Out of the Box...
My fascination with 1/10th scale 4wd buggies began early in my R/C career. I have owned everything from Yokomo YZ-10 Dogfighters to a Tenth Technology Predator. Kyosho has been a player in the 4-wheel class for just as long but, like Tamiya, you never know if the next kit they release will be a competitive race-grade model or an ABS plastic toy with friction shocks. What I know for sure is that when Kyosho targets a specific class for competition, they get serious - and the end result is going to be an outstanding product. The ZX-5 is bred from that determination.
Twelve hours. That's what it took for me to complete this kit - from cutting the factory seal to placing the last sticker on the body. When I opened the box, I was reminded of one of the key differences between Japanese and American kits (i.e., AE and Team Losi): the parts trees. I knew right away that I would be in for some careful filing of parts to give the car a clean finished look. Nothing looks worse than rough flashing hanging off of every suspension component! I don't know about you, but I don't build kits - I build models. As I perused the parts bags for eye catching anodized aluminum bits I noticed something else...wheels but no tires! Thank You Kyosho! Thanks for not bumping up the price of my kit by throwing in some useless stone-hard tires that I'll never even bother wasting a good set of wheels on! Well... enough looking; let's start building.
Before starting the build, I highly recommend having a hex drive screw kit for the ZX-5 on hand. Replacing the Phillips screws now will not only make the assembly go faster but will reward you every time you work on the car in the future. I don't know what it is about hex screws but they also give kits a cleaner, more professional look - a finish that says to competitors, "you should be worried."
Kyosho gets the adrenalin going by throwing you right into the heart of the power delivery system - the differentials. If you have ever built an Associated TC3/4 or nitro, you will experience some deja-vu moments when opening these bags. The bevel gear parts look to be straight from AE. They even use 1/16 thrust balls and 3/32 diff balls in here, which seems strange considering every other bearing in the kit is metric. I did get a bit curious, so I held the diff gear up to an AE gear; the OD of the ZX-5 gear is a bit bigger and the center hole is drilled for a metric bearing. The pitch of the two gears, however - a perfect match! You can hold the two gears together tooth to tooth and they mesh perfectly. Hmmm. Drill the AE gear center hole out to fit the ZX-5's metric bearing race, re-shim the pinion and off you go. Parts commonality can be your friend at the track in desperate times! The front diff can also be built as a one-way unit or rigid (spool) type with parts that are included in the box! Nothing extra to buy!
After the diffs are built, it's time to place each of them in the gearbox along with the other 45deg driveshaft gear. This step is one of the most critical and precise steps of the build. I have experience shimming these types of gears from building on-road racing chassis. In that genre, drive-train drag is very important to eliminate. I do that by giving the gears as much backlash as possible, without letting the gears skip past each other under hard acceleration or breaking load. But this process was not only ineffective, but downright destructive for the ZX-5. My rear diff and pinion gear set were pretty well shredded within the first four laps of the car's debut at my local track when I followed that principle. When I rebuilt the gearbox and reset the mesh for the second round, I reversed my thinking and shimmed the gears as close together as possible while making sure that they still spun smoothly together with a flick of the index finger. I believe that the need for tighter gear mesh is due to the more jarring shock loads the car is subject to on a dirt track. And, all of this might also be less of an issue for those of you who won't be running the highest grade motors and batteries money can buy. My Lazer, for example, is powered by six 1.19v SMC 3800's charged @ 7amps feeding a Team Checkpoint 12 single. I'm surprised the wheel hexes aren't stripped!
The next major process in the build is the shock assembly. Building the cartridges is a bit tedious, but time spent now pays off later. If done right - taking the time to remove ALL flashing from the parts tree pieces - you will have a set of the smoothest, most precise dampers you've ever had the pleasure of squeezing between your fingers. I used the recommended pistons and shock spacers to start with, but replaced the mystery shock oil with AE 30 weight silicone.
The remainder of the kit assembly goes pretty smoothly. The only other non-stock substitution I made was the use of Lunsford titanium tie rods in place of the steel turnbuckles. The steel units are plenty beefy, but are too short to make the links as long as they want you to build them. I wasn't confident that there was enough rod threaded into the plastic ends to hold up under the rigor of dirt racing. And the more professional look of titanium is an added bonus. I recommend having these on-hand during the initial build - why build these twice?
As usual, Kyosho's instruction manual is top notch. The detailed pictures and screw length silhouettes take all of the guesswork out of each step. The body is a true work of art. It fits the chassis so well that you don't even need body clips to hold it in place, and the tight fit completely seals off the chassis from dirt and dust -- great news for the exposed pinion and spur gears. Kyosho has set the standard in this regard with the ZX-5.
On the track...
After working out the above mentioned driveline issues, it was time to lay down some laps. By the second round of qualifying at my local track, I was able to pilot the car around a challenging dirt course with amazing ease. The carís precision suspension gave me the confidence to run through rough, high speed sections of our track unlike ever before. At the end of the straight away, I was able to apply breaks very late and very hard without experiencing any chassis pull to either side. Under breaking, the car just squats down, squares up, and takes a set that lets you roll through the corner. Acceleration out of the corners is like no other car Iíve ever driven. With the ZX-5, I could roll up to the longest double jump on the track, pull the trigger at the last minute, and clear the entire 14-foot section without a second thought. Amazing. As I came off the track, I was swarmed by onlookers remarking about how smooth the car looked through each section of the layout. All I could do was reply, "Trust me, it felt just how it looked."
My overall ranking of the Lazer ZX-5 is very high. A few choice upgrades along the build process make this kit equal to any other high-end kit on the market. Although I have quite a few more setup adjustments I can tweak, the performance right out of the box will give you an instant A-main contender.