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just to get back to the original question, "is there a performance gain by useing a larger "RIM"

no.

"a larger rim and low profile tire"?


yes.

But if you put a 215/30/15 tire on a 15 inch rim you would also gain performance (Cornering grip) at the expense of harsh ride and bent rims.

its the stiff side wall due to the low profile that is stablizing the tire and keeping most of the tire face in contact with the road, the size of the rim has nothing to do with it

my 17 inch adr's might be a cheap brand of rims but they weight less than 14 pounds

Originally posted by mxprecidia:
my 17 inch adr's might be a cheap brand of rims but they weight less than 14 pounds

yes adr= replica wheel company like rota. replica wheels are not usually as light weight as the originals. like konigs copy of the volk te37. it looks similar but its much heavier. the rota slipstream is a copy of desmonds regamaster evo, once again rota are heavier than the desmonds. rota subzero's are a copy of the racing hart cp035. the real racing harts are 10.5# 15's and rotas subzero is 14#'s. which adr's have 14# 17's? i had no idea adr was trying to compete in lighter weight wheels as most of their 17's are at least 19-26# a pop. 14# is not bad for a cheap brand but it is a cheap brand light weight wheel as another comparison... velox progear 17x7.5 start at 12.5#'s. get it now? there is a difference between knock offs and real stuff. majority of replica's tend to be much heavier.

light weight wheels will improve throttle response, increase accelerating and deceleration. like a lightened flywheel, or lightened engine internals... kind of...

do is the only gain with going a smaller rin/larger tire just weight?

it depends what you want, its all subjective.

whats the biggest bennifit.

well to me its beating the hell out of my car for 2 years at the track, in the snow, on the high way and on our crappy streets with potholes the size of VW's on my stock 15X7 14 pound rims. where do I sign up

15 inch snow tire are easy to get, 15 inch drag tires are easy to get, 15 inch Auto X tires are reasy to get.

ok, first off, the size of the rim has NOTHING to do with unsprung weight, acceleration numbers, etc. its all about the weight. if you have a 15 lb stock rim, and a tire weighing 13 lbs, you have a total weight of 28 lbs of rotating mass. if you properly size the rim and tire to match the diameter of the oem rolling stock, then you haven't changed the final gearing. now, if you can get a rim that only weighs 12 lbs, but the tire for it weighs 16 lbs, (more anti-flex material in the low profile tires), you STILL have a rotating mass of 28 lbs. regardless of the size of the rim, the weight of the rotating mass is the same. Now, since the 17 is most likely more open on the inside of the rim than the 15 is, most of the weight is shifted to the outside of the circle (rim+tire). You are going to need more inertia to initially start the rotation process, but once it starts moving, less inertia is required to keep it rotating. Its a tradeoff. think of it this way, take a string, 12" long, and tie a paperclip in the middle, and one on the end, now swing it around. It takes less momentum to get it moving, but more power to keep it moving. Now take a 12" long string, and tie 2 paperclips to the end of it, and do the same thing. see how you have to swing it a little harder to start with, but once its going, you don't use as much energy to keep it moving. Same weight, same diameter, same mass, but the mass is displaced differently.

Now as far as a performance issue, with a wider rim, you are going to lengthen and widen the footprint of the tire (amount of tire in contact with the road at one time), which is going to do a few different things. First, it is going to increase the amount of friction between the road and the tire surface. But as a tradeoff for that friction, you are going to have more grip for braking, more grip and less sidewall flex for cornering, more grip for acceleration, and less sidewall flex for less body roll and overall improved handling. Chances are the negative effects are going to be outweighed by the positive ones in the long run, no matter what sport you are in, with the exception of drag racing. Although running the 1320 will always benefit from a bigger footprint, the best way to acheive that is from a small rim with a big sidewall tire that is soft. That is why a wrinkle wall tire is the best choice. It allows the tire to flex on takeoff, and by not being as stiff the tire gives and grips, rather than just breaking loose and spinning.

Sorry about the long post, but I hope this helps. If anybody doubts me, just know that I have helped in the setup of about 50 different Cavaliers, some set up for strictly racing applications, and while I may be new to the MX-3 board, I am certainly not new to sport and racing suspension setups.

Have a wonderful day

Aaron

finally a newer member that has brains. 2 months late but, welcome.

Please put aaron bales post in the FAQ section.
It's the first post about this subject that is correct. I'm tired of reading all the other crap posted about 17" tires/etc .