18" tire contact patch compared to a 15"
 

Is the less rolling resistance and loss of camber on 18" tires the better set up on the race track than 15" tires and their wider tire contact patch for braking???

Do the 18's wear better overall or the 15's ???

Here are the forces acting through a tire
http://forums.pelicanparts.com/uploa...1547576520.gif

and here are some randomly selected 225s compared

You can't make a blanket statement about any thing,
rolling resistance will depend on pressures and sidewall construction/height and tread compound, in general shorter stiffer sidewalls running at higher pressures will have lower rolling resistance. But not necessarily better grip, you need to balance that w/ tire pressures, Note that using a wider wheel will stiffen the side wall too

the contact patch is going to depend on sidewall stiffness and tire pressures, it will be roughly the same for all of the same width tires but will have different shapes depending on the sidewalls the MpSs has the shortest sidewall and will have the least circular contact patch, it will run at the lowest slip angle and develop the most grip all other things being equal( obviously they are not tread compound is big here), the Yok will have the tallest most flexible sidewall and will run at the highest slip angle and develop the least grip
http://forums.pelicanparts.com/uploa...1547577453.gif

breaking grip depends on the patch which also depends on camber, more camber = less braking grip, it also depends on speed, aero and suspension, the shorter the tire the easier it is to stop, best braking tire(all other things being equal) will be the 15" BFG
http://forums.pelicanparts.com/uploa...1547577346.gif

all other things being equal the tallest tire will wear best, that would be the 18" RE71

The advantage of 18" wheels is a lot wider selection of tire compounds and sizes. This to me overshadows differences in sidewall by a large margin. The disadvantage is that 18" wheels tend to be somewhat heavier overall.