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9 minute read
The BMW E28 Wheel and Tire Tutorial
Compliments of Shawn D. @ www.scrappycrow.com
As with most any vehicle, one of the easiest ways to change the look and performance of an E28 is by changing the wheels and tires, and this tutorial is geared to helping you find a setup that fits properly. Considering the range of opinion with regard to appearance, performance goals, driving environment, and one's financial wherewithal, trying to determine which setup is "best" is rather subjective and won't be discussed here.
The subject of wheels and tires is actually less complicated than it often seems to be, and this tutorial should clear up almost any question you might have about properly fitting wheels and tires to an E28. However, this tutorial isn't intended to be a complete A-to-Z education on the subject of wheels and tires. For that, visit a library, use Google, and check out Tire Rack's excellent wheel tech and tire tech sections.
Stock Wheel and Tire Sizes
US-spec E28s were fitted with the following wheel and tire combinations...
Size, Offset, & StyleTire SizeComments 528e
"Bottlecap"195/70-14Wheel: BBS "Basketweave" wheels in the same size and offset were offered on early models.
Tire: The 195/70-14 tire size is widely available in many tread types and performance ratings from many manufacturers.
Fitment: Will fit all non-M5 E28s running stock brakes. 533i
"Bottlecap"200/60-390Wheel & Tire: This is the infamous TRX wheel and tire setup. At the leading edge of tire technology when introduced in the early 1980s, the TRX used a unique bead design which was incompatible with standard designs. To preclude intermixing TRX and non-TRX wheels and tires, the TRXs were given non-standard sizes; 340, 365, 390, and 415mm diameters were offered on many makes and models; the 390mm is equivalent to 15.35". Over twenty years after its introduction, the TRX is considered obsolete, yet new TRX tires (when they can be found) command upwards of $200 each! If you must absolutely have new TRXs, Coker Tire is reproducing them using the original Michelin molds. IMPORTANT: 15" tires CANNOTbe safely fitted to 390mm wheels!
Fitment: Will fit all E28s running stock brakes or the common E32/E34 "Big Brake Upgrade." M516x7.5" et20
"Basketweave"225/50-16 Wheel: One of the most-common upgrade sizes for E28s, with many BMW and aftermarket wheels available.
Tire: The 225/50-16 tire size is widely available in many tread types and performance ratings from many manufacturers.
Fitment: Will fit all E28s running stock brakes or the common E32/E34 "Big Brake Upgrade." Non-M5 E28s might encounter rear fender lip interference with this setup (more on this in the "Fender Rolling or Trimming" section below); M5 rear fender lips are pre-trimmed by the factory.
Stock Wheels with Non-Stock Tire Sizes
There are a few options if you want to run non-stock tire sizes on stock E28 wheels...
Size, Offset, & StyleNon-Stock
Tire SizeComments 14x6.5" et20
225/60-14The 205/70 was fitted to E23s and E24s and will have a minimal effect on speedometer readings. Some 225/60s will fit the wheel (this must be checked against the tire manufacturer's acceptable width range), but will cause the speedometer to read approximately 7% faster, and rear fender lip interference is possible. 390x165mm et22
"Bottlecap"220/55-390The speedometer reading will be unaffected, but rear fender lip interference is possible. Due to the aforementioned obsolescence of the TRX design, this is not considered an "upgrade."
Bolt Circle, Lug Size, and Hub Diameter
E28 wheels have a bolt circle of 5x120mm, with lug bolts that thread into the hub, as opposed to fixed studs onto which lug nuts are threaded. The bolts themselves have a 12x1.5mm thread size, with a proper torque of 75ft-lbs. E28 wheels are hubcentric, with a hub diameter of 72.5mm. Note that while the standard GM bolt circle of 5x4-3/4" (5x120.65mm) is veryclose, GM wheels are not suitable for use on an E28, except in an emergency.
List of Known Wheel and Tire Combinations
The majority of wheel and tire combinations known to fit the E28 can be found in the E28 Wheel & Tire Database. It's important to understand that the database is inclusive, in that all of the combinations listed have been proven to fit. It is notexclusive, meaning that the listed combinations are not all that could possibly fit.
Spreadsheet Page TitleDescription READ THIS FIRST!So named for good reasons, the "READ THIS FIRST!" page fully explainshow to use and interpret the spreadsheet. E28 Wheels TiresThe listing of the wheel & tire combinations. If a combination you're considering isn't listed, you can input the data for it on any line after the first entry, or on the two lines labeled "TEST" at the bottom of the sheet. Size CalculatorContains formulas for "Plus X" conversions, tire diameter comparisons, wheel offset/backspacing/frontspacing calculations, and metric-to-inch & inch-to-metric conversions. These calculations can be used for most any vehicle, not just an E28. ConstantsValues which are used in the calculations in the "E28 Wheels & Tires" sheet.
Download the E28 Wheel & Tire Database in MS Excel format here (right-click and select the "save" option). This file is a zipped MS Excel spreadsheet; for questions or problems regarding .zip files, refer to Winzip's "Basic Information" and FAQ pages.
For those without Excel, you can view the E28 Wheel & Tire Database in table format. This table doesn't have the functionality of the spreadsheet (user inputs, calculations, variables, etc.), but it can be viewed by anyone with a browser. Note that this version contains only the list of wheel & tire combinations.
Spacer and Hub Bore Adaptor Usage
Some of the wheel and tire combinations listed in the E28 Wheel & Tire Database will require the use of spacers or hub bore adaptors.
Spacers are required when the offset of the wheel causes the inboard side of wheel and/or tire to interfere with the suspension. The spacer fits between the hub and the mounting face of the wheel, pushing the wheel further outboard. Two factors are essential for proper use on an E28: 1) to ensure hubcentricity, the spacer's back side bore must be 72.5mm and the spacer's front side snout diameter must be 72.5mm, and 2) correspondingly longer lugs must be used to ensure proper thread engagement. Thus, if 15mm spacers are to be used, the lugs would need to be 15mm longer than stock; if such lugs are not available, a good rule of thumb is this: for a 12x1.5mm lug, 6.5-8 full turns of the bolt are necessary to attain proper thread engagement. Spacers thicker than 20mm are generally considered too large, and spacers thinner than 5mm will likely not have the required snout to maintain hubcentricity.
E39 wheels have a hub diameter of 74mm, which is too large for the E28's 72.5mm. Thus, to properly fit them to an E28 and maintain hubcentricity, a hub bore adaptor ring is necessary. The adaptor ring doesn't change the relative position of the wheel to the hub, but ensures hubcentricity by taking up the 0.75mm gap between the E39 wheel and the E28 hub. Not using these adaptor rings can result in an imbalance/vibration condition similar to that of an out-of-round wheel and tire assembly. These adaptors can be purchased from Tire Rack, among others.
Fender Rolling or Trimming
Many wheel & tire combinations will require minor modification of the rear fender lip due to tire-to-fender interference. There are two methods: "rolling" and "trimming"...
"Baseball Bat"Depending on the available working gap between the tire and fender, a thick wooden dowel or baseball bat is placed between the between the tire and the fender lip at either end. One person guides the dowel/bat and another slowlymoves the car forward or backward. Multiple passes might be necessary.Pros: Maintains fender lip integrity and strength. The quicker of the two methods.
Cons: Imprecise. Can affect fender lip and fender profile and crack paint and detach undercoating. Forms a tight, pinched channel on the inside of the lip which can attract and hold grit, fostering formation of rust. Difficult or impossible to clean or paint/undercoat inside the pinched channel. TrimmingA Dremel or die grinder with an abrasive cutoff wheel is used to remove a slice of the inner fender lip at the interference point.
See this diagram for more information on this technique.Pros: Maintains fender lip profile. The more precise of the two methods. Does not crack paint or undercoating, and does not leave a grit-attracting pinched channel. Easy to touch up raw edges with paint or undercoating.
Cons: Takes more time. Can burn paint close to cut and affect temper of the metal if not done carefully. Slightly reduced fender lip strength.
Still Have Questions?
If, after thoroughly reviewing the info on this page, you have questions on wheels and tires for your E28, feel free to ask questions in the MyE28.com Forums!