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tire size help

1302 Views 18 Replies 6 Participants Last post by  biped
hey guys and gals,

after i get my new rims i'll be looking to mount some decent tires. i'll be using a 7" wide rim and basically i'm looking for a minimal decrease in sidewall height. i know absolutely nothing about tire size ratios and am looking to become educated.

what is the minimal amount of decrease i can get from the oem tire sidewall? i just want something a little bit smaller, though not too small since i've seen thin tires on a dropped car and it looks like the car isn't dropped at all. i just basically want the next size down in sidewall height from oem.

any help anyone can give me would be great.
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im assuming you're getting 17s

here's how to read a tire size.

stock: 205/50/17 (on a s model w/ 17s.)

205 is the width of the tire in mm.
50 is the aspect ratio that determines the sidewall height. so 50% of the width in mm. in this case it's 102.5mm...pretty tall sidewall
17 is the diamater of the tire for the wheel.

a good size for 17s is 215/45/17. you get a wider tire without sacrificing too much sidewall. that's what i ran on my stock 17s after i changed tires.

you could do a 205/45/17 but that gives you a tiny sidewall which is not what you're looking for.
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thanks, 415. that was a big help. and yes, i did mean 17s. i'll look into it. think i'm gonna go with the kumho ecsta asx. i know that is a popular choice, but damn, it is a good tire.
also keep in mind that you have to change the aspect ratio when chaning tire sizes if you want to keep the overall tire circumference the same, otherwise you will alter the speedometer calibration. eg, 215/45-17 and 205/50-17 will have approximately the same overall circumference and your odometer will remain accurate. but 205/45-17 tires will reduce the overall circumference and your odomoter will read faster than you are actually going (by 3.2 mph @ 100 mph to be exact).
the difference is so minute, that it's not even really a big issue.
I believe that it is the 225/45/17 that has the same overall circumference as the stock 205/50/17s. The 215/45s will be about 1.8% off, which as 415 says is not an issue. If you drive 100,000 miles, your odometer will read 1,800 miles off from actual.
yeah but a 225 on a 7" wheel is a little much as far as sidewall rolling.
[quote author=the415 link=topic=65357.msg1120817#msg1120817 date=1167166168]
yeah but a 225 on a 7" wheel is a little much as far as sidewall rolling.

depends on the tire, but yeah, for 7" wheels, 215/45 is about ideal, I've been running that size for quite a while and LOVE it, great steering response, great grip, no rubbing whatsoever, and ever so slightly shorter gearing. Its about perfect IMO, unless someone makes a 225/40-17, and I don't know of anyone who does. . .
thanks for the help, people.

everyone always preaches about the kumho ecsta asxs. i'm pretty much sold on them but i'm also wondering about tire choices.

my priorities are:

1. tread wear rating
2. noise
3. grip
4. inclement weather traction

i'm more or less looking at all-seasons, but more towards the performance end of the spectrum. are there any other "high-performance" all-season tires available that even match the hype of the kumhos, in keeping with my priorities. i know the price on them is killer as well. there seems to be no downside.

also, the reason why i place grip fairly low is because i don't track my car and rarely reach the limits of it on dry pavement.

any quick picks that i can research? sorry to jack my own thread.
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the kumho spt
yeah they're around the same price too. looks like kumho ftw.
Just be aware that the SPTs are a summer tire, so if you get snow up where you are (Canada?) you should probably stick with the ASX.
oops...i saw high performance but didn't pay attention to the all-season part.
[quote author=the415 link=topic=65357.msg1120817#msg1120817 date=1167166168]
yeah but a 225 on a 7" wheel is a little much as far as sidewall rolling.

225 is the max for a 7" wide wheel. I run 225 on my 7's and my 7.5s with no adverse effects. The 7s are on my autocross setup. The 225/45 is like .03% smaller than stock, so you get a wider footprint and the same overall height (sidewall).
i'm also drawn towards the pirelli p zero nero m+s.
Good choice, I just switched to those as well.
what's the verdict so far? they seem to be a bit better, not only all-around but in looks as well. they're a little more money but seem like i'll know why i spent the extra dinero.
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