I'm late to this thread (work was busy all week), but thought I'd contribute. Weight is the force multiplier of the vehicle performance world. It is a parameter that affects nearly everything you ask a vehicle to do. Ignoring weight distribution for a moment (weight distribution is important, too, but not as much as weight itself), lighter vehicles accelerate at a higher rate, brake better, and turn quicker. In other words, less weight has the same effect as more engine torque and better brakes. However, it's even better than that. When the designer makes significant progress reducing weight, that weight loss can compound because structural members can be lightened even more if their loads are reduced by overall vehicle weight reductions. In building a Jeep, though, getting some of the compounding effects is costly, in terms of time and money spent getting there.
Weight is recognized by many racing sanctioning bodies as a very important parameter. As a result of that recognition, minimum weight requirements are usually written into the rules. The rule is put there to level the playing field and put on a good show for the fans (a very well funded team can use expensive, exotic materials to dramatically reduce weight, giving them a huge competitive advantage, which is boring to watch, week-after-week.) Back when I was involved in open wheel cars, the C.A.R.T. rules did have a minimum weight requirement. I worked for a well-funded team that, at that time, built their own cars. Those cars were purposely designed to be significantly under-weight so that ballast plates could be attached in various locations. These ballast plates were made in several different materials so that, in addition to adding the requisite weight to get to the minimum, weight distribution could be varied to suit the driver's preferences or track needs (we ran both ovals and road courses back then).
I say all this because that experience taught me to pay close attention to vehicle weight and weight distribution. I also learned that overall vehicle weight is not reduced substantially by looking at a few components. The lightest, best-performing vehicles were made lighter by looking at
every component, and optimizing them all. For instance, there are very few steel fasteners on an open wheel car. If strength is required, titanium is used. If not, aluminum is used. It may seem trivial, but when you add up all the weight saved on these fasteners, it's not trivial.
Of course, with a Jeep build, it's very difficult to take the approach of reducing weight of every component because we are not starting with a clean drawing board, but it's still important to look for weight reduction at every opportunity. I do this for my LJ build by weighing every component I remove or add to the vehicle. I keep a spreadsheet of these weights, and I use it to track overall change in weight from my modifications. For instance, here's the effect of changing to Mr. Blaine's Big Brake Kit, from that spreadsheet:
View attachment 334819
Just under 7 pounds for much better brakes. A justifiable weight addition, in my opinion! However, I easily offset that "good" weight added, by replacing the heavy rear bumper that the previous owner installed:
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Side note - notice that is the unpainted bumper weight. I forgot to weigh it again after powder coating (shame on me!) Yes, paint adds significant weight to a vehicle. When I worked for a motorcycle roadrace team, we weighed a set of carbon fiber bodywork before and after paint and were astonished at the difference - several pounds! The entire motorcycle only weighed about 350 pounds, for perspective.
My LJ is far from done, and with many of the components already on the vehicle, I don't have their weights, yet. My grand total right now is an estimated addition of 446 pounds, for a much better vehicle. However, it will likely be considerably lower than that number once I get the mods done and the weights for the parts removed in that spreadsheet. Work continues, but never at a pace fast enough for my quest for information, knowledge, and experience...
To sum up - weight is incredibly important in vehicle performance, and you can't address it fully, if you don't weigh components and make decisions with weight in mind.
