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Discussion Starter · #1 ·
Hi guys,

I have searched even in google and can't find anything on the topic, maybe I haven't searched hard enough. The thing is, I keed reading about 225/40 tires in 18" wheels, but I want to put 225/40 tires on my stock 17" SX wheels.

Toughts on that guys? I really am not good when it comes to car things.
 
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Go on Treadepot.com and look. They have a tire/wheel size chart that will show you what size tire will fit on what size rim. Usually a 225 goes on 7.5 or 8" wide rim, but i could be mistaken.
 

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Discussion Starter · #3 ·
Thanks, but do you happen to know the width of the stock SX rims?
 

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If you did this your speedometer will not read the correct speed. You will actually be going faster. Stock tires are 215/45r17 and you wanna put 225/40r17.....so....

Speedometer Difference: 2.200% too fast
Diameter Difference: 2.16%

Not recommended.
 

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One problem with 225/40-17.... that is not a common size.

I have a set of 225/45-17 on my stock SX Koup rims and they are fine with no speedo issues at all.

On a tech side of things, most 215/45-17 and 225/45-17 tires are good to go on rims from 7 - 8.5 inches wide with the measured rim normally being 7 or 7.5 inches.
 

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Discussion Starter · #6 ·
I was told by a service tech of my kia dealer that it had to be 225/40 if I anted them wider because 225/45 would be out of proportion or would have too muh height or something like that.
 

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Why the interest in 225? Most people I know are running 215/45....I know people who have this tire size on their wheels and they don't have any problems. However as mentioned your speedo will be off by a few mph so as long as you remember to take that into consideration you will be fine. The stock 17" SX wheel is 7" width!!
 

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Discussion Starter · #9 ·
I see, well guys, thanks for the answers
 

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Discussion Starter · #10 · (Edited)
I just saw my friends BMW 325ci 2005, and he has the stock 17" rims, with a 225/45R17 tire, and it looked better, I mean the width of the tire I'm looking for, but the tire had more height, which I didn't like that much. Hence, why I'm asking, in that case a 225/40R17 will give me a tire with almost the same heigth as the stock one but with more width. I think I will go for it.
 

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Discussion Starter · #12 ·
Well, thanks, but my dilemma is if it is better, to put 225/40r17 or 225/45r17
 

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Well, thanks, but my dilemma is if it is better, to put 225/40r17 or 225/45r17
What 225/40-17 tires are you looking at? I don't understand why the dealership would recommend such an odd size. If you stay with 215/45-17or 225/45-17 there are tons of options available.

Some manufactures will have a tire in both sizes, others will only be in one size. For example, Bridgestone only makes their Potenza RE960AS tires in a 215/45-17. Goodyear makes different versions of their Eagle GT. The W speed rated tires are available in both 215/45-17 and 225/45-17. They also make a V speed rated version (with a 50k mile tread life warranty) that is only available in 225/45-17.

On a side note, a 205/55-16 tire that the EX models come with has a 25" diameter which is the same as a 225/45-17. I only say this because some people have questioned their speedometer/odometer accuracy. I'm not sure that the gauge cluster is calibrated specifically for the EX vs SX models.
 

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It's because he wants a 225/40....not 45...and that is going to throw off the speedometer. It sounds like his question is will they fit his wheels and the answer is yes....It will be fine..Yes, it's also a odd size but I don't think that is his concern. Like I mentioned once you know your speedometer is off, all you have to do is go 23 instead of 25...and I don't think most people worry about being 2 mph off anyway...Where I live a state boy won't pull you over if your going 72 in a 65...You have to be damn near 10 mph over....
 

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Discussion Starter · #16 ·
well, seeing the recommendations I get it that I should be going 225/45 because 225/40 is a very odd tire size.

But my dilemma began when the KIA tech told me If I go 225/45r17 when I made full turn it will touch with some part of the car and scratch the tires and damage them or the car part it touches. Thats why he recommended 225/40r17 and in my ignorance I thought that was the only way, hence why I cam to you guys for advice.

Also I want to mention that I want to lower the car with eibach suspension. Is still safe to go 225/45r17 then?
 

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Still not sure what the tech is referring to. On average, a 215/45-17 will have a section width of 8.5" and a 225/45-17 will have a section width of 9". That would mean again, on average a 225/45-17 would be about 1/2" wider. That would also mean that the tire would stick out about 1/4" more on each side of the rim. If a car's suspension has less room than that, I would think it would be really bad. Imagine hitting a bump while making a turn and your tire hits the frame or fender and that's with stock tires.

Now here's the tricky part... tire manufactures will have section widths that are based on rims with different widths. A tire with a section width based on a 7.5" wide rim will be slightly wider than the same exact same tire on a 7" wide rim. This is why they specify a measured rim width. All things being equal, it ends up being about a quarter of an inch difference in the section width by going to a different rim width.

So, getting back to the first comment.... there is a 1/2" difference in section width of the tires (provided they have the same measured rim width). If you look around, most 225/45-17 tires have their measurements based on a 7.5" wide rim. That would mean if you put it on our stock rims which are 7" wide they would have a section of width of appx 8.75." Now you are talking about an extra 1/8" inch on each side of the rim. I have a problem believing 1/4" would cause issues let alone 1/8".

I hope this makes sense...

Now, the suspension question would be a little more involved. It's not just if you drop the chassis to the point where there is no room for the tire to travel before hitting the fenders. The lowering springs could change your geometry drastically depending on how much lower they are from the stock springs. Toe-in should be the same, but caster and camber will probably both be off to some degree. Someone else who has the lowered springs should take this one.
 
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