THE BULLWINKLE EQUATION
Dear MXperts,
Why don’t racers run solid-foam rubber tubes that can never go flat? To my way of thinking, this would be the perfect tube for local racers to use. Why aren’t they more popular?
What you are referring to is called the “bib mousse.” It was first introduced by Michelin in 1984. It is named after Michelin’s mascot, Bibendum (aka “Michelin Man”). A bib mousse is a foam ring insert that takes the place of a regular air-filled tube. The closed cells of the butyl honeycomb foam are filled with air or nitrogen. A smooth outer skin, much like the coating on chocolate pudding, allows the solid foam tube to be slipped inside a tire. Today, people refer to them as “mousses”—without the “bib” prefix.
Mousses are rider, tire and motorcycle suspension setup-sensitive. European GP riders love the soft feel of mousse tubes, and often race with them in both the front and rear tires. GP riders have developed a taste for the distinct handling sensation of the mousse tubes and use them on all types of courses. Once a rider adapts to a mousse-equipped bike, he will have trouble adjusting to the feel of standard pneumatic tubes.
American riders, as a rule, don’t like the way a mousse feels under cornering loads. Mousse tubes tend to create more sidewall rollover, which is especially noticeable in the front tire. American factory riders use mousses in their rear tires only—and only when the danger of a rear flat offsets the downsides of a mousse tube. The American tracks where punctures are a major concern are Glen Helen, Unadilla and Washougal. Mousses have found some favor on super-hard, slippery indoor courses. The mousse delivers a low-tire-pressure feel that some riders believe flattens the contact patch for improved traction.
To achieve the best performance from a mousse, the fit between the mousse and the tire is critical. The mousse needs to put a certain amount of internal pressure on the inner tire casing in order for the tire to have good stability and to lessen sidewall rollover. This is a problem, since most tires vary in their inflated size for any given tread width and overall diameter. A 110/90-19 Michelin mousse in a Michelin tire won’t give the same feel as it would in the same size Dunlop tire. Since a mousse’s tire pressure cannot be changed, the mousse’s tire-pressure feeling is dependent on the tire’s casing size.
A tire with a mousse rides like a tire with 12 psi of pressure, but as it ages, it gets softer. The backyard solution for this problem is to use a NitroWedge. It is an 8-inch section of brand-new mousse that can surgically be transplanted into a used mousse (by cutting 8 inches out of the old mousse and installing the new NitroWedge in its place). Conversely, if the mousse feels too stiff, it is possible to take a hole bit and drill holes down the center line of the mousse to soften it up. This will shorten its lifespan but make it feel more supple. This is best used on the rear mousse, not the front.
There are six major downsides to mousse tubes:
First, they are at least 1 pound heavier per wheel than a heavy-duty air-filled tube (and the weight disadvantage is even greater against the lighter race-issue tubes). All of the mousse’s weight is unsprung.
Second, installing a mousse into a tire is very difficult. It requires tire-bead clamps, very long tire levers and lots of lubricant. Tire experts suggest that you don’t try to install a mousse yourself until you have watched a pro mount a mousse. MXA uses a Rabaconda tire-changing stand because it works best when installing mousses.
Third, mousse tubes are close to 10 times more expensive than a tube and have a relatively short shelf life. They shrink in size in only a few months. They run hotter than an air-filled tube, and when they heat up, they change in size, get stiffer, and often bond to the tire carcass. Don’t expect to get more than a few tire changes out of a mousse before it has to be replaced.
Fourth, silicone mousse lube should be used to reduce friction and heat buildup between the tire and the mousse, which can damage the mousse, and potentially lead to a flat tire, especially during off-road riding. Proper installation involves thoroughly lubricating the mousse with silicone grease before installing the tire.
Fifth, getting an old mousse out of a tire is a major pain.
Sixth, if you bounce a wheel with a mousse installed and then do the same with a standard air-filled wheel, the one with a mousse tube will bounce much less. On a track, the wheel with the mousse gives a much deader feel when hitting bumps, rocks, and square edges. There are several aftermarket mousse options on the market. Here is a quick list:
NUETECH NITROMOUSSE
The Nuetech Nitromousse is a foam insert that replaces the standard inflatable tube to guarantee that you won’t ever get a flat during a race. Nitromousse is designed for both off-road riders and motocross racers. The Nitromousse gets its name because the micro-bubble matrix of the foam mixture contains a high concentration of nitrogen. This lessens the dead feel of a normal mousse. Nitromousses come in different sizes to fit your specific tire and wheel size. Nitromousse foam inserts come in two different densities: The Platinum mousse mimics the feel of an inflated inner tube with 12 psi. The Plushie version replicates the feel of an inner tube at 8 psi and was created for slow-speed enduros or EnduroCross races. For more information, go to www.nitromousse.com.
MR. WOLF MOUSSE BALLS
Mr. Wolf Mousse Balls are a segmented mousse replacement for the traditional mousse foam tube. It uses 22 foam inserts to install a full mousse tube. Thanks to the innovative and patented sector structure, also known as “balls,” you can completely customize your tire’s hardness to suit the terrain you are riding on while providing no-flat confidence. Mr. Wolf claims that the operating temperatures can drop up to 33 percent. Furthermore, the complete absence of vibration reduces tire overheating, which increases the feel of the tire. The Mousse Ball design has a longer lifespan and can be regenerated over time by adding the two new balls contained in the package. Installation of the Mr. Wolf Mousse Ballsis slightly simpler than installing a full mousse tube, but all mousse installations are a bit of a wrestling match. With Mousse Balls, we only had to insert a 4-inch section at a time; this was easier to deal with than a full mousse tube. For more information, go to www.innteck-usa.com.
MICHELIN BIB MOUSSE INSERT
Michelin’s bib mousse is not a puncture-proof inner tube. It is an innovative foam-based technology that is inserted between the rim and the tire instead of a classic inner tube. Because of its foam composition, it can’t go flat! It is lighter than a reinforced inner tube and provides a pressure equivalent to 13.5 psi. With Michelin bib mousse, you can enjoy your off-road rides without worrying about tire punctures. The Michelin bib mousse is specially designed to fit best with the dimension of Michelin StarCross tires (e.g., mud, sand and hard). For more information, go to
www.michelinman.com.
DUNLOP MOUSSE
Dunlop mousses used to be only available to elite Dunlop-sponsored riders but are now available to the public. The Dunlop mousse is intended to prevent tire deflation in case of punctures caused by perforation, shock or pinching. Unlike other brands, Dunlop’s proprietary mousse compound offers a two-year shelf life against shrinkage and degradation in storage. Dunlop’s foam formula is the equivalent to 13 psi. For more information, go to www.slavensracing.com.
