Weight watchers, get your machine on a diet

A wise man once said “Watch the ounces and the pounds will take care of themselves”  Now I don’t know if this quote was used in the context of increasing performance, but it easily applies to our never ending search for maximum performance out of our machines (regardless of the type).

A general rule of thumb is for every 10 percent reduction in weight has a comparable 10 percent reduction in the force required to accelerate or decelerate an object.  Ok, so what does this mean for us enthusiasts?  Well its like adding horsepower and torque without having to do any engine modifications. Best part of it all is some of these modifications cost no money at all just some time and ingenuity.

Before we can go into some into some specifics its important to understand the 3 places (excluding the rider) weight (more correctly mass) lives and its general affect on performance. Note: I realize that weight and mass are not interchangeable but for the sake of discussion the lay person will more often use the term weight when the correct term would be mass, the discussion is written as if gravitational pull, altitude, and barometric pressure being constant.

Weight distribution model

Unsprung weight is the weight that is not held by the vehicles suspension. For example unbolt the a-arms and swing arm leaving everything else attached and the parts that got unbolted are what make up the unsprung weight of the machine.

Sprung weight includes everything that is supported by the suspension. Using the previous example everything that is left (basically everything attached to the frame) comprises the sprung weight of the machine.

Rotational weight is everything that has weight and spins on an axis. For example this includes but not limited to the axle, wheels, tires, flywheel, chain and sprockets.

A reduction in weight in any or all three areas reduces the total “curb” weight of the machine. Curb weight includes all fluids usually with 1/2 tank of fuel.  The question might arise from the lay person as “Why would there be any reason to shave weight, I paid $XXXX shouldn’t I be getting the lightest, best designed machine?”   In one word, no.   Their are many hidden factors that most consumers cannot fathom.  While light weight and high performance is nearly at the top of a design criteria list for an engineer, they do have to make compromises for things like ease of manufacture, machining, and cost of raw material.  For example using mild steel where carbon fiber would be stronger and lighter, but if the stress levels of the part will never exceed, the mild steel is what will be chosen.  Durability also is a big factor.  Not all lightweight designs and materials are suited for long term durability before failure or being out of tolerance, even though they may give the highest performance.

Carbon fiber lever

As you read (in the coming weeks) on the suggestions given are just that “suggestions” some may require a bit of engineering or fabrication skills while others will not. As with any performance tip it usually comes at a compromise, usually to gain performance means to reduce longevity or reliability of a particular part at times. It will be up to the reader to determine their skill level and confidence to attempt some of these modifications.  Also most of these modifications will void manufactures warranty because you will be modifing the orginal design or specs of the part or machine.

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Last 5 posts by Jon Rhodig

• Take control, adjust your controls that is - August 20th, 2010
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