Trim the Foam

Soft compound tires require foam inserts to help them keep their shape. In some cases, the foam inserts make the tires too stiff for crawling and don’t allow the tire to conform to the rock’s surface. You want the tire to be flexible yet stiff enough support for the tire to prevent it from folding over. Some people cut their inserts in a star type pattern to make flexing a little easier. Making this modification is easy. Mark the foams with the desired pattern, and carefully cut the sections out using a sharp hobby knife. How much foam you remove will be based on the flexibility of your tires. Softer tires require more foam to be left for support.

A key to good traction is to have the tread of tire to be generally as flat as possible. A larger contact surface means more traction. An insert that is wider than the tire will distort the tread of the tire and potentially reduce the contact patch. You can eliminate this problem by cutting the foam insert so that it’s the same width as the tire.

Rims
A common practice in rock crawling is to narrow the rims. Doing this provides more clearance between the links and the tires when steering, and since the tire is pulled in, it will increase the tire’s “side bite” by bringing the tread down the side slightly. If cutting rims and gluing them back together isn’t your thing, you can pick up some rims that are already narrowed. are available from Axial, RC4WD and RPM. Axial also offers Maxx-size rims in a narrow form.

A flat tread works better on the rocks than a rounded tread. The more tire contact you have on the rocks, the better your truck will crawl.

Weight
The only thing you need to know is that generally you want more weight up front than in the rear of the truck. This helps the truck handle vertical climbs. Some guys like to add equal weight to both ends of the truck. Either way, you’ll want a lit- tle weight in all four tires. When considering the weight dis- tribution, also remember one of the best things you can do to improve your crawler is to lower the center of gravity. So, moving the battery from the top of the chassis over to the front axle or links accomplishes two things: it moves weight forward for a better balance and lowers the CG

PELLETS
A great way to add weight to your tires is to fill them with used in air powered pellet rifles. The pellets roll around and stay at the bottom of the tires at all times,and that keeps the truck’s center of gravity low and reduces rollovers. The pellets also replace the foam inserts. Filling the tires can be a bit tricky. Attach your tire to one side of the wheel and stick a small funnel into the open side of the tire and use it to direct the pellets into the tire. Fill the tire about halfway, and make sure that you have an equal amount in each tire. There is a downside to this setup; it doesn’t work well when side hilling when you drive your truck perpendicular to its incline.

STICK-ON WEIGHTS
You can also add weight to your tires by using stick-on lead weights on the rims. Start with 3 to 7 ounces of weight on each rim, and make sure you prep the surface of the rims by cleaning them with motor spray before you stick the weights to the rims.

When adding weight to your rims, you can add the same weight all around, or more weight up front than in the rear; 60/40 is the typical split.

[ MYTH ]
Tubers are for looks, not performance
Comp tubers weigh about the same as or sometimes less than a twin vertical plate chassis running a Lexan body. When set up correctly, they can be just as deadly on the rocks. It’s all in the geometry, driving style and setup.

[ MYTH ]
Slower is always better.
Slow and methodical crawling is the key to success on the rocks, but a number of obstacles require wheel speed to get up and over. You want your crawler to have the ability to crawl slowly with high torque as well as the ability to launch, if need be. A 3-cell LiPo and 35-turn or 45-turn motor is a good combo to get the best of both worlds.

[ MYTH ]
Heavier rigs are always better
A light, nimble rig set up correctly with proper forward weight bias will perform better than a heavier rig. It’s basic physics. The heavier something is, the harder it is to go uphill, and the easier it is to flip while side-hilling.

[ MYTH ]
You need tons of articulation
This is a very common misconception. Although lots of articulation might look impressive, your crawler will perform best with around 30 to 45 degrees of articulation. Anymore, and your rig will try to twist and wont’ be stable on the rocks. The truck will also feel less predictable on the rocks since the front and rear axles are not working together and are in extreme positions on the rocks. More often than not, excessive articulation leads to a truck doing an impression of a pretzel when it encounters a difficult obstacle.

[ MYTH ]
Full-size and RC crawlers are very similar
Bogus claim alert. Power plants, transmissions, tire setups and driving style are all different from the RC counterparts. There are, in fact, far more dissimilarities than similarities. The power-to-weight ratios are not even remotely close. The contact patches on the tires, the compounds and the tread designs are not really that much alike. Some of the principles are the same, but what works in the real world might not work in RC and vice versa.

[ MYTH ]
Dig is mandatory
Dig definitely gives you an advantage on courses, but it isn’t necessary. If you can’t compete on a local level without dig, then the course designers are building a “dig-favored” course. Tight corners could definitely make any course more challenging but the rocks themselves should be the obstacle, not the gate markers. The bottom line is: a good driver without dig will still beat a hack with dig.

[ MYTH ]
Crawling is expensive
Crawlers used to be fairly expensive when you had to piece everything together, but many purpose-built kits are now offered and even RTRs are starting to enter this segment. There are a number of inexpensive ways to get into crawling. The axial RTC, Axial RTR, HPI Crawler King and PTI Goliath RTR are all inexpensive ways to get going in crawling, and all you need is a battery and charger.

[ MYTH ]
You need gobs of clearance
Ever see those crawlers that are jacked up to the sky? Lower that monster down to the correct height! You want the bottom skid plate and lower links on your crawler to be almost parallel with the ground or slightly up. Clearance of 2 ½ to 3 inches is usually ideal, and anything over 3 inches is starting to push your limits. After you’ve set up your rig correctly, approach the rocks, and point your tires toward the tallest rocks. This will lift up the axle and keep your axles and skid plate out of harm’s way. You also want your rig to have a super-low center of gravity, so it doesn’t flip on vertical climbs.

[ MYTH ]
Trucks with independent suspensions can’t crawl
Have you seen the Traxxas Summit? It crawls extremely well. Sure, solid axles have the advantage over independent system; but independent-suspension-equipped trucks more than pull their weight on the rocks. With a progressive independent suspension system as used on the Traxxas Summit, trucks can be formidable on the rocks. Will we see independent suspension rigs win comps? No, but you can still crawl with them.

[ MYTH ]
The super class is dead
The 2.2 class is a larger class, but Tamiya, Red Cat Racing, XTM Racing, Gmade and Integy all continue to sell Super class products with success. The 2.2 class might be more popular, but clubs all over the country are still running Supers.