Thomson's System Motorsports 2022 Toyota GR86

[Espi]

very nice previous builds and looking forward to this build!

[systemmotorsports]

Originally Posted by Espi

very nice previous builds and looking forward to this build!

We are too! We have been waiting on GR86 order for some time. Ready to dive head first.

[shinsentuner]

Subscribed.

[Jucostud]

Pretty excited to follow this.

[systemmotorsports]

Result!






With the arrival of the new ZN8 / ZD8 2022+ Toyota GR86 / Subaru BRZ chassis, it was only right for us to document in detail our procedure for wheel fitment on the new chassis. While the previous gen FRS/BRZ/GT86 (ZN6/ZD6) conventionally utilized sizing ranging from ~18x9.5 +35 to 18x10 +44, the new gen GR86/BRZ is a bit more conservative in nature. After extensive measuring sessions and trial and error on our new car, we have accrued great data indicating exactly what it took for us to fit our “ideal spec” on this platform: #systemspec Rays Volk TE37SL in 18x9.5 +40 5x100, which can be found here in a variety of colors through us.

By now, as many of you are well aware (simply due to the fact that you are reading this), the chief issue with wheel fitment on the new generation 2022+ GR86/BRZ is the presence of the rear fender “flare” and protrusion where the quarter panel meets the rear bumper cover, alongside front inner wheel-well clearance. Under the rear “flare” where the quarter panel meets the rear bumper cover tab, there is metal that is part of the chassis that severely inhibits fitting anything that is more aggressive than an ~18x9.5 sized wheel with an offset ranging from +35 to +45. While we empathize with customers and don’t necessarily agree with permanently modifying and cutting into a brand new car, there are definitely a few steps and precautionary measures that we took in order to fit our ideal spec on this platform: 18x9.5 +40. First and foremost: Adjustable coilovers. The ability to adjust and fine-tune the ride height has proved to be invaluable to us. Ideally, we would highly recommend coilovers with adjustable tophats and linear springs, as this would afford us more inner barrel clearance in both the front + rear, which is already lacking on the new platform. Coilovers with progressive springs will definitely lack front inner strut clearance so we do not recommend it when fitting this size, and instead go with a more conservative sizing approach. Ride height is a chief factor in determining whether or not a specific fitment will cause any fouling issues, and the ability to adjust the final set height can certainly mitigate and reduce any chance of rubbing both on the inside + outside if the car is setup properly by a professional. This post discusses in great detail the data we have amassed with the new platform, and we are excited to share this with our clients who wish to run our #systemspec sets.

Like many of our customers with the new 2022+ GR86/BRZ, most have been asking us whether they can fit our 18x9.5 +40 5x100 Volk TE37SL sizing. This size is desirable, not only because it boasts a concave face which has become increasingly popular since the inception of the TE37, but also because this is the sizing that is incredibly popular with the previous gen 13+ FRS/GT86/BRZ (ZN6/ZD6), and we are finding that many of our clients are upgrading to the new gen. The desire to “re-use” previous-gen fitments will become more prevalent with our customers due to the cost-saving nature of recycling an old set they might have lying around, so we sought to document what it takes to employ this size. Below are some of the options we took in order to make the fitment work. Please keep in mind that the end-user assumes all inherent risks when choosing to modify their car; we are not held responsible for the modifications that you choose to do to your own car simply from the information provided in this blog.

Option 1: For us, compensating with a smaller sized tire, i.e. 245/35/18 or 245/40/18 allows 18x9.5 +40 to work on the street. This is a mild-stretch on an 18x9.5 width tire, but in our opinion it is still usable. We would not go any narrower than a 245 sized tire on an 18x9.5, as the stretch would become substantial if we went any smaller, leaving the inner and outer lip of the wheel dangerously exposed. Contrarily, a 255 or a 265 section tire would cause minor rubbing or require cutting of the rear fender at certain ride heights or full compression, unless further suspension modification is performed (See Option 2 below) or fender modification (See Option 3). We do indeed have clients running this size and they have not cut the rear fender flare. It has been reported that they have not experienced any rear rubbing issues when taking the aforementioned measures of compensating with a smaller sized tire (245/40/18). This is likely the most cost-effective route.

Option 2: For those who are looking to fit larger than a 245-sized tire on 18x9.5 +40 in order to maximize mechanical grip, such as a 255/35/18 or a 265/35/18, a bit more suspension modification is required. Option 2 is for those who still do not wish to cut the rear fender/rear bumper tab, but want to take advantage of the benefits of running a 255/265 tire. On our 2022+ Toyota GR86 shown above, we are running Rays Volk TE37SL, in 18x9.5 +40 5x100 effectively with a 255/35/18 Falken RT660K all around. The base specification of the wheel is 18x9.5 +43 5x100 but we have added a 3mm spacer to effectively make 18x9.5 +40 in order to simulate our #systemspec TE37SL 18x9.5 +40, and what it takes for it to fit. The presence of the 3mm spacer will also afford us more inner barrel clearance on the front of the car which is severely lacking especially at full-lock at certain ride heights. Furthermore, the rear has also benefitted from the 3mm spacer as the inner clearance with the rear inner fender liner is already dangerously close to the inside of the tire. We are equipped with 2022+ GR86/BRZ KW Clubsport 2-way adjustable coilovers which come equipped with a factory camber/caster plate on MacPherson-style suspension setups, helper spring + linear spring combo. Additionally, we have equipped our car with adjustable Rear Upper Control Arms (RUCA) - as we have learned that on a multi-link rear suspension setup, dialing the the negative camber from the top of the rear upright not only reduces the inherent stress placed on the axles, but it also affords us more outer fender clearance due to the the way the rear geometry is setup and adjusted. Contrarily, dialing solely from adjustable Rear Lower Control Arms (RLCA) does not afford us as much adjustability as we are effectively increasing the track width by extending the RLCA and pushing the bottom of the upright and hub outwards, which not only places more stress on the axles, it also brings the tire closer to the rear bumper tab due to the wider track width. While additional outer fender clearance is still gained by adjusting negative camber from the RLCA, it is marginal and not nearly as effective as utilizing the RUCA. It is recommended to use the RUCA for the bulk of camber adjustment, in conjunction with the RLCA in order to fine-tune the final alignment. It is also important to note that when equipping the car with adjustable RUCA/RLCA, sometimes the factory toe arm w/ the eccentric bolt is not enough to “zero” out the toe, therefore; we recommend pairing it with a set of adjustable rear toe arms as well. Some aftermarket adjustable toe links will come with an eccentric lock-out kit, but for those who are dialing in more than ~-4 degrees of camber which is already quite excessive, certain aftermarket toe links may not have enough threaded adjustment to “zero” out the toe after the RUCA is adjusted inward or the RLCA is adjusted outwards. We essentially combined the factory eccentric bolt with an adjustable aftermarket rear toe link to gain enough range in order to “zero” out our toe to minimize tire wear. Although not required, we also have adjustable rear trailing arms installed to provide another degree of adjustment/movement in case we needed it.

We have kept our rear fenders + rear bumper tab untouched. Even at full compression, we have not experienced any rubbing issues. It is important to note that with our adjustable RUCA paired with RLCA, we were able to achieve ~-4 degrees of camber which is what it took for us to not rub/foul on the inside and outside in the rear. The fronts are sitting at ~-2.5 degrees which came just from the factory KW adjustable camber/caster plates and a pair of camber bolts. If we took off the rear 3mm spacer (which makes 18x9.5 +43 effectively), we would rub on the inside of the fender liner at the shown ride height. Please keep in mind that all cars will be set-up differently, however; this is what it took for us to get 18x9.5 +40 effectively to work on our car. Other cars when set-up will produce varying results, so please be prepared to make any fine-tuning adjustments required, this is just what has worked for us and is proven for us. Please also modify at your own risk and own discretion. Although not required, the presence of adjustable aftermarket trailing arms would also be helpful in dialing the caster to move it away from the rear fender/bumper tab, subsequently providing additional outer clearance. It is important to keep in mind that different ride heights + different alignments settings + different tire sizes/brands will produce varying results that may not be consistent with the information we have documented, however; the information we have provided here should be a great starting baseline for determining what may work for another car.

To many, -4 degrees may be excessive on the street, however; the handling and turn-in response is improved when the front camber is dialed alongside the rear in moderation. When lowering the car on adjustable coilovers, The ZD8/ZN8 chassis may exhibit as much as -2 to -2.5 degrees of negative camber just due to the natural static ride height with stock control arms, depending on the final height of the car. Conventionally, most would utilize adjustable RLCA to “zero” out the camber for even tire wear. Due to the presence of adjustable RUCA, we were able to squeeze a bit more top clearance in order to ensure that even at full compression, no rubbing is exhibited. However, by raising the car, we were able to get away with as little as -3 degrees of camber to make this fitment work with minor rubbing issues on the plastic fender LINER (not the metal fender/metal bumper tab). Slight trimming and convincing of the plastic wheel fender liner would effectively reduce any chance of rubbing. However, we wanted to account for extreme circumstances (i.e. track ride-heights / alignments) so we pushed the envelope to see what could be done without cutting into the car, and the results are shown above. 255/35/18 Falken RT660K with about ~-4 degrees of camber, achieved through the use of adjustable RUCA, RLCA, and toe arms. We also have adjustable rear trailing arms installed, and moved the wheel forward substantially to get it away from the rear fender tab as an extra precautionary measure. However, the bulk of the topwards fender + bumper tab clearance came from the RUCA. It is also important to keep in mind that dialing in too much camber from the RUCA will bring the inner tire/barrel incredibly close to the rear inner fender liner (as if it weren’t close enough already at 18x9.5 +43. Increasing the offset above +43 would bring it even closer. +40 seems to be the sweet spot for us). Everything has been done in moderation, and a great deal of trial-and-error was performed in order to document these details in case any of our clients wish to go this route as well. (Scroll down to see Option 3 if you do not want to run this alignment / do not want to upgrade to aftermarket RUCA).

Option 3: In order to run a 255/35/18 or 265/35/18 with 18x9.5 +40 with a moderate alignment without upgrading the RUCA of the car, you will have to cut the rear fender flare + rear bumper tab of the car. Please do so at your own risk. Due to the design of the new ZN8/ZD8 chassis, this is what it will take to fit 18x9.5 +40 effectively. Below, we have highlighted and circled in red a portion of the rear flare + bumper tab that is known to cause issues at this size. This is what we will need to trim in order to make this size work while preserving a moderate alignment at our ride height, with a 255/35/18 tire. It is important to note that the Falken RT660K is an extreme summer performance tire and conventionally runs wider than most 255/35/18 tires. It will fit like a 265/35/18 when compared to some other brands. Certain tires even at 255/35/18 & 265/35/18 may not require the modification that we are performing, however; we are documenting this entire thread to illustrate and exemplify what it took for us to make this work on our 2022+ GR86. The information provided in this entire thread should only be used as reference; please modify at your own risk.



Closing Remarks: We figured that most of our customers will be going with Option 1 as this is the most cost-effective approach of fitting our ideal spec onto the car. It is important to note that during our various measurement sessions, field testing, and trial-and-error, we found that for us, 18x9.5 +40 is technically the sweet spot in terms of wheel fitment if you would like to run a 255/35/18 or 265/35/18 tire. While we could run a narrower wheel while keeping the effective offset the same without permanently modifying the fenders i.e. 17x9 or 18x9, a 255 or a 265 tire would be too pinched on a 9” wide wheel, and we figured that many are looking to maximize mechanical grip with the aforementioned tire sizes of 255/35/18 or 265/35/18. Furthermore, if we were to increase the offset to +43 or higher on 9.5” wide wheel, even at certain ride heights due to lowering the car, we have found that the natural camber brings the rear inner tire/barrel dangerously close to the rear fender liner/fender wall depending on the final ride height. This issue is further exacerbated if more rear camber is run, whether from the RUCA or the RLCA. The remedy would be to use a spacer in the rear or run an 18x9.5 +40 effective sizing, in order to keep the rear inner barrel/tire away from the rear inner firewall, or run a smaller tire size. If we were to go any lower on the offset, i.e. 18x9.5 +38, further negative camber or fender work is required on both the front + rear of the car to make it work. On the front of the car, at 18x9.5 +43, the inner barrel/tire also comes very close to the inner firewall/fender liner at full lock depending on the front alignment + ride height, so a small spacer would effectively reduce the chances of rubbing. We ran a 3mm spacer to make 18x9.5 +40 effectively to simulate our #systemspec TE37SL sizing in 18x9.5 +40 5x100. One could also raise the car to mitigate or reduce the chances of inner rubbing, in the front + rear. On our KW Clubsport 2-way adjustable coilovers, the fronts come equipped with adjustable camber + caster plates, which allowed us to fine-tune the alignment and fitment. Furthermore, we employed the use of camber bolts as well to gain additional front outer clearance.

With the great deal of information and data we have extracted from our trial-and-error sessions with the new 2022+ GR86/BRZ platform, it is imperative to keep in mind that all modifications mentioned by us are to be done at the user’s sole discretion, and that the user assumes any risks when modifying their car. We are not responsible for any modifications or any inherent risks that one chooses to perform on their vehicle.

Now, for some more photos! If anyone has any questions, feel free to give us a call or message us here, we are happy to help and assist!






In an effort to preserve the integrity of this thread and not derail the discussion / topic at hand, we have discussed in great detail the fitment guide for the new-gen GR86/BRZ, which can be found on the blog section of our site. More photos there as well!

[timurrrr]

Originally Posted by systemmotorsports

Result!

Thanks for a very detailed write-up!

Here are some of my thoughts:
1. Which RUCAs did you use?
Is that model allowed in the SCCA STX/STR/etc classes?
I believe using both RUCAs and aftermarket toe arms at the same time would not be allowed in STX/STR/etc.

2. This doesn't look like track-oriented ride height.
I know it's a matter of preference and even taste, but IMO the ride height is too low.
Even on the 1st gen car ride height like that would sacrifice how much bump travel the suspension has.
Given all the issues squeezing the tires into the fender liners of the gen.2 cars, I'd personally raise the car quite a bit to give the suspension more space to work with.
That would possibly also move the suspension closer to the "sweet spot" of its geometry and optimize dynamic camber.

3. Did you play with the amount of bump travel on the coilovers?
I see you've used KW which I believe don't provide an option to adjust the amount of suspension travel.
Since you've experienced rubbing both on the inside and outside in the rear, would it help if you used something like packers, top hat shims, or simply different model of coilovers to limit how high the wheel/tire can go by a few millimeters?
Same as (2) above, I would rather do that than focus on getting the car as low as possible.

4. -4º of camber in the rear is too much for a track alignment.
Even with soft-ish springs and stock roll bars, and relatively high ride height, -2.5º was enough for me on RE71R's at AutoX.
The wear on my rear tires has never touched the "triangles" on the shoulder of the tread.

[systemmotorsports]

Originally Posted by timurrrr

Thanks for a very detailed write-up!

Here are some of my thoughts:
1. Which RUCAs did you use?
Is that model allowed in the SCCA STX/STR/etc classes?
I believe using both RUCAs and aftermarket toe arms at the same time would not be allowed in STX/STR/etc.

2. This doesn't look like track-oriented ride height.
I know it's a matter of preference and even taste, but IMO the ride height is too low.
Even on the 1st gen car ride height like that would sacrifice how much bump travel the suspension has.
Given all the issues squeezing the tires into the fender liners of the gen.2 cars, I'd personally raise the car quite a bit to give the suspension more space to work with.
That would possibly also move the suspension closer to the "sweet spot" of its geometry and optimize dynamic camber.

3. Did you play with the amount of bump travel on the coilovers?
I see you've used KW which I believe don't provide an option to adjust the amount of suspension travel.
Since you've experienced rubbing both on the inside and outside in the rear, would it help if you used something like packers, top hat shims, or simply different model of coilovers to limit how high the wheel/tire can go by a few millimeters?
Same as (2) above, I would rather do that than focus on getting the car as low as possible.

4. -4º of camber in the rear is too much for a track alignment.
Even with soft-ish springs and stock roll bars, and relatively high ride height, -2.5º was enough for me on RE71R's at AutoX.
The wear on my rear tires has never touched the "triangles" on the shoulder of the tread.

We used RacerX RUCA, but cannot comment on the compatibility with SCCA STX/STR classes - would recommend double checking with the rulebook. Ride height has settled so it appears much lower than we anticipated, but we are able to raise it to an adequate height where we have gotten away with -3 at the minimum, and this is to fit the size that we are pushing. Still a good amount of camber but again, this is not for everyone. After much testing on and off the ground, if the sole purpose is to compete in SCCA and comply with rules, we would recommend perhaps going with a 9J wide option which some of our customers with the new ZN8/ZD8 chassis have done, with offsets ranging in the 9 +~41-+46 range with luck. The 9 +46 would effectively have the same inward clearance as the 9.5 +40, but you would gain 12mm of outward clearance. The 9.5 is an aggressive fit for sure and this guide was produced to provide a baseline for what it takes to fit 9.5 as we have hundreds of weekly inquiries asking what it takes to do it as many clients have kept their older sets from the previous gen. Any higher of an offset (I.E +45 on a 9.5J) could fit by raising the car substantially, and the use of the RUCA would not be required but we would recommend downsizing the tire to compensate for additional inner fender well clearance if cutting the fender/bumper tab is not an option (I believe modifying the bumper is not allowed, but feel free to double check on this). The KW's have a height-adjustable spring seat which allows for ride height adjustment that should not inherently affect the travel. The SPL RLCA has multiple eyelet mounting points for the bottom of the strut to limit to a degree how high the wheel/tire combo can go at full stuff, but sometimes this may not be enough. Although we already knew the answer before throwing it on the car, it is worth mentioning that we also tested an 18x10 +40 effective and this is no-go, especially for inward + outward clearance, lost ~2-3mm of inner clearance compared to ET+43 and lost ~8-9mm of outward clearance compared to ET+43. The sizing the chassis demands is far more conservative than we anticipated. Even by downsizing the tire on a 9.5J wide wheel at +43 offset, the inner barrel still does come very close to the rear inner firewall so we do recommend raising the car as the natural static camber would effectively be reduced affording you more inner clearance the higher the car is. We have much more experimenting to do but these are baseline data points we have gathered, so hopefully this helps!

[systemmotorsports]

Update - After minor shaving of the rear tab- we were able to dial back the camber to just -2.5 degrees all around. We are still sitting at 18x9.5 +40 5x100 effectively on a 255/35/18 RT660 which tends to run wide.

There is no rubbing at our height + alignment settings. Car looks and drives great!

[timurrrr]

Originally Posted by systemmotorsports

There is no rubbing at our height + alignment settings. Car looks and drives great!

Time to take it to the track?
First round of 86DC is on February 19th!

[GRinAR]

Would a +38 offset make much difference for running the 18x9.5?

[systemmotorsports]

Originally Posted by GRinAR

Would a +38 offset make much difference for running the 18x9.5?

Yes, we would likely recommend compensating with a smaller tire to make that work. Of course, this depends on what is done suspension and chassis wise at the tab.

Our blog discusses this in great detail and we have since updated it with more photos this week.

[systemmotorsports]

Recaro RSG in Alcantara installed.

[_____That_-_GUY_____]

Great info. Very detailed.
What's your thoughts on the most aggressive wheel/tire combo you could do with stock suspension + camber bolts up front, with no rubbing?

[systemmotorsports]

Originally Posted by _____That_-_GUY_____

Great info. Very detailed.
What's your thoughts on the most aggressive wheel/tire combo you could do with stock suspension + camber bolts up front, with no rubbing?

In my opinion, likely 18x9 with an offset of around ~40 to ~45 depending on tire size.