First of all, we want to start by saying the subject we are about to cover is highly subjective. (Heh Heh) The truth of it is simple, it’s all about taste. That being said, it’s also good to know how to define what you like. So without further ado, we want to go over the basics of wheel fitment. To kick things off we should clarify that around here we prefer the wheels to fall in line with the edge of the fenders. This is known as flush. (Or hella flush for you scene kids) The other most popular style is poke, or stretch. This is where the wheels are stretched over an over-sized wheel and the wheel’s outer lip extends past the fender and tire. To understand these to modifications (If you can call them that) you need to understand factory or stock stance. From the factory most of our cars tend to come with a narrower wheels and sit inside the fenders. This is what gives it a sort of pokey look.
Older cars did it more, but as taste and style change, manufacturers are starting to fill out the wheel well from the factory. Now back to flush and poke, think all wheels are the same? Good, we didn’t think you were that dumb either. There are many combos of tire sizes and wheel sizes available today. Each combo creates a different look to the stance and seat of your car. For example a 215 tire will look very different on an 8.5 inch wheel when compared to a 245 tire. The first step to figuring out what combo is right for you is understanding the measurements of both tires and wheels.Tires are sized as follows: Width/Sidewall/Size. (IE: 235/40/18r) From the example we can tell the tire is 235MM wide with a sidewall height ratio of 35 (The ratio is the aspect ratio of the width to side wall) and will fit an 18Inch wheel. Now for wheels, they are sized a bit differently. Wheels will come in diameter by width expressed in inches (IE: 18×8.5) and they will have what’s known as an offset. The offset is the distance from the center line of the wheel to the hub. It is expressed in millimeters and will be shown as ET. (IE: ET35mm) Next is the hub size, this is the size of the mounting ring found on your car. Older Audis are 57.1mm hubs, however newer Audis are now 66.1mm. Last but most important, is the bolt pattern. This is the spacing and number of bolts needed to match your cars hub. (Most Audis use 5x112mm) So an example wheel size looks like this: 18×8.5 inches with an ET of 35mm and wheel bore of 57.1mm. The bolt pattern would be 5×112.
Now what does this all mean? Well regarding wheels, the diameter is straight forward. The width of the wheel is important because it determines what size tire you can run, as well as if the wheel will fit under the car’s wheel wells. A larger width wheel will “poke” out from under the fenders and often have a tire stretched over it. “Stretch” is where the tire’s side walls have an aggressive angle due the width of the wheel they are mounted on. The best fitment we have found for our B5 is a width of 8.5inches with an offset of ET35mm. Now ET, or the offset, is the other huge factor for wheel fitment. This number is what determines where the wheel will sit in the wheel well as well as the depth or amount of concavity of the wheel. For example an ET45 with sit 10mm farther away from the fender edge then an ET35 would. (Remember ET is the distance in mm from the center line of the wheel to the bolt hub. See the figure above for more detail) An ET45 would also in most cases be less concave then an ET35. This is because the outer lip of the wheel is 10mm closer to the bolt hub with an ET45 compared to the ET35 wheel. However with all things there is a catch. The lower the ET, the farther away the wheel sits from the car’s hub. Too low of an ET, and you run the risk of hitting the fender wall or fender lip, both not good things. The same goes for the width of the wheel. To deep or wide of a wheel, and you will hit the control arms and/or the fender as well. For our B5, 8.5 with an ET35mm is about the best fitting wheel for a flush look without spacers, rolling or pulling. Some of us out there want the “poke”, so to get that on a B5, they will run spacers or a 9.5 inch wheel with an ET20 offset. This allows them to clear the control arms, but they have wheels sticking out pass the fenders and the fenders must be rolled. See the picture below:
The poke in the picture above is modest compared to some of the examples out there, however it illustrates the point. If you look again, you can also see the tire has a bit of stretch on it. Tires are the next step to getting the stance of the car right. Too wide and you overpower the wheel and rub on the control arms and fenders. Too skinny and you get an overly stretched wheel and crappy contact patch. We prefer a very minor amount of stretch, so we run a 225/40 tire with our 18×8.5s. However some people like to exaggerate the poke they have by running a skinnier tire to stretch it out more. However be warned that stretching tires causes uneven wear and can be dangerous if overdone. Finding the right size tire is one of the more important parts of wheel fitment, so be sure to read all the specs before buying. Last but not least, it’s worth noting that ride height plays a role in how your setup will look, so be sure to account for that as well when buying wheels. The lower the car, the more limited you are in tire sizes as well as wheel sizes. Fender rolling and pulling can help, as well as spacers, but they are limited in how much they can make up for. So there you have it, a crash course in wheel fitment. As always, happy wrenching. We also linked a handy fitment calculator you can play around with to figure out what will work. Enjoy