Can my car handle two different tire sizes?

Different tire diameters mess up the ABS and skid and stability controls. They all function on the presumption that tire diameters approximately match.

 

People who use Prius for racing at the track use different size tires with the big ones in front to handle the powertrain and small tires in back. So if I were you before you spend any more money get out your jack and spare and swap your tires front to back and see if that solves the problem for free!

 

Act in haste, repent at leisure.

Was there some extreme time pressure so that you couldn't wait a few hours or a day to get the right tires?

Seems kind of fishy to me that in a major city like Chicago it wasn't possible to find a set of tires in the correct size within a reasonable period of time. In suburban Los Angeles the tire shops can generally get anything one wants within a few hours from the warehouses, at worst a day if you go to the tire shop in the late afternoon. (This is prepandemic, of course.)

Seems much more likely that the shop didn't want to be bothered and foisted off the wrong size tires on you because they were sitting on the shelf already.

 

Regardless I just ended this problem I had 185/60 in the front and 65s on the back and the traction control and the skid control would activate anything over 56 miles an hour and worth gas mileage went down just maybe 2 mi to the gallon. I did not reverse the situation as this is the tire configuration I kind of run on the Corolla 65s in the back and the '60s in the front whatever the width is and of course those cars have no traction control so no issue. So I didn't try it backwards I just put the 185/65 that I had on the right rims and put them back on the car and everything stopped

 

The problem you're seeing is that the skid control system looks for a difference in wheel speed between the 4 wheels. It ignores differences until it exceeds a threshold. A small tire needs to make more revolutions than a large tire to go the same distance. The faster you drive, the bigger the difference is that the car computer sees. At 60mph (in your case) the car is detecting the threshold difference and thinks you have a tire slipping, which is activating the skid control to protect you. Once you get back to equal size tires, the problem should go away.

 

As others have mentioned, the different tires sizes are making the "skid control" ecu (ABS, brake control, etc) unhappy. Specifically when you are just driving and not braking, the ecu looks at the front wheel speeds vs. the rears.

If those are "too different", then the ecu thinks you're spinning the drive wheels and steps in - you get weirdness along with the amber "squiggle line" indicator- this is the traction control function.

Posted via the PriusChat mobile app.

 

For the 195 width the height ratio should be 60. While the diameter might not be exactly the same as 185/65, it will be much closer than 195/65.

 

Some Porsches & Tesla's (maybe other manufacturers too? ) use different tire sizes between front & rear. It's OK - if the cars' ABS accounts for the difference. Otherwise it's going to be an issue.