PTI Racing (Performance Technologies Inc.) first got our attention with its highly detailed Lexan bodies. The PTI Concept Mustang body is just fantastic. In 2005, the Goliath mini monster truck proved that PTI Racing could do more than cover up cool RC vehicles; it could make them. Since the release of the 1¼ 18-scale Goliath, rock crawling has really taken off and proven to be one of the hottest trends in RC. Even so, no RC manufacturers offered rock crawlers; they were all conversions until PTI unveiled its Goliath Rock Crawler. Based on the same chassis, drivetrain and suspension design as the original Goliath, the Rock Crawler is 1¼ 18 scale but adds a 2-inch-longer wheelbase, huge Imex Red Rock 2.2 tires, locked differentials and a new body, and it is fully ready, willing and able to hit the rocks.

Round 1
I took the PTI Goliath Rock Crawler to my favorite crawling location—my backyard. With a variety of obstacles to choose from, I’ve run large Super-class crawlers in my rock garden and found it challenging and fun; but most often, I run 2.2 class crawlers that are similar to the Goliath. The 2.2 refers to the size of tires required by the competition rules—specifically, the rim size. The 2.2 crawlers are about 2 inches longer than the Goliath that’s 1¼18 scale. I was curious about how the Goliath would perform with its short wheelbase and relatively high stance. I had also never used Imex tires for rock crawling. With the first pull of the trigger, I realized that it needed some quick adjustments. The torque generated by the Novak Rock Crawler brushless system squeezed down the front end and bound the tires into the body. Dialing in a fairly generous preload instantly fixed this problem. Off the bench, my initial setting of just a few turns of preload proved way too mushy. The included springs are rather soft, and the leverage created by the cantilevers makes the springs downright limp. Good news: it was easily fixed. Once I had the Goliath set up a little better, I hit the rocks. The Imex tires worked just fine; I was impressed. (The lesson here: personal experience is valuable; Internet “experts” are not.) The Imex Red Rocks will stay in my arsenal; they grip as well as everything else I’ve tried at home. The Goliath Rock Crawler’s short wheelbase hurt its performance in a few areas where my other crawlers navigate without much ado: it fell victim to gravity and tipped over backwards on steep climbs. But keep in mind, it’s still box stock. The ball-bearing-supported cantilever suspension worked exceptionally smoothly and yielded plenty of articulation. I immediately saw that this chassis has a lot of potential. I slowly dialed out the heavy preload and settled on a decent setup. I wanted to lower the truck’s center of gravity, and since the photos were all done, I hacked up the body that high-swayed in the wind. It was off to the workshop to get busy with a set of body scissors.

Round 2
I removed about 25 percent of the body (all around the wheel wells), and I slammed the shell down by well over 1¼ 2 inch. Think this won’t make a big difference? Think again. After I had made this change and messed with the shocks a little more, the Goliath Rock Crawler’s performance was getting pretty close to that of a competition 2.2 crawler. With this setup, I’d start having some fun. I still liked the big Imex tires and got a good feel for the new and improved Novak Rock Crawler brushless system. If you heard that the Novak system didn’t have strong enough drag brakes for rock crawling, know that this problem has been solved in spades. With the highest drag-brake setting, my Goliath did rear-wheel-lifting stoppies when I let off the gas quickly—without actually touching the brakes. Instead of wishing for stronger drag brakes, I immediately lowered the setting. The Novak’s torque and smooth throttle make it the best brushless system I used for rock crawling. Rock-crawling also tests a vehicle’s durability, and after numerous runs over a few days of testing, I’m happy to report that nothing broke. I pulled a steering link out of a ball end because I hadn’t threaded it deep enough; once fixed, it never happened again. The touring-car-based spools held up fine as did the ring and pinion gears in the axles. Overall, I’m impressed with the Goliath Rock Crawler and can’t wait to try PTI’s wheelbase extension when it’s available.

Tuning Tips

Add weight
Rock crawlers can perform nearly gravity-defying maneuvers, and one of the common tricks to keep the front end planted is to add weights to the inside of the rims. The easiest method is to use model airplane self-adhesive weights such as Great Planes segmented lead weights (item no. GPMQ4485). You can find them at most hobby stores.

Cut the foams
Typically, you cut foam inserts on rock-crawler tires into very pliable star patterns, but the Imex Red Rocks work best if you only hollow out a trench down the center of each foam insert. This leaves enough foam to give the Red Rocks the sidewall support they need.

Tweak the preload
The Goliath Rock Crawler includes aluminum, threaded-body shocks; take advantage of this and adjust preload to compensate for the mushy cantilever suspension. Add more preload to the left front shock to prevent the supension from compressing too much when you get on the gas. Unlike race machines, rock crawlers don’t need identical shock preload.

Hack the body
Immediately after our photo shoot, I hacked the body for extra tire clearance. It might not look as pretty as a full-fender truck, but not having the tires rub really improves performance.

Chassis >> Stamped-aluminum side plates >> Square tube frame rails The Goliath chassis is simple. The main pieces are the 1¼ 4-inch-thick aluminum frame rails. Two thick plastic bulkheads squeezed between the aluminum side plates along with a plastic center skidplate help tie the two chassis halves together. Thin fiberglass top plates finish the job to create a sturdy chassis. The overall design is lightweight yet should prove very durable. A plastic, Y-shaped plate secures the battery that rides up high in the rear of the chassis. A single clip allows easy access to the battery. Drivetrain >> Full-time 4WD >> Locked differentials >> Locked center differential >> Steel- shielded ball bearings The drivetrain is as simple as the chassis. An aluminum mount positions the motor between the upper frame rails and the front of the chassis. This is excellent, as the torque generated by the motor works to keep the front of the Goliath Rock Crawler planted. Long motor-screw slots in the motor plate allow a wide gearing selection. The Goliath’s solid axles use components from Team Associated touring cars, and PTI includes an 84-tooth Kimbrough spur gear and a 12-tooth pinion—all good stuff. Inside the axle tubes are steel dogbones, but the center driveshafts are universal types for smooth movement during suspension articulation. The C-hub parts of the axles are stout and should present no durability issues. Suspension & steering >> 4-link suspension >> Threaded aluminum shocks >> Steel turnbuckle tie rods >> Cantilevers If you’re familiar with the original Goliath, you’ll recognize the Goliath Rock Crawler’s suspension design. This new truck includes new, longer turnbuckle suspension links that provide the stretched wheelbase. This, in conjunction with the cantilever design, allows 7 inches of articulation—more than enough for rock crawling. The Rock Crawler version does include upgraded ball-bearing-supported cantilevers and longer all-aluminum shocks. The Goliath Rock Crawler has a rather new but improved steering design. The servo now lies flat with a drag link that runs to the right hub. A steering link connects the two hubs. Body, wheels & tires >> Clear body with overspray film and precut window masks >> Imex 2.2 Red Rock Tires >> White RPM Torkerz rims Like the original Goliath, the Rock Crawler is dubbed 1¼18 scale, but the longer, 10-inch wheelbase, bigger body and large 2.2 Red Rock tires make it much more like a 1¼ 10-scale crawler. It’s a little short compared with a competition 2.2 rig, but it hardly seems 1¼ 18 scale. The Red Rock tires are extremely flexible and, as expected, fit perfectly on the RPM rims. The PTI body doesn’t declare a brand identity, but it has nice clean, modern lines. The shell comes clear, so I sent mine to Zegers R/C Graffixx for the Parma Faskolor treatment.

Above: the finished product looks great, and those Imex tires are huge. PTI designed its own axle for the original Goliath. Inside is a spool for a Team Associated touring car. the aluminum motor mount does a great job of pulling heat away from the motor.

PTI Goliath Rock Crawler Contact: Ptiracing.net (818) 834-8568 Price: $195 (varies with dealer) SPECIFICATIONS Length w/body 16.5 in. (419mm) Wheelbase 10.5 in. (267mm) Width 10.25 in. (261mm) Weight as tested 3.5 lb. (1,588g) Chassis Aluminum, square-tube ladder frame Drivetrain type Shaft-driven 4WD w/locked center and axle differentials Transmission ratio 7:1 Differentials Spools Drive axles Steel dogbone Suspension type 4-link with cantilevers Shocks Threaded aluminum Upper shock positions (F/R) 1/1 Lower shock positions (F/R) 1/1 Wheels 2x2.2-inch RPM Torkerz, white nylon w/12mm hex Tires Imex 2.8x5.5-in. 2.2 Red Rock w/foam inserts Body Clear Lexan w/included masks Electronics Not included Bonus >> Ready-built rock crawler—not a conversion >> Great value; includes RPM wheels and Imex tires >> Longer-wheelbase option BoGus >> Lots of hand-fitting

the shocks are threaded aluminum units. Preload adjustments are easy as a result. the steering setup is new on the rock-crawling version of the Goliath. The servo is now positioned flat. here you see the cantilever suspension design. This setup adds a lot of leverage on the shock.

On the Bench
If you’ve never built a kit, you can certainly cut your teeth on the Goliath Rock Crawler, but be prepared to take your time and hand-fit a few parts.

Tight fit. It’s easier to bolt the motor to its mount before you attach the rear upper fiberglass plate. This allows more room to tighten down the screws.

Cantilevers. Make sure you don’t overtighten—and inadvertently bind—the cantilevers. It’s better that they’re slightly loose than too tight.

Thread-lock. Use medium-strength thread-locking compound on all metal-to-metal connections. The metal screws that are threaded into the square chassis tubes should definitely get the thread- locking treatment.

Kit Ratings
Instructions 8
Photo-heavy, black-and-white assembly manual with plenty of good tips. Parts fit & finish 5
Lots of hand-fitting required, but the finished product comes out solid. Adjustability & maintenance 8
Easy to work on and easy to adjust.

Performance Ratings
Power 9
The gearing on the Goliath Rock Crawler provided plenty of wheel speed and abundant climbing power. Turn radius 7.5
Like most crawlers with locked differentials, the Goliath Rock Crawler makes fairly wide turns. Articulation 9
The Goliath Rock Crawler boasts an impressive 7 inches of articulation. Any more, and you’d just get in trouble. Stability 8
Even with the motor and battery up high, the Goliath Rock Crawler is surprising stable. A careful line and smooth throttle will keep this truck on all fours.

THE VERDICT
PTI deserves a lot of credit for releasing the first production rock- crawler kit. Compared with how much converted crawlers wind up costing, the Goliath Rock Crawler is an exceptional value at around $200. This kit also has plenty of potential, and although it isn’t intended to be used in hardcore rock-crawling competitions right out of the box, with a few key tweaks, it is just as capable as the much more expensive models. As rock crawling continues to grow in popularity, the PTI Goliath Rock Crawler is a good, no-fuss choice to get in on the action.

SOURCES

DuraTrax duratrax.com
Hitec hitecrcd.com
Imex imexrc.com
Novak teamnovak.com
Pro-Line pro-lineracing.com
PTI ptiracing.net
RPM rpmrcproducts.com
Tamiya tamiyaamerica.com
Venom venom-racing.com