hey guys..since summer is looming..i have a quick question. so i have rears that have thread left but my fronts are done..my rear tire size is 245/35/19. i was wondering if getting used front tires of 225/40/19 would be safe since their two different sidewall sizes. obviously my wheels are stretched and im broke! hahaha **** it..its summer!!!! thanks guys!

Mine have different sidewalls and I've been driving it for about 3 months. Nothing catastrophic has happened so far

what is the offset and size of the wheel? is your car slammed? the front might rub depending on your setup since a 40 series is a lot taller than a 35 series

While its not much, but the rear tires will be about .25" shorter than the front.
I would look for other tires for the front, or depending on the width of your front tires maybe move the rears to the front and buy new rear tires.
Aspect ratios and sidewall heights can vary front to rear, but it's usually best to keep the larger diameter in the rear.

Yea Drew, they'll work if your not too slammed!
Gary

I'm running 245/40 rears and 245/35 fronts for now. No vdc issues whatsoever

As long as the diameter of your tires is within 3% of each other you'll be fine. But I wouldn't run shorter tires in the rear as you have suggested unless it's an absolute emergency.

+1 there is a tire diameter calculator that will tell you the difference in rolling radius, I am just not sure where the link is.. I know it is on some miata site though.

Beat me to it!! Thanks NightShift.