Running 18" Wheels On GR Supra? Choose your tires wisely.

TECHNICAL DISCUSSION (https://www.apexraceparts.com/blog/category/apexraceparts-technical-engineering-info/)

RUNNING 18” WHEELS ON GR SUPRA? CHOOSE YOUR TIRES WISELY.

Our 18” flow formed wheels have become a very popular option for GR Supra owners looking to decrease wheel diameter in pursuit of reduced rotational mass and lower cost of consumables. However, we’ve received feedback that some aggressive tire fitments in taller sizes have caused rubbing issues with the OE spring perch on the front struts. We wanted to create this post to give Supra owners an idea of what various tire fitments look like on the A90 platform with our 18×10” ET30 wheels, and bring up additional points to consider when selecting tires in general.

BACKGROUND

Our 18×10” ET30 SM-10 wheels for GR Supra can be run either as a square setup or as the front wheels on a staggered fitment with our 18×11” ET40 SM-10 wheels in the rear. Had these wheels been designed for use purely as a front wheel, the ideal offset would be lower than ET30 to give more clearance around the front strut assembly. But because we knew a rotatable 18×10” square fitment was in demand, these wheels needed to be a direct fit in the rear of the car as well, thus the slightly higher offset. As you can see in these images, an 18×10” ET30 sits just within the rear wheel well of the car.

18×10” ET30 SM-10 with 285/35-18 Pirelli P Zero tires front & rear. Front 5mm spacer required for clearance. Photo/Car credit: @nibble (https://www.supramkv.com/members/3673/)​

With the ET30 offset in the front, the OE spring perch within the A90 Supra wheel wells becomes a factor when it comes to tire clearance. The spring perch captures the lower end of the coil spring and consists of a metal plate and rubber isolator pad. Aggressive tire models that run wide in taller 18″ fitments (e.g. 275/40-18) can contact not only the rubber isolator on the spring perch but also the metal plate.The portion of the pad that comes into contact with a wide wheel-and-tire package can either be trimmed or allowed to “self-clearance” to gain a few more mm of space on the inner edge, but if the steel perch is contacting the tire, the plate needs to be ground down slightly. Here are some images of the strut assembly and perch itself with the potential areas that might experience rubbing highlighted.

This limited clearance issue with the OE suspension affects the models and sizes of front tires you can run on these wheels as a direct fit. And if your goal is to run these wheels and tires as a rotatable, square fitment, this would necessarily impact your rear tire choice as well.

There are a few options to improve inner clearance that do not involve the tires themselves:

• Upgrading to aftermarket suspension with better inner clearance​
• Upgrading to a coilover with a smaller overall diameter than the OE spring-and-perch configuration, or a reduced stack height that moves the springs up and away from the tire, will improve inner clearance. Motorsport-oriented coilovers like MCS or JRZ tend to have a more compact design and a slimmer overall silhouette that maximizes inner clearance on most applications.​
• This is obviously the most expensive option and should be done primarily for improved suspension performance, with better inner clearances being a secondary benefit of the upgrade.​
• Certain HAS (height adjustable spring) kits have been reported as increasing inner clearance as well. We have a customer running an HKS HAS kit with 19×11” ET40 wheels up front with no spacers. Not all HAS kits will increase inner clearance, though, so purchase with care.​

• Running a front spacer
• This is the simplest option for customers looking to run taller tire configurations in aggressive tire models that run wide.
• Spacers move the wheel-and-tire package away from the strut and spring perch. 5mm spacers have typically been enough to resolve any rubbing issues with the tires we’ve seen and leave enough of the OE hub-centric ring exposed to keep the wheels hubcentric and prevent vibrations.
• The spacer may move the wheel and tire out far enough to create contact between the upper portion of the tire on the outside edge and the fender during heavy suspension compression. This can be dialed out with additional negative camber.
• Be sure to run extended length bolts or a stud conversion kit with any wheel spacers.

• Trimming of the rubber isolator pad and grinding of the OE steel spring perch
• There is enough rubber material on the outer edge of the strut to remove some of it, and to grind away a portion of the perch to improve clearance, but this needs to be done with care.
• This is the cheapest option but it is obviously the most invasive.

TIRE DATA

While the above alternatives are all viable options, we recognize that the majority of our customers running these wheels are looking for a bolt-on solution with their wheel-and-tire setup. With that in mind, this section will cover the fitments we’ve seen thus far that have either been a direct fit with zero modifications needed, or had rubbing issues, as well as what steps were taken to resolve those issues. Tire data and measurements used in this section are taken from Tire Rack or the manufacturer’s website when available.

A brief summary for this section: If you are looking for an easy fitment, tires with shorter sidewalls are the go-to option, including most 275/35-18 and 265/35-18 tires.

265/35-18

Tire model: Hankook RS-4 (200 TW) Section Width: 11″ Overall diameter: 25.1″ APEX Notes: Direct fit RS-4s are known to run wide across their range so most other 265/35-18 tires will have much better clearance than the RS-4 pictured below. Photo credit: Joe McGuigan

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265/40-18

Tire model: Continental Extreme Contact Sport (340 TW) Section Width: 11.2″ Tread width: 9.4″ Overall diameter: 26.3″ APEX Notes: Direct fit. This is another tire that runs wide despite the listed size. This tire clears the OE perch, but is quite close to the rubber isolator because of the taller overall tire package. This is a great option for owners looking to run a taller tire without modifications. Photo credit @Last Lemming

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275/35-18

Tire model: Falken Azenis RT615k+ (200TW) Section Width: 10.8″ Tread Width: 9.7″ Overall Diameter: 25.6″ APEX Notes: Direct fit. This Falken runs narrower than the Hankook RS-4 that are one listed-size smaller, plus it has great clearance thanks to its shorter sidewall. Photo/Car Credit: @Evolution (https://www.supramkv.com/members/5555/)

Front wheels pictured are 18×10” ET30, rears are 18×11” ET40. No spacers were used in any of these photos.

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275/40-18

Tire model: Yokohama Advan A052s (200TW) Section Width: 11″ Tread Width: 9.8″ Overall Diameter: 26.7″ APEX Notes: Mods required. This tire was used for our initial testfit and photoshoots. At the time, we thought they were a direct fit, as the cars tested drove fine without signs of rubbing or witness marks on the tire sidewalls. However, after a second test-fit, we noted that the tire touches the rubber isolator and would not be a direct fit. Corrections will be made to our previous posts and we have updated our fitment guide with this new information. 5mm spacers should allow these tires to clear, but they will not be a direct fit. These tires do run wider than many other tire models in this size. Less aggressive tires with narrower section widths may clear without a spacer in this size.

Front wheels pictured are 18×10” ET30, rears are 18×11” ET40. No spacers were used in any of these photos.

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275/40-18

Tire model: Goodyear Eagle F1 Supercar 3 (220TW) Section Width: Unlisted Tread Width: 9.4″ Overall Diameter: 26.7″ APEX Notes: Mods required. These tires rubbed both the rubber isolator and metal portion of the perch. Based on our test fitment of the A052s in the same size, we suspect that their section width is wider than 11″ based on their fitment compared to the Yokohamas, despite a narrower tread width being listed on Goodyear’s site. Neither Goodyear’s site nor Tire Rack list a section width for these tires, but they are quite wide. Photo Credit: @gcmak (https://www.supramkv.com/members/5525/), Joe McGuigan.

Without Spacers

With a 5mm Spacer

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285/35-18

Tire model: Pirelli P Zero (220 TW) Section Width: 11.6″ Tread Width: 10″ Overall Diameter: 26 APEX Notes: Mods required. These tires are the widest size we recommend for the 18×10 ET30 wheels, but even with the shorter sidewall these tires are not a direct fit. 5mm spacers will be required with most tires in this size, with wider tire models requiring thicker spacers. Additional negative camber can help increase outer tire/fender clearance when spacers are used, but alignment adjustments aren’t always necessary. Photo/Car Credit: @nibble (https://www.supramkv.com/members/3673/)

Without Spacers

With a 5mm Spacer

Isolator wear caused by fitment prior to the addition of spacers.

Alignment notes for this setup:

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ADDITIONAL CONSIDERATIONS

True tire dimensions are not always reflected in the listed sizes under which the tires are sold. This is especially prevalent on the higher-performance end of tire sizes; as manufacturers seek to bring tires to market that outperform the competition, those tires tend to run wide on both the tread and the section width, which can result in unwanted rubbing. We occasionally hear about this from customers who want to run taller 18″ tires to match the OE rolling diameter of the stock 19″ wheels and tires. While ideally we would like to have a perfect match for this, the realities of the fitment constraints on this A90 chassis mean that a 265/35-18 or 275/35-18 tire will be a much easier fit overall. We have customers running 265/35-18 and 275/35-18 square setups with no traction control or stability control issues on the track or street. Plus, tire availability is excellent in these sizes, giving you access to a wider range of performance tire options. The taller tires can be used, but modifications can be required. This should be kept in mind when purchasing tires.

275/35-18 Maxxis Victra RC-1s on our 18×10.5 et38 EC-7Rs

Lastly with the true width of some of these aggressive 275/40-18 tires, a wider wheel is really the more ideal choice for overall sidewall support and tire performance. R compound tires with thick sidewalls benefit from the additional sidewall support a wider wheel provides and 275/40-18 is an extremely common size to see on our 18×10.5 ET38 square EC-7Rs:

18×10.5 et38 EC-7Rs with 275/40-18 Hankook RS-4s front & rear. 12mm front spacers required. Owner’s IG: @timkainu

HAVE SOME FITMENT FEEDBACK FOR US?

A huge thank you to the customers who have already worked with us and provided photos and feedback about tires on these wheels. (We believe we have properly attributed photo credits for the images used in this article, but please reach out with corrections if that isn’t the case.) Our GR Supra fitment guide has been updated with the feedback we have received thus far, and we are always ready to receive more. If you are running APEX 18” wheels on your A90 and have additional notes or questions, please send them to expert@apexraceparts.com (mailto:expert@apexraceparts.com). The fitment guide with notes about tires and additional fitments can be found here (https://support.apexraceparts.com/hc/en-us/articles/1260802325669-GR-Supra-Wheel-Tire-Fitment-Guide).

Click here to shop for GR Supra wheels: (https://www.apexraceparts.com/shop-by-vehicle/toyota/gr-supra.html)

Matt became the JDM Product Expert at APEX Wheels in 2022. Prior to joining APEX, he worked extensively in automotive sales. As an enthusiast he made the shift from street driving to track driving in order to fully experience his cars at the limit without putting the public at risk. Matt has owned six Hondas (‘94 Integra LS, ‘95 Integra RS, ‘96 Integra GS-R, ‘06 RSX Type-S, ‘95 Civic VX, ‘17 Civic EX-T), two Subarus (‘15 Impreza, ‘22 BRZ), and is likely shopping for the next addition to his stable. When he’s not helping JDM owners figure out the best wheel setups for their cars, he enjoys playing racing video games and indulging his interest in automotive photography. Fun fact: Matt knows every quotable line in The Fast and the Furious by heart.

Have questions about wheels for your JDM vehicle? Use our contact form and ask for Matt.