ok u know how they say when u go do a larger wheel u increase the rotational mass, there for losing performance.

for example take a 17 inch wheel with a 215 45 17 that together weighs about 45 lbs.

then take a 18 inch wheel that is lighter with a 215 40 18 that weighs about 39 lbs together {wheel and tire}

wouldnt that actually increase the cars performance slightly becuase the car is actually rotating something that is lighter making it easier to move???

they are basically the same height side by side. so what do u think am i right or wrong??

so even though going up an in size but down in weight it should gain insted of lose correct

 

ANYONE?

 

Rotational mass isn't relative to the weight of itself, BTW. So technically whether or not it may be faster in the 1/4 mile, your gearing still changes, and then again, gearing affects 1/4 mile performance.

So on one side, you gain performance(weight advantage), but on the other you lose performance (see gearing). How much? almost not noticeable.

 

yea but what if the 17 inch wheel standing next to the 18 inch wheel is exactly the same height. how does it affect gearing

 

Wow, your posts are difficult to read with all those text message abbreviations. You (NOT "u") might want to type them out in English if you want people to bother reading them...

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DeDonDeRosa &raquo;</TD></TR><TR><TD CLASS="quote">yea but what if the 17 inch wheel standing next to the 18 inch wheel is exactly the same height. how does it affect gearing</TD></TR></TABLE>

Assuming you really mean the tires, rather than the wheels, it doesn't.

However, that's not usually true, when comparing 17 inch tires with 18 inch tires, because for most of our cars (most Civics, Integras, CRXs, del sols, etc), they don't make 18 inch tires whose outer diameter is as small as the stock tires or the 17-inch tires you would normally use.

Regardless, wheel/tire weight is not a big factor in performance. Differences in performance between different models of tires is nearly always much greater than differences in wheel/tire weight. And lack of tire availability for our cars in 18-inch sizes is a major factor in performance, much bigger than anything you have mentioned. So arguing about the weight of 17 vs 18 inch wheels is rather pointless.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DeDonDeRosa &raquo;</TD></TR><TR><TD CLASS="quote">ok u know how they say when u go do a larger wheel u increase the rotational mass, there for losing performance.

for example take a 17 inch wheel with a 215 45 17 that together weighs about 45 lbs.

then take a 18 inch wheel that is lighter with a 215 40 18 that weighs about 39 lbs together {wheel and tire}

wouldnt that actually increase the cars performance slightly becuase the car is actually rotating something that is lighter making it easier to move???

they are basically the same height side by side. so what do u think am i right or wrong??

so even though going up an in size but down in weight it should gain insted of lose correct</TD></TR></TABLE>


Hard to say. Rotational mass doesn't exactly mean the mass itself, it's more of a rotational inertia/polar moment of inertia thing of thing. Essentially it's not just the mass, it is where the mass is located in relation to the centre of the rotation. If some mass if farther away from the centre it is harder to spin. Take for example a bottle. If you are playing spin the bottle, well it's easy to spin it because the centre of rotation is really close. Now if you take that bottle and tie it on the end of a string and then spin it, well it takes a lot more energy.

You can see figure skaters do this, they will start spinning with their arms stretched out, when they bring their arms closer to their body they will all of a sudden speed up. They have reduced their polar moment of inertia with out changing the mass.......thus they speed up.

So in the case of the 18" versus 17" rim, the 18" rim has mass that is farther away from the centre of the rim. Now, does it necessarily mean that it will have a greater polar inertia of mass? I don't know. For that I would have to see skematics for both rims and start doing a bunch of calculations.

I hope this helps you out. But like ken said, it's an indistinguishable difference. There are a lot more important factors that come into place....tire make/model and getting a size that works for your car. 18" and even 17" don't usually work all that well for hondas.

 

JUST BY THE 18'S STOP CRYING AND MAKING ALL THESE POST AND JUST DO IT!