what does each number on the tire size stand for? - Mazda3 Forums : The #1 Mazda 3 Forum
 
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post #1 of 10 (permalink) Old 01-03-2008, 09:10 AM Thread Starter
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what does each number on the tire size stand for?

I looked on the FAQ for this and I only got some offset calculations which to be honest I didn't even remotely understand. Regardless my questions are what do the first two numbers (205 and 50) stand for and why is it that the 215 should also fit my car? I'm a pretty aggressive driver, so will having 215s instead of 205s affect the driving in a dramatic way?

I'm really close to the day where I'm going to by the tires and like anyone with a deadline I'm second guessing myself.
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post #2 of 10 (permalink) Old 01-03-2008, 09:16 AM
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Re: what does each number on the tire size stand for?

the first number, 205, is the over all width of the tire in millimeters. i dont know about the second number though. im sure someone on here knows though... i cant imagine the width of the tire changing all that much with the ride performance, your only going less than half an inch wider... i think more than anything it would change how it looks

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post #3 of 10 (permalink) Old 01-03-2008, 09:57 AM
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Re: what does each number on the tire size stand for?

205 ='s tire width (wider allows for more grip)
50 ='s tire sidewall height (shorter sidewalls allow for less tire flex in cornering)
17 ='s rim size
Offset ='s the distance the wheel sticks out.

If you want the overall best performance go with a 225/40/18 rim with a 45 offset. If you're rolling on a 17" rim, go with 215/45/17 tire with a 45+ offset. Good luck.

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post #4 of 10 (permalink) Old 01-03-2008, 10:01 AM
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Re: what does each number on the tire size stand for?

tooold ya! these guys know to much... its sad really... lol

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post #5 of 10 (permalink) Old 01-03-2008, 10:09 AM
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Re: what does each number on the tire size stand for?

actually the middle # is not the sidewall height.

225/40/18
xxx/yy/zz

xxx - they already told you
yy - this is the aspect ratio, not the physical measurement of the sidewall. it's a percentage of the width of the tire. so in our example above, the width of the sidewall = 225mm x 40% or 225mm x .4 = 90mm
zz - they already told you.

as for why 215's will fit, that is just the width of the tread on the tire where it meets the ground. it is not the same width where the tire is mounted to the wheel. that width is slightly smaller. tires are shaped kind of like this \ /
because of that, they will fit a variety of wheel widths. when mounted the sidewall gets more perpendicular(sp?) to the ground | |. our stock 6.5" wheel will work with 205 and 215. some people put 225 on but most tire manufacturers will advise that a 225 will need a 7" wheel.

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post #6 of 10 (permalink) Old 01-03-2008, 10:10 AM
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Re: what does each number on the tire size stand for?

http://auto.howstuffworks.com/tire2.htm

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post #7 of 10 (permalink) Old 01-03-2008, 10:16 AM
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Re: what does each number on the tire size stand for?

[quote author=BLACK MZ3 link=topic=98810.msg1963862#msg1963862 date=1199372945]
actually the middle # is not the sidewall height.

225/40/18
xxx/yy/zz

xxx - they already told you
yy - this is the aspect ratio, not the physical measurement of the sidewall. it's a percentage of the width of the tire. so in our example above, the width of the sidewall = 225mm x 40% or 225mm x .4 = 90mm
zz - they already told you.
[/quote]

Thanks for the added detail. I was going for a more elementary explanation but more detail is better!

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post #8 of 10 (permalink) Old 01-03-2008, 12:07 PM Thread Starter
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Re: what does each number on the tire size stand for?

Thank you so much guys you've answered my questions and then some. I am very grateful. This is around a 600 dollar investment to replace all 4 tires and now I have some more piece of mind with options. Again thank you I am very grateful.
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post #9 of 10 (permalink) Old 01-03-2008, 12:44 PM
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Re: what does each number on the tire size stand for?

any of you guys know how I can determine my offset of my wheels now? When I first got my wheels awhile back I really didn't care that much and the tire shop said they fit....so I said cool...LOL.

I have a 17x7 rim with 225/45/17 tires. Looking to install 235/45/17 within the next couple months.

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post #10 of 10 (permalink) Old 01-03-2008, 02:08 PM
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Re: what does each number on the tire size stand for?

there is no reason why you need a 235.

find your wheel manufacturers website and look their to see what the offset is.

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