Understanding (and choosing) the right rallycross class for you
If you're signing up for your first rallycross, one of the first things you’ll need to figure out is choosing the right vehicle class. There are three main classes: Stock, Prepared, and Modified. Each class allows progressively more freedom for modifications. Here's what you need to know about what's allowed in each.
[It is the driver’s responsibility to read the full regulations and ensure they’re selecting the correct class. If you have questions after reading through them, we’re always here to answer questions.]
Stock Class
Who this is for: Cars that are essentially how they came off the dealer lot. A few minor additions or changes are allowed. Stock class keeps it simple with minimal performance upgrades and the goal is close competition among everyday vehicles.
Key allowances:
Vehicles must match their original factory specification with only stock or factory-option components.
You can change small wearable items like air filters (as long as they fit the stock air box) and add/replace the exhaust from the catalytic converter back. Pro-tip: test your exhaust against the sound regulations in the rules before racing so you don’t have any surprises at tech inspection.
Radiators can be swapped as long as they fit in the stock location and dimensions.
Brakes can use aftermarket pads or rotors (with stock dimensions), and safety systems like ABS/traction control can be disabled but not removed.
You can add lights, skid plates, harness, and mud flaps.
Pro-Tips: Take advantage of what you can do in stock class.
Install fresh shocks
Add a skid plate
Get a high void snow tires
Install mud flaps
If your wheels are over 15” in diameter, find used wheels that are 1” smaller and tires that fit. The will give you more sidewall which helps with the off-road courses.
Prepared Class
Who this is for: Cars that are largely stock but want a bit more performance or durability. Prepared class is a balance between keeping the car close to its original configuration and allowing small upgrades that help performance and reliability.
Key allowances:
All stock class allowances plus a range of permitted modifications.
You can replace most of the exhaust system back to the cylinder head (still meeting sound rules) and high-flow catalytic converters are allowed.
The intake system upstream from the throttle body can be replaced.
Accessory drive changes (smaller or bigger pulleys) and modified engine control electronics (including piggyback systems) are okay.
Mechanical upgrades like limited-slip differentials (or spools), short-shift kits, and alternate radiators are permitted with some restrictions.
Brakes and suspension components get more flexibility though major changes remain limited.
Some aerodynamic production parts like rear wings or hood vents can be installed if they were available as a factory or catalog option.
Pro-Tips: These upgrades will have the most bang for their buck:
Get a set of rally tires. If you’re new, get used rally tires to save a little $$ while you learn.
Install a race seat and hardness. Being held tighter in the seat allows you to use your strength to control the car.
If you’re ready for power upgrades, you can get a tune, intake or upgrade your exhaust. (When planning for an intake, be mindful of sucking in mud and water. You’ll want a pre-filter!)
This may be a good opportunity to size your brakes to fit rally wheels
Modified Class
Who this is for: Cars with significant modifications and performance upgrades.
Key allowances:
All stock and prepared class allowances.
Engine and drivetrain are highly flexible: turbocharged or supercharged engines, electronic engine controls, and any drivetrain layout are permitted.
Exhaust systems can be fully custom with no catalytic converter requirement, as long as noise limits are respected.
Fuel systems get more leeway, including aftermarket fuel cells and pumps (with safety considerations).
Suspension, geometry, and components can be extensively changed.
Non-essential weight can be removed, and bodywork can be altered or replaced — though the vehicle must still retain its basic manufacturer silhouette.
Aerodynamic components (wings, splitters) are allowed.
Choosing Your Class
Your choice depends on your car, budget, mechanical skills, and goals. Each class has drivers of all skill levels so whether you’re brand new to racing or have been around the block, you’ll find competition in whatever class you select.