# How We Know What Fits



## Eric @ TIRE RACK (Jan 27, 2000)

*HOW WE KNOW WHAT FITS*

Wheels come in all different styles, sizes, bolt patterns and offsets. So how do we know
which wheels will fit your vehicle? We can only do this by first knowing your vehicle inside
and out. Measuring your vehicles critical components with sophisticated electronic tools
allows our fitment engineers to create extremely accurate drawings of these parts. We do
the same for the wheels that we offer and then use Computer Aided Design (CAD) programs to match the wheels to the vehicles. Using these electronic tools we verify numerous different critical areas before a wheel can be listed for a vehicle.
Proper fitment engineering allows The Tire Rack to offer Tire and Wheel Packages that are
specifically designed for your vehicle. Our attention to detail prevents vibration, wheel/
tire interference and unbalanced handling that can result from improperly designed pkgs.
If the offset of the wheel is not correct for the car, the handling can be adversely affected.
When the width of the wheel changes, the offset also changes numerically. If the offset were to stay the same while you added width, the additional width would be _split_ evenly between the inside and outside. For most cars, this won't work correctly. My Tech Department has test fitted thousands of different vehicles for proper wheel fitment. That database along with my extensive VAG knowlegde allows me to offer you someone who knows what you need to know. If I list it for your car that means it will fit on your car sans modifications.

*OFFSET*
ET = Offset of a wheel. This (typically), two digit number is normally stamped somewhere
on the wheel. See the above diagram to see how Et is measured. The offset of a wheel is the distance from its hub mounting surface to the centerline of the wheel. A higher Et will bring the wheel inbound, lower brings the wheel outbound. The offset can be one of three types.
Zero Offset
The hub mounting surface is even with the centerline of the wheel.
Positive Offset
The hub mounting surface is toward the front or wheel side of the wheel. A + Et wheel has the hub mounting surface toward the front (outbound side), of the wheel. *Positive offset wheels are generally found on front wheel drive cars and newer rear drive cars*. A +Et wheel has the hub mounting surface toward the front (outbound side), of the wheel. 
Negative Offset
The hub mounting surface is toward the back or brake side of the
wheels centerline. "Deep dish" wheels are typically a negative offset.
To understand Wheel Offset (Et) for the typical/non-technical user, I'll use this analogy: Vehicle Alignment - You don't normally tell your Alignment Specialist/Shop/ Mechanic what you want your alignment specs to be. You normally just take him (or her), the car and let 'em have at it. The Mechanic then sets your vehicle's alignment based on the information that the Vehicle Manufacturer has stipulated. The alignment gets set "within spec," i.e., within the OEM recommended range + or - whatever the Specifications specify. As long as the shop stays within that range then there is normally nothing to be concerned about. This is totally understood and acceptable by most.
Wheel offset (ET) is pretty much like that. With some exceptions, as long as the wheel doesn't stick out past the fender lip or rub on the inner fender well, or suspension component(s), then you're pretty much good to go. For the majority of the folks that I talk to, rolling fender lips, etc. are things that most don't want to mess around with. So in general terms, when it comes to ET, don't second guess the Wheel manufacturers. They employ Design Engineers that make the big bucks. I'm pretty sure that they know what they're doing.
As long as you purchase wheels from a reputable company, such as *The TIRE RACK* you are assured that the wheels that are offered for your vehicle are designed, engineered and manufacturered for your specific vehicle.
Caution: Sometimes Coilovers use longer springs and can sometimes relocate
the spring perch. This could/may/will put the spring perch in closer proximity
to the tire sidewall. In this scenario, spacers may be needed.
*OFFSET -VAG SPECIFIC* 
*The "ideal" offset for the majority of VAG cars is approximately Et 35*, Plus or minus (+ or -), a little bit one way or the other. A "range of Et's will work on your vehicle, you are not limited to one specific Et just because it's the one that came on your vehicle OEM. Since I only sell guranteed wheel fitments for your vehicle, you can check FAQ - Wheel Tech, or *UPGRADE GARAGE* to find the size you are looking for, view the listed wheels, compare the Et and wheel width's that are provided against what you are thinking of
going with and thus have a pretty good idea what will fit.
Once again, bottom line, ET is + or - so much, i.e. there is a range that works on
your vehicle. You are not limited to one particular, or identical ET for your vehicle.
Wheel & Tire Package Benefits
Centerbore / Hubcentric Rings
Proper Lug Torque
Lug Hardware 
Tools 

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As Moderator of The Wheel & Tire Forum, I ask
that if you require my technical input, please
include my name, *Eric* as the 1st word in your
post/question Topic Title.
If at all possible, Please refrain from Emailing Me.


_Modified by Eric @ TIRE RACK at 12:59 AM 5-4-2005_


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