jaspendlove
08-24-2009, 11:31 AM
This is from awesomesick from UN. Though it would be good info for here.
I've seen some confusion with wheels and tires here. Even from people who I wouldn't expect to be confused.
I'll start with tires.
http://www.futuretire.com/images/determining-tire-size.gif
The above picture explains tire markings correctly. When you're describing your tire size, don't say you have an 8" tire, that's incorrect, if the tire runs true to it's size, it's most likely a 205.
When selling tires, you can read the size off of the sidewall, and is almost always in that format. If there is a Z or some other letter before the wheel size (R) it's not really important, just speed rating.
This is another example, just to help it make a little more sense. I'll break down a 215/45ZR17 to help you understand all the numbers.
215 is the tire's width. It's 215mm wide. Inches aren't relevant here.
The "/" is to separate the width from the aspect ratio.
45 is the tire's aspect ratio. Obviously, the lower the number is, the smaller the sidewall will be (the lower the profile of the tire will be).
Z is a speed rating, not important. (to me at least). R is designating the next number as being the wheel size, in this case it would be a 17" wheel. Wheels and tires MUST be the same size, duh.
Now you know how tire sizes work. So, how do you choose the correct size tire for your aftermarket wheels on your car? Easy! Use an online tire calculator. It will give you what you need. I've seen some of you s14 guys with ridiculous tire sizes like 245/45R18's. That is a HUGE tire for a 240, and if you intentionally wanted a tire that size that's cool, but you can get a tire closer to the stock size if you'd like...
http://www.miata.net/garage/tirecalcold.html
This is a good calculator to use. Here you can enter your stock tire size, and your desired larger size to find a decent tire size.
Say your car came stock with a 205/60R15, on a 15x6" wheel. You want to put on a 17x9" wheel, and don't know what tire size would keep the rolling diameter close to stock.
Go to the calculator link I gave you above, and put your stock tire size (205/60R15 for S13) in. Then Put in your desired size. If you don't like stretching tires you would want somewhere around a 235 or 245, if you like stretch you could use anything below there. Then find an aspect ratio that leaves you with close to the correct rolling diameter. The tire you'd want to use is 235/40R17 or 245/40R17. For a stretch, you could run a 215/45R17. The calculator is good, because it will even show you the percentage your speedometer will be off from the "aftermarket" size.
You have to be careful, because if you end up needing an oddball size, they may not even make it. In that case you'll have to choose the closest thing. If you put 20's on a Sentra, obviously you'll have trouble keeping the rolling diameter.
There's still more to it than this, but this will give you a good place to start. I'll add the wheel size/ offset section a little later. Post here with any questions!
Now for wheels, this is more preference based. With enough work, you can get almost anything to fit.
If you walk into a tire store, and tell them to give you some "good looking" 17" wheels, they'll almost for sure sell you something along the lines of a 17x7+45 wheel. Which is fine, but sunken like a battleship.
If you want to get into wheel fitment, you'll have to familiarize yourself with some simple math, and terms. Offset is very important for determining where the outside of the wheel will sit, but unless you know the width of the wheel ALSO it's worthless.
http://www.discounttiredirect.com/images/wheel.offset.gif
This image explains what offset is, without numbers. You can see which direction positive is, and which direction negative is.
Here is a calculator for comparing your stock wheel size, to your new wheel size.
http://www.1010tires.com/WheelOffsetCalculator.asp
My s13 came stock with a 15x6+40 wheel, and now has a 17x9.5+15 wheel on it. No tire store would sell you that size though if you didn't specifically ask for it.
Tire stores have "fitment guides" that give them some guidelines for what sizes fit on certain cars. Generally, they try to keep specs on the wheels somewhat close to stock, which is sunken.
Using that offset calculator, you can find how much the clearances of the inner and outer side of the wheel will change. You can use a tape measure to see if the wheel you want will fit.
If you get too low of an offset, you will be forced to stretch your tire, unless you choose to go "widebody," or run a lot of negative camber.
Wheel fitment is complicated stuff, it takes some time to figure out. But these things should help you know what to do more.
I forgot to mention that offset is also measured in millimeters, and is almost always stamped on the backside of the wheel. Usually, it will say ET and then the offset. Sometimes it can be pretty hard to make out, especially when the wheels are dirty.
http://hondaswap.com/%7Emike/xb/motegi/28_back_3.jpg
This wheel is +40 offset. This means that the mating surface of the hub is 40mm toward the outside of the wheel from the centerline. If that makes sense.
You can see that adding spacers will reduce the effective offset of a wheel, and is basically extending the backside of the wheel.
There will be other stamped things on the back of your wheels too. The size is usually there, along with some other symbols, "JWL" is usually there too.
http://www.cartype.com/pages/2101/jw...n_alloy_wheels (http://www.cartype.com/pages/2101/jwl_stamp_on_alloy_wheels)
For examples of how a wheel can look on your car, you can look in the rimtuck database. I've never looked for Sentra's, etc in there, but if they're not on there you guys can add them.
http://rimtuck.com/
Kinda tricky to figure out the first time, but it's a really cool gallery of pictures, and includes wheel specs. I usually like to put in the make and model, etc, then push gallery. That way it will you give you a full list of all of that particular car.
You can find bad ass stuff like this...
http://rimtuck.com/photos/1248996138.jpg
I've seen some confusion with wheels and tires here. Even from people who I wouldn't expect to be confused.
I'll start with tires.
http://www.futuretire.com/images/determining-tire-size.gif
The above picture explains tire markings correctly. When you're describing your tire size, don't say you have an 8" tire, that's incorrect, if the tire runs true to it's size, it's most likely a 205.
When selling tires, you can read the size off of the sidewall, and is almost always in that format. If there is a Z or some other letter before the wheel size (R) it's not really important, just speed rating.
This is another example, just to help it make a little more sense. I'll break down a 215/45ZR17 to help you understand all the numbers.
215 is the tire's width. It's 215mm wide. Inches aren't relevant here.
The "/" is to separate the width from the aspect ratio.
45 is the tire's aspect ratio. Obviously, the lower the number is, the smaller the sidewall will be (the lower the profile of the tire will be).
Z is a speed rating, not important. (to me at least). R is designating the next number as being the wheel size, in this case it would be a 17" wheel. Wheels and tires MUST be the same size, duh.
Now you know how tire sizes work. So, how do you choose the correct size tire for your aftermarket wheels on your car? Easy! Use an online tire calculator. It will give you what you need. I've seen some of you s14 guys with ridiculous tire sizes like 245/45R18's. That is a HUGE tire for a 240, and if you intentionally wanted a tire that size that's cool, but you can get a tire closer to the stock size if you'd like...
http://www.miata.net/garage/tirecalcold.html
This is a good calculator to use. Here you can enter your stock tire size, and your desired larger size to find a decent tire size.
Say your car came stock with a 205/60R15, on a 15x6" wheel. You want to put on a 17x9" wheel, and don't know what tire size would keep the rolling diameter close to stock.
Go to the calculator link I gave you above, and put your stock tire size (205/60R15 for S13) in. Then Put in your desired size. If you don't like stretching tires you would want somewhere around a 235 or 245, if you like stretch you could use anything below there. Then find an aspect ratio that leaves you with close to the correct rolling diameter. The tire you'd want to use is 235/40R17 or 245/40R17. For a stretch, you could run a 215/45R17. The calculator is good, because it will even show you the percentage your speedometer will be off from the "aftermarket" size.
You have to be careful, because if you end up needing an oddball size, they may not even make it. In that case you'll have to choose the closest thing. If you put 20's on a Sentra, obviously you'll have trouble keeping the rolling diameter.
There's still more to it than this, but this will give you a good place to start. I'll add the wheel size/ offset section a little later. Post here with any questions!
Now for wheels, this is more preference based. With enough work, you can get almost anything to fit.
If you walk into a tire store, and tell them to give you some "good looking" 17" wheels, they'll almost for sure sell you something along the lines of a 17x7+45 wheel. Which is fine, but sunken like a battleship.
If you want to get into wheel fitment, you'll have to familiarize yourself with some simple math, and terms. Offset is very important for determining where the outside of the wheel will sit, but unless you know the width of the wheel ALSO it's worthless.
http://www.discounttiredirect.com/images/wheel.offset.gif
This image explains what offset is, without numbers. You can see which direction positive is, and which direction negative is.
Here is a calculator for comparing your stock wheel size, to your new wheel size.
http://www.1010tires.com/WheelOffsetCalculator.asp
My s13 came stock with a 15x6+40 wheel, and now has a 17x9.5+15 wheel on it. No tire store would sell you that size though if you didn't specifically ask for it.
Tire stores have "fitment guides" that give them some guidelines for what sizes fit on certain cars. Generally, they try to keep specs on the wheels somewhat close to stock, which is sunken.
Using that offset calculator, you can find how much the clearances of the inner and outer side of the wheel will change. You can use a tape measure to see if the wheel you want will fit.
If you get too low of an offset, you will be forced to stretch your tire, unless you choose to go "widebody," or run a lot of negative camber.
Wheel fitment is complicated stuff, it takes some time to figure out. But these things should help you know what to do more.
I forgot to mention that offset is also measured in millimeters, and is almost always stamped on the backside of the wheel. Usually, it will say ET and then the offset. Sometimes it can be pretty hard to make out, especially when the wheels are dirty.
http://hondaswap.com/%7Emike/xb/motegi/28_back_3.jpg
This wheel is +40 offset. This means that the mating surface of the hub is 40mm toward the outside of the wheel from the centerline. If that makes sense.
You can see that adding spacers will reduce the effective offset of a wheel, and is basically extending the backside of the wheel.
There will be other stamped things on the back of your wheels too. The size is usually there, along with some other symbols, "JWL" is usually there too.
http://www.cartype.com/pages/2101/jw...n_alloy_wheels (http://www.cartype.com/pages/2101/jwl_stamp_on_alloy_wheels)
For examples of how a wheel can look on your car, you can look in the rimtuck database. I've never looked for Sentra's, etc in there, but if they're not on there you guys can add them.
http://rimtuck.com/
Kinda tricky to figure out the first time, but it's a really cool gallery of pictures, and includes wheel specs. I usually like to put in the make and model, etc, then push gallery. That way it will you give you a full list of all of that particular car.
You can find bad ass stuff like this...
http://rimtuck.com/photos/1248996138.jpg