ROCK CRAWLINGTIRE TECHJust about anyone can take a truck and crawl oversome rocks, but the ones who dial in their rigs can gofurther and make the impossible possible. Getting thesetup on your tires and rims is one of the most impor-tant parts of your truck to tweak. Selecting the besttire tread and correct compound is important, butthere are a few additional things you can do to opti-mize performance. These tips may or may not behelpful on the specific terrain you’re driving on, sodon’t be afraid to experiment.

MONSTER SHOPBY KEVIN HETMANSKI

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FOAMSToday’s soft compound tires require foam inserts to help them keeptheir shape. In most cases, the foam inserts make the tires too stifffor 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 tireto prevent it from folding over. A lot of guys cut their inserts in a startype pattern to make that happen. Making this modification is easy.Mark the foams with the desired pattern, and carefully cut the sec-tions out using a sharp hobby knife. How much or how little foam youremove will be largely based on the flexibility of your tires. Softertires require more foam to be left for support.

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

Above: cut your inserts in a star patternto soften up the foams. This will allowthe tire to conform to the rocks and stillgive it enough support. Left: memoryfoam is the latest trend in tire inserts.

The latest trend in foam inserts is memory foam. It’s avail-able from Kreepy Krawler Designs and RCP Crawlers. Sincethe memory foam is denser than standard foams, it addsweight to the tires to increase traction. Memory foams arealso often run without any modifications such as cutting intoa star pattern.

I used some of the techniquesshown in this article when buildingmy own rock crawler.

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RIMSA common practice in rock crawling is to narrow the rims. Doing this provides moreclearance 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. You cansee how to do this in the May 2007 issue of Radio Control Car Action. If cutting rims and

gluing them back together isn’t your thing, you can pick up some rimsthat are already narrowed. Narrow 2.2 rims are available

from Axial, RC4WD and RPM. Axial also offersMaxx-size rims in a narrow form.

The rim on the right is a standard 2.2 inches wide. A narrow rim (left) will give yourtire more “side bite.”

A flat tread works better on therocks than a rounded tread. Themore tire contact you have onthe rocks, the better your truckwill crawl.

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WEIGHT DISTRIBUTIONThe only thing you need to know is that generally you wantmore weight up front than in the rear of the truck. This helpsthe truck handle vertical climbs. Some guys like to add equalweight 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 toimprove your crawler is to lower the center of gravity. So, mov-ing the battery from the top of the chassis over to the frontaxle or links accomplishes two things: it moves weight for-ward for a better balance and lowers the CG.

PELLETSA great way to add weight to your tires isto fill them with 6mm plastic pellets used inair-powered pellet rifles. The pellets rollaround and stay at the bottom of the tiresat all times,and that keeps the truck’s cen-ter of gravity low and reduces roll-overs.You can pick them up wherever Airsoftguns are sold. The pellets also replace thefoam inserts. Filling the tires can be a bittricky. The easiest way we’ve found is toattach your tire to one side of the wheel and

stick a small funnel into the open side ofthe tire and use it to direct the pelletsinto the tire. Fill the tire about halfway,

and make sure that you have an equalamount in each tire. There is a

downside to this setup; it does-n’t work well when side-

hilling—when you driveyour truck perpendicularto its incline.

STICK-ON WEIGHTSYou can also add weight to your tires by usingstick-on lead weights on the rims. You can getthese weights are you local auto parts store orat the hobby shop. Start with 3 to 7 ounces ofweight on each rim, and make sure you prep thesurface of the rims by cleaning them with motorspray before you stick the weights to the rims.

Airsoft pellets are all youneed here. Use a small funnelto fill the tires with the peskypellets. If you use pellets,weigh your tires to ensurethey are filled equally.

When addingweight to yourrims, you canadd the sameweight allaround, or moreweight up frontthan in the rear;60/40 is the typical split.

These stick-on weights are available at auto partsstores and hobby shops. You only need to use 3 to7ounces of the sticky stuff.

GET OUT THERE!These tips go a long way and will make a notice-able difference in the performance of your truckon the rocks. If you have bead-lock rims, you’llhave even more of an advantage over your bud-dies because you can fine-tune the weight andweight distribution in your tires for differentrock-crawling courses. If you’re really seriousabout rock crawl-ing, pick up ascale so thatyou’ll know theweight you addedto each tire is perfect.

SourcesAxial axialracing.comRC4WD rc4wd.comRPM rpmrcproducts.com

An inexpensivedigital scale is aninvaluable tuningaid to accuratelymeasure the per-centage ofweight in your trucks’front andrear tires.

60%

40%

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