Set Y rotation on already spinning object

OK, I feel like such a noob with constant rotation questions, but I have yet another one (just 2 years in now!).

I have a wheel spinning happily enough on it’s x-axis. However, I would like to give it a specific y rotation based on the steering wheel rotation (ie between -45 and 45).

But I’m tinkering away and can’t find the “right” answer. If I use euler angles, the wheel does this weird backwards and forwards spin.

leftWheel.eulerAngles = new Vector3 (leftWheel.eulerAngles.x, rotationAmount, leftWheel.eulerAngles.z);

Pretty sure this because euler angles converted to quaternions can give the y and z values a 180, and then reduce the x amount. All rather bonkers, but I know that quaternions are a place only for the super brainy!

So does anybody have a clue on how I can get the y value set to a specific rotation without screwing up the “roll” of the wheel?

Thanks Firedan, but the thing is that I don’t know what one of the rotations will be (because the wheel is spinning). The y-axis is the one I want to change, but its Euler angles flip from 0 to 180 during rotation of the x-axis for some reason.