Testing: Kyosho Ultima RB6.6 RC Off-Road Racer

By Terry Dunn

Terry tests another off-roader from Kyosho: the 2-wheel-drive Ultima RB6.6.

Not long ago, I reviewed Kyosho's re-release of the Optima 4-wheel-drive off-road RC racer. I was pretty excited to do that review because I had always pined for an Optima as a kid. This time around, I'll be looking at another off-roader from Kyosho: the 2-wheel-drive Ultima RB6.6. I'm feeling a little nostalgic here as well because an Ultima was the car that I did get as a kid.

The RB6.6 is not a re-release of the vintage Ultima. Rather, this is the latest iteration in a long line of variants dating back to 1987. The design has evolved to stay competitive while keeping pace with ever-changing technology and racing trends. A cursory glance reveals that this car shares only its name with my former Ultima.

About the Ultima RB6.6

Kyosho offers the latest Ultima in two forms. The kit version ($400) is intended for hard-core racers, while the Readyset ($250) is better-suited for beginning racers and backyard bashers. This review covers the Readyset variant.

The core design of both cars is the same. The kit version includes higher-end racing hardware such as aluminum-bodied shocks, a ball differential, and even several different transmission configurations. You must assemble the kit (not a bad thing) and provide all of the electronics. One advantage of the Readyset option is that it includes a 2.4GHz radio system and the onboard electronics. The only things you have to add are a battery, charger, and four AA cells for the transmitter.

The Readyset arrives factory-assembled. You could literally open the box and be driving the Ultima a few minutes later. A positive aspect of this situation is that rookie RC mechanics need not worry about knowing the correct way to install a given component--it's already done. The flip side is that they will eventually need these skills. Maintenance and repair is an important aspect of owning an RC car. Thankfully, the hefty manual dedicates many pages to proper maintenance steps.

The Readyset version is factory-built and includes all of the necessary electronics.

A black-anodized aluminum plate chassis provides a solid core for the Ultima. All of the other chassis components are made of molded nylon. The Readyset also includes a factory-painted Lexan body and wing.

Even though the RB6.6 Readyset is a budget-minded vehicle, it has several race-inspired upgrades that I appreciate. First of all, it has a full set of ball bearings. There is also an adjustable clutch on the transmission. I was really surprised to see turnbuckles on all of the steering and suspension links. Turnbuckles are super-handy because you do not have to remove either end of a rod to adjust its length. You simply turn the hex in the middle of the turnbuckle.

Factory turnbuckles on the steering and suspension links really simplify chassis adjustments.
The Syncro 2.4 GHz radio system includes a pistol-grip transmitter. It has the basic features needed for racing and works well.

A Kyosho Syncro radio system is provided. This includes a pistol-grip transmitter, receiver, and steering servo. The transmitter has basic features such as trim and end-point adjustment. I think the radio has a comfortable grip and it works well. No complaints here.

Mounted atop the steering servo is an Electronic Speed Control (ESC) for brushed motors. The ESC is connected to a 15-turn can motor. Per my usual, I omitted the motor connectors and soldered the wires directly.

The ESC includes a Deans Ultra Plug power connector, which happens to be the plug I use on my batteries. I found that all of my 6-cell NiMH batteries fit easily into the battery compartment. My Duratrax 2-cell 5000mAh hard-case LiPo packs also fit, but just barely. The ESC has a jumper for selecting the battery type. This sets the correct cut-off voltage so you don't ruin your LiPo.

The ESC is compatible with NiMH or LiPo batteries. A jumper is used to set the correct cut-off voltage.

I performed a quick check to make sure that the factory radio set-up was working properly (it was). I then grabbed a handful of batteries, a few tire options, and headed to R&L Speedway in North Tonawanda, NY.

Driving the Ultima RB6.6 at the Track

R&L Speedway is an indoor facility with a very hard-packed dirt surface. The track has a lot of tight turns and large jumps. The Readyset includes ribbed front tires and rear tires with small pins. I quickly discovered that the Ultima's stock tires are not well-suited to this track. I had enough bite to get around the course, but it was difficult to find traction on the rear end.

I used a few different tires during testing. Left to right: stock rear tires, JConcepts Dirt Webs, JConcepts Goose Bumps.

The Ultima uses common 2.2"-diameter (56mm) wheels that bolt to 12mm-hex wheel hubs. Based on my experience with the Optima at the R&L track, I installed J Concepts green compound Dirt Webs tires (part #3077 front, #3076 rear) mounted on a spare set of stock wheels. This change improved my traction situation considerably.

It was during these tire swaps that I found my only real gripe about the Ultima. The nylon 12mm-hex wheel hubs would often stick to the wheel during removal. I expected the hubs to stay in place on the axle. More than once, this caused the pin that engages the hub to fall out of place and land on the pit table or floor. Those pins are small but critical pieces. I quickly learned to keep an eye on the hubs and the pins when removing any wheels.

The Readyset version of the Ultima RC6.6 is not a thoroughbred racer, but it is a good starting point. The car allows numerous tuning adjustments and accepts a variety of upgrade parts.

If you assumed that the Readyset Ultima is slow just because it has a brushed motor, think again! No, it isn't going to light the tires on fire. This car is, however, surprisingly quick. The Ultima had no trouble clearing the large double jumps at R&L. It was plenty fast on the straightaway as well. I'm not sure whether my rusty driving skills could have handled much more power.

6-cell NiMH batteries (top) fit easily in the battery holder. My Duratrax 2S-5000mAh LiPo (bottom) is a tighter fit.

LiPo batteries seem to give the best overall performance in this car. But it also performs well with the NiMH packs. I found the differences to be subtle. Use whichever battery chemistry you're comfortable with.

I ran the Ultima with the box-stock suspension setup and it worked pretty well. The only thing I plan to address is that the rear of the car would smack the track when landing from large jumps. I think that heavier oil in the rear shocks will help.

In addition to shock oil, there are lots of options for adjusting the Ultima's handling. Camber, rear toe-in, shock springs…you name it. It is as adjustable as any full-fledged racing buggy I've ever owned. You may not know what all of those options can do for you at first. Local racers are often happy to educate you. There are also lots of online guides to help get you started. Trial-and-error will fill in the blanks.

Don't knock the Ultima's 15-turn brushed motor. It's actually pretty quick.

The Ultima's transmission is quiet and smooth. This was especially apparent when running the Ultima immediately after a few hot laps with the chain-drive Optima. The Optima seems to claw its way around the track by sheer brute force. Not so the Ultima. It glides through the turns in relative silence. Both are fast. Both are fun. But the experience of driving them is undeniably different.

Driving the Ultima RB6.6 at the Park

While the Ultima is designed for the track, it makes a pretty good basher too. I took it to my favorite park to cut loose. On my previous visit, the clay softball infield was dry and dusty. Things were very different this time. The entire field was covered with about an inch of day-old snow. There were also a few frozen puddles scattered about.

I started out with the stock tires. They actually worked okay in the snow…not great, but not bad either. I made another tire switch to see if I could improve things. This time, I used JConcepts Mono wheels (part #3327 front, #3348 rear) and JConcepts green compound Goose Bumps tires (part #3019 front, #3018 rear). Once again, the new tires provided more grip. This was especially true on the front end.

I never expected a 2WD buggy to perform well in the snow. The Ultima surprised me.

Driving on the snow was interesting. I thought it would be very slippery, but that wasn't the case at all. The fluffy stuff provided really great traction as long as I wasn't too heavy-handed with the throttle. I also had to be careful to not venture into the thicker patches of show. Whenever I did, the Ultima would begin to bog down and soon become high-centered, forcing a rescue.

It was easy to tell when I hit one of the frozen puddles. The car would instantly lose all traction and spin uncontrollably! It's pretty fun once you figure out where all of the slick spots are. Then, you can hit them with a running start! The real trick is to recover from a spin and keep driving as if nothing happened.

The Ultima RB6.6 Readyset is somewhat of a hybrid. It's not quite a full-blown racer. Nor is it a dedicated basher.

I went through several batteries, driving until my hands were too cold to continue. When I was done, the Ultima looked almost as clean as when I had started. It was a little wetter and somewhat colder, but definitely clean. When I arrived home, I used compressed air to jump-start the drying process and remove snow lurking in a few hidden areas.

Finish Line

The Ultima RB6.6 Readyset is somewhat of a hybrid. It's not quite a full-blown racer. Nor is it a dedicated basher. Assuming your local track has a racing class that would allow the Ultima Readyset, I think it could be competitive in club-level races. The car has all of the fundamental adjustment options to fine-tune its handling. If you ever decide to get serious about racing, the Readyset will accept all of the hop-ups found on the kit version. In short, it's adaptable.

On the bashing side of things, the Ultima is not overly expensive or complex. Most importantly, it's tough. Simply throwing on different tires will allow you to drive on many different types of surfaces. You can take the car out and have fun with no worries.

Although RB6.6 Readyset is a very different car than my Ultima from 30 years ago, it retains the same spirit. I spent a lot of time driving the legacy Ultima on pavement, grass, and dirt. I learned what made the car tick. And when necessary, I figured out how to fix it. Those were all valuable tidbits when my Ultima gave me my first tastes of competitive racing. The Ultima RB6.6 is ready to teach a new generation the same lessons.

Terry is a freelance writer living in Buffalo, NY. Visit his website at TerryDunn.org and follow him on Twitter and Facebook. You can also hear Terry talk about RC hobbies as one of the hosts of the RC Roundtable podcast.