Kyosho MP-7.5 sports

Radio Control Car Action, Feb 2002 by Vieira, Peter

track test

'1/8-SCALE NITRO

THERE IS NO MORE SUCCESSFUL %-scale buggy series than the Kyosho Inferno. With five consecutive IFMAR World Championship titles between the MP-5, MP-6 and the latest MP-7.5, Kyosho has made an indelible mark on the nitro racing scene. With that kind of performance, who wouldn't want an Inferno? Next question: given its $700+ price tag (kit, engine and accessories), who can afford one?

Kyosho has long known that many would-be Inferno customers can't (or don't want to) plunk down the cash for a full-race 7.5, and it has always made less extravagantly equipped versions of the Inferno available-originally as "DX" models, and most recently, as "Sports" kits. That brings us to our test subject, the Inferno MP-7.5 Sports. Everything that makes an Inferno MP-7.5 handle like an MP-7.5 is still there; most of the exotica isn't. But you do get a .21 engine with pull-starter and tuned pipe; that's stuff you would still be shopping for after buying the standard Inferno MP-7.5. Let's get to the particulars.

VEHICLE TYPE 1/8-scale 4WD nitro off-road buggy

BEST BUYER Nitro enthusiast who appreciates the Inferno's IFMAR cred but can't afford the full-on MP-7.5

KIT RATINGS (poor, satisfactory, good, very good, excellent)

Instructions Good

Parts fit and finish Very good

Durability Very good

Overall performance Good

SPECIFICATIONS

MANUFACTURER Kyosho

MODEL Inferno MP-7.5 Sports

DISTRIBUTED BY Great Planes

SCALE 1/8

STREET PRICE $490

DIMENSIONS

Wheelbase 12.7 to 12.9 in. (323 to 328mm)

WWM 12.1 in. (307mm)

WEIGHT

Total, as tested 120 oz. (3,402g)

CHASSIS

Type Stamped plate with radiused sides

Material 3mm aluminum

DRIVE TRAIN

Type Shaft-driven 4WD

Primary 13T clutch bell/46T spur gear

Center drive shafts Dogbones

Drive axles Dogbones

Differentials Bevel gear

Bearing type Metal-shielded ball bearings

SUSPENSION

Type Lower Warm with wishbone upper arm (front), threaded camber link (rear)

Shocks Blue-anodized, aluminum-- body, oil-filled

WHEELS

Type One-piece 10-spoke

TIRES

Type Kyosho medium-compound multi-pin

KIT FEATURES

CHASSIS. The Sports' chassis is almost identical to the standard 7.5's; the only difference is an extra opening behind the engine-mounting holes for pull-start housing clearance. Otherwise, it's the same 3mm-thick sheet of aluminum with countersunk screw holes, gently radiused sides, pads for droop screws and stamped-in blisters that allow the diffs to sit lower in the chassis than is possible with a flat chassis.

Up top, a 2mm-thick aluminum radio tray is joined to the main chassis with plastic standoffs and a flange on the front of the dual-compartment radio/battery box. A rod brace stiffens the rear of the chassis, but the front end isn't braced except where a zmm plate joins the steering bellcranks to the front bulkhead.

DRIVE TRAIN. In addition to dropping the cliffs lower in the car by stamping clearance blisters into the chassis, MP-7.5 designer (and reigning IFMAR World Champ) Yuichi Kanai downsized the MP-7.5's cliffs to further concentrate drivetrain mass as low as possible on the chassis. In Sports trim, the (relatively) small-diameter cliffs have plastic housings and cast ring gears with two internal spider gears. O-rings seal the outdrives, and a gasket seals the case to the ring gear, allowing silicone fluid to be used for cliff tuning (which you'll have to supply yourself, since the Sports' diffs are factory-built with grease). In fact, the entire center drive train is assembled on the chassis for you by Kyosho.

Dogbones connect the front and rear diffs to the center diff, which is mated with a plastic spur gear. I have little love for plastic spur gears on 1/8-scale buggies, but I'll reserve judgment until I find out whether it holds up or not. The center diff is also home to the Sports' brake system: single steel discs on each side of the diff. Padded calipers grab the discs, and molded disc guides on the chassis help keep the parts lined up for sure stopping. That good stuff is offset by cost-cutting cheeriness in the brake linkages; they are merely music-wire with Z-bends. Brake bias may be adjusted by repositioning screw collars on the linkages.

Power gets from the diffs to the wheels via dogbones, and metal-- shielded ball bearings are used throughout. New to the 7.5 series are 17mm hex hubs that permit any brand of wheel to be used with the car; older models had i9mm hexes that limited wheel options.

SUSPENSION AND STEERING. The Sports' aluminum shocks are attractively blue-anodized and conventionally constructed with volume-compensation bladders beneath the caps and bottom-loaded, factory-- installed seals. Kyosho includes its homebrew "medium" green oil to fill the shocks.

The shock towers are 2mm-thick aluminum plate with six locations for each shock, while the typically thick, lower suspension arms each offer two shock positions. The arms also have droop screws for down-travel adjustments-no need for messy, internal shock-spacer fiddling. Threaded upper links make rear camber adjustments possible (albeit with some minor disassembly); likewise, the Sports' front upper wishbones use short lengths of threaded rod to facilitate camber changes. Cast steering arms, plastic C-carriers and plastic rear-- hub carriers complete the suspension system.