Tamiya Shadow Shark 18704: AR Chassis Kit Guide
Shadow Shark (item 18704) is an AR-chassis Mini 4WD kit for someone who wants a race-car silhouette with unmistakable shark details. Its nose, cockpit fin and wings are the main reasons to choose this model; the box is also a full motorized assembly kit, not merely a decorative body. Tamiya identifies it as Mini 4WD REV Series No.4. The manufacturer's assembled dimensions are 155 mm long and 97 mm wide. If you are comparing it with another AR car, compare the actual shell and included wheels as well as the shared chassis name.
A shark body built like a formula car
Look at the body from the front and side before applying stickers. The narrow, raised nose and the fin rising behind the cockpit evoke a shark, while the front and rear wings and side pontoons borrow from full-size racing cars. Tamiya also molds an intake beneath the nose. These are visible design details, rather than evidence that a stock Shadow Shark will run faster than another kit. The model photographs on Tamiya's site show a painted and assembled example; expect to assemble the retail kit yourself. Plan any paint and sticker placement before clipping the shell onto the chassis, especially around the tall fin and narrow nose where your fingers will have less room.
The supplied matte-blue plated five-spoke wheels are another unusual part of this specific package. They carry low-profile tires. If you like the car as Tamiya designed it, build and run these first before buying replacement wheels. A different wheel and tire choice changes both the look and the car's relationship with the track, so the stock set is a sensible reference. The broader body guide explains material and shape choices if you later want to change shells.
What the AR chassis contributes
The AR chassis puts the motor at the rear and uses a shaft to drive the front wheels. On this kit, Tamiya highlights access to the underpanel and diffuser without removing the body. That is useful when clearing debris or checking the underside after a run: you do not need to disturb the decorated shell every time. Its molded passages and air intakes are part of the platform design, but treat Tamiya's cooling claims as design intent, not a guarantee of measurable gains on your own circuit. The box includes a motor and uses snap-together assembly. Supply two AA/R6 batteries separately.
Lay out the AR parts before assembly, make sure the wheel shafts sit squarely, and spin the wheels by hand before putting the decorated body on. A drivetrain that binds on the bench will not be fixed by changing rollers. The AR chassis guide covers adjustment after you have a reliable stock build. Its tuning advice applies to the platform; this article is about what item 18704 actually supplies.
Check the included gears on your particular box
There is one specification worth handling carefully. Tamiya's English product description gives Shadow Shark's gearing as 4.2:1, while its current Japanese page states 3.5:1 for the same item number. The manufacturer pages do not agree, so neither figure should be treated as a promise about the retail box in front of you. Identify the gears from the printed instructions and parts in your own kit, and use the specified matching gear components together. Do not buy a replacement ratio solely from an online description. If you need help reading a parts chart, the instruction and parts-matching guide is a useful companion.
For a first run, keep the factory configuration together. Confirm that the battery contacts are seated, the motor and gears turn freely, and the body catches fully. Add rollers or stays only after you have verified that they clear the nose, wings and rear fin through the full range of wheel movement. Do not interpret the shark fin as a practical handle: lift the car by the chassis so that the body decoration remains intact.
Who should choose Shadow Shark?
Choose it if the formula-car and shark combination is what you want to build and display, while still learning a normal AR race chassis. Choose by item number 18704 rather than by a photo alone: other AR cars share the platform without sharing this body or plated wheels. If your main interest is learning AR first, compare this kit's shape with an Aero Avante or another AR body, then use the same stock-build checklist for either. The direct product listing is Tamiya Shadow Shark (AR Chassis); it shows current availability separately from this evergreen guide.
Frequently asked questions
Is Shadow Shark already assembled?
No. Item 18704 is an assembly kit. Tamiya's photographed car is a finished, painted example.
Which gear ratio comes with it?
Tamiya's English and Japanese product pages disagree. Check the instruction sheet and gears in the box you receive before stating or changing its ratio.
Do I need batteries?
Yes. Tamiya lists two AA/R6/UM3 cells as separately required.
Sources checked 26 September 2026: Tamiya English item 18704 and Tamiya Japan item 18704. Product specifications describe the manufacturer's kit, not a track test.