It's time to replace my stock rear tires, so, looking to improve
performance, I want to go with 255/45-16 tires.
The diameter of this tire is 0.6 inch less than stock (2.4 %).
So it should work like a bigger gear ratio, which in my case,
it should go from 3.23 to about 3.31 (my best estimate).
It should also grip better because it's wider.
Can somebody verify this for me ?
Any possible drawbacks to doing this ?

 

There's so much more to a tire than that. Coumpound, tread design, and sidewall construction are going to make a lot more difference than the small difference in diameter. A smaller diameter is also going to have a smaller footprint front to back (though it's listed as a 255mm width, actual tread width varies between tires). If this is for drag racing the shorter sidewalls are going to make it even more difficult to launch.

I'd go with tried and true and not have to worry about correcting the speedometer.

 

i think it's not a good thing
first, like buttercup said it's harder to launch with smaller sidewalls
if you ever watch drag cars you can see pics of where at the launch the tires actually "crinkle" up
why do you think the run such big sidewalls?
also, that extra 10mm of tire is debateable, that's your call
lastly, you will throw your speedo off by going 45
while it may nto be much, it will be off, just to let you know
it's your call man, let us know what you decide to do

 

Yes, they do go with taller sidewalls, but they also go with
wider tires. I think the extra width would offset
lower sidewalls. I want somebody to verify my numbers.

 

Going just by those numbers there is less sidewall. The aspect ratio is just a percentage of the width.

245*50%=122.5mm sidewalls
255*45%=114.75mm sidewalls

To get into the fine detail you're talking about however you really need to know the exact specs from the manufacturer. Between two identically "rated" tires you can have different rolling diameters and tread width.

What tire is this? What application is this for? Street, drag, autocross? I think your expecting too much of a single variable. You need to look at the whole picture to choose the right tire. Not to mention it'll look goofy

 

OK, let me rephrase my question.
Going from 25.6 inch diameter to 25.0 inch diameter tires,
what equivalent in changing gear ratio would that be,
when starting with 3.23 gears ?
I will worry about all the variables and differences
between manufacturers later.
My claim is, that going from 245/50-16 tires to
255/45-16 will improve both handling and accelaration,
and I'm sticking with it until somebody proves otherwise.
By how much is a different story, that is what I'm trying
to find out.

 

well, it can only improve acceleration if you can get it to stick (which is why i like the bigger sidewall)
it will improve handling i suppose, i'm not really the guy to ask abotu that
good luck though, i'm curious as to if this will meet your expectations or not, let us know