The Problems with Foam...

The use of anti-slosh foam is widely accepted in many forms of motorsports.  Race cars use foam to reduce oscillations when cornering, braking and accelerating as well as to add safety from explosion in serious accidents.  In the trucking industry, anti slosh baffles in tanker trucks appear to provide similar results.


The effect of fuel slosh on motorcycles is especially dramatic.  The fuel weight is high up and subjected to constant acceleration and pitching movements.  One slosh could help and the next one could make things worse.  It's the equivalent of a liquid loose cannon.

How is it possible that we don't use anti-slosh foam in motocross?  Anti-slosh foam helps keep the fuel stable and lower in the tank.  A bike will feel more stable, but also feel lighter in corners.  They are also more predictable when the throttle is chopped at the end of a straight and hard braking commences.  There are whoop sections and all those times when you see something late and have to just hit it.  Some riders swear it has saved them trips over the handlebars.  This is a safety issue.  It seems crazy to spend hundreds or even thousands on suspension tuning and then let the fuel just flop around.

Using foam in our tanks can create two new problems.  One is getting gas to cross over that hump in the middle of our tanks.  Usually we only have a petcock on one side of the tank and sloshing managed to keep the level on the two sides pretty even.  When foam is used, fuel can't slosh over and instead gets stranded on the side without the petcock. 

The other big problem is simply monitoring fuel level.  Other than a few bikes with clear or white tanks, once a tank is stuffed with foam, the fuel level is hidden from view.  To know the fuel level you'd need to measure what is put in, then drain and re-measure again after each ride.  For factory teams this may be well worth the effort and time, but definitely not for most of the rest of us.

An external "sight" gauge tube solves both problems...  A clear tube next to the tank that shows the fuel level and then a crossover line at the bottom that could prevent the fuel from getting stranded.  

They are fairly common in industry, but the fittings needed to add one to a plastic gas tank didn't exist.  It took quite a few attempts and the realization that the fuel could flow around the threads instead of through the center of the bolt, like a banjo fitting.  Eventually we arrived at our current product with two pins to hold the nut when tightening.

We've been using these systems for over a decade now, in different forms.  The fittings have changed slightly and we changed tanks a few years ago (to change color) and found no problems with the foam either.  We replace the fuel lines occasionally to keep them looking new and fresh.

In the past, we used to fill our tanks before every ride.  With gauges, we found that on most rides we would use less than 1/2 a tank of gas.  For us this is for about an hour of cinders riding at 7000'+ elevation.  Now we start rides at 3/4, saving several pounds of high up and badly behaved weight.  For a 15 minute race, starting with 1/2 gallon might be plenty, saving 9 lbs. from a full tank.  A true weight savings was not the goal, but it turned out to be a major benefit.