RacingSystem.cs(28,96): error CS0201: Only assignment, call, increment, decrement, and new object expressions can be used as a statement

Attempting to make a racer go around corners. (they collide with an arrow and then get the rotation of the arrow object so they go around the corner.)
RacingSystem.cs(28,96): error CS0201: Only assignment, call, increment, decrement, and new object expressions can be used as a statement
(ignor raycast, this works for my racer potitioning.)

using UnityEngine;
using System.Collections;

public class RacingSystem : MonoBehaviour {


	//checkpoint handler
	public GameObject Checkpoint;


	// RacerStats
	public float Speed = 1;
	public float MaxSpeed = 12;
	public float acceleration = 2;
	public float TopspeedTime = 7;
	public float Turnspeed =  6f;
	public float RacerPotision = 0;
	public float TrickActive = 0;
	public float DriftActive = 0;

	public GameObject RacerPotition;
	public GameObject ThisRacer;


	public  void OnCollision(Collision collision)
	{
		if (collision.gameObject.name == "Turn") {
			ThisRacer.transform.rotation == collision.gameObject.transform.rotation;
			// when a Racer detects a corner, the racerrs rotation becomes that of the corner and turns.
			// turnsped is for smoothing.
	}

	}


	public void Update (){
//-----------------------------------------------------------------------------------------
		if(Speed > MaxSpeed){
			Speed == MaxSpeed}// Limit Topspeed.
			// Accelleration Amination.

			// Tunrning The Racer.

//-----------------------------------------------------------------------------------------

	}




// Racer Position
	void HitByRay () {
		// Get Raycast Number to determan Position of Racer.
		Debug.Log ("Hit by RacerLine Raycast");
		RacerPotision == RacePotiotionRayCast.PotiosionCalculator;
	}

}

Line 28. You could’ve caught this one by yourself. It’s literally what the error means. You wrote == which is a condition instead of = an assignment

ThisRacer.transform.rotation = collision.gameObject.transform.rotation;

not

ThisRacer.transform.rotation == collision.gameObject.transform.rotation;