Can someone please explain what all of the 255/40/17 and 245/50/18 and all that junk is? I have 245/40/17s on my car.. 17" rims.. so.. yeah.. i dont understand what all that means and what a good tire size is for our cars... id like it to be kinda low profile with some tire just not a really big one but i want it to fill the wheel well nicely.. also i want it wide as possible without ANY rubbing..Thanks guys, and gals!

 

OK, tire sizes. The numbering scheme used on our tires is the "metric" style of measurements.

For example: 245/40/17

The first number, 245, means that the section width of the tire is 245mm wide. This is the width of the tire at it's widest point, and it is an approximation.

The second number is the height of the tire. It is expressed as a percentage of the section width. In this case 40% (of 245). This means that the "thickness" of the tire between the edge of the wheel and the surface of the tread is about 98mm. Again, this is an approximation. "Low Profile" tires have a small number here.

17 means that the tire fits on a 17-inch diameter wheel.

If you want to convert this stuff to inches, the conversion factor is 25.4 mm to one inch. So this tire is about 10" wide.
If you want to approximate the outside diameter of the tire, then add up Wheel size + 2x Height.

There are different sizes you can use, but you need to first decide what kind of wheels you want. For a given wheel there are only certain size tires that can be fitted on it. Of course, the diameters have to match. You can't put a 18" tire on a 17" diameter wheel. The width is also important. Every tire will have a range of specfied wheel widths that are OK for it. So, if you're using your stock wheels then your tire size choices are limited. If you are changing your wheels to aftermarket ones, then there are many other options available to you.

 

thanks for the explanation, im looking for a bigger rim, i have 17's now and i want somethin bigger but nothing thats gonna look rice

 

All of the above is correct. It's best to check the "specs" of the tire you want on Tirerack.com to see what width wheel it will fit.

Now as far as sizes, if your looking to change tires and want to keep the same tire height as not to throw off your speedo a quick trick is to do this. For every 20mm increase in width you should drop down the aspect ratio by 5. Also, for every 1" you increase rim size you drop down aspect ratio by 5.

Therefore roughly 235/55r17 = 255/50r17 = 255/45r18 = 275/40r18 and so on.






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i was thinking about just get my tire size that i liked and then have the speedo fixed.. its only like 200 bucks right?

 

Get a CAI (Cold Air Intake) and a Tuner if you don't already have them. They're worth some good HP anyway.

Then, you can use your tuner to correct the speedo yourself.


If you're browsing around for tires, the stock size is about 27" outer diameter. You will want to choose something similar.