RC Roll Out Explained
What Is Roll Out?
Roll Out is the distance your RC car travels forward in one full rotation of the drive wheels. It combines your Gear Ratio and your tire size into one simple measurement.
Instead of thinking in terms of pinion/spur teeth or internal ratios, Roll Out answers a more practical question:
“How far does my car move every time the wheels spin once?”
Roll Out is usually measured in inches or millimeters and commonly refers to foam tires on-road, oval and carpet racing where precision matters.
Simple idea:
• Higher Roll Out = more distance per wheel rotation (higher top speed)
• Lower Roll Out = less distance per rotation (more acceleration)
How Does Roll Out Affect Your Car?
Acceleration
Lower Roll Out gives stronger acceleration. The motor spins the wheels more times over a shorter distance, helping the car launch harder and pull out of corners.
Higher Roll Out reduces acceleration because each rotation covers more ground, requiring more effort from the motor.
Top Speed
Higher Roll Out increases top speed potential. The car travels farther per rotation, which translates into higher maximum speed on long straights.
Lower Roll Out limits top speed but improves responsiveness.
Motor Load and Temperature
• Too high Roll Out = motor works harder – higher temps, possible overheating
• Too low Roll Out = motor spins freely – cooler temps but may lack speed
This is one of the biggest reasons racers use Roll Out in foam tire applications – it helps balance speed and motor efficiency.
Drive Feel and Consistency
• Lower Roll Out = smoother, easier to drive, more forgiving
• Higher Roll Out = faster but more aggressive and harder to control
On tight tracks, lower Roll Out often leads to faster lap times despite lower top speed.
How Do You Change The Roll Out?
You adjust Roll Out by changing either your gearing or your tire size.
1. Change Pinion Gear
• Larger pinion – increases Roll Out
• Smaller pinion – decreases Roll Out
This is the fastest and most common adjustment at the track.
2. Change Spur Gear
• Smaller spur – increases Roll Out
• Larger spur – decreases Roll Out
Spur changes are less frequent but useful for larger setup shifts.
3. Change Tire Size
• Larger tires – increase Roll Out
• Smaller tires – decrease Roll Out
This is often overlooked. Tire wear alone, especially when using foam tires, can change Roll Out during a race run.
4. Use Roll Out Calculators
Many racers use a Roll Out calculator (or apps) to match setups across different cars or track conditions. This keeps performance consistent even when gear ratios differ.
When To Change The Roll Out
Tight Tracks (Indoor / Technical Layouts)
• Use lower Roll Out
• Improves corner exit and control
• Helps reduce wheel spin
Large Tracks (Outdoor / High-Speed Layouts)
• Use higher Roll Out
• Increases straight-line speed
• Takes advantage of long sections
Low Grip Conditions
• Lower Roll Out
• Makes power delivery smoother
• Reduces traction loss
High Grip Conditions
• Higher Roll Out
• Allows you to push top speed
• Works well when traction is not limited
Motor Running Hot
• Reduce Roll Out
• Lightens load on the motor
• Improves efficiency and runtime
Car Feels Sluggish
• Increase Roll Out
• Gains top speed and improves straightaway performance
What To Check After Changing Roll Out
Changing Roll Out affects more than just speed. Always check these areas:
Motor Temperature
Run the car and check temps immediately after a run.
• Too hot = Roll Out is too high
• Very cool = you may be leaving speed on the table
Battery Life
Higher Roll Out can increase current draw and reduce runtime. Make sure your battery can handle the load.
ESC Settings
You may need to adjust:
• Punch control
• Timing
• Turbo/boost (if applicable)
Higher Roll Out setups often benefit from smoother throttle delivery.
Tire Wear
Since tire size affects Roll Out, worn tires effectively lower it over time. Re-check your setup as tires wear down, especially if you’re using foam tires.
Gear Mesh and Drivetrain Stress
Higher Roll Out puts more load on:
• Gears
• Differentials
• Driveshafts
Make sure everything is smooth and properly maintained.
Lap Times (Most Important)
Always validate changes on track. The “fastest” Roll Out on paper is not always the fastest in lap times.
FAQ
Q: What is a good starting point for Roll Out?
A: In rubber-tire racing, Roll Out is generally not an issue. With foam tires, a safe starting point is whatever your class or motor manufacturer recommends (see the kit manual for a good starting point). From there, adjust based on track size and motor temperature.
Q: Is Roll Out better than using Gear Ratio?
A: Yes – for consistency. Roll Out accounts for tire size, which Gear Ratio alone does not. It gives a more real-world measurement.
Q: Does tire wear really affect Roll Out?
A: Yes. As foam tires get smaller, your Roll Out decreases, which can increase acceleration but reduce top speed.
Q: Should I always chase the highest Roll Out?
A: No. Higher Roll Out only works if your motor can handle it and the track allows it. Balance is key.
Q: How often should I check Roll Out?
A: If running foams, it’s not a bad idea to check it every 2-3 runs. Otherwise, after changing tires, any major gearing changes or when track conditions change.
Q: Can Roll Out help with consistency?
A: Absolutely. Matching Roll Out across different setups helps keep your car predictable and repeatable.
Related Tuning Adjustments
To get the most out of this setup change, review these related guides:
• Gear Ratio
• Tire Compound
Back to the RC Suspension Tuning Guide.
