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      01-07-2011, 11:43 PM   #1

Drives: E30 M3, F10 M5
Join Date: Jun 2009
Location: Bay Area, CA

iTrader: (6)

Post APEX ARC-8 Product Details: Z4 M & non-m

APEX ARC-8 Product Details and Specifications:
Light Weight Wheels for the E85 and E86 Z4

Use this thread to discuss any fitment questions regarding the ARC-8 wheels and the E9X M3 application. With the product line up continually expanding, we will keep this first post updated with added sizes, and specification details.


17x8.5" ET40 (17.0lbs~)
17x9" ET42 (17.2lbs~)
18x8.5" ET40 (18.45lbs)
18x9" ET42 (18.65lbs)
18x9.5” ET35 (18.85lbs)
18x9.5” ET22 (19.00lbs~) Available February-March 2011
18x10” ET25 (19.95lbs)
18x10.5” ET27 (20.45bls) Available 1st week of February 2011

All wheel are produced with a BMW specific center bore. No centering rings used.
Wheels accept TPMS sensors, OEM Lugs, and OEM center caps


APEX ARC-8 wheels were designed to meet the specification needs of HPDE, race, and autocross drivers, while exceeding the requirements for every day street use. This makes them the perfect cost effective, dual duty wheel.

Meeting the Performance Enthusiast’s requirements:

Light-weight: Flow-forming allows for a significant reduction in rotational mass by reducing barrel weight. This manufacturing technique allows the ARC-8 wheel to be almost as light as a traditional forged wheel, but without the significant increase in price.

Strength: Track duty requires a wheel that can handle the punishment of high lateral G’s, hitting berms, and every once in a while a small off track excursion. Spoke and barrel design are a major factor in wheel strength. The flow-forming technique uses high pressure disks/rollers to roll the wheel’s barrel into its final shape. This gives the barrel the same strength properties as a forged wheel, since monoblock wheels go through a similar step to form their barrels. The ARC-8's mesh design helps evenly distribute loads from the barrel to the center of the wheel. The lack of a front lip, and spokes directly connecting to the edge of the wheel, also add increased strength to the outer lip of the wheel. Although a front lip can reduce weight, it can also make the wheel much more prone to bending, and this was an important factor when developing the wheel.

Once a design is selected, it needs to be tested and certified for strength. The ARC-8 wheels were not just FEA tested in a computer simulation, or in house tested to an unregulated standard. They follow Japans JWL standard, and are 3rd party tested there by the VIA in Japan. All 18" ARC-8 wheels have a 690KG load rating.

Proper tire fitment: Stretched rubber, narrow tires, and fender rubbing are not elements to look for in a competitive wheel/tire setup. The ARC-8 wheels were designed with offsets that allow for proper fitment of extreme summer, and r-compound tires. This means keeping the tire under the fender, and away from suspension components. Track oriented wheel widths are also important as they provide proper sidewall support under hard cornering. Too much rubber for a wheel results in excessive sidewall deflection, which translates into sloppy and delayed turning response.

Multiple fitments: The ARC-8 comes in a wide range of fitments so that the correct wheel and tire combination can be selected for each specific application. There is no "one size fits all" in the wheel and tire world.

Most BMW’s come with a staggered setup. Some choose to keep their car this way, while others like to switch out for an easy to rotate, square/neutral setup. This is generally based on driver’s preference in addition to costs. The Z4 M and non- M can be run as either a square or staggered setup.

Square setups are great for budget minded enthusiasts who want to extend their tires life by rotating between events, in addition to preferring the balanced feel of a square setup. Square setups are popular on all 3 series models for track use due to the significant increase in front grip and turn in response. Non-m Z4's will be limited to 8.5" and 9" widths for optimal wide tire fitment. The Z4 M, can even run 9.5" wheels square, but it will require added negative camber up front. For those who prefer more rubber in the rear, a staggered setup is the way to go. 9.5", 10” and in certain applications the 10.5" wheels can be run on the rear of the Z4 M. These can be combined with 8.5", 9" or 9.5” fronts. The Non-m cannot run wider then a 9" rear due to offset limitations.

BBK clearance: Many owners install Big Brake kits on their cars. Having an 18” wheel that can clear large calipers is a must. Barrel clearance was increased during the design phase to accommodate StopTech’s 380mm kit. The only kit that poses an issue at this time is the 380mm Brembo setup.

Meeting the needs of Daily/Street use:

Aesthetic design: Although the ARC-8 put function over form when meeting the above requirements, there is no denying that concave mesh wheels look at home on a BMW.

Paint finishes: All the wheel have a multi-coat painted finish including a full clear coat except for the Satin finish which does not have a clear (that would have made it gloss black). To give owners more options the wheels are offered in 4 different finishes. Hyper Silver, Hyper Black, Anthracite, and Satin Black. Not everyone wants their track day wheels to be grey.

Multiple fitments: Due to the more conservative nature of street use, the ARC-8 wheel is also available in sizes that can fit more street oriented rubber, at offsets that are an easier fit. Wider more aggressive wheels can be used by those who like a more flush/filled out look. The choice is yours.

Abuse of street use: The world is full of pot holes and random things to run over. APEX wheels have an excellent history of handling abuse. To date we’ve only had one wheel with a minor bend and another with a hair line crack on the inner barrel lip. Both these wheels came from the same dedicated race car, and the bent wheel is still out there racing today.

Certification: The race track has no wheel strength requirements, but the street does. Sadly the USA has very lenient/minimal regulations of wheel strength, unlike like Japan and Germany. APEX wheels are independently tested by the Vehicle Inspection Association of Japan (VIA) to the JWL standard. Wheels tested to the JWL standard require all wheels on the road to meet specific load rating requirements based on the bolt pattern, and dimensions of the wheel, the application/vehicle model has nothing to do with it. In comparison, wheels tested to the SAE standard in the USA can pick their own load rating, which can be as low as they want. This defeats the purpose of the test, as a wheel manufacturer can choose to underrate their wheels in order to reduce wheel weight. Wheels claiming JWL testing, but no 3rd party verification are prone to certifying untested/unproven wheels. VIA certification can not be done in house. It requires sending wheels/tires to japan for crush testing. Sadly a large number of vendors claim their wheels are VIA, JWL and even TUV certified, when in fact they were never tested by those organizations at all, and in some cases don't even meet the standard requirements of those tests. For this reason the certificate numbers for the ARC-8 wheels have been listed below. Self regulate the market, and ask all vendors to back up their claims. If they were tested, then they'll have the registration numbers.

18x9.5” ET35: VIA15-0461
18x9.5” ET22: in testing
18x10” ET25: VIA15-0462
18x10.5” ET27: VIA15-1388

Originally Posted by
Only after VIA registration has been completed can VIA marks or limited load marking be displayed on products. However, specified marks and load indication marks should be used.
As the VIA mark is a registered trademark, using it without VIA registration means unauthorized use, hence illegal.

VIA marks cannot be used simply because the products have passed the internal inspection test.
Products also have to undergo a documentary judgment with data (test report) from a certified testing equipment and file for an application to have them registered with VIA before displaying any VIA mark.

Z4 M Wheel/Tire size recommendations

Fitments are general recommendations and not guarantees. They will continue to get more precise as feedback from customers is collected

Square Setup

18x9" Front & Rear with 245/40/18 - Spacer used in the rear
18x9" Front & Rear with 255/35/18 - Spacer used in the rear - Front spacer may be needed depending on tire type used
18x9" Front & Rear with 265/35/18 - Spacer used in the rear - Front spacer needed, spacer thickness depends on tire type used
18x9.5" Front & Rear with 255/35/18 - Front spacer and negative camber needed
18x9.5" Front & Rear with 265/35/18 - Front spacer and negative camber needed

Staggered Setups

18x8.5" - 235/40/18
18x8.5" - 245/40/18
18x8.5" - 255/35/18
18x9" - 245/40/18 - Popular fitment
18x9" - 255/35/18 - spacer may be needed depending on the tire type used
18x9" - 265/35/18 - spacer needed, thickness depends on tire type used
18x9.5" - 245/40/18 - Spacer and negative camber needed
18x9.5" -255/35/18 - Spacer and negative camber needed
18x9.5" -265/35/18 - Spacer and negative camber needed

18x9.5" - 265/35/18 - Popular fitment
18x9.5" - 275/35/18
18x10" - 275/35/18 - Popular fitment
18x10.5 - 275/35/18 - aggressive fitment

Z4 non-M Wheel/Tire size recommendations

Fitments are general recommendations and not guarantees. They will continue to get more precise as feedback from customers is collected

Square Setup

18x8.5" Front & Rear 235/40/18
18x8.5" Front & Rear 245/35/18 - Front Negative camber needed - front spacer most likely needed
18x8.5" Front & Rear 255/35/18 - Front Negative camber needed - front spacer needed
18x9" Front and Rear 245/35/18 - Front Negative camber needed - front spacer needed
18x9" Front and Rear 255/35/18 - Front Negative camber needed - front spacer needed

Staggered Setups

18x8.5" - 225/40/18 - Popular fitment
18x8.5" - 235/40/18
18x8.5" - 245/35/18 - Negative camber needed - front spacer most likely
18x8.5" - 255/35/18 - Negative camber needed - front spacer needed
18x9" - 245/35/18 - Negative camber needed - front spacer needed
18x9" - 255/35/18 - Negative camber needed - front spacer needed

18x9" - 255/35/18 - Popular fitment
18x9" - 265/35/18 - depending on tire type

Photo Threads for ARC-8 wheels:
APEX Official wheel gallery


Last edited by Eddy@ApexRaceParts; 01-13-2011 at 04:03 PM.