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Old 06-11-2008, 10:37 PM   #1 (permalink)
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Tires and Rims

Hi, I've always wondered this, but I haven't been able to figure it out by pure intuition, so I'm wondering if someone KNOWS the answer.

I have 97 civic ex with 200k miles, runs great... anyway, it has the 15" stock steel wheels. You know how all the kids (im 19, but im not one of THOSE kids) put huge rims on their civics because they think it makes them faster... well I'm about 6 months away from new tires, so I'm wondering if I should get new wheels while I'm at it.

So which is lighter: Large rims and thin tires, or small rims and fat tires? What about steel vs. aluminum vs. whatever else?

Note: Cost isn't really an issue. For me, FE means fuel efficiency, not fuel economy.

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Old 06-11-2008, 11:07 PM   #2 (permalink)
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optimally what you want is a lighter, narower tire rim combination. by going to a larger rim and lower profile tire (assuming the actual OD (outer diameter) remains the same) you achieve better handling due to less side wall flex, now if we also assume that in this process you switch to a narrower tire (from a 195/xx/15 to a 175/xx/15) you will effectively reduce the amount of surface area touching the ground thus reducing rolling resistance.

basicly, what i am saying is
1) you want the lightest possible tire/wheel combination
2) you want the narrowest tire you can get
3)bigger isnt always better, but then again it is not always worse.
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Old 06-11-2008, 11:15 PM   #3 (permalink)
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just to clarify, by narrowest i am refering to contact patch, not the side wall, sidewall height mostly affects handling, which if you are driving for efficiency you may rarely see a difference.

also in general magnesium wheels (most expensive) are the lightest, then aluminum (which is what you should buy) and then steel, but this is not always true, i have seen cheap aluminum wheels weigh more than some factory steel wheels.
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Old 06-11-2008, 11:23 PM   #4 (permalink)
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Why not small and thin? If some insight wheels will fit on, that's what I'd go for.
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Old 06-11-2008, 11:53 PM   #5 (permalink)
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I know that a thinner tire is better, but if I get a larger diameter rim do I have to get a wider tire?

by thin and fat i'm referring to the thickness between the rim contact and the outer circumference, not the width.

But I'm just asking in general: is large rim/thin tire or small rim/fat tire lighter?




by the way, the insight wheels idea is good. I'll look into that also, thanks.
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Old 06-11-2008, 11:55 PM   #6 (permalink)
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Shoot for either Insight rims, or HX rims
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Old 06-12-2008, 12:09 AM   #7 (permalink)
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Well it is not just the weight of the tire/rim you care about. The rotational moment of inertia is even more important, because you have to spin the wheel up to speed and then spin it down to zero rpm when you stop. You want the least amount of weight located at the maximum diameter. This will vary with each model (style) of wheel, no matter if it is steel or aluminium. Also, if you have never driven in a car which came from the factory with "normal" profile tires, and you put on bigger rims with "low" profile tires, you will discover that the ride is punishing. You will feel every crack in the road and every pebble you run over.

So after all that, it boils down to "It Depends"
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Old 06-12-2008, 12:13 AM   #8 (permalink)
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Yea well somehow my civic came stock with 15" steel rims. Don't ask me how. Seems to me that the RMI would be smaller if the tire is thinner, hence the reason all the ricers get huge rims and 1 millimeter thick tires. I'm just looking for a small upgrade... if my car looks nicer and I use less gas, its a win-win in my book. Maybe moving up to 16" rims and a slightly thinner tire. Also, it seems like reducing RMI is less effective for highway driving. Are my assumptions above correct?
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Old 06-12-2008, 12:17 AM   #9 (permalink)
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Quote:
Originally Posted by abshnasko View Post
if I get a larger diameter rim do I have to get a wider tire?

But I'm just asking in general: is large rim/thin tire or small rim/fat tire lighter?
it depends on what is on your car now,you could possibly go up to a larger rim and maintain the same width, but this is usually unlikely. considering the vehicle you have you more than likely would not benefit from larger wheels and tires with lower sidewalls.

out of curiosity do you know what size tires you have? if you dont know the size is easy to find, on your car it should look something like this: p195/65/15 but your numbers will vary.
in case you dont know this is what that line means:
p-pasenger
195-tire width (milimeters)
65-aspect ratio (percentage of tire width equal to sidewall height)
15-wheel size

definately look into a smaller set though.
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Old 06-12-2008, 12:23 AM   #10 (permalink)
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its dark outside right now, but ill get the info for you in the morning. like I said I'll need new tires soon and I just got an extremely well-paying summer internship, I was thinking of doing a LRR tire/lighter wheel combo.

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