Tire size vs gas mileage question

[ericsmith32]

I've pondered if i've asked this question before, and all besides that crazy voice in my head says I haven't. Okay.. I have 175/80/13's on my aspire, the factory size was 165/70/13, the normal size seems to be 175/70/13. I wonder how much those taller tires are throwing off and possibly hurting my fuel economy? The ride can be horrible at times, but I would think these bigger tires would help rather than hurt. I might have a chance in the next week to get a good deal on the normal factory size tire/wheel (165/70) combo and i'm wondering if I would be better off changing them even though the tires on there look like they'll last another 30-40k easily. Also the handling is terrible which I know is characteristic of taller tires, sort of unnerving in rain and such. Although I guess that would pretty much be the same with 165's. To change or not to change that shall be the question.

[ericsmith32]

I went ahead and changed out the 175/80/13's for 165/70/13's. Those tires are small compared to the others. Funny thing is that the 165's wider than the 175's. The 175's were crappy wal-mart tires so that shouldn't surprise me. I know for a fact that I don't have to struggle up hills like before.. only time will tell on the mpg. With the gear ratio's of the aspire I defiantely recommend that you run 70 or 60 series only (of course depending on the actual rim size...)

[Andrew]

I went ahead and changed out the 175/80/13's for 165/70/13's. Those tires are small compared to the others. Funny thing is that the 165's wider than the 175's. The 175's were crappy wal-mart tires so that shouldn't surprise me. I know for a fact that I don't have to struggle up hills like before.. only time will tell on the mpg. With the gear ratio's of the aspire I defiantely recommend that you run 70 or 60 series only (of course depending on the actual rim size...)

it's probably because the 175s were crap I'll bet that it's moreso a thing with quality than size.

[PaulLehr]

I noticed on my car that after I went from my Wal-Mart 12in tires to the stock aspire wheels and tires with my brake swap that my acceleration did suffer somewhat from the increased curcumference of the wheel and tire

[ericsmith32]

I found a website where you compare tire sizes and shows you how much your speedo's off. Mine was actually 5.68mph off. I guess the hi-po was right they said I was going 68 when according to the speedo I was going 60. No wonder it seemed like I was flying at 70, and passing people like crazying.

http://www.net-comber.com/tirecalc.html

[PaulLehr]

Once I finally order the tires I want for my Miata wheels they will be 195/45/14 and according to the tire calculators my speedometer will show I'm going faster than what I actually am. I can easily live with that since when I think I'm going 5 over ill be going the speed limit he he