APEX Wheels | Forged Wheel Development For 991 GT3, GT3RS & GT2RS

Reply Subscribe

Thread Tools

Search this Thread

05-18-2023, 07:48 PM

Apex Wheels

Basic Sponsor
Rennlist
Site Sponsor

Thread Starter

Join Date: Nov 2017

Location: Pleasanton, CA.

Posts: 1,250

Likes: 440

Received 635 Likes on 404 Posts

APEX Wheels | Forged Wheel Development For 991 GT3, GT3RS & GT2RS

Porsche 991 GT3, GT3RS & GT2RS Forged Wheel Development Thread

For over 15 years APEX has engineered motorsport wheels for driving enthusiasts, weekend track day warriors, and competitive wheel to wheel racers at an unprecedented value. That theme continues as we broaden our offering for a wide variety of Porsche models in both 5 lug and centerlock applications, including new fitments for the highly desirable 991 GT3 and GT2/3RS chassis.

APEX is located in the Bay Area of California, and is owned and operated by passionate enthusiasts and racers that have a keen understanding of what drivers desire in a well performing wheel. Market-specific Product Experts like myself work hand-in-hand with enthusiast communities like Rennlist to ensure that APEX is providing the best possible wheel solutions for your specific needs, and our team of experienced engineers bring them to life.

The purpose of this thread is to provide insight and transparency regarding how APEX approaches all aspects of wheel development and engineering, and to highlight the functional features and 3rd party testing that set our forged wheels apart. We'll walk through existing solutions that are readily available, as well as new fitments that are on the horizon while providing detailed notes regarding fitment, tire options, and any required suspension/alignment modifications. If you would like to see a new fitment or finish from APEX, or you have fitment or product related questions, please jump in!

Forged Sprint Line

This line encompasses the lightest motorsport wheels we make, engineered for drivers looking to shed as much weight as possible to improve lap times.

➡︎ 10K ton forged 6061-T6 aluminum

➡︎ Stronger Sprint™ spec inner lip

➡︎ Side-milled spokes for reduced weight

➡︎ Unmatched replacement program

➡︎ Independently tested and certified

Porsche 991 GT3/RS Specific Fitments

Engineering Highlights

True Motorsport Blanks - Many companies use 3rd-party blanks intended for non-motorsport wheels which can severely limit sizes, concavity, spoke design, and critical brake clearance. We designed our very own blank profiles from scratch which gives us total control over the final product, resulting in exceptionally deep spokes and stronger designs. Learn more about this interesting topic by reading our blog article, or by viewing the video below.

How APEX Engineers a Better Track Wheel - Many of you have probably heard the phrase, “All forged wheels are not created equal”, and this couldn’t be more true. Watch the video below to get a better understanding of how APEX Wheels delivers functional features that can actually be felt in the real world.

3D Laser Scanning, Brake & Suspension Clearances - When we say that we develop wheels from the ground up for each vehicle application, we mean it. Prior to the engineering phase of wheel development, we bring test vehicles into our facility for 3D laser scanning and extensive fitment testing. We use our handheld Creaform 3D scanner to scan front and rear brakes, along with other components under the fenders like suspension and brake ducting where proper wheel and tire clearance is critical.

In addition to 3D scanning the standard 380mm steel and optional 410mm PCCB brake packages for the 991 GT3/RS, we also reviewed aftermarket brake templates from PFC and Essex AP Racing as these are popular upgrades for hardcore track enthusiasts. Our team of engineers leverage the 3D scans and aftermarket 2D template files to optimize spoke and barrel designs for strength to weight, stiffness, and critical brake clearance.

Initially our goal was to provide the community with 19” wheel solutions that could clear the optional 410mm PCCB front brakes, however, even when our experienced engineers implemented a zero degree draft on the barrel (the maximum amount of space any wheel barrel can offer), the tolerance between the front caliper and the inner barrel is dangerously tight at 1 - 2 mm and did not meet our internal safety standards. In the garage, 19” wheels can technically clear, but it is important to note that wheels flex under load. At that minuscule tolerance, even if the calipers do not directly make contact with the barrel of the wheel (which we have experienced first hand with 19” motorsport wheels from other wheel manufacturers), debris will inevitably get lodged in between causing damage/scoring to the barrel. In conclusion, our policy is that 20” wheels must be used with 410mm PCCB equipped cars for proper tolerances.

FEA Analysis - We conducted extensive Finite Element Analysis (FEA) to reinforce high-stress areas and to remove material where it didn’t improve strength. The result is a wheel that is exceptionally light without the strength compromises found on typical lightweight wheels. First, we carved out as much material as possible, then we purposefully added one pound back to reinforce critical areas, creating a stronger inner lip and a higher load rating. What’s the point of a lightweight wheel if it’s fragile?

Independently Tested - We don't rely solely on computer simulations or unverifiable in-house testing. We believe independent testing is critical to protect consumers in this unregulated industry. We chose STL, an independent lab in Ohio, to test our Sprint™ wheels far above JWL standards, including increases in testing duration, impact drop height, and total load. At the end of the day, drivers deserve to know if wheel companies are truly delivering on the promises they are making. Click here to learn more about our rigorous independent testing.

Functional Features

Side-milled Spokes - To be as light as possible these forged wheel designs feature extra-deep, side-milled spokes. Any excess material that doesn’t add strength is carved out using a precision CNC ball cutter. Side-milling is often deemed cost-prohibitive by others, but for true performance without compromise we believe it's essential. Click here to learn more about our wider and deeper side-milling.

Paintless Knurled Beads - Whether it's a day at the track or months of street driving, repeated hard braking and acceleration can make a tire slip along the bead seat and go out of balance, causing vibration. Knurled beads help, but are less effective when painted over. Our forged line features unpainted knurled beads that stay sharp and maximize grip. Click here to learn more about why our forged wheels have unpainted knurled beads.

Laser-Engraved Specs - As track enthusiasts ourselves, we know how frustrating it is to try to locate and decipher wheel specs that have been hastily hammered into the rim or become unreadable over time. With our new Sprint™ wheels, we chose to invest a little extra and laser-engrave the specs on the barrel, in plain sight, making them easy to find and read. (You’re welcome.)

Forged Enduro Line

The Apex Enduro line consists of the strongest wheels we’ve ever made . Featuring our highest load rating and our strongest lip, allowing them to withstand abuse, lap after lap.

➡︎ 10K ton forged 6061-T6 aluminum

➡︎ Heavy-duty Enduro Spec inner lip

➡︎ Stiffer side-milled spokes

➡︎ Stronger 2100 lb. load rating

➡︎ Capless hub design to reduce weight

➡︎ Unmatched replacement program

➡︎ Independently tested and certified

Porsche 991 GT3 Specific Fitments

VS-5RE

The VS-5RE is the forged Enduro version of our popular VS-5 design. These wheels bring serious strength and durability to the split 5 spoke design that BMW enthusiasts love and gives endurance racers and hardcore HDPE participants a wheel that focuses on longevity and consistency.

To view all of the VS-5RE fitments available for your Porsche and order your set, Head over to our website via the link below or by clicking any of the images of these wheels.

Learn More

SM-10RE

The SM-10RE brings higher load ratings and measurable increases in strength and stiffness to our popular 10-spoke design. Initially available in fitments focused on modern M cars that are often tracked, these are perfect for wheel-to-wheel racing and focused HPDE sessions.

To view all of the SM-10RE fitments available for your Porsche and order your set, Head over to our website via the link below or by clicking any of the images of these wheels.

Learn More

Our Strongest Wheels

Most motorsport wheel designs prioritize reducing weight over increasing strength, but some applications require extra strength. High grip tires and lots of downforce put extra strain on wheels. Pair that with a faster driver and regular load ratings are not enough. Enduro line wheels are about 30% stronger than their RS counterparts.

Stiffer Spokes
Wheel stiffness matters but it gets overlooked and undiscussed. The redesigned spokes of the SM-10RE are about 20-25% stiffer than the Sprint Line version. Stiffer spokes help reduce camber loss, which reduces outer edge tire wear and improves feel and responsiveness.

Toughest Inner Lip
Introducing the Enduro™™ spec inner lip - our strongest ever. With 50% more reinforcement, these wheels are better-protected against the harsh conditions found on (and off) track.

Reinforced Front Lip
We added extra material in the front lip for more durability so you can keep attacking those berms. You can easily spot the beefed up design of an Enduro lip vs. the lightweight lip on a Sprint Line wheel.

10K Tons of Pressure
To make our forged wheels the strongest we can, we applied as much pressure as possible using a 10,000 ton forge. This extreme pressure increases the strength of the aluminum by eliminating porosity and improving the grain structure.

True Motorsport Blanks
Many companies use 3rd-party blanks intended for non-motorsport wheels which can severely limit sizes, concavity, spoke design, and critical brake clearance. We designed our very own blank profiles from scratch to give us total control over the final product.

Side Milled Spokes
One of the most prominent features of our Enduro line wheels are the extra wide and deep side-milled spokes. Any excess material that doesn’t add strength is carved out using a precision CNC ball cutter. This allows our endurance wheels to be surprisingly light for their strength. Side-milling is often deemed cost-prohibitive by others, but for true performance without compromise we believe it's essential.

Weight Optimized
We conducted extensive Finite Element Analysis (FEA) to reinforce high-stress areas and to remove material where it didn’t improve strength. The result is a significantly stronger wheel with a minimal weight penalty over their RS counterparts.

Independently Tested
We don't rely solely on computer simulations or unverifiable in-house testing. We believe independent testing is critical to protect consumers in this unregulated industry. Our Enduro Line wheels are independently tested by ITS at their Michigan facility following JWL standards but pushed to much higher loads and much longer durations.

Big Brake Clearance
From day one, Apex has been on a mission to build wheels that clear big brakes. These Enduro Line wheels are the product of everything we’ve developed over the past 15+ years. We utilize 3D scans to produce vehicle-specific spoke profiles, and our wheels feature an innovative high-clearance barrel design.

Deeper Concavity
Our new forgings were redesigned to create extra deep, concave spoke profiles. Their new shape allows us to make any profile, from flat to deep and everything in between, each optimized for a specific application using 3D laser scans of factory and aftermarket brake kits.

Paintless Knurled Beads
Whether it’s a day at the track or months of street driving, repeated hard braking and acceleration can make a tire slip along the bead seat and go out of balance, causing vibration. Knurled beads help, but are less effective when painted over. Our forged line features unpainted knurled beads that stay sharp and maximize grip.

Paintless Barrel
To be as light as possible, and to reduce rotational inertia, we removed paint from the outer barrel. It’s only a fraction of a pound but it’s in an area that has the biggest impact on acceleration and deceleration, so it packs a bigger punch vs. the same weight savings near the center of the wheel. These small tweaks add up.

Capless Hub Design
We know most track day organizations ask for center caps to be removed. To further reduce weight that doesn’t directly correlate to strength, we incorporated a capless hub design on all Enduro Line wheels in our pursuit of Real Performance.

Built for Impact Sockets
Track wheels need track tools. Don’t settle for wheels that require undersized tuner lugs or thin walled sockets. All Apex wheels accommodate over-sized race lugs and impact sockets to make swapping wheels lightning fast.

Outer Lip Pocketing
A lot of areas get extra thick when the load rating is raised to 2100 lb. By CNC machining ‘pockets’ between each spoke, our Engineers were able to further reduce weight from an area that has a high impact on rotational inertia.

Laser-Engraved Specs
As track enthusiasts ourselves, we know how frustrating it is to locate and decipher wheel specs that have been hastily marked on a wheel or become unreadable over time. Our Enduro wheels have laser-engraved specs on the barrel, in plain sight, making them easy to find and read.

Questions?
Call: 925-245-0773
Email: expert@apexraceparts.com
Web: www.apexraceparts.com

__________________
APEX Wheels - expert@apexwheels.com

Website - Blog - Instagram - Porsche Fitment Guides

Last edited by Apex Wheels; 03-19-2024 at 03:20 PM.

Reply Like

The following users liked this post:

Dreamer99 (05-18-2023)

05-18-2023, 07:49 PM

Apex Wheels

Basic Sponsor
Rennlist
Site Sponsor

Thread Starter

Join Date: Nov 2017

Location: Pleasanton, CA.

Posts: 1,250

Likes: 440

Received 635 Likes on 404 Posts

19” Performance Street & Track GT3 Wheel Setup

Front: 19x9.5” ET50 - 265/35-19
Rear: 19x12” ET46 - 325/30-19

As a performance/motorsport oriented company, our wheel development journey for the 991 GT3 naturally started out with an easy to install, versatile, and lightweight 19” setup that can be used on and off the race track. The two primary reasons enthusiasts pursue a smaller 19” wheel and tire configuration are to reduce rotational mass and to unlock a wider variety of desirable tire compounds. As many of you HPDE and W2W racers know, tires are one of the more costly consumables (think cash incinerator) and in many cases the move from 20” to 19” can help reduce the annual tire budget. Anytime we can simultaneously gain performance AND divert more cash annually towards seat time, we’re all for it!

The GT3 has alway been very impressive straight off the showroom floor, but like most cars in factory trim it has a tendency to understeer when pushed around a race track. You don’t have to be Jörg Bergmeister to experience this fun-sucking trait, it can even rear its ugly head during Sunday canyon drives and “spirited” commutes. Aside from suspension and alignment tweaks, one of the easiest ways to mitigate understeer is to increase front end grip by installing wider front tires, therefore, we took the opportunity to increase our front wheel width to 9.5 inches (1/2” wider than stock) to better support 265/35-19 tires which is the most popular front tire size upgrade. While a 265 tire can technically be installed on a 9” wheel, most tire compounds are going to perform, feel, and wear better on wider 9.5” wheels due to the added sidewall support, and the good news is that all of this is easy to implement on a stock GT3 with the right wheel offset. After 3D laser scanning and performing several rounds of on-car fitment testing with various tire compounds, we landed on an ET50 offset which positions our 9.5” front wheel near the edge of the bodywork while essentially maintaining the same inner suspension clearance as the factory 9” wheels. The result is a front wheel fitment that looks and performs better than stock, leveraging all of the extra real estate under the front fenders that Porsche left on the table.

On GT3 models dating back to the 996.2, Porsche has done an excellent job selecting rear widths and offsets that fill out the rear fender wells, and the 991 GT3 is no exception. Our 19x12” ET46 rear wheel is 1mm more aggressive than stock, and a near bolt-on solution that supports the popular 325/30-19 rear tire size that most enthusiasts desire. With that said, it is important to note that the inside lip of smaller 19” rear wheels get extremely close to the factory rear lower control arm bolts, therefore, to avoid contact these bolts must be replaced with a more low profile version from Porsche (part #999-073-530-01) to provide extra clearance. This accessible and inexpensive factory part from Porsche is easy to install, and is the only thing standing in your way from enjoying the benefits of a 19” wheel and tire package.

As mentioned, a vast majority of enthusiasts who install 19” wheels opt to run 265/35-19 front, and 325/30-19 rear. These tire sizes fully leverage our 9.5” and 12” wheel widths improving grip and overall performance, but they also replicate the 1.5% difference in rolling diameter between front and rear axles to prevent issues with vehicle electronics like TCS, ESC, ABS, etc. A vast majority of these tire compounds can be installed without any alignment modifications, but if you are going to be enjoying your GT3 on the race track where it belongs, we strongly encourage a track oriented alignment with increased negative camber to improve handling and tire life, and to get the most performance out of your tires. For hardcore (and hopefully talented) track enthusiasts looking to “win their D.E.”, there are also a few racing slicks like the Pirelli DH compound that work very nicely with these wheel specs.

On-Car Photography

Last edited by Apex Wheels; 07-27-2023 at 04:13 PM.

Reply Like

The following users liked this post:

vernontwg (01-30-2024)

05-18-2023, 07:49 PM

Apex Wheels

Basic Sponsor
Rennlist
Site Sponsor

Thread Starter

Join Date: Nov 2017

Location: Pleasanton, CA.

Posts: 1,250

Likes: 440

Received 635 Likes on 404 Posts

20” OEM+ GT3 Wheel Setup

Front: 20x9” ET47 - 245/35-20
Rear: 20x12” ET47 - 305/30-20

While the 19” setup above is our favorite performance-oriented option for the 991 GT3, there are several reasons why enthusiasts might prefer to stick with the factory 20” diameter, therefore, the second fitment we developed for this chassis was an “OEM+” 20” setup. As mentioned in our original post under the engineering section, after 3D laser scanning the optional 410mm PCCB’s our engineers concluded that only 20” wheels could provide safe tolerances between the front calipers and the inner wheel barrels. For more detailed information on this topic, you can read the engineering section in the OP or our blog article HERE.

Aside from superior brake clearance for cars equipped with the massive PCCBs, our 20” forged wheels allow enthusiasts to re-use their factory 245/305 tires while shedding a considerable amount of weight (rotational mass) in the process. Sticking with the “OEM+” theme, we took the opportunity to improve the offset of our 20x9” front wheel fitment to better fill out the front fenders and to slightly increase front track width. To be precise, our 20x9” ET47 will sit 8mm further outboard towards the front fenders in comparison to the factory 20x9” ET55.

As stated in the 19” configuration above, Porsche has historically mapped out great offsets for GT3 rear wheels resulting in a flush fitment, therefore, we decided to keep the factory ET47 offset. The final result is a bolt-on 20” wheel fitment that offers tremendous brake clearance and weight savings benefits, that sits flush with the fenders without any suspension or alignment modifications required.

We believe that a vast majority of enthusiasts that choose to run 20” wheels will stick with the factory 245/305 tire sizes. We took the liberty of listing some notable tire compounds below for your reference, and the good news is that we are slowly seeing more support from tire manufacturers in this diameter. With that said, if maxing out performance and dramatically increasing grip is your priority, you’re better off running our lighter 19” wheel setup covered in the post above which offers a wider 9.5” front wheel to better support 265 front tires.

If you enjoy your GT3 on track often and you optioned the car with the optional 410mm PCCBs, there are a couple wider tire configurations that can be used, however, tire availability is quite scarce and the overall height is going to increase which can lead to rubbing under suspension compression, etc. 255/35-20 front and 315/30-20 rear is not much taller than stock and should not result in any major issues, however, the only notable tire compounds available are the Ferrari K1 Spec Michelin Cup 2 and Cup 2R. If we move to the 265/35-20 front and 325/30-20 rear combination (which is the GT2/3RS front tire size), the front tire is tall enough that some attention may be required to prevent rubbing and tire availability is essentially nonexistent.

Notable Tire Options For 245/35-20 & 305/30-20

Max Performance Summer: Michelin PS4S (300 TW)
Extreme Performance Summer: Nankang CR-S (220 TW), Michelin Cup 2 Connect (240TW), Yokohama AD09 (200TW),
R-Compound: Nankang AR-1 (100 TW), Michelin Cup 2 (180 TW), Michelin Cup 2R (140 TW), Pirelli Trofeo R (60 TW)
Semi-Slick: Hoosier R7 (40 TW)

On-Car Photography

Last edited by Apex Wheels; 07-27-2023 at 04:14 PM.

Reply Like

The following users liked this post:

Larry Cable (05-19-2023)

05-18-2023, 07:50 PM

Apex Wheels

Basic Sponsor
Rennlist
Site Sponsor

Thread Starter

Join Date: Nov 2017

Location: Pleasanton, CA.

Posts: 1,250

Likes: 440

Received 635 Likes on 404 Posts

19” Aggressive GT3RS Track Wheel Setup

Front: 19x10” ET42 - 265/35-19 or 295/30-19
Rear: 19x13” ET45 - 325/30-19 or 345/30-19

After releasing multiple fitments for the 991 GT3 chassis covering both street and track applications, it only made sense for us to divert our attention and resources to the all mighty GT2/3RS platform. By now many RS owners had reached out requesting a lightweight 19” track oriented solution that could accommodate desirable tire configurations. Instead of mimicking the factory 9.5”/12.5” wheel widths in a smaller 19” diameter, we decided to push the limits to give enthusiasts the ultimate solution capable of supporting up to 295/30-19 front tires, and 345/30-19 rear Hoosier R7 tires. This will be the go-to fitment for those of you chasing every tenth in a Time Attack event or looking to get the most out of your RS at a track day.

Our 19x10” ET42 front wheels were carefully mapped out to accommodate 265/35-19 tires, as well as the more extreme 295/30-19 tires for hardcore track applications. The 265’s are available in a variety of popular compounds listed below, and are quite easy to fit. Depending on the compound and ride height, a small increase in negative camber may be required for fender clearance.

On the contrary, the 295 Hoosier R7 uses ALL available real estate under the RS front fenders and can get quite close to the suspension, so aside from a very healthy amount of negative camber that is considered par for the course for a semi-slick tire, other adjustments and suspension modifications will be required. At the end of the day, this type of extreme tire fitment will require ongoing special attention and may still rub at full steering lock and under heavy suspension compression, but this should come as no surprise to any driver that warrants this much grip. We plan to take much more detailed photos of this extreme fitment to help document the modifications and clearances, and will update the thread accordingly.

The rear 19x13” ET45 fills out the wide RS fenders beautifully, and has the ability to accommodate both the popular 325/30-19 and more extreme 345/30-19. The 325/30-19 is a relatively easy fit, while the wider 345 will require additional negative camber to clear the fenders. As a reminder, 19” rear wheels get extremely close to the factory rear lower control arm bolts, therefore, to avoid contact these bolts must be replaced with a more low profile version from Porsche (part #999-073-530-01) to provide extra clearance. This accessible and inexpensive factory part from Porsche is easy to install, and is the only thing standing in your way from enjoying the benefits of a 19” wheel and tire package.

Notable Tire Options For 265/35-19 & 325/30-19

Max Performance Summer: Michelin PS4S (300 TW)
Extreme Performance Summer: Goodyear Eagle Supercar 3 (220 TW), Continental Extremecontact Force (220 TW)
R-Compound: Nankang AR-1 (100 TW), Michelin Cup 2 (180 TW), Toyo R888R (100 TW), Goodyear Supercar 3R (100TW)
Semi-Slick: Hoosier R7 & A7(40 TW)

Notable Tire Options For 295/30-19 & 345/30-19

Semi-Slick: Hoosier R7 & A7(40 TW)

Another large benefit of our 19x10” ET42 fitment is the exceptional brake clearance for large/wide motorsport oriented aftermarket kits. As depicted in the brake clearance table in the OP, this wheel clears every important aftermarket brake kit we’ve tested including the PFC Race and Sport kits in both 405mm and 380mm, as well as the AP Essex CP9669 and CP9661 394mm kits. This wheel configuration truly delivers!

On-Car Photography

Last edited by Apex Wheels; 07-27-2023 at 04:16 PM.

Reply Like

05-18-2023, 07:50 PM

Apex Wheels

Basic Sponsor
Rennlist
Site Sponsor

Thread Starter

Join Date: Nov 2017

Location: Pleasanton, CA.

Posts: 1,250

Likes: 440

Received 635 Likes on 404 Posts

19/20” Performance Street & Track GT3RS Wheel Setup

Front: 19x9.5” ET50 - 265/35-19
Rear: 20x12.5” ET48 - 325/30-20

Notes & photos coming soon

Last edited by Apex Wheels; 06-02-2023 at 06:46 PM.

Reply Like