A wheel is useless if it doesn’t clear your brakes. When it comes to clearance, most people focus on the spokes. You can fix that problem with simple spacers. But if the barrel touches the caliper, there’s almost nothing you can do to make that work.
Most aftermarket wheels available today are built to clear standard factory brakes and some aftermarket kits. If a wheel doesn’t fit, then wheel manufacturers expect you to simply move up in diameter. That’s fine and dandy on the street, but on the track, there’s a big advantage to running smaller-diameter wheels and tires.
Recently, BMW and other automakers have started to build cars with brakes that are equal to or larger in diameter than typical aftermarket kits used. The last thing you want is to be forced to move up to 19” or 20” wheels for track use when a smaller diameter could fit. We cringe just thinking about the extra weight and costs!
At APEX Wheels, we strive to get the smallest-diameter wheel onto a car when possible, and that goal has made a big impact on the design of our barrel profiles. For over 10 years now, we’ve been collecting caliper-clearance data and tweaking our profiles. We carried that knowledge forward into our new forged line—which brought us to a major obstacle.
Most of the forged blanks readily available on the market suck for our needs. The blanks are usually designed for street use, where caliper clearance wasn’t much of a consideration before developing the forging dies.
After reviewing our options, we were forced to develop our own new dies and toolings to create the profiles we need. It’s a major investment: Just one new die set is about $100,000, and we needed many of them. But doing so has given us full control over every part of the design.
Developing these toolings and dies has delayed the release of our wheels, but we’d never compromise on this important feature by rushing.
The APEX difference
What does this all mean? It means our 18” wheels have the barrel clear for a 380mm Brembo BBK at all widths. Our 19” wheels can clear the factory carbon–ceramic brakes on the F8X M3 and M4, and the competition brakes on the M2.
It’s easy for us to spot when unoptimized profiles are being used in performance applications by the competition, as the barrel shape doesn’t make sense for the application the wheel’s are being sold for. We came across tons of non-ideal forgings during our initial supplier research and factory tours.
Below is a comparison of the profile we use on our 18×9” BMW wheels versus the barrel found on a Titan 7 TS-5 wheel. You can see that our barrel curves up and around the caliper instead of cutting directly through it. This has a big impact on what does and doesn’t fit. Note: it looks a bit like our barrel is touching the caliper, but the line thickness on this small scale image makes that gap look much smaller than it is.
The table below helps illustrate the impact a barrel profile can have on an entire line of wheels. It compares the clearance of a Brembo 380 mm BBK behind various 18” BMW wheel sizes from APEX, Titan 7, and BimmerWorld. Almost all of their sizes require you to move up to a 19” just to fit this kit, which is far from ideal for track use.
|Brembo 380mm BBK Clearance: BMW Fitment|
|Size||APEX Forged||APEX EC-7
|18 × 8.5”||Yes||Yes||No||No|
|18 × 9.0”||Yes||Yes||No||No|
|18 × 9.5”||Yes||Yes||No||No|
|18 × 10”||Yes||Yes||No||No|
|18 × 11.0”||Yes||Yes||N/A||N/A|
Similar issues emerge when comparing 19” sizes. Ours barrels can clear the factory carbon ceramics on the M3 and M4 and the competition brakes on the M2, whereas some others cannot.
|M3/M4 Factory Carbon-Ceramic Brakes|
Do your research, or it may not fit
In summary, when you’re researching wheels, be sure to check caliper clearances. Companies are often vague about clearances, leaving you with a surprise after you buy, which could block a future brake upgrade or require an immediate return.
“Clears most big brake kits” is a line used to advertise many wheels that can’t clear the large kits ours can. This downplays the issue. Know before you buy. Confirm whether you will get the clearance you need.
We’ve been rolling out caliper-clearance matrix tables in our vehicle fitment guides, and we’ll continue to expand on those for our forged line of wheels so we can be as transparent as possible.