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.