… and its lineage

The Kyosho Legend

After the Optima Mid series, Kyosho came to the off road World Championship in Australia 1989 with the 4×4 prototype of what would become commercialised as the Lazer ZX. It was codenamed ‘Legend’. The situation was quite similar as in 1987 when they took the prototype of the Mid to the Championship.

‘The’ prototype would be quite incorrect. A good 100 cars were provided to drivers worldwide, and were hand built.

The Legend came with a carbon fibre chassis, two belts as opposed to the single-belt Optima Mid, long wheel base and 3 ball differentials. The center diff integrated the balls into the spur, sandwiched between two drive plates. It’s a compact, smart setup with the motor in a central position.

The top deck was made in 2 separate parts, one on each side of the front drive belt. Both front and rear drive belts (no tension control, P3M shaped and sized teeth, so smaller than on the Optima Mid) wrapped around the drive pulleys over 180° and are kept in place with brass bushes, which meant the car could take a lot more power without adding too much drag through belt tension.

The drivetrain could be tensioned up on both sides of the car. The spur side could be tensioned for distributing the power split between front and rear. You could tune it from 100% front to 100% rear! The other nut at the opposite side of the layshaft acted just on the front and could provide a permanent 4×4 lock. Its natural bias was more towards the front to make the car very easy to drive at speed, albeit at the cost of traction off the line and out of corners. More heavyhanded racers complained the center diff would send all power to the front wheels when those started spinning. Those often removed the balls from the spur and clamped down the setup.

It was easy to swap out the ball diffs for geared diffs (off the Optima Mid), although these were cast and the enclosures weren’t sealed. You can’t just take these now and fill them with silicone oil or diff putty or shim them to tune them. Racers grabbed thick sticky grease instead to add some lock.

The Legend featured lexan protection for the spur and plastic protection for the belts. Although some racers removed them – sometimes it’s better to make sure debris can get out again rather than get trapped in an enclosed environment.

Compared to the Optima Mid, the car featured longer suspension arms with the c-hubs inside the wheels (like on the Schumacher Cat at the time). The Legend also came to the drivers with an explanation on how to make a front and rear anti-roll bar, but it was not delivered in the package.

The drive was delivered to the fronts with regular dogbones, although the rear featured homokinetics to the wheels.

Being a prototype, Kyosho offered an overload of possible setups. Just for the rear suspension geometry there were 18 holes at the center and 6 holes at the hub side. 18 x 6 means 108 different possible setups. The provided Option House Gold Shocks had 19 possible positions on the shock stay and 3 on the arms, but with an extra part this could become 13. Meaning 247 possible shock positions. The front offered universal joints, 12 possible suspension geometry positions and 182 possible shock positions.

Although some parts were taken from the Optima series (like the dogbones, drive cups, outdrives, wing stay, wheels, bumper,…) the Legend was a complete rethink of a competition car and although it was clearly based on the concept of the Optima Mid, the layout and other solutions were such an overhaul that it was a new car. With 28 ball bearings, clearly Kyosho wanted this car not to become a drag.

As for appearance, the Legend featured the Optima Mid body, awaiting a new undercowling and body that wasn’t ready yet.

The Legend was also easier to maintain. Both front and rear units containing the diffs were easily accessible.

Rick Howarth was one of the drivers enjoying the Legend at the World Championships, finishing 3rd, his best Worlds finish ever.

The Lazers never won the worlds, but they were incredibly successful at just about all other races, even beating Masami Hirosaka’s 1989 IFMAR World Championship winning Yokomo 870C (prototype of the YZ10) at the ’89 Japanese national.

The Kyosho Lazer ZX

Following the Legend, Kyosho commercialised the Lazer ZX in 1989. The Lazer ZX, compared to the Legend, featured new shock stays (LA-14 and LAW-7), gear diffs (LA-1 case with LA-28 gears) as standard and of course its own body (LA-36).

Although the shock stays featured less setup options than the Legend, there were still an impressive amount of positions available.

The rear arms (LA-26, with the same webbing as featured on the Legend) were slightly adapted through manufacturing so the mounting point for the optional anti-roll (LAW-2) bar came to the front rather than the entire setup being located at the rear of the car. This made for longer rear anti-roll bars which were easier to tune. And the same was true for the front, where the Legend featured a short-armed anti-roll bar located on the front of the shock stay, leading to the front of the suspension arms. The ZX changed this, leading the bar to the rear of the suspension arms through the arm / driveshaft / steering arm setup. On full lock though and depending on setup, this sometimes led to the antiroll bar touching the steering arm.

On the Legend, a small motor mount cooling plate was changed for a thin version (LA-19) and the entire chassis and top deck changed to graphite reinforced versions (LA-16 and LA-15) rather than the carbon fibre items off the Legend.

At the front, Kyosho now used a special ball end (LA-29) to get enough space with regards to the rims when the front suspension was fully compressed. This replaced the standard Optima ball end (W-5015) that was on the Legend, which was at that time the same as the one on the bottom of the Gold shocks. The drive was provided through homokinetics (W-5061) at the front, and regular dogbones (OT-6) at the rear.

With regards to the steering, the setup was the same as on the Legend, but many replaced the standard bushes with ball bearings – flanged 3 x 6 for the steering plate (LA-17) and regular 5x8x3 for mounting the steering setup on the chassis posts (LA-23).

No motor came with the Lazer, as it was oriented towards racers that chose their own, mostly modified, motors. The kit did come with a 20T pinion, which was more suited to stock motors however. The kit also featured multiple battery post configurations, supporting batteries like a 2×3 battery, stick pack and 2 x 4.

And of course, the central differential from the Legend was kept in the Lazer ZX. It featured wavy washers (TM-19) for tensioning the differential and doubled up as a drivetrain protector as well. In fact if you wanted to actually use it more like a slipper diff or as a drivetrain protector on rough terrain, the OT-88 (asbest plate) kit from the optima could be installed to protect against wear and offer more fluent setup changes.

The ZX also kept the belt cover structure (LA-34). While this was meant to make sure the long front belt (LA-13) was kept free of dirt, sand and tiny rocks, it was often removed by racers. This was due to the fact that it often did quite the oposite of its intention, namely keeping tiny stones pinned inside that did get in the structure. A more open setup made the belt throw these objects away, causing less damage while admittedly allowing dust to enter the gearboxes. This didn’t create much of a problem as the gearboxes were free of grease and are in fact quite accessible to clean out and replace the (ball) bearings.

The very first (and very few) Lazer ZX boxes in fact had a small design flaw, where the differential carrier bearings floated a bit loose in the casings. This was very swiftly corrected by Kyosho, who added an extra bag of updated casings to the boxes, ensuring customers got a car without known flaws. It should be said however, while the differentials (LA-1, LA-28 and OT-5) came pre-assembled, it was worth opening them to add some more grease. While at it, adding some thread lock to the small allen nuts that locked the drive cups on the differential axles was also highly recommended.

Upon its launch and with the standard setup from the manual, the Lazer ZX was considered a car that was really easy to drive, with a very neutral stance. But that setup came at the expense of some of the agressivity that was found in the Optima Mid for example. Many opted to lock up the 4×4 to get a more reactive driving behaviour.

The ZX-R evolution

And then came the update: the Lazer ZX-R. It actually featured the same chassis plate (LA-16). The main difference was actually the layshaft configuration. From now on, the Lazer would feature a slipper kit that Kyosho partially grabbed off the Triumph. While not a documented change, the 48dp (TM-7) spur gear now got extra locating pins casted in to lock the slipper pads (TM-12) in place. The optional 0.6 mod spur gear (LA-2) that came off the Lazer ZX also received these pins in a mold change. The slipper plate was held under tension by wavy washers (TM-19) instead of a regular spring. These wavy washers were a consumable as they got squashed and lost their tension, meaning they have been getting harder to find. The front hub was replaced by a new one (LA-56), larger, to allow enough surface for the slipper pads. The setup no longer used the thrust bearing between the belt pulleys (LA-11) rather a plastic spacer (part of the LA-55 main shaft set). At the non-slipper end of the layshaft, the adjustable nut (LA-5) allowed for spreading the torque between front and rear of the car, making it more front or rear biased.

The ZX-R also featured a new front shock stay (LAW-6), allowing for the use of the medium sized shocks rather than the short ones for longer suspension travel. In came a new, sleeker body (LA-52) that took some styling clues from the 2WD Triumph and also the wing off the Triumph (TM-28). The steering knuckles (OT-16) were changed with plastic items, which were a bit more flexible and less brittle than the original metal ones (also OT-16…) featured in the ZX. In terms of geometry, the ZX-R featured easily adjustable turnbuckles (OTW-11 and OTW-12) as upper wishbones and steering rods.

Structurally, the upper deck (LA-57) was now changed to be made in one single part which increased the torsional stiffness of the car. This actually was a change that had another merit: as the R model did away with the belt cover and trapezium belt guide that went through the ZX chassis, this got rid of the problem of keeping tiny stones caught in the belt enclosure.

Another big change in the driveline was the adoption of standard ball diffs (LA-1 case, WBD-1 balls and plates, WBD-2 adjustment shaft) front and rear. At the time, racing was often done in quite loose dirt instead of the (often) carpet / astroturf surfaces of now. The ball diffs allowed for great tuneability of the lock between left and right. It was crucial to luck the adjuster screws using red threadlock as the ball diffs would otherwise work loose at the rear when steering to the right. Ceramic balls are a worthy upgrade, although more sensitive to adjustment.

Also the steering plate was changed with a part giving less ackermann (less bumpsteer) (still LA-17). This had the added effect of bringing more agressive steering to the car.

Stabilizers (LAW-2) were optional.

Other changes were the use of a lighter, more flexible wing stay (UMW-1) which Kyosho took off the Ultima, and larger 2.2 inch wheels (W-5026 and W-5027) rather than the 2.0 wheels featured on the ZX.

Battery holders were changed to allow a stable tray (TM-4) for stick packs.

The updated ZX-R: mk2

The ZX-R mk2 was a ZX-R that came with some optional parts. The main change was to change the weight distribution of the car by using a different chassis (LA-60) and top deck (LA-61). This alone required mostly just a different motor plate set. At the front, new front hubs (LA-59) were fitted that did away with the Lazer specific ball ends at the front wheels, rather changing the king pin (from OT-4 to LA-63), featuring a thread in the top to insert ball studs where now the longer adjustable upper rods (OTW-13) attached. The front hubs brought a wider track and more camber, requiring the longer universal joints (W-5063). New battery posts were added (OTW-9) as well, the slipper’s wavy washers replaced by the Triump slipper spring (TM-32). The rear hub carriers received extensions for attaching the rear upper rod.

The ZX-RR

Sold in regular ZX-R boxes with a ZX-RR sticker, the ZX-RR was a further evolution of the ZX-R mk2 and featured the splendid Ultimate Shocks (same as the famous Equalizer Shocks but without the threaded body). The knuckle arms changed, although in a pretty weird way: the manual tells to put the ‘L’ arm right and the ‘R’ arm left. They are indeed assymetric and this brings the point for attaching the steering rod on a different level. The steering plate received a treatment with tapered washers to have less friction and the ball diffs received some updates (even keeping parts number for replacement bags the same, in Kyosho style, although they were not always just straight swaps part by part). A major change was the ingenious Hyper Clutch slipper setup, which bolts the spur fixed to the outer slipper plate. This allows to set up the slipper, but then changing the spur without having to redo your entire setup. There were some changes to the layshaft setup as a new main shaft was used and a new spacer took the place of a 4 x 6mm shim. The side plate (other side of the slipper) was changed as well. Another change was the front shock stay shape. Lastly, the kit came with a big nylon wing in white.

Some typical complaints about the cars

The front gearbox was considered to be a weak point, with the front lugs breaking off on a roll over where the shock stay would twist / bend / break. The bending / breaking point of the shock stay can be significantly improved by using longer screws through the front shock stay, so these hit the upper deck and keep those parts as a more sturdy whole. Another solution is a thicker shock stay or a shock stay with the tops joined together.

The same goes for the rear shock stay mount which drapes over the rear gearbox. In a crash this part quite easily cracks.

The wishbone brackets are mostly replaced by alloy ones, as these has a tendency to break when clipping a wheel. The outer ones (frontmost and rearmost) are more sensitive to breaking than the inner ones.