Weight Watchers, get your machine on a diet. Part 2

Not the way you want to reduce un-sprung weight

If you did not catch the intro to this series you can read it here http://www.atvmagonlineblog.com/2008/10/09/weight-watchers-get-your-machine-on-a-diet/

Before starting any of these modifications one tool I recommend is a small digital scale.  Its not a requirement, but if you want to chart your weight shaving techniques this is a good way to keep track of them.

First lets examine unprung weight. As mentioned in the intro article, this is weight attached to the suspension so in effect reductions here will help make the suspension work better and be more responsive. Reducing the unsprung weight also makes the suspension work less to try and keep all that weight controlled and the tires on the ground where they can do the most good. One of the biggest places weight hangs is the wheel and tire combo, examine yours and determine if you have the lightest combination for your particular situation.  Usually in trail and mx applications you can eliminate a few pounds (total) as aftermarket rims and tires are usually lighter than the stock equipment.  There are exceptions of course, but trying to find the lightest wheel and tire combo and still achieve other performance goals like traction (ie. mud boggers) might be difficult.  It will be up to the rider to determine if its an acceptable compromise.  Next, take a look at your lug nuts and studs, there are a few companies making titanium lug nuts and studs not only are they stronger, but lighter.

Brake rotors are another easy area to shave some weight by cross-drilling or purchasing “wave” style rotors. Also if you have access to a milling machine you can mill the rotors thinner but of course you will reduce the life of the rotor as well. Using aftermarket (or build your own) a-arms made out of lighter but stronger tubing. Recently companies have been experimenting with carbon fiber.  This would be the ultimate but at a considerable price as well.  A generally neglected part, the Final drive sprocket (rear) using an aluminum, titanium or bi-metallic sprocket (steel teeth ring on an aluminum or titanium hub) will save a few ounces over the stock stamped steel, although with an aluminum sprocket you do sacrifice some durability over time. Use a standard chain although most people (including me) really like the advantages of an O or X ring type chain, standard chain is still by far the lightest and most efficient at transferring power.  Rear swing-arm for those that use one building or using an aftermarket swing arm can shave some weight over the cast aluminum stock piece, as well as being adjustable and easier servicing of the bearings.  Removing the E-brake cable and mechanism is easy and eliminates somewhat of a useless device that will/can cause more problems than it saves.  One thing to note is most brake calipers require the mounting plate to stay intact so either a custom or aftermarket block off plate may be needed.  The last suggestion is the sprocket and brake rotor skid plate The stock ones are generally made of steel and not very strong. Swapping to an aluminum or fabrication a stronger steel plate then drilling numerous 1/2″ holes can shave weight and lighten the whole package. Also adding the holes lets water, mud, and other debris to fall through rather than get trapped. All these will reduce the effective weight of parts suspended by the rear end of the machine.

Digital Scale

A word about a-arm skid and swing-arm skid plates.  Most machines do not come with them, but however most riders have them on their list of “goodies” to put on.  You might think that I am totally against adding these such parts.  Isn’t the point to reduce weight not add it?  My opinion on such parts are as follows.  If your primarily a casual rider like most of the atving population is, I think they are unnecessary with provisions, If all you ride is big rocky trails where getting hung up on obstacles is a regular occurrences they are necessary. However if you only encounter a few of these type of obstacles picking a good line will eliminate the need. MX riding is where they are definitely not necessary because of muddier days they just end up trapping mud (extra weight) to the machine. Although a sprocket and brake rotor skid plate is however a necessity to prevent damage to those vital parts.

Lastly picking up an inexpensive digital scale can be nice to sort of “chart your progress” by weighing the new or modified parts before and after.  If you keep good records you can actually get a good estimate of how much “pork” you have eliminated from your machine.

Of course this is just a few examples of where you can possibly reduce some weight. This in no way is a complete list. Check back next week for part 3 of this 4 part series.

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