Originally Posted by Brocklee

Let's dissect what's happening here. I still stand by my statement about less weight increases tire efficiency. I agreed with your statement, but noted that it looked like a very simplified situation and was for onroad. Looking at the graph, both my assumptions were confirmed. On road tires have little to no profile, resulting in routhly the same contact patch regardless of the vertical load placed on them. This is not the case in offroad, where tires are designed for a certain weight to deform properly for the best contact patch.The problem with tires is they are never consist and and are always changing. From surface to contact patch to weight transfer humidity, ambient air pressure, tire air pressure, sidewall flex, ect. And will change with each tire, so the constant we have to tune for is how grip is effected by weight, and I still stand by the fact that a tire with less weight will be more efficient than a tire with more vertical load. I reiterate what I've said before. You are applying a graph for one set of conditions to a completely different set of conditions. Offroad, ESPECIALLY with any loose dirt on the surface does NOT behave this way.Now let's not confuse grip with driveability. A light car with too much grip will change directions quickly, so now let's look into the heavier buggy in your example was easier to drive and thus quicker.Never said anything about driveability. I said they handled better and in my prior example I showed how a car with a higher spring to unsprung mass ratio will be able to maintain contact with the track more often than a lighter car. For now let's assume I'm wrong and that tire grip vs weight is linear (the function might be t=w or maybe t=w/2 or possibly t=w*2 where t=traction and w=vertical load or weight. Or better yet let's just ignore traction for a minute). I never said the ratio of mass to cornering force was linear. I agreed that to a point in offroad your graph stands, but as tire conformity and surface penetration become a factor in offroad, there is a diminishing return on losing weight to the point that a lighter car will have a lower traction efficiency.Now what we want to focus on is the variables that have changed and how they have effected the buggy. Let's take three identical buggies and name them A, B, and C. Buggy a is a buggy that was built with now weight added and has a perfect l/r and f/r balance and weighs 7lbs. Buggy B is one that is identical to buggy A except for one thing, buggy B added 1lb of weight directly on the center balance point of the chassis. Now buggy C is the same as buggy B except for the .25lbs was added to each corner for a total of 1lbs. Now let's apply newtons law of motion to these buggies and compare how they act in a turn. Newtons law of motion summarized is that an object in motion stays in motion and an object at rest stays at rest unless acted upon by an outside source. So from the we can see that buggy A is the lightest buggy and will be the twitchiest of the 3 buggies, well buggy B and C weigh the same so they should act the same right? Actually no, now if we look at how the car rotates buggy C will have more body roll in the corners regardless of the weight, and it will also be the numbest car of the 3. The reason being is that the further out the weight is from the center balance point, the further the weight has to travel and more speed is required to make it change angles (think of swinging a bat with a ten pound bag on the tip of it vs a ten pound bag on the handle of the bat) what's going on in your example (more so than how tire traction is effected by the extra vertical weight) is the effects of weight transfer on these buggies, buggy C is going to push on entry more than buggy B and buggy B will do the opposite in comparison. When you change one aspect if the suspension many things are effected and that's where people get lost. Now when I said more traction does not make a car easier to drive, the best example I can think of is with onroad touring cars. If you are running a rubber tire and change to a rubber based foam tire without changing anything else, the car will be many times harder to drive with the higher traction of the foam vs the rubber. This is my take on things I'll leave it up to you to take it or leave it.
Never argued on a cars ability to rotate and know all about inertia. In my examples about the cars mass going to infinity and 0 were to show how effective a suspensions ability to keep the tire in contact with the racing surface is directly effected by the mass of the car, with a heavier car being able to maintain contact with the ground more than a lighter car. As an example, ignore cornering. Lets just do a drag run on a surface that is 'whooped out'. Assuming both cars have had their suspensions properly tuned for their respective mass and have equal amounts of unsprung mass, the heavier car's tires will be in contact with the ground a larger % of the time.


Edit: the reason suspension wasn't added into the tire grip equation is that no suspension is perfect and varies from car to car (including chassis from the same manufacturer, the traction numbers listed above should NEVER be used to tune you suspension rather they are there to show the relationship of grip to weight and that's what we use to tune our suspension. If you have a 4000lbs car it will never pull 1g of mechanical grip. At best you might be able to reach .75g's but again that will vary from car to car)
Again, I point to the fact that this graph is only roughly relevant to offroad racing.