2023 Toyota GR Corolla: Aftermarket Parts Measuring Session Takeaways

Its brakes are bigger than the Toyota GR Supra 3.0's.

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There's been immense excitement about the 2023 Toyota GR Corolla after its official unveiling back in April. Driving impressions are now live, too, which only deepens our interest in this high-performance, all-wheel drive hot hatch. Recently, I had the opportunity to take a closer look at this latest Gazoo Racing creation in Core, Morizo Edition, and Circuit Edition trims, and see some of the engineering behind what makes each a capable, corner-carving contender. From unique aerodynamics to chassis tuning, substantially upgraded stopping power, and a closer look at what makes it a drift-able sport compact, I gained some solid perspective from performance engineering staff who were on-hand to show me around and answer any questions.

Full disclosure: Toyota invited me to SEMA's (Specialty Equipment Market Association) headquarters in Diamond Bar, California, to examine the 2023 Toyota GR Corolla. It partnered with DG-Spec's team of experts (the same team behind this beastly and badass Toyota C-HR) to host what the industry calls a measuring session, which is when aftermarket companies are invited out to test-fit parts and measure components for product development. The event also lets the media take a closer look than what you typically see at a press drive event—naturally, I had to take part. I was also treated to a free box lunch and all the coffee I could drink.

One of the most immediately noticeable differences between the GR Corolla and its more everyday-looking counterpart is its bodywork. It's wider and more aggressive and features some neat aerodynamic and cooling properties that help up its track-ready posture. On the hood are two vents for helping pull out heat coming off of its 1.6-liter three-cylinder G16E-GTS turbo engine. They've got rain gutters underneath to protect the engine's electronics from any unwanted moisture, but these can be quickly removed at a track day to help cool off the angry little engine.

On the front bumper, there's a direct feed to the air box to get a healthy dose of fresh air to the intake, as well as two brake cooling ducts and two air curtains to improve stability on track. When you look closely at its expansive grille, you notice that it's not only very open to the outside world, but there's also a flap that helps send more air over the intercooler to the GR's large radiator.

Underneath the hopped-up Corolla lives a substantial undertray, and right in the middle of it, aft of the front wheels is a large cut out to direct air. However, what this air is intended for isn't perfectly clear to me yet—perhaps it's meant for the area where the driveshaft exits the transmission to bring power to the rear wheels, or, perhaps it helps increase the amount of air that's heading to the rear coupling and differential at speed. Folks on hand weren't entirely sure either, but there's a good chance its intentions are for cooling.

One of the coolest features about the 2023 Toyota GR Corolla is the ability to change the torque split between the front and rear wheels—60:40 (Normal), 30:70 (Sport), or 50:50 (Track), which is done by a quick turn of a knob on the center console. This means that the GR can be configured for a generous helping of grip, or some hilarious and controllable tail-out slip. To make slides easier, Morizo and Circuit Editions get Torsen limited-slip differentials (LSDs) as standard, whereas LSDs are part of the Performance Package that's available on the base Core trim.

An electronically controlled, electromagnetic multi-plate clutch pack, otherwise known as an Intelligent Torque Controlled Coupling is attached to the rear differential and is where changing the torque split takes place. Inside are a series of wet clutches, and the front-rear torque split is altered by changing their clamping force. The higher the clamping force, the more torque is sent to the rear wheels (such as at 30:70), allowing for glorious drifts.

Interestingly, when the Corolla is lifted in the air and in first gear, unloaded, the rear wheels spin 0.7% faster than the fronts. In other words, the rear differential is geared faster than the front. According to Nik Romano, a member of the on-hand staff, this is necessary for more torque to be sent to the rear wheels. "This system would not bias the torque unless they were going different speeds," Romano said. "It would just be engaging or disengaging the rear diff, it would not be changing the torque split."

Pun intended here—the GR Corolla's brakes are quite cool. I had an inkling they'd be after doing a little investigating back in April, but Toyota's press materials didn't allude to as much as I found out at SEMA's headquarters. First of all, its front rotors are bigger than those found on the much more powerful and heavier GR Supra 3.0. The Corolla's measure in at 14 inches, whereas the Supra's are 13.7 inches.

Not only that, but the two-piece front rotors are sourced from renowned performance brake company Advics, and the pads that occupy their accompanying four-piston fixed calipers are from Akebono. As on-hand engineering staff pointed out, Akebono builds brakes for Japan's bullet trains, so we can be confident that the brand is up to the task of making a compound that slows down a 300-horsepower hatchback.

Taking a closer look at the front discs, they feature unique venting to help rid them of heat—check out the vent's curvature and v-shaped ends compared to the more conventional single-piece rear rotors. Combined with massive pads and cooling ducts, there's no question that the GR Corolla has well-above-average braking force for its size and power.

Engineering staff also pointed out that the brake pads appeared to have at least 75% of their material left, meaning a week's worth of journalists' thrashing at the press drive event at Utah Motorsports Park (UMP) barely wore them down. Granted, Toyota technicians could've swapped the pads during their week at UMP, but if not, mad respect is due. This will also translate to powerful, confident stopping power on the street—isn't it great when track performance comes in handy elsewhere?

Something that my fellow aftermarket wheel nerds will dig, is that the Morizo Edition's lightweight, forged, satin black 10-spoke wheels are made by BBS Japan. This firm also produces the 19-inch wheels found on the Lexus RC F Fuji Speedway Edition. The engraving on the lip of the wheels is such a cool little touch, too, and on-brand for wheels of a similar caliber by big names like Rays, Work, and Yokohama.

Lower-priced models aren't left out in this department, either, as their gloss black 15-spoke wheels are made by Enkei, another brand that's a byword for quality.

At first glance, the GR Corolla's suspension isn't much different from the base, everyday, front-wheel drive model. Like the Corolla Apex or XSE, it has very conventional front MacPherson strut suspension, which will get the job done, but isn't exactly exotic fare. At least camber adjustment is quite easy with a set of aftermarket camber bolts.

However, the GR's business end is a very complex-looking multi-link setup, with a sway bar and accompanying end links that appear to be of above-average beefiness, a divorced spring and damper (meaning, not bolted together) design, and parts that just look more substantial than you'd expect from a compact hatchback. Time will tell how much meat will be left on the bone for aftermarket suspension companies to play with here, and figuring out a rear sway bar shape that will clear the rear differential will have to be a special consideration, as these two components are pretty close to each other from the factory.

Unfortunately, I wasn't able to dig deeper into the GR Corolla's damper tuning and spring rates. However, the Morizo Edition gets KYB performance shock absorbers, and damping across all trims is passive, not adaptive (meaning, comfortable or sporty damping at the press of a button) like the units found on the Veloster N or Honda Civic Type R. Still, by all accounts and by our very own Kristen Lee's driving impressions, the GR Corolla has excellent suspension.

The suspension top hat mounts appeared to be thinner and of a stiffer rubber material than I've seen before, which could contribute to the GR's stiffer, sportier suspension tuning.

As far as chassis rigidity goes, Toyota did some cool stuff to enhance the GR Corolla's over the base (non-GR) hatch. It features 349 more chassis welds and over 9 feet of additional structural adhesive, with the Morizo having almost 20-whole-feet of additional adhesive tacked on. That's the modern version of Acura stitch-welding up the Integra Type R back in the day.

Then, in place of rear seats in the Morizo are two large pieces of chassis bracing, plus a rear strut bar. The braces are configured so that hauling track day supplies, or even a second set of wheels, would be very easy and convenient to do. Who says hatchbacks need rear seats? If cargo is thrown in with conscious craftiness, the bracing would act as a great way to organize and tie stuff down, too. Hilariously, the rear doors have handles and cup holders in their cards, but special blank plates occupy where the window switches would be. So, if you happen to ever ride illegally in the back of one, you can set your drink down in the card's designated cup holder, but you're not allowed to roll down the window, and must instead ask the driver to do so.

I had a grand time taking a closer peek at the 2023 Toyota GR Corolla. Heck, it was just nice to get away from a laptop screen for a few hours and nerd out about engineering with some fellow car nerds.

There's a lot of cool stuff going on under this hot piece of kit's skin, and sadly, it might be the last of its kind. At least in ICE form and well-below Porsche 911 GT3 money. Props to Toyota for putting so much into it, and again, if you haven't already, check out Kristen Lee's on-track impressions, which truly bring all of the cool stuff I discovered to life.