Please see the screenshot I attached, I am trying to make skid marks using trail renderer, but one side of trail is going upwards just after it renders, it was working fine Unity 5.4, but when I upgraded it to 2017, it is behaving like this.
Most likely this happens because your object starting point is
(0,0,0) (world origin), hence the trail is being rendered from that position too.
You should create your object to a given position rather that creating it at the origin and then moving it to another place: this way the origin will not count as a valid coordinate for trail rendering.
If that doesn't work, you can use a different approach: when the object is created, its trail has a
Time value equal to 0. Next step, you can set
Time to a desired value, for the very first coordinate (world origin) will not count as timing out in respect of the
Time value, but the next will because the timer will be greater than 0.