What Wheels Should My Robot Use?

Designing a mobile robot and wondering what wheels (and how many) you should incorporate? You've come to the right place. Mobile wheeled or tracked robots have a minimum of two motors which are used to propel and steer the robot. Hobbyists tend to choose skid steering (like a tank) because of its simplicity to design, incorporate and control. A three wheeled robot’s third (rear) wheel usually prevents the robot from falling over. Four wheeled robots have either two or four drive motors and use skid steering. Six wheeled robots most commonly have either two, four or six drive motors. Individuals who use an R/C car as a basis for their robot use rack and pinion steering where one motor is connected to a drive train and the other (usually a servo motor) is used for steering. Increasing the number of drive motors helps the robot to climb steeper inclines by increasing the torque.

Adding “idle” wheels (wheels not connected to a motor) often has the unfortunate consequence of removing weight from the drive wheels resulting in slip and loss of traction. In the image below, the center wheel, chosen mistakenly as the driven wheel, often loses contact with the ground. The way around this is to add suspension.

How Many Wheels Should My Mobile Robot Have?

A track system (or linking all wheels with gears or drive belts) also helps to prevent this from occurring. Tracks are not necessarily a better choice than using multiple driven wheels. Military tank manufacturers around the world produce both wheeled and tracked tank models and both offer comparable performance. Most users agree that tank tracks look more intimidating, they are far from being a refined method of transportation and have a tendency to "tear up" the ground beneath them. When making a tight turn, or turning on spot, tank treads encounter significantly more resistance than wheels as both halves are pushed against the ground perpendicularly to the turning radius.

Common types of wheeled robots

Skid steering (using 2, 4 or 6 wheels)

You can make a self-balancing robot using two wheels, or a more stable platform using four or more.

2 driven wheels + one or two idler wheels

The two drive wheels are used to propel and turn the robot (skid steering) and the one or two idler wheels to prevent the robot from falling forward or backward. The "idler" wheel can be a caster, a ball or omniwheel.


Usually have three arranged in a triangular pattern, or four arranged at 90 degrees. Omniwheels have small free-spinning roller wheels on the outside diameter. The central wheel is usually driven. This allows the wheel to be driven forward but slip sideways.


These currently need two pairs of specific wheels arranged two left and 2 right. Each wheel pulls the robot at an angle instead of purely forward and as such, you can get a variety of additional motion above and beyond that of a normal 4WD robot.

Tri-Star Design

A variant on the "wheel" design would be the tri-star. This design places three wheels of equal diameter about the axis of rotation. Normally these wheels are all driven via pulley from a centra shaft. It an be argued that the added complexity of this design allows it to more easily overcome large obstacles. Not many robots incorporate this design as of yet.
Tri-Star WheelTri-Star Wheel


Large vs Small Wheels

Robots with large wheels are often more eye-catching than robots with small wheels, but don't let looks affect your design! The right wheel size is very important and care should be taken to choose the right one for each specific robot.Two main equations need to be considered:

(forward) velocity = angular velocity (of the wheel) x radius (of the wheel)

This means that both the radius of the wheel and the angular speed at which it's turning will affect the forward velocity.

force (exerted by the wheel on the surface) = torque (of the motor) / radius (of the wheel)

For a wheeled robot to move or climb an incline, the wheel exerts a horizontal force on the surface. If you need to exert a high force (because your robot is heavy), then you need to increase either the torque or decrease the radius of the wheel. Increasing the torque is usually expensive, and increasing the radius usually means a heavier wheel, requiring more torque, but also reducing the maximum speed (since they have to rotate faster). Very small wheel diameters may also be impractical.

Tread Type

Choosing the right grip is all about maximizing the contact area. If your robot will be travelling on a ceramic or wood floor, a flat t rubber tire will provide the most grip, since both surfaces are very flat. If you also want it to roll on carpet, then you might add a small tread, but nothing too deep. At the opposite extreme, if you want your robot to get through deep mud and dirt, you would choose a tire with deep grooves to "scoop" the mud away to move forward.

What happens when you use a tire with a deep tread on a flat surface? There is almost no contact between the tire and the floor, so it's a lot easier for the tire to lose traction. What about a flat tire in the mud? There's certainly a lot of contact, but without a "shovel" effect, the wheel will just spin in place



This is a companion discussion topic for the original entry at https://community.robotshop.com/tutorials/show/what-wheels-should-my-robot-use

force (exerted by the wheel on the surface) = torque (of the motor) x radius (of the wheel)
is incorrect. It should be
force (exerted by the wheel on the surface) x radius (of the wheel) = torque (of the motor)
which means, smaller wheels apply larger force.

@Prasanth Good find and thanks for bringing it to our attention. Corrected.

Conclusion from this also needs to be corrected.

If you need to exert a high force (because your robot is heavy), then you need to increase either the torque or [decrease] the radius of the wheel.
To achieve the same forward speed for the robot, smaller wheels have to rotate faster. Even if we have a faster motor, we cannot indefinitely reduce the size of wheel due to physical size limits of motor or the shaft.

@Prasanth Corrected and keep the feedback coming!

hello sir,
i am making a robo car for racing in my university.i am little confused about the type of motor and wheels to be used.

@prashant Take a look at the Drive Motor Sizing Tutorial here: https://www.robotshop.com/blog/en/drive-motor-sizing-tool-9698

what is better chain driven robots or wheel drive?

@jeanpierre Each has its advantages and disadvantages - smaller robots tend to use direct drive because of simplicity, whereas a chain drive system which connects the motor’s drive shaft to a separate shaft which turns the wheels can add a gear ratio and takes the weight of the robot off the motor’s output shaft.

@Sam Try something with soft rubber, and ensure your robot has enough weight to compress it a bit. You might also want to consider tracks with rubber grip / pads.

@Sam Since you’re just in the design stage, we suggest creating a new topic on the RobotShop Forum and provide as much information as possible: https://www.robotshop.com/forum/

Hi Sir,

Can you let me know which plastic to make wheel?

@Julia It depends on your application, but most smaller wheels are made out of injection-molded ABS and covered by a rubber tread.

sir i m going tontake part in a fest robot race
which type of motor should i use to get max speed in 12volt battery
and one more problem is there on that track they had spread oil on a glass on which we have to pass and it is inclinded 45° please help

@shashank To confirm, the robot needs to climb a glass surface at 45 degrees with oil spread over it? We suggest creating a new topic on the RobotShop Forum with additional details.

I m making a robo for robot war.
It would be around 10 kg pyramid shape
which motors should I use to get maximum speed
I would be using 4 motors please help

@shubham: As a general rule, to get a very high speed you would want the DC motors with the highest RPM possible. Of course, there is always a trade-off between torque and RPM. Therefore, you should first determine your input voltage (12 V, 24 V DC ?) and torque requirements to move your robot (also include more if you need to push other things, too). Then, you can search our catalog (here & here) for a motor that meet those requirements with a high RPM. For more details on all of this, we recommend that you check the following articles:
How Do I Interpret DC Motor Specifications?
Vehicle Speed, RPM, and Wheel Diameter Finder
How to Make a Robot – Lesson 3: Making Sense of Actuators

What type of steering mechanism should I use for making a six wheel robot car of length 65inch and breadth 40inch and what type of motor should I use?

@Vedant There is no ideal solution. If you are set on a 6WD platform, you can either have one motor per wheel, and all wheels fixed (skid steering like a tank) or have the front two and rear two pivot using rack and pinion.

Hi. I’m having a problem in my tank drive design. I’m using 2 x bike chain for each track which is driven by total of 4 motorbike teethed wheels, one at front and one at back I welded the gears to the motor coupling. No idler wheels/teethed wheels are used.

Now the all metal design presents considerable weight, I can’t give exact weigh but I can say it’s around 2 large watermelons. My 5kg/cm motors can move but barely, if I drive uphill even at the slightest inclination the motor will stall.

I want to know if I can add a teethed wheel in the space where “idler” wheels are supposed to go powered by motors that run at the same rpm and torque. I’m not particularly worried of the powered idler wheel slipping in the tracks since the teeth will catch on the bike chain. So do you think it will work?

Another thing, sry for using Unknown but I don’t like leaving my tracks in the Internet.