How The Foam Insert Affects The Performance Of Your Rc Tire

By: Douglas Taylor

The rc foam insert is the one big factor that plays into how your rc tires perform. Since a rc tire does not use air pressure to maintain the shape of the tire a foam insert must be used. Unlike air that maintains the same pressure in all directions around the inside of the tire. A foam insert can have places in the tire that have a high pressure area and a low pressure area. This could and does cause a rc tire to react differently at different points on the tire. So, working with and understanding your tire foams is very important.

There are three basic types of foams.
1. Regular foam inserts. That are square cornered and flat faced.

2. Dual staged foam inserts. These are also square cornered and flat faced. But will usually have a firmer band of foam on the outer edges and a softer foam in the center. Some have a firmer center foam and a softer outer foam.

3. Molded foams. The face of the foam insert is molded like the inside of the rc tire. On some molded foams the inserts center is also molded to fit the sidewall curve and the ridges on the rim. These foams are a little higher priced, but give you the options of reusing them. With the option to reuse helps offset the higher cost.

In choosing rc tire foams is also an area that be some what confusing. Rc tire manufactures will most always include foam inserts with your new tires. But, if you are serious about racing these foams may not be the best choice. You have the options of getting soft, hard, wide, narrow or dual stage. All these options where do we begin?

Let us start with width. Wider is most often better than narrow. The foam has to be at least as wide as the tire or 10 to 20% wider than the tire seems to work well. While a foam insert that is narrow will cause the rc tire to be floppy and not hold its shape in corners.

A foam inserts firmness can be some what harder to understand. Plus, there are compromises to be made. A firm insert is good because it supports the tie carcass better. The rc tire will not loose its shape in the corners and fold over itself. With a firm insert the tire looses its ability to absorb bumps. So, for a smooth track go with a very firm insert.

Now here is where the compromise comes in. On a bumpy track a too firm of a foam insert and the truck or car will bounce all over the place. While with a too soft of an insert your car or truck will slide very wide in the corners. This is where the dual stage foams come into play. With the firm outer edges you will have great cornering ability and soft centers to absorb the bumps. The best of both worlds.

Now enter the molded foam insert there first big advantage is that they are reusable. This type of foam does not break down so you can just keep reusing them. They are molded to the contour of the face of the tire and the shape of the rim. The big advantage in using molded foam inserts are they almost do away with the high and low pressure areas on a rc tire. This lets the tire work to its full potential and lets you feel if your tire combination is working to your satisfaction.

Another factor to keep in mind about rc tire foams is how they fit on the rim. You need to check the inner diameter of the foam to the outer diameter of your rim. Your foam inserts need to fit very tightly over the rim. This will keep the foam insert from moving around inside your rc tire.

So you are thinking that you are getting the feel to just how the foam rc tire insert works? Now let us look at the most mysterious factor about foam inserts. The foam inserts height or the "air gap" between the foam insert and the rc tire.

There are two basic theories on height.

Theory one: A firm, wide, but low height foam insert. This gives the rc tire carcass great support, but there is a air gap between the foam insert and the face of the tire or contact patch. This allows the contact patch to move around and lets the carcass work. You get what is called internal slip in the tire. This theory works very well on very hard, no grip surfaces. The surface is almost asphalt like. The downside to this theory is your rc tire will feel a little floppy and inconsistent in throttle response. This is a very good way to generate grip on slick, no-traction surfaces.

Theory two: A really big firm insert. This does the exact opposite of theory one. Using a firm over sized foam insert locks the carcass in place and lets the pins do all the work. This big insert stretches the rc tire over the foam insert, much like a rubber band. This results in the pins standing tall and they resist bending very well. The downside to using an over sized insert is that the tire will not absorb bumps very well. On the plus side, the traction generated is very high and extremely consistent.

Keep notes on surface conditions and even weather conditions. Plus how your rc vehicle handled this type of tire or foam insert. The better you are at keeping notes the better you can be on race day. That is, if racing is what you want to do.

Even if you are a basher, keeping notes is a good idea. The places where you bash at will also having changing surfaces. It is much more fun to be driving instead of chasing your rc vehicle around on foot and up righting it after a roll over.

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Douglas Taylor an avid Radio Control car and truck hobbyist, who enjoys helping other rc enthusiasts get the most out of theirrc cars and trucks. If you are looking to get into the hobby or need help with some aspect of the hobby let us help at

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