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i'm well aware that the 205/40/17 are about an inch lower than stock while the 215/45/17 is about the same size as stock. i'm also aware that with the 205/40/17s that it registers more mileage onto your odomoter due to its smaller diameter. for instance if you're traveling a distance of 100 miles, it'll register on the odometer as actually 104 miles. therefore every 10000 miles you travel, an addition 400 miles is added on. however, i am wondering if which tires would waste more gas if you were traveling from point A to B. while the 205s have a smaller diameter, i read somewhere on this forum that due to the fact that it weighs less than the 215s, that the 205s would save gas. im not sure if this is all entirely correct so i'm asking you guys which ones do you think save more gas if you're traveling from point A to point B? i'm also wondering which ones would allow the car to go faster. although the 205s have that smaller diameter, the 215s also weigh more, so this might be another tossup. another thing i'm wondering is if the 205's will interfere with the normal operation of ABS. i read in the manual that you shouldn't replace with tires of a different size because the ABS compares the diameter of the tires or something like that.

p.s. sorry, this might be a stupid question with an obvious answer, but i have tried doing research on tires and have searched the forum and have found nothing on these questions. thanks.

 
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Bro, it is not a stupid question... I have wondered many times how my wheel and tire package effects my car. When I first bought my wheels I wasn't even thinking about getting a tire that matched up with the stock wheel and tire size. I bout 17's with 205/40/17 tires. Yes they are smaller and yes they do add extra miles to your odometer. But I really don't think that it will save you any gas. The weight difference between an inflated 205/40/17 and a 215/45/17 is probably very minimal and obscure. That's like saying will a 125 lb driver save more money on gas than a 225 lb driver.

Gas mileage is all dependent on alot of factors not just the total weight of your car. So if your shopping around for tires use your best judgement, the 45's to keep it close to stock or the 40's for looks...

 
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a smaller tire contact area will always save you on gas, but with your new adjusted gear ratios, it will be lost. Your engine will be working harder to compensate for the lower drive ratio because of the new tires. You will be reving higher at 75 with smaller tires than you would with bigger tires, so It is really a push. I would presume that you would actually waste MORE miles per gallon taching an extra 3-400 rpm,s vs. the 10 centimeter contact patch....

 
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with 205/40/17 how do they add more miles to your car?[IMG]i/expressions/face-icon-small-confused.gif[/IMG][IMG]i/expressions/face-icon-small-confused.gif[/IMG] and whats the recommended size for a 17" rim?

 
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the recommended size for 17s are 215/45/17. they add more miles because the diameter of the 205/40/17 is smaller than stock. there is a tire calculator at the top of this page that tells u how each tire size will affect the mileage.

thanks for the responses. you guys make alot of sense. i was thinking that too because if the speedometer said 45, you're probably only going 43 on 205/40/17. so the engine will have to work harder to compensate for that difference.

im still not sure which tires will allow the car to go faster. but what i think you guys are trying to say is that the 215s will go faster because of its larger diameter???

also, i would like to know if the smaller tire size on the 205s will jeopardize my safety. i wouldnt want to get in an accident just because my ABS failed to perform as intended. once again, thanks in advance.

 
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with an overall smaller circumfrence tire you will actually change your final drive which will in affect allow your car to acclererate faster.

 
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i did a little more searching on the forum and i discovered that the abs compares the relative speeds of the wheels to each other so as long as all four wheels have the same diameter, abs will function properly. in other words, abs will fail if the front two wheels have a different diameter than the back ones because abs will register the wheels spinning at different speeds.

 
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the largest factor is rolling and wind resistance. the wider the tire the more these factors increase, hindering both performance and MPG in a straight line application. wider tires also tend to hydroplane eaiser. you must fint the appropiate average between traction and size.

 
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THey are both 17's, so it'd be the same. The only difference is ride comfort.