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Adjusting Your Nitro 4-Tec
Gear Ratios
Another Nitro 4-Tec feature is the ability to change the
gear ratios. Currently, there are three optional gear ratios
for the Nitro 4-Tec. The stock gear ratio will provide very
high (60+ MPH) top speeds. Because of the extreme top
speed, the stock gear ratio is primarily intended for flat-out
running on large, unobstructed, paved areas. Organized, 1/10
scale, nitro touring car racing is typically done on smaller, closed
courses. For this type of racing change to a lower (higher
numerical) gear ratio. The following chart gives the four possible
gear ratios sets. The ratios are arranged from highest (lowest
numerical) to lowest (highest numerical). A brief application
recommendation follows each gear ratio set.
Nitro 4-Tec gear ratios must be changed as 1st and 2nd gear sets in
order to maintain compatible gear center distances. The gear ratio
chart gives the only four compatible ratio choices.
40
Clutch
Spur
Gear
Teeth
Teeth
Nitro 4-Tec Stock
1st
16
41
Equipment
2nd
20
37
Ratio Characteristics:
Moderate acceleration, highest top speed
Recommended Application: Sport/recreational running in very large areas
Optional Clutch Gears
1st
15
41
w/Stock Spur Gears
2nd
19
37
Ratio Characteristics:
Good acceleration, very high top speed
Recommended Application: Sport/recreation running in very large areas
Stock Clutch Gears
1st
16
45
w/Optional Spur Gears
2nd
20
41
Ratio Characteristics:
Very good acceleration, high top speed
Recommended Application: Sport/recreation, racing on large 1/8 scale size tracks
Optional Clutch Gears
1st
15
45
w/Optional Spur Gears
2nd
19
41
Ratio Characteristics:
Explosive acceleration, moderate top speed
Recommended Application: Racing on small tracks. Recreational running in small areas.
Changing the Clutch Bell Gears
1. Remove the right, rear wheel. Remove the E-clip from the
two-speed shaft. Slide the pulley and belt off of the shaft,
being careful not to lose the pin that sits under the pulley.
Remove the pin. Slide the spur gears off of the shaft (If you
are using optional gears, you may have to loosen the right
Theoretical
Speed
Primary
Overall
(MPH) at
Reduction Reduction 36,000 RPM
2.56
5.81
46.54
clutch bell, gently grip the clutch bell with channel-lock,
1.85
4.19
64.47
adjustable pliers. Cover the gears with a cloth to protect the
teeth. Using the pliers, unscrew the gears counter-clockwise.
2.73
6.20
43.6
4. New clutch gears simply screw onto
1.95
4.41
61.2
the clutch bell. Reinstall the clutch
bell and caphead screw onto the
2.81
6.38
42.4
pilot shaft. Reinstall the spur gears,
2.05
4.65
58.2
pin, pulley and belt. Secure them on
the two-speed shaft with the E-clip.
3.00
6.80
39.8
2.16
4.89
55.3
5. To adjust the gear mesh, first loosen the four 3x10
countersunk hex screws in the slotted holes in the bottom of
the chassis. Next, remove the two countersunk Phillips head
screws in the bottom of the chassis which hold the slotted
engine mount. The engine should now slide back and forth.
Slide a strip of thin note paper between the spur gears and
the clutch bell gears. Push the clutch bell gears against the
spur gears and tighten the screws on the bottom of the
chassis. Remove the paper and the gear mesh is now correctly
adjusted.
chassis stiffener to remove the spur gears).
2. Lock the flywheel with a flathead
screwdriver to immobilize it. Use a 2.5mm
allen wrench to unscrew the caphead
screw that holds the clutch bell
to the pilot shaft. Remove the
clutch bell.
3. To separate the gears from the
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