sx sonic
New member
That's actually a really fuzzy line.
A lower profile tire (i.e. bigger rim) is supposed to decrease tire roll over during hard cornering. As in hard cornering causes the sidewall of the tire to flex and try to roll underneath the rim, a gross exaggeration is the sidewall will flex until it is contacting the road.
This tire rollover can be felt, most noticeably right as the turn is initiated. It can also cause the contact patch, the part of the tire that is touching the road, to distort and possibly lower the amount of available traction. Note that in reality the traction aspect is unlikely to be noticed by 99% of the people that hit public roads.
Now if you take the same O.D. tire and put it on a bigger rim (a sonic with 15's vs a sonic with 16's, 17's, etc) there will be less tire sidewall. Less sidewall makes it harder for the tire to roll over, because it is essence stiffer and the contact patch has less leverage to act against it.
This provides "crisper" turn in, which may be noticeable during hard cornering. The downside is a harsher ride since the sidewall will flex over bumps and with less sidewall to flex more impact is transferred over bumps, particularly pot holes.
On the other side of the coin is wheel weight and given the same design smaller rims will be lighter. Now a smaller rim means more tire will be needed for the same O.D. but the weight difference in rim size is always more substantial than the difference in tire weight.
This weight is called "unsprung" weight since the suspension does not support it. Less unsprung weight means the suspension can compress and rebound more readily, this means the tire can more easily follow road contours on rough surfaces for keeping the tire in contact with the road which means more traction. This difference, in sonics with different rim sizes, is likely about as noticeable as the difference in tire roll over.
Here's the big one, any weight that rotates at vehicle speed is equivalent to 3 lbs of body mass (the car body or anything inside the car). As you can imagine any wheel weight dropped can have a big difference in acceleration and by proxy the amount of energy it takes to accelerate to a given speed. 17's are ~4lbs heavier than 15's per wheel which equates to about a 48 lbs of body weight.
that is substantial and can easily be observed in marginally faster 1/4 mile times and MPG. As evidence the sonics with the best MPG have all had 15in rims.
TL;DR- Bigger, heavier rims MAY feel better during hard cornering, although the majority of people don't take turns hard enough to notice a difference. Smaller, lighter rims provide better suspension movement which is unlikely to be noticed. They do yield slightly better acceleration and MPG.
