ASK THE MXPERTS: HOW DOES MXA WEIGH ITS TEST BIKES
I’m a little confused. I read on another website that 2016 KX450F weighed 239.6 pounds and the KTM 450SXF weighed 233 pounds. But, I noticed that MXA said that the KX450F weighed 231 pounds and the KTM 450SXF 227 pounds. How can two scales be so far off on the same bikes?
The answer lies in how you choose to weigh motocross bikes. MXA weighs bikes using the AMA Pro Racing system–which is no fuel in the gas tank, but all other fluids (oil, water, fork oil, etc). However, some manufacturers list the “curb weight” of their bikes in their brochures, which is the bike with a full tank of gas. Many websites and magazine use curb weight because it is on the spec sheet and doesn’t require them to actually weigh the bike (they take the manufacturer’s word for the curb weight based on the assumption that they wouldn’t lie to the high side of the scale).
MXA doesn’t use curb weight—largely because the majority of the time we go to the starting line with gas tanks that are half full. Thus, when we weigh a test bike, we drain the fuel tank of every drop of gasoline before lifting it up on the scale. On our scale the KX450F weighed 231 pounds and the KTM 450SXF weighed 227 pounds. Why don’t we weigh them with a full tank? Three reasons:
(1) Weighing a bike with a full fuel tank just tells you how much gasoline weighs, not the necessarily the bike as you ride it. A bike with a small 1.5 or 1.6 gallon gas tank will be lighter than a bike with a 2.0 or 2.1 gallon gas tank when it comes to fuel weight. At 6 pounds a gallon, a manufacturer who gives you a 1/2 gallon larger fuel capacity runs the risk of adding 3 pounds to his bike’s weight. A larger fuel tank is a plus for a rider who trail rides, play rides in the hills or uses his bike for both motocross and cross-country races—a smaller fuel tank benefits a manufacturer who lists “curb weight” in the specs. Although, as you can see, listing “curb weight” can also makes the consumer think that the KX450F weighs over 12 pounds more than the KTM, which lists its weight via the AMA method (when in fact, the difference between them is only 4 pounds). If you were in the technical department of a major manufacturer you would want the brochure to list the dry weight (derived from the AMA mandated method), not the curb weight which makes the bike seem heavier than the competition.
(2) Every MXA test riders starts his race day with a full tank of gas—which would mean 2 gallons of gas in a KTM. A Kawasaki KX450F rider starts with 1.6 gallons of gas. As a rule of thumb, MXA test riders do not refill their bikes after practice. They go to the starting line with less than a full tank. The KX450F rider might have one gallon in his tank, And depending on the length of the moto at this particular race, one gallon could be enough, but 1-1/2 gallons surely will be. For the second moto, the KX450F rider will have to add gas, but the KTM 450SXF racer will just add a splash of gas because his tank most likely still has almost a gallon left in it.
(3) No matter how you slice it, the 2016 KTM 450SXF will be lighter than the 2016 KX450F. We drain the fuel because that is the official AMA Pro Racing method and it doesn’t penalize a manufacturer who wants to give his customers more fuel capacity to allow them to ride longer without stopping. As a consumer, you need to know the difference between curb weight and dry weight (and whether it is “claimed weight.” or actual weight).