Wheel FAQ

The primary purposes of aftermarket wheels are aesthetic appeal, the potential reduction of weight by their reduced rotational mass, and the ability to accommodate wider tires.

Which manufacturer is best? This topic is highly debated. There are just too many factors to consider. The main category breakdowns are:
a. Price
b. Looks
c. Wheel weight savings over current wheel weight.

What wheel material is best? Most wheel manufacturers use various proprietary alloy compositions. There is no irrefutable evidence that one alloy is better than the other.

Which wheel construction method is best?
There is no irrefutable evidence that one design is better than the other. This website has an excellent description of the different wheel construction methods.

What is wheel offset? The offset of a wheel is the distance from its hub mounting surface to the centerline of the wheel.

Why is wheel offset important? Wheels using improper offsets can cause damage or accelerated wear on suspension components or body panels. Correct Impreza wheel offsets are:
Width …….. Offset

6.5″ ……. +53 to +55
7.0″ ……. +50 to +53
7.5″ ……. +47 to +50
8.0″ ……. +43 to +47

If your wheel width and offset is within this chart or close (+/- 2mm), your wheels have the proper offset.

Just because it fits does not mean it is right

Are there any downsides to wheels? There have not been significant amounts of problems with wheels. Heavier weight wheels, through rotation mass can multiply their weight which will result in decreased performance. For example, an additional 5 lbs per corner of wheel weight (20 lbs total) has an equivalent effect on acceleration of 50-80lbs of weight in the car. Also, as you increase wheel size, realize that you are increasing the wheel’s distance from the center of rotation. Due to wheels having rotational mass, larger wheels have a larger rotational mass. For example, spinning a 1lb weight 8 inches from the center of a wheel requires less work than spinning that same weight 9 inches from the center. Unsprung weight: “Unsprung weight is the total weight of components not supported by the springs. This includes control arms, brake components, spindles, wheels and tires. Reducing unsprung weight is a key factor to improving a vehicle’s handling.” Among other things, it allows the suspension to react faster and improves the tires’ contact with the road, producing more grip on rougher road surfaces. The easiest way to reduce unsprung weight without otherwise compromising performance is to reduce the combined wheel/tire weight. As a benchmark 205/55R16 T1S (a fairly light tire) are 21.2 lbs (RE92s are similar), and stock WRX alloy rims are 16.5 lbs, for a total of ~38 lbs/corner. See this webpage for more details on unsprung weight.

How can I be sure my new wheels will fit? You have a few options to ensure proper fitment prior to purchasing. Ask the wheel retailer and ensure you are aware of their return policies. Ask fellow Subaru owners via the Tire & Wheel Forum. Get a general idea via the calculator found on this website.

Will I need new lug nuts? This is a question to ask the retailer. It can also be an additional expense to keep in mind during the time of purchase. There are three different types of lug nuts with the main difference being the seating surface shape of the lug nut to the wheel. Remember: always keep a set of OEM lug nuts around for use with the spare, if using another type of lug nut.

What about my OEM wheels? Subaru’s OEM offering is a surprisingly good wheel. 2002-2005 Stock WRX wheels are 16 x 6.5 with a +53mm offset and weigh 16.5 pounds. Lug Pattern: 5 x 100, Lug Thread: 12 x 1.25, Lug Torque: 65 ft/lbs, Lug Nut size is 19MM. 2006-2007 Stock WRX wheels are 17 x 7 with a +55mm offset and weigh 23.5 pounds. Lug Pattern: 5 x 100, Lug Thread: 12 x 1.25, Lug Torque: 65 ft/lbs, Lug Nut size is 19MM. 2004 STI wheels are 17 x 7.5 with a +53mm offset and weigh 19.2 pounds. Lug Pattern: 5 x 100, Lug Thread: 12 x 1.25, Lug Torque: 65 ft/lbs, Lug Nut size is 19MM. 2005-2007 STI wheels are 17 x 8 with a +53mm offset and weigh 19.2 pounds. Lug Pattern: 5 x 114.3, Lug Thread: 12 x 1.25, Lug Torque: 65 ft/lbs, Lug Nut size is 19MM. When removing/installing OEM lug nuts, a deep well 19mm socket provides the best response, though a 3/4″ socket may be used as a suitable substitute. A 3″ extension will also provide additional clearance when removing/installing lug nuts. Appearance aside, the OEM wheels are strong and light with an excellent protective finish. OEM tires are Bridgestone Potenza RE92 205/55/16.

Where do I buy wheels? Every Subaru/Import performance store sells wheels. For purchasing, support your local economy or the NASIOC Vendors.

If I change wheel size, will it effect my speedometer? No, however, if you change the tire circumference, there will a speedometer variation. This website contains a nifty calculator that will assist you determining your new speedometer tolerances.

Is there a difference between wagon and sedan wheel fitment? Yes, due to the flared fenders on the sedan, it may accommodate aftermarket wheels that would cause rubbing issues with the wagon.

How important is wheel balancing? Very. Wheel balancing is a procedure that improves tire performance by ensuring that the weight of the wheel is evenly distributed. Conversely, an out of balance wheel can accelerate tire and/or suspension component wear. Traditional tire balancing methods are cheap and effective methods to prevent the downsides of an out of balance wheel.

What is radial force balancing? Advanced users, and those with wheel/tire vibrations not solved by normal balancing, might consider the additional cost of radial force balancing. Traditional balancing uses weights to offset minor variations in the weight of the wheel/tire combination around its circumference. In actual use, though, the wheel/tire combination is pressed against the road surface, and so variations in the “springiness” (or radial force) of the tire around its circumference can also cause problems. This radial force variation (RFV) does not necessarily have any connection to “high” or “low” spots in the tire/wheel, and so it cannot be corrected just by measuring runout on an unloaded wheel. The wheel/tire combination needs to be loaded (usually done by pressing a spinning cylinder against the wheel/tire combo, as in a dyno) to measure RFV and calculate weight placement to counteract it. See here for more details. This method is more expensive and runs around $20 per tire depending on your locale. Radial force balancer locator.

What about wheel weight placement? Advanced wheel balancing machines have the technology to let the technician know the optimal placement of wheel weights. This can be in the form of outside the rim, inside, or middle of the wheel “tape weights”. Other than purely aesthetic reasons, it is always best to default to the judgment of technology vs. appearance. Always specify your wishes prior to wheel balancing. Some technicians assume the owner does not want externally mounted wheel weights in the case of aftermarket wheels.

How hard is it to install wheels? Allow around one hour for install time. Professional installation, depending on your area, is around $75. This is one vehicle modification that is very simple and can be successfully accomplished by even the greenest shade tree mechanic.

How do I install wheels? Refer to the wheel manufacturer’s instructions. For wheels without instructions, below is a link to one of the better known wheel installation instructions:
tirerack.com’s instructions

Editors Note

This post was created because I wasn’t able to find a good wheel FAQ. I came up with the text based on LOTS of searching here. Upon reading this you should have an idea of what type of wheels best suit your needs. The manufacturer is up to you.

If you find an error in this FAQ, please PM me with factual details and I will update this post. Responses such as, “I have XXX’s wheels and they are great!” or “XXX’s wheel cracked after 1 month” are not appreciated here, that is what the Car Parts Review Forum is for.

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