What is the proper size for a front RIM if 18x10 on rear?

I have noted that when using a 10” rear always an 8.5” is used in front. I was wondering, if there is a problem If I use a rear 10” with 275/35/18 and the fronts 8” with a 235/40/18? Does the 8" instead of 8.5" will make any difference?

If anyone knows please advice

Ricardo