The 2018 Cadillac CT6 sits at the modern end of Cadillac’s full-size luxury sedan tradition, blending long-wheelbase comfort with contemporary chassis tuning and a more driver-focused feel than many large sedans in its class. Tire selection on this car is less about vintage-style construction and more about matching the exact wheel and trim setup, because the CT6 uses four different radial sizes: 235/50R18, 245/45R19, 245/40R20, and 265/45R18. Available choices include blackwall performance-oriented radials along with select redline and raised white letter options in some sizes. The key is confirming the exact sub-model and wheel diameter before comparing brands, sidewall appearance, and intended road use.
Which Tire Size Is Right for The 2018 Cadillac CT6
The 2018 Cadillac CT6 uses four primary tire sizes, and the right one depends on the exact sub-model and wheel package. All of them are radial sizes, but they span 18-inch, 19-inch, and 20-inch rims, so confirming wheel diameter is the first step. After that, the decision shifts to the exact size your CT6 uses and the kind of tire presentation you want, from conventional blackwall sport radials to select redline or raised white letter options.
235/50R18 is a metric radial size in which 235 identifies the section width in millimeters, 50 is the aspect ratio, R denotes radial construction, and 18 is the rim diameter in inches. On the 2018 Cadillac CT6, this size supports an 18-inch wheel setup and is used on certain Base, Luxury, and Plug-In Front configurations. Available choices include BFGoodrich, Nitto, and Pro-Trac tires, with blackwall, redline, and RWL sidewall styles offered in this size. It is the right size to evaluate only after confirming that your CT6 is running the 18-inch front fitment rather than a 19- or 20-inch package.
Fit(s): Base, Luxury, Platinum, and Premium Luxury
Construction: Radial|Rim: 20 in
245/40R20 is a metric radial size that uses a 245-millimeter nominal section width, a 40-series profile, and a 20-inch rim diameter. For the 2018 Cadillac CT6, this size appears on several configurations, including Base, Luxury, Platinum, and Premium Luxury models equipped with 20-inch wheels. Product choices include BFGoodrich, Nitto, and Pro-Trac offerings, with blackwall, redline, and RWL sidewall treatments available. This size is the one to compare when your CT6 already has a 20-inch wheel setup and you want to balance appearance, series choice, and wheel-width compatibility.
245/45R19 is a metric radial size, with 245 indicating width in millimeters, 45 indicating aspect ratio, and 19 showing the wheel diameter in inches. On the 2018 Cadillac CT6, it applies to certain Base, Luxury, and Premium Luxury setups that use a 19-inch wheel. Available products in this size come from BFGoodrich and Nitto, and the assortment here stays focused on blackwall radial performance and all-season style choices rather than decorative sidewall treatments. It is the size to pursue when your CT6 has the 19-inch package and you want to stay within the correct modern radial format for that configuration.
265/45R18 is a metric radial size with a wider 265-millimeter section width, a 45-series profile, and an 18-inch rim diameter. On the 2018 Cadillac CT6, this size is used on the Plug-In Rear application, making it specific to that rear-wheel position rather than a general CT6 fitment across all models. The wider section makes it especially important to match the tire to the intended wheel and vehicle setup instead of assuming interchangeability with the front 18-inch size. This is the size to verify when replacing tires on the rear of a Plug-In CT6 or checking a staggered-style 18-inch arrangement.
Sub-model fitment matters on the 2018 Cadillac CT6 because wheel packages vary across the range, and not every trim uses the same tire size. The first step is identifying the exact CT6 sub-model and wheel diameter so the tire search stays aligned with the correct radial fitment.
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2018 Cadillac CT6 Base
The 2018 Cadillac CT6 Base can use 18-inch, 19-inch, or 20-inch radial tire fitments depending on its wheel setup. That makes wheel confirmation especially important before selecting among blackwall performance radials or, in some sizes, appearance-focused options such as redline or RWL.
The 2018 Cadillac CT6 Luxury also spans multiple radial sizes tied to different wheel diameters. Tire selection starts with confirming whether the car has 18-, 19-, or 20-inch wheels, then narrowing the choice by brand, series, and sidewall treatment where those options are available.
The 2018 Cadillac CT6 Platinum uses a single 20-inch radial fitment, which makes the size question more straightforward than on other trims. The main choice here is comparing the available 245/40R20 products by series, brand, sidewall style, and wheel-width compatibility rather than sorting through multiple primary sizes.
The 2018 Cadillac CT6 Plug-In Front uses an 18-inch radial front tire fitment. Selection centers on staying with the correct 235/50R18 size and then choosing the product style that suits the car, whether that means a conventional blackwall look or one of the available appearance-oriented sidewall treatments.
The 2018 Cadillac CT6 Plug-In Rear uses a different 18-inch radial size from the front, making it a fitment that should be treated separately. Rear replacement starts with confirming the wider 265/45R18 size and checking that the wheel and overall setup still match the intended rear application.
The 2018 Cadillac CT6 Premium Luxury uses either a 19-inch or 20-inch radial fitment depending on wheel configuration. That means tire choice begins with wheel-diameter confirmation, followed by comparing the available products in the correct size for the appearance and driving character you want to maintain.
The tire sizes listed on this page assume factory-standard vehicle configuration. The following modifications may affect tire fitment and are not reflected in this guide:
Suspension changes (lowering, lift kits, spring replacements)
Body alterations (fender modifications, custom bodywork)
If your vehicle has been modified from factory specifications, verify tire clearance before purchase.
Best 2018 Cadillac CT6 Tires for Sale
Available 2018 Cadillac CT6 tire choices center on modern radial products from BFGoodrich, Nitto, and Pro-Trac. Depending on size, the product grid can be compared by tire series, blackwall or appearance-style sidewalls, and wheel-width compatibility across the CT6’s 18-, 19-, and 20-inch fitments.
These FAQs focus on the real tire decisions for a 2018 Cadillac CT6, including size by sub-model, wheel-diameter differences, available radial choices, sidewall options, and the fitment checks worth making before regular road use.
Tire Size & Fitment
What tire size fits a 2018 Cadillac CT6?
The 2018 Cadillac CT6 uses four primary tire sizes: 235/50R18, 245/45R19, 245/40R20, and 265/45R18. All are radial sizes, but they do not apply across every CT6 configuration, because wheel diameter and sub-model affect which size belongs on the car.
The most important step is confirming the exact trim and the wheels currently on the vehicle. Base and Luxury models can appear with more than one wheel package, Premium Luxury can use either 19- or 20-inch fitment, and the Plug-In uses different front and rear sizes, so matching the tire to the actual wheel setup matters more than assuming one CT6 size covers them all.
What size rim does a 2018 Cadillac CT6 use?
A 2018 Cadillac CT6 can use 18-inch, 19-inch, or 20-inch rims, depending on the tire size and sub-model configuration. The 235/50R18 and 265/45R18 sizes use 18-inch rims, 245/45R19 uses a 19-inch rim, and 245/40R20 uses a 20-inch rim.
Wheel diameter should be confirmed before looking at tread style, brand, or sidewall appearance because it determines which tire size family even belongs on the car. Aftermarket wheels can complicate that picture, so checking the wheel marking and current tire size together is a smart step before replacement, especially on CT6 trims that were offered with multiple wheel packages.
Why does the 2018 Cadillac CT6 have more than one tire size?
The 2018 Cadillac CT6 has more than one tire size because different trims and wheel packages use different rim diameters, and the Plug-In application separates front and rear fitment. That creates a range of primary sizes rather than one universal CT6 tire across the entire model line.
In practice, that means the tire decision starts with vehicle configuration, not just the year and model name. A Platinum uses a single 20-inch size, while Base and Luxury trims can appear with several wheel setups, so the safest approach is to verify the exact sub-model and compare it against the wheel currently installed before choosing a replacement tire.
Choosing the Right Tire
What should I consider when choosing a 2018 Cadillac CT6 tire?
Start with the exact size and wheel diameter your CT6 uses, since this model spans 18-, 19-, and 20-inch radial fitments. After that, compare tire series, brand, sidewall style where available, and any wheel-width information tied to the size you are replacing.
The right choice depends on whether the goal is maintaining the current appearance, staying with a sport-oriented blackwall radial, or selecting one of the available redline or raised white letter options in certain sizes. It also helps to look at load figures and weight where those details are available, especially if the car sees regular highway use rather than occasional short drives.
What sidewall styles are available for 2018 Cadillac CT6 tires?
Sidewall style depends on the tire size. Blackwall options are available across the supported CT6 sizes, while 235/50R18 and 245/40R20 also offer appearance-oriented choices such as redline and RWL, giving those fitments more visual variety than the 245/45R19 selection.
That means sidewall appearance can only be part of the decision after the correct size has been confirmed. Owners replacing 18-inch or 20-inch tires may have the option to add a more distinctive look, while a 19-inch CT6 setup stays focused on conventional blackwall radials, so visual preference and exact fitment need to be considered together.
What brands offer tires for the 2018 Cadillac CT6?
The available 2018 Cadillac CT6 tire options include BFGoodrich, Nitto, and Pro-Trac, depending on size. BFGoodrich appears across the supported sizes, Nitto is offered in several of the modern radial fitments, and Pro-Trac brings additional sidewall-style variety in selected 18-inch and 20-inch applications.
Brand choice is most useful once the correct size has been narrowed down, because the assortment changes by fitment. Some sizes have only blackwall sport-radial choices, while others add redline or RWL treatments, so the better comparison is not brand alone but brand plus size, series, sidewall presentation, and the wheel-width range that matches the tire.
Restoration & Appearance
Which tire should I choose for a period-style 2018 Cadillac CT6?
A period-style 2018 Cadillac CT6 still starts with the exact modern radial size used by the car, since this is a contemporary luxury sedan rather than a vintage bias-ply application. From there, the appearance decision is mainly between standard blackwall tires and selected redline or RWL offerings in sizes such as 235/50R18 and 245/40R20.
The better visual match depends on how the car is being presented. A blackwall tire keeps a more restrained modern luxury look, while redline or raised white letter sidewalls create a more personalized appearance, so the choice is less about historical originality and more about staying within the correct fitment while matching the style of the finished car.
Does correct tire fitment matter for a 2018 Cadillac CT6 restoration or presentation build?
Correct tire fitment matters on a 2018 Cadillac CT6 because the car uses several different radial sizes tied to different wheel diameters and, in some cases, different front and rear positions. Even on a presentation build, the visual result depends on getting the size and wheel relationship right before focusing on sidewall styling.
A CT6 that sits on the wrong diameter tire or an incorrect wheel package can look out of proportion and may also create clearance or drivability issues. Matching the exact trim and wheel setup first gives the best foundation, then appearance details such as blackwall, redline, or RWL can be chosen within the proper size range for the way the car is being finished.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 2018 Cadillac CT6?
Yes, modifications can affect tire fitment on a 2018 Cadillac CT6. Changes such as aftermarket wheels, different wheel widths, altered offsets, suspension lowering, or body modifications can change how much room is available for the tire even when the nominal size looks close to the original fitment.
That matters especially on a model like the CT6, where multiple factory sizes already exist across 18-, 19-, and 20-inch wheels. If the car has been changed from its original setup, measure the actual wheel diameter and width, then check steering, fender, and suspension clearance before replacement instead of assuming the stock trim-level size still applies.
What should I inspect before driving a 2018 Cadillac CT6 on new tires?
Before driving a 2018 Cadillac CT6 on new tires, inspect the wheel size, confirm the new tires match the intended position on the car, and check inflation pressure, bead seating, and visible clearance around the fenders and suspension. A quick visual check for rubbing during full steering lock is also worthwhile.
It also helps to recheck the vehicle after the first short drive. Look for uneven contact marks, air loss, vibration, or any sign that the wrong size was mounted on a trim with a different wheel package, especially on Plug-In models where front and rear fitment are not the same. Catching those issues early helps prevent wear and drivability problems.
How often should tires on a 2018 Cadillac CT6 be inspected?
Tires on a 2018 Cadillac CT6 should be inspected regularly rather than only when tread looks low. A routine check of pressure, tread wear, cuts, punctures, bulges, and sidewall condition helps catch problems early, particularly on a car that may alternate between long trips and extended periods of lighter use.
A monthly inspection is a sensible habit, with an extra check before longer highway driving. Uneven wear can also point to alignment or suspension issues, and mixed wheel packages make it important to confirm the front and rear tires remain in the correct positions where applicable, especially on CT6 configurations that do not use the same size at all four corners.
