I am constantly running into a bug where my rear rim offset (never the front) gradually increases with each tab change, it can get to monstrous proportions if I dont keep it in check, last time I had an offset of over 11 inches! I can not tell you how to reproduce it since it always happens on every car I have built since the last update. All files have been verified through Steam and none were corrupted. Only mod being used is the Pyrlix’s “High Quality Essentials” mod(s).
Win 7 x64
Automation Build 150707
No idea what’s happening there and never heard of it before (as this is not the good old steamroller bug). In the next update the wheel morphing and sizing will be completely redone internally, so we think those problems should be fixed by then. 
I think I figured it out!! Build a car completely and max out your offset. Now switch to the Model tab, go back to the trim tab and then to tires, click the arrow for a larger rim offset on the rear tire, go back to the model tab then back to the trim tab, on my game the game adds that click to the offset AND calculates it in even though it shouldnt work, you can keep clicking the button for ridiculous sizes. Let me know if this makes any sense at all.
EDIT:Photo
Now, thats som serious spacers, man. 
xD Stance is so 1999 compared to THIS!
I also encountered this problem and managed to replicate it in this video : youtu.be/SQIHNSx5GkM
To fix this you just have to decrease the offset.
Yep but it manages to come back from time to time, usually on loading for me.
