Spur gear
The spur gear is the main gear that sits on the transmission input shaft. It is jointly responsible (with the clutch bell) for defining the main gearing of the transmission. The spur gear incorporates a slipper clutch to reduce shock on the drivetrain. The slipper clutch uses a cast aluminium back plate, a polished aluminium slipper plate, soft pad attached to the spur with adhesive backing, and a tensioning spring.
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Available teeth counts
Spurs are available in 47, 49 and 52 tooth variations for nitro Savages, and 43, 44 and 45 tooth variations for the Flux.
Official spur gears
Plastic single sided
All pre-X models, and the current X models come with plastic single sided spur gears. A brass bushing is required in the center and must be retained when replacing the gear.
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Part numbers:
- 47T plastic spur #76937
- 49T plastic spur #76939
- 52T plastic spur #76942
Plastic double sided
When first introduced, the X came with a double sided slipper gear and additional integrated rotational shock damper. The design was removed from production after a short time, possibly due to extra wobble caused by the more complicated set up. It has not been re-introduced since.
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Part numbers:
- 47T plastic double sided spur #77092
- 49T plastic double sided spur #77094
- 52T plastic double sided spur #77097
Two piece steel
The two piece steel spur has an aluminium hub and interchangeable hardened steel ring gear pieces. They are joined with 6 screws. The two piece design has been noted to be difficult to keep attached. The screws must be threadlocked, preferably with red threadlock.
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Part numbers:
- 47T steel spur set #86806
- 49T steel spur set #86807
- 52T steel spur set #86808
- Aluminium hub #86805
- 47T steel spur only #77117
- 49T steel spur only #77119
- 52T steel spur only #77122
Heavy duty steel
The heavy duty steel spurs are standard on the XL and Flux. They are machined from a single piece of hardened steel. They are the strongest but also heaviest official spurs available.
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Part numbers:
- 43T HD steel spur (Flux) #102091
- 44T HD steel spur (Flux) #102093
- 45T HD steel spur (Flux) #102095
- 47T HD steel spur #77127
- 52T HD steel spur #77132
Compatibility
Main article: Gear compatibility
Plastic vs steel
It is important to note that plastic spurs generally do not become damaged under normal circumstances. A stripped spur gear is usually a symptom of a different problem such as an incorrectly set gear mesh, slipping clutch (causing heat build up) or binding drive train. One should never switch to a steel spur gear if they are experiencing several stripped spurs. Instead the root cause should be found.
Advantages of plastic
Plastic spur gears are very light, reducing rotational mass in the drive train and therefore increasing acceleration. Because of their nature they also will tend to be the first part of the drive train to be damaged if excess stress is encountered. This is desirable as spur gears are inexpensive and by stripping first may save more expensive and harder to replace parts of the transmission.
Advantages of steel
Steel spur gears are extremely resistant to stripping and heat so may be useful for racers who need endurance parts that will not break during the stress of a race. They will also resist damage if the slipper pad is ruined, whereas a plastic spur may melt.
