TongMan

When I changed my rims to 19" from 17" and I travelled 200 miles, Is it the same distance on both size rims?

I would assume "no." Anybody got any info on this?

engifineer

It all depends on the profile of your tires. The overall height of wheel and tire is what you need to know.

SquallLHeart

^^ yup.. what size are your tires??

you need to have a smaller profile to maintain the same circumference.

TongMan

on my 17" rims the tires are 225/45/17 and on the 19" rims the tires are 215/35/19.

engifineer

You should be ok then. Here is the way to get an idea:

The profile percentage (35, 45, etc) times the width (215,225, etc) equals the profile. Unless my quick calcs are off, your overall profile is 1 inch lower with the new tires, meaning two inches overall. You went up 2 inches in rim diameter, so the overall diameter should be the same (approximately). Now, with all of that said, I have seen this be off a bit depending on manufacturer and the way they measure. But you should be close enough that your odo isnt too terribly off.

SquallLHeart

well.. even with the 225/45/17

there was a 1.45% difference vice the stock 215/45/17

now basing off the 215/45/17.. the 215/35/19 has a 1.25% difference

making the speedometer read that much slower.

meaning... you're going slightly faster than the speedo...

TongMan

how much faster? would you say 1-2mph or 5mph?

rrimportracer

yep man you guys are fast i was just about to say that, whip out my calc and do the math, and actually a lil but makes a bigger difference than you think, on my old car i had 185/65/15 stock size and i was planning to sell, i needed new tires though so i got 195/65/15 and it was off by 5 mph

engifineer

225 * .45 = 101.25 mm
215 * .35 = 75.25 mm

This means the profile height went down 26mm/25.4 mm per inch = 1.02 inches

Multiply this times two (top and bottom if you will) = 2.04 inches decrease in profile with a 2 inch increase in wheel height

Now, like I said, I have seen the way the measurements are taken vary slightly from manufacturer to manufacturer (for some reason) and even tire to tire. But if I am calculating correctly, you should have almost broken even

But... I am not really a tire manufacturing guru... and I have spent a while soldering tonight, so I could be missing something

SquallLHeart

^^ careful with those fumes.. ..... whoa.... heheh.. i think i'm gonna go brain dead or die from lead poisoning...

it's cumulative... it's a 1.25% difference
if you're going 20.. you're actually going 20.25

if you're going 100... 101.25 in real life.... yeah... not that big of a deal..
1mph difference if you go over 100..

but over a long long period of time.. sure.. the odo's gonna be off... by much? neah..

TongMan

Well then. If the 19" rims w/ 215/35 tires are actually smaller in diameter than the 17" rims w/ 225/45 tires, then performance-wise, the 19" rims will be better for drag racing?

I know that weight of the rim makes a difference, but I hear that the OEM rims weigh like 22lbs which is the same as the 19" rims that I have. So is it true in my situation?

rrimportracer

easiest way to test it out is have a friend with stock tires and wheels drive next to you at 50mph, or whatever you want, and see what your speedo says

engifineer

Well, reading my calcs above, your new setup should be .04 inches shorter.. so not a big difference. About 1/8th inch difference in circumference. Keep in mind, I am comparing your old to your new tire size. Not your new vs old vs 215 stock