The 2018 Mercedes-Benz Trucks GLA45 AMG blends compact crossover packaging with AMG performance character, making tire selection more about exact wheel setup than broad model-year assumptions. On a vehicle like this, stance, response, and everyday drivability are all tied closely to the tire size already on the car. The 2018 Mercedes-Benz Trucks GLA45 AMG uses radial tires in either 235/45R19 or 235/40R20, so the first step is confirming which rim diameter your 4Matic is wearing. Since both sizes are modern metric radials with nearly the same overall diameter, the decision centers on matching the existing wheel package and verifying clearance if the vehicle has been changed from stock.
Which Tire Size Is Right for The 2018 Mercedes-Benz Trucks GLA45 AMG
Two primary tire sizes apply to the 2018 Mercedes-Benz Trucks GLA45 AMG, and the difference comes down to wheel diameter rather than a change in basic tire construction. Both sizes are radial fitments used on the 4Matic sub-model, so the first thing to confirm is whether the vehicle is riding on 19-inch or 20-inch wheels before comparing tire options.
The size 235/40R20 identifies a metric radial tire with a 235-millimeter section width, a 40-series aspect ratio, and fitment for a 20-inch rim. On the 2018 Mercedes-Benz Trucks GLA45 AMG, this size suits vehicles already equipped with the 20-inch wheel package and keeps the low-profile look associated with larger-diameter wheels. Its modern radial construction aligns with contemporary handling and road-use expectations for this platform. Choosing this size starts with confirming the actual wheel diameter on the vehicle and checking for any wheel, suspension, or ride-height changes that could affect clearance.
The size 235/45R19 uses the same 235-millimeter section width but pairs it with a 45-series profile for a 19-inch rim. For the 2018 Mercedes-Benz Trucks GLA45 AMG, it belongs on vehicles running the 19-inch wheel setup, making wheel confirmation just as important as the size itself. This is also a modern radial format, so the construction choice is straightforward compared with older collector vehicles that may have bias-ply considerations. It is the right size to evaluate when the vehicle remains on its 19-inch wheels and you want to preserve the intended fitment relationship between tire and rim.
Sub-model fitment is straightforward here because the covered 4Matic configuration uses the same two primary tire sizes. What matters most is not trim variation, but confirming whether the vehicle has 19-inch or 20-inch wheels before selecting a replacement tire.
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2018 Mercedes-Benz Trucks GLA45 AMG 4Matic
The 2018 Mercedes-Benz Trucks GLA45 AMG 4Matic uses either 235/45R19 or 235/40R20 radial tires, depending on the wheel package on the vehicle. Tire selection therefore starts with wheel-diameter confirmation, then moves to matching the installed setup and checking for any modifications that may affect clearance.
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.
Frequently Asked Questions
Owners of a 2018 Mercedes-Benz Trucks GLA45 AMG usually need clarity on the two tire sizes, the 19-inch versus 20-inch wheel question, and what to inspect before replacing tires on a performance-oriented crossover.
Tire Size & Fitment
What tire size fits a 2018 Mercedes-Benz Trucks GLA45 AMG?
The 2018 Mercedes-Benz Trucks GLA45 AMG uses two primary tire sizes: 235/45R19 and 235/40R20. Both are radial sizes, and both apply to the GLA45 AMG 4Matic, so the correct choice depends on which wheel package is currently on the vehicle rather than on a different tire construction.
The practical next step is to check the wheel diameter already installed on the car. A 19-inch wheel requires 235/45R19, while a 20-inch wheel requires 235/40R20. Since many vehicles in this segment may have had wheel changes over time, confirming the actual wheel size is more reliable than assuming fitment by model name alone.
What size rim does a 2018 Mercedes-Benz Trucks GLA45 AMG use?
A 2018 Mercedes-Benz Trucks GLA45 AMG can use either a 19-inch or 20-inch rim, depending on the tire size on the vehicle. The 235/45R19 tire fits a 19-inch rim, and the 235/40R20 tire fits a 20-inch rim, with both sizes used on the 4Matic configuration.
That makes rim confirmation the first fitment check before ordering replacement tires. Looking at the existing tire sidewall is often the quickest way to verify what the vehicle is wearing now. If the wheels have been changed from the original setup, also check width and clearance so the replacement tire matches the current package rather than an assumed factory combination.
Do all 2018 Mercedes-Benz Trucks GLA45 AMG sub-models use the same tire size?
The covered sub-model here is the 2018 Mercedes-Benz Trucks GLA45 AMG 4Matic, and it uses both 235/45R19 and 235/40R20 as primary radial fitments. That means fitment does not split into separate sizes by a different trim name, but it does vary by the wheel diameter installed on the vehicle.
For tire replacement, this means the sub-model alone does not answer the full fitment question. The important detail is whether the 4Matic is on 19-inch or 20-inch wheels today. A quick inspection of the tire sidewall or wheel itself will prevent ordering the right width and profile in the wrong rim diameter.
Choosing the Right Tire
What should I consider when choosing a tire for a 2018 Mercedes-Benz Trucks GLA45 AMG?
Start with the exact size already fitted to the vehicle: 235/45R19 for 19-inch wheels or 235/40R20 for 20-inch wheels. Since both are modern radial fitments for the 2018 Mercedes-Benz Trucks GLA45 AMG, the key selection factors are correct rim diameter, the current wheel setup, and the intended balance of appearance and road use.
It also helps to inspect whether the vehicle still has its original-style wheel package or has been modified. A different wheel width, offset, or lowered suspension can change how much room the tire has at the fender and steering points. Matching the tire to the actual hardware on the vehicle is more important than choosing by model year alone.
How do I choose between 235/45R19 and 235/40R20 for a 2018 Mercedes-Benz Trucks GLA45 AMG?
The choice is determined by the wheel diameter on the vehicle, not by personal preference alone. A 2018 Mercedes-Benz Trucks GLA45 AMG with 19-inch wheels uses 235/45R19, while one with 20-inch wheels uses 235/40R20. Both sizes are proper radial fitments for the covered 4Matic application.
Because the two sizes fit different rim diameters, they should not be treated as interchangeable without checking the complete wheel and vehicle setup. If the vehicle has aftermarket wheels, confirm the actual diameter stamped on the wheel and compare the tire sidewall marking already in use. That keeps the replacement focused on the installed package rather than guesswork.
Why does the 2018 Mercedes-Benz Trucks GLA45 AMG have more than one tire size?
The 2018 Mercedes-Benz Trucks GLA45 AMG has more than one tire size because it can be equipped with different wheel diameters. The two sizes, 235/45R19 and 235/40R20, are both radial fitments and both belong to the 4Matic configuration, so the variation reflects wheel package choice rather than a separate construction type.
For an owner, that means the right tire cannot be chosen by the model name alone. Checking the wheel diameter and the tire size currently mounted is the safest starting point. This is especially important on vehicles that may have seen wheel upgrades, seasonal wheel sets, or previous-owner changes that altered the original wheel-and-tire combination.
Restoration & Appearance
Does correct tire fitment matter for a 2018 Mercedes-Benz Trucks GLA45 AMG restoration or preservation project?
Yes, correct tire fitment still matters even on a newer collector-oriented AMG vehicle. The 2018 Mercedes-Benz Trucks GLA45 AMG uses either 235/45R19 or 235/40R20, and staying with the right size for the installed wheel package helps preserve the vehicle’s intended stance, wheel-to-tire proportion, and overall presentation.
Appearance is only part of the picture. The wrong rim diameter or profile can also create avoidable fitment issues and change how the vehicle sits visually. Anyone preserving the vehicle in a more original-style configuration should confirm the wheel package currently on the car and keep records of any wheel changes made over time.
How does tire size affect the appearance of a 2018 Mercedes-Benz Trucks GLA45 AMG?
Tire size has a visible effect on the 2018 Mercedes-Benz Trucks GLA45 AMG because the two approved sizes pair the same section width with different sidewall profiles and rim diameters. The 235/45R19 presents a 19-inch wheel fitment, while the 235/40R20 creates the look associated with a larger 20-inch wheel and shorter sidewall.
That visual difference is one reason it is important to replace tires by the wheel package already on the vehicle. For a preservation-minded owner, maintaining the correct size for the installed wheels helps keep the intended proportion between wheel opening, rim, and sidewall. It also avoids mixing appearances that can make the vehicle look mismatched from side to side.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 2018 Mercedes-Benz Trucks GLA45 AMG?
Yes, modifications can affect tire fitment on a 2018 Mercedes-Benz Trucks GLA45 AMG even when the nominal tire size remains 235/45R19 or 235/40R20. Changes such as aftermarket wheels, altered wheel offset, suspension lowering, spacer use, or body modifications can all influence clearance at the fender, strut, and steering points.
That is why replacement tires should be matched to the vehicle’s current setup, not only to the original fitment range. Checking wheel diameter, width, and visible clearance before installation can prevent avoidable problems. On a modified vehicle, even the correct nominal tire size should be treated as something to verify against the actual hardware on the car.
What should I inspect before driving a 2018 Mercedes-Benz Trucks GLA45 AMG on new tires?
Before driving a 2018 Mercedes-Benz Trucks GLA45 AMG on new tires, inspect the tire size, mounting direction if applicable, visible bead seating, and inflation pressure. It is also smart to look over the wheels for damage and confirm that the vehicle is wearing the correct 19-inch or 20-inch tire-and-wheel combination for the size installed.
A short follow-up inspection after the first drive is equally useful. Recheck pressure, look for any rubbing marks, and pay attention to steering feel or vibration that could point to balance or clearance issues. Since this model can use two different rim diameters, verifying that the tire matches the wheel already on the vehicle is a key final step.
How often should tires on a 2018 Mercedes-Benz Trucks GLA45 AMG be inspected?
Tires on a 2018 Mercedes-Benz Trucks GLA45 AMG should be inspected regularly, not just when tread appears worn. A quick visual check before longer drives and a more careful inspection at routine service intervals helps catch uneven wear, cuts, bulges, punctures, and pressure loss before they become more serious.
Performance-oriented vehicles can be more sensitive to alignment and wheel-condition issues, so tire inspections should also include the inside shoulder whenever possible. Look for anything that suggests rubbing or abnormal wear, especially if the vehicle has changed wheels or suspension settings. Consistent pressure checks and condition checks matter just as much as choosing the correct size.
