Let's say we have a car with four wheels and the center of the car has a speed of 50km/h. There is no friction or air resistance. If the car is moving straight each wheel will also have a speed of 50km/h, since that's the speed of the center of the car.
If the car's front wheels would turn a little bit, then we would have uniform circular motion (since there is nothing to slow down the speed). Each wheel would have its own speed (since their radius to the center of the curve would be different for each wheel). What I wonder is if the speed of the center of the car is still 50km/h?
I realize that there need to be friction to turn. What I meant was that there is no friction that will slow down the speed. When the car turns there will be a centripetal force perpendicular to the car's velocity. Which should indicate that the car's speed will remain the same, but it's direction will change.
Here's a simulation I made: https://vid.me/HYz9. The red line is the car's velocity, and the green line is the front wheel's velocity. You will notice that the red line only changes direction, whilst the green line (the front wheel's velocity) also gets a higher speed as the wheel is turned. Is this simulation accurate?