So I have been looking around the forum on stickies, FAQ's, and other whatnot threads. I do have a couple of questions regarding rims and fitment. Some are general questions while some are more involved. (Don't mind the very basic ones! :?)
-What exactly is the offset of the rims? (Hopefully clarifying with the practical use of a rim and the brembo caliper)
-Advantages/disadvantages of rim size?
-Oem lug nuts vs. aftermarket? (type, size, ect.)
-The amount of spokes on a rim? (5 spokes or less = less rotating mass? 5+ = more rotating mass?) *****This is a joke***** :lol:
Anything else that needs to be addressed?
I'm definitely going to be thanking all the contributors in advanced on this one! :tup:
offset is the distance from the center of the wheel that the mating surface is. So, for a given width a big offset means the wheel is more sunken and a small offset means the wheel sticks out more.
a larger rim size means you can fit a wider tire. now you can fit a 245 on something like a 7.5" rim (ok so here tire sidewall makes a difference) and on a 9" rim. On the 225 the tire will be "stretched" an on the 9" rim it'll bulge a bit. Ideally you dont want too much of either. All else being equal, a wider rim weighs more, but you can fit a wider tire.
If you're talking about "rim size" being 17s vs 18s: well, it affects the sidewall height. A smaller sidewall means a "stiffer" tire. Some will say that's better, some worse. Its a bit of both. Look at f1, they dont run ultra-skinny tires, so dont get too hung up on that. Its more of a looks things. GRM did an article a while ago about that, and found (IIRC) that the larger rim actually ran slower around their particular track...all else being equal.
lugs: most OEM wheels have a particular seat for the lugs that does not match with aftermarket wheels. The BBS STI wheels HAVE the aftermarket profile (60 degree taper) but they are a narrower hole. I recently found a good thread discussing this, i'll try to link later. The point is a lot of aftermarket lugs on the BBS wont be ideal. OEM lugs on aftermarket wheels are probably fine.
As far as wheels, spokes, weight: Go for what looks good. Rotating mass is a big deal, especially un-sprung rotating mass. But be more worried about the "unsprung" part than the "rotating" part.
Here's a post I made somewhere else about lightweight wheels:
...the extra amount of power required to spin the wheel, (or stop it when braking) is really quite minimal compared to moving the car. You'd notice almost 0 improvement in 0-60 time with a lightweight wheel/tire setup (on a smooth road). The big reason why lightweight wheels make a difference in lap time is because they're unsprung. (lighter
[COLOR=blue !important][FONT=inherit !important][COLOR=blue !important][FONT=inherit !important]brakes[/FONT][/FONT][/COLOR][/COLOR], for example, will have almost the same effect as lighter wheels/tires in terms of lap time improvements). Lighter unsprung components let the suspension do its job without all the inertia of pieces in contact with the road.
Now wheels are like a "best of everything" improvement because it lowers total weight of the car, unsprung weight of the car, AND rotational weight. And it's true, that wheels are the worst kind of rotating weight due to their high polar moment of inertia (compared to say, a crank pulley or
[COLOR=blue !important][FONT=inherit !important][COLOR=blue !important][FONT=inherit !important]drive [/FONT][COLOR=blue !important][FONT=inherit !important]shaft[/FONT][/COLOR][/FONT][/COLOR][/COLOR])... but rotational weight really isnt helping you anywhere near as much as the unsprung weight savings.
