal ratio

1:1

Typical pinion

32–36T

1/12 2WD touring/gt setups. For your motor and track →

Pinion	Spur ÷ pinion	FDR	Rollout
30T	1.60	1.60	84.4 mm
31T	1.55	1.55	87.2 mm
32T	1.50	1.50	90.1 mm
33T	1.45	1.45	92.9 mm
34T	1.41	1.41	95.7 mm
35T	1.37	1.37	98.5 mm
36T	1.33	1.33	101.3 mm
37T	1.30	1.30	104.1 mm
38T	1.26	1.26	106.9 mm

Shaded rows are the pinions most 1/12 2WD touring/gt setups run on the stock spur. Rollout at a 43 mm tire.

What pinion should I run?

Tell us your motor and track and get a starting pinion for the TWR ACR, with the range racers in the class run.

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What pinion gear should I use on the TWR ACR?

It depends on your motor and the track. Racers in the 1/12 2WD touring/gt class run a 32–36 tooth pinion in most setups, usually on a 66T spur for a final drive ratio near 1.96. Hotter motors (lower turns, higher Kv) take a smaller pinion; tight tracks gear down, open tracks gear up. For a starting pinion matched to your motor, use the So Dialed Pinion Recommender with the ACR selected.

What is the internal ratio (transmission ratio) of the TWR ACR?

The ACR has an internal ratio of 1:1. Final drive ratio = spur ÷ pinion × 1. With the stock 48T spur, a 30T pinion gives an FDR of 1.60 and a 38T gives 1.26.