FMS ROCHOBBY 1:7 Ridge Racer U4 Desert Buggy RS

Stock is as the vehicle ships. Calculated is worked from the stock figures on this page rather than stored beside them, so the two cannot drift apart. Derived is worked out from gear tooth counts the maker publishes rather than printed as a ratio; the notes below say how. Not published means it exists but no source we could find prints it.

Gearing parts

Tooth counts are the ones in the specifications above. Pitch is given as metric module (Mod 1, Mod 0.8) or diametral pitch (32P, 48P). They are different standards and are not interchangeable, even where the numbers look close. Bore is the pinion’s hole, listed separately from the motor shaft. Linked part numbers go to the maker's or official distributor's page for that part.

How these numbers were settled

FMS prints a pinion chart instead of a stock pinion: 11T gives 1:14.55, 12T 1:13.34 and 13T 1:12.31, all on the 63T, 1.0 module spur.

• The manual's motor step shows 12T, 13T and 14T pinions as alternatives without saying which one is fitted, so the pinion and the overall ratio are left blank.
• The ratio after the spur, 2.538, comes from the 33/13T spiral differential gears FMS lists, and it reproduces each line of the chart.
• FMS gives the tire as 145 x 56mm on the product page and 146 x 56mm in the manual, so the diameter is left blank.
• The motor is a 4274 at 1600KV, and the manual says the 150A ESC is set up at the factory for 4-6S LiPo.
• The 50 mph figure is FMS's claim on a 6S pack; it cannot be checked without the stock pinion.
• FMS now lists the model as discontinued.
• ROC10701RSRD is the red version and ROC10701RSBU the blue one.

Documents

• ManualInstruction manual MAN-G0181 V2 (FMS PDF) (opens in a new tab)Specification p. 2; center differential p. 10
• Gearing chartPinion and gear ratio chart (in the manual) (opens in a new tab)Specification p. 2
• Parts listSpare parts list (in the FMS manual PDF) (opens in a new tab)p. 20

Sources

• rochobby-1-7-ridge-racer-u4…fmshobby.com (opens in a new tab)
• Manual (PDF)cdn-files.myshopline.com (opens in a new tab)
• 1-7-ridge-racer-u4-steel-sp…fmshobby.com (opens in a new tab)
• 1-7-ridge-racer-u4-brushles…fmshobby.com (opens in a new tab)

Every figure on this page traces to one of these. Where they disagreed, the note above says which was used and why.

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