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Tire Rack's Tires, Wheels, Brakes & Suspension
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Old 03-31-2005, 09:46 AM
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LMC LMC is offline
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E46 M3 rear wheel offsets

Follow this train of logic, please:

Stock E46 M3 wheel: 18 x 9.0 ET26
Stock E46 M3 tire: 255/40ZR-18
this combination obviously clears everywhere without any issues

But 275/35ZR-18 also fits on the stock wheel without any issues, yes? Which means that the tire projects 10mm (20mm total; 10 per side) further. Assume, for a moment, that the 275 tire is the widest that will fit without any modifications (fender rolling or whatever), OK? So we'll assume that the gap between tire and fender = 1 mm.

OK, put the original 255 tire back on the wheel. The clearance should now be 11mm.

Now replace the original 18 x 9.0 ET26 wheel with a 18 x 9.0 ET15 wheel. This moves that 255 tire 11mm outwards from the centerline of the car. Now the tire ever-so-slightly brushes the fender of the car. Clearance = 0mm.

Finally, replace the 18 x 9.0 ET15 wheel with an identical wheel that is 1/2inch (12mm) narrower. 6mm less rim width = 2.4mm less section width, IIRC. Clearance = 2.4 mm.

The BBS RC wheel is manufactured in 17 x 8.0 ET38 for E46 applications and should fit the E46 M3 front just fine, although it will move the tire 9mm further out (offset went from 47 to 38mm.) This wheel would not accomodate a tire wider than 255.

The BBS RC wheel is also manufactured in 17 x 8.5 ET15 for other applications. Using the above logic, I would think it would fit the rear of an E46 M3. Admittedly the rim is a little narrower than OE and would not be good for a wider rear tire; but an 8.5 can accomodate tires up to 255.

While I still think that the BBS forged RG-R is the "hot ticket" for an upgraded 18-inch setup, the BBS RC has possibilities.

Future discussions while I await the M3:
-- OE versus aftermarket trunk lid struts: Worth upgrading?
-- Does polishing inside the fuel tank improve performance?
and others as I think of them...

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'14 X3 35i M sport
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Old 03-31-2005, 10:23 AM
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The HACK The HACK is offline
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Yes, the front will fit any normal E46. No, the rear won't, the offset is wrong and you need to roll your fenders...

Oh wait, this isn't another one of those noobs asking if M3 wheels will fit their 323Ci so they can make their Ci look like an M3. Sorry.

What is the actual rim width of the factory M3 rear and offset? I think you'd be much better off finding someone with their OEM set-up, and measure the distance from tire to fender and from tire to shock on the inside. Also, keep in mind that as the suspension move up and down, your clearance WILL CHANGE.
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Old 03-31-2005, 10:34 AM
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LMC LMC is offline
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Quote:
Originally Posted by The HACK
Yes, the front will fit any normal E46. No, the rear won't, the offset is wrong and you need to roll your fenders...

Oh wait, this isn't another one of those noobs asking if M3 wheels will fit their 323Ci so they can make their Ci look like an M3. Sorry.

What is the actual rim width of the factory M3 rear and offset? I think you'd be much better off finding someone with their OEM set-up, and measure the distance from tire to fender and from tire to shock on the inside. Also, keep in mind that as the suspension move up and down, your clearance WILL CHANGE.
What? You mean I can't put M3 wheels on my 325iT? Bummer!

As stated in the original post, factory = 9.0 wide and offset 26. And of course, you're right on the measuring part. My point was that if I calculate changes one at a time and track the theoretical differences, it appears that this odd wheel would fit. But before anyone spent hundreds on buying wheels, measurements on an actual car would be a must!

There are also centerbore/hub considerations. My E46 BBSs have 72.5mm bores. The cited E39 wheels are fitted with what BBS calls "PFS" (BBS-speak for adapters for various applications?)
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Old 03-31-2005, 03:58 PM
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The HACK The HACK is offline
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Location: People's Republic of United States
 
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Mein Auto: '06 MZ4C, '09 WRX Wagon
Quote:
Originally Posted by LMC
What? You mean I can't put M3 wheels on my 325iT? Bummer!

As stated in the original post, factory = 9.0 wide and offset 26. And of course, you're right on the measuring part. My point was that if I calculate changes one at a time and track the theoretical differences, it appears that this odd wheel would fit. But before anyone spent hundreds on buying wheels, measurements on an actual car would be a must!

There are also centerbore/hub considerations. My E46 BBSs have 72.5mm bores. The cited E39 wheels are fitted with what BBS calls "PFS" (BBS-speak for adapters for various applications?)
The current RGRs that I have comes with hubcentric rings to make sure the wheel sits on the brake rotor hub properly, the rings are snapped on with an expanding spring.

By my quick calculation, the RCs will push the edge of the rim out by ~4mm, so you are well within the acceptible range for offset, running 255s would in essence be like running a small 5mm spacer in terms of outside clearance. You would actually gain rim clearance on the inside.

The only issue here is if the "hub" will fit right, if the RCs are designed for the E39.
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