Vehicle modifications span appearance, handling, power, comfort, accessibility, and emissions-related equipment. In the United States, automotive specialty-equipment sales reached $52.3 billion in 2023, while wheel, tire, suspension, and brake products alone generated $12.51 billion in 2024. The figures below put those categories, their users, installation patterns, and safety implications into context.
Contents
- Market size and sales mix
- Who modifies vehicles
- Vehicle segments owned by accessorizers
- Most common modification categories
- How parts are installed
- Adaptive equipment and perceived safety
- Emissions tampering and enforcement
Market size and sales mix
The U.S. automotive specialty-equipment market has remained above $50 billion in the latest annual figures supplied by the Specialty Equipment Market Association (SEMA). SEMA reported $51.8 billion in sales in 2022, with 2% year-over-year growth. Its 2023 estimate rose to $52.3 billion, about 1% above 2022. These are market-sales estimates for the stated years, not a count of individual modifications or vehicles.
- 2022: $51.8 billion in U.S. automotive specialty-equipment sales, with 2% year-over-year growth (SEMA, “Automotive Aftermarket Continues Growth Streak, Surpasses $51 Billion in Sales in 2022”).
- 2023: $52.3 billion in U.S. sales, up about 1% from 2022 (SEMA, “AUTOMOTIVE SPECIALTY-EQUIPMENT SALES GROW TO $52.3 BILLION”).
- 2024: Wheel, tire, suspension, and brake products together generated $12.51 billion in U.S. sales (SEMA, “2025 SEMA Market Report Unveils New Research on Wheel, Tire, Suspension and Brake Products”).
Pickup-related spending is a particularly large part of the mix. Pickup accessorization generated more than $15 billion in U.S. specialty-equipment sales in 2022. In 2023, pickups, crossover utility vehicles (CUVs), and sport utility vehicles (SUVs) together accounted for more than 50% of accessory and performance-parts sales. That concentration matters for anyone interpreting modification statistics: a market-wide percentage is strongly influenced by what pickup, CUV, and SUV owners buy.
SEMA’s 2020 classic-vehicle market profile gives a separate view of older vehicles. It covered 4.0 million vehicles and recorded $1.19 billion in classic-vehicle specialty-equipment sales. Enthusiasts represented 70% of owners in that profile. Within the same 2020 classic-vehicle sales mix, intake, fuel, and exhaust products represented 18% of sales dollars, while engine-internal and cooling products represented 16%.
Who modifies vehicles
The available consumer profiles describe “accessorizers,” a broader group than people who perform engine modifications. SEMA’s 2020 U.S. consumer segmentation divided accessorizers into 48% enthusiasts and 52% non-enthusiasts. This split shows why vehicle modification statistics include both performance-focused projects and practical, cosmetic, comfort, or maintenance-related purchases.
Age distribution in the 2020 U.S. accessorizer profile was concentrated among adults under 40:
| Age group | Share of U.S. accessorizers, 2020 |
|---|---|
| 16–29 | 29% |
| 30–39 | 31% |
| 40–49 | 17% |
| 50–59 | 12% |
| 60 and older | 10% |
The five reported age shares total 99%, so the profile should be read as rounded or category-reported percentages rather than treated as an exact whole-number partition. The source is SEMA’s 2021 Market Report, which presents the 2020 consumer profile (SEMA, “2021 SEMA Market Report”).
The profile’s 48% enthusiast and 52% non-enthusiast split also cautions against equating every accessory purchase with a high-performance build. A chemical product, interior upgrade, lighting product, or wheel purchase can belong to a different use case than a powertrain modification.
Vehicle segments owned by accessorizers
SEMA’s 2021 consumer profile reported the following shares of vehicles owned by U.S. accessorizers. The categories below are selected segments with quantified values in the profile, and they should not be added as a complete ownership distribution because other vehicle types are not listed here.
| Vehicle segment | Share of vehicles owned by accessorizers, 2021 |
|---|---|
| Pickups | 25% |
| CUVs | 19% |
| SUVs | 12% |
| Classic vehicles | 5% |
Pickups were the largest of these reported segments at 25%, followed by CUVs at 19% and SUVs at 12%. Classic vehicles accounted for 5%. Together, the four listed segments represented 61% of vehicles owned by accessorizers in that profile, but the remainder is not specified by the figures used here. The ownership data comes from the 2022 SEMA Market Report.
This vehicle mix aligns directionally with the sales evidence: pickups, CUVs, and SUVs together accounted for more than half of accessory and performance-parts sales in 2023, while pickup accessorization alone exceeded $15 billion in 2022. The years differ, so the figures describe related snapshots rather than a single synchronized survey.
Most common modification categories
The 2021 SEMA consumer profile measured whether products were installed on accessorizers’ vehicles in the 2021 U.S. profile. Exterior-body products were the most frequently reported category at 29%, followed by wheels and tires at 27% and chemicals at 25%.
The next group included suspension, brakes, and steering products at 22%; interior products at 20%; and lighting products, excluding standard replacement lightbulbs, also at 20%. Engine electrical and ignition products were installed on 15% of accessorizers’ vehicles, while mobile-electronics products reached 14%.
Power-related intake, fuel, and exhaust products were reported on 13% of vehicles. Driver-assist-system products were reported on 5%, the lowest share among the listed categories. These percentages describe the share of accessorizers’ vehicles with the category installed, not the share of all vehicles in the United States and not the dollar share of the market.
The category pattern is useful for separating visible modifications from mechanical ones. Exterior-body products, wheels and tires, chemicals, suspension, brakes, steering, interior, and lighting all reached at least 20% in the profile. Intake, fuel, exhaust, engine electrical, ignition, and mobile electronics were reported less often, and driver-assist products were less common still.
How parts are installed
Installation choices vary substantially by product category. In SEMA’s 2020 U.S. accessorizer profile, professional installation accounted for 66% of chemical-product purchases and 61% of interior-product purchases. The professional share was 49% for intake, fuel, and exhaust purchases and 48% for lighting purchases.
Other reported professional-installation shares were:
- Safety gear: 41%.
- Engine-internal and cooling products: 38%.
- Suspension, brakes, and steering products: 39%.
- Drivetrain products: 42%.
- Exterior-body products: 37%.
- Wheel-and-tire products: 24%.
The figures describe purchases in the 2020 accessorizer profile, not a guarantee that every item in a category was installed by a professional. The source is the 2021 SEMA Market Report. The spread—from 24% for wheel-and-tire purchases to 66% for chemical-product purchases—shows why a single “professional installation rate” would conceal meaningful differences between modification types.
Adaptive equipment and perceived safety
Adaptive vehicle modifications address access and control needs rather than styling or performance. In the NHTSA adaptive-vehicle survey, hand controls were reported by 50% of respondents, representing 200 respondents. Wheelchair securement was reported by 32%, or 127 respondents; steering control devices by 30%, or 119 respondents; automatic door openers by 29%, or 114 respondents; and lifts by 27%, or 106 respondents.
Overall, 73% of respondents rated the safety of their modified vehicle as 4 or 5. Ratings varied by listed modification. Left-foot accelerators had the highest reported 4-or-5 safety rating at 85%, while horizontal steering had the lowest at 56%.
These results are survey findings for the period reported by NHTSA, not a universal safety score for every adaptive installation. The equipment categories can overlap, and the respondent counts and percentages are reported as survey results. The source is NHTSA’s “The number of vehicles with adaptive equipment is expected to continue to increase as the U.S. population ages”.
Emissions tampering and enforcement
Some vehicle modifications affect emissions controls and are treated differently from ordinary accessory installation. EPA investigations summarized through 2024 found that controls on more than 500,000 diesel pickup trucks had been fully removed or deleted through tampering. EPA said those pickups represented about 13% of pickups originally certified with emissions controls.
EPA estimated that the excess nitrogen-oxide emissions from the tampered pickups were equivalent to adding 9 million trucks to the roads. For known sales of defeat devices for certain diesel trucks after 2009 and before 2020, EPA estimated more than 570,000 tons of excess NOx over the trucks’ lifetimes and 5,000 tons of excess particulate matter over those lifetimes. EPA analyzed sales records from 26 companies in the evidence review for investigations occurring after 2009 and before 2020.
The enforcement evidence is not a measure of all modified vehicles. It concerns investigated diesel-pickup tampering and known defeat-device sales, with estimates tied to the stated truck populations and lifetimes. The primary enforcement summary is EPA’s “National Enforcement and Compliance Initiative: Stopping Aftermarket Defeat Devices for Vehicles and Engines”, supported by the agency’s “Tampered Diesel Pickup Trucks” evidence review.
Earlier evidence provides historical context but should not be presented as current prevalence. In EPA’s 1990 survey, 19% of surveyed 1975-and-newer light-duty vehicles had at least one tampered emissions-control component. Vehicles with tampering were twice as likely to fail an inspection-and-maintenance test using New Jersey idle standards. Those results belong to the 1990 survey and are reported in EPA’s “Motor Vehicle Tampering Survey -1990”; they were not independently rechecked for the later market figures above.