Steering Rack different between 15" wheel and 17" wheel

The steering rack is different between the 15" and 17" models in the US. Main difference is a quicker steering ratio on the 17 inch wheel rack.

Your 15 inch rack will handle 17 inch wheel just fine, go for it.

 

The 17" wheels require more power to turn or "handle" so the rack was upgraded for that. Your steering will feel "heavy" with 17" wheels. Your mileage will drop a bit. You will have more traction as the contact patch will be larger due to the wider tyres. Those are the effects that will happen. If you're ok with that then have fun. I doubt the larger wheels would "overload" the steering rack of the 15" model.

 

Some of the differences are the Prius V (five after 2010) (17 inch wheels) has a more powerful brushless steering motor, and a different rack and pinion which provide a quicker ratio, almost 1 turn less from lock to lock.

As stated above you will have no problem with 17s on your car. Quite a few people are using them as a replacement for the OEM 15s.

 

According to CSG ( link ) the circumference of the 15" tire is larger than the circumference of the 17" tire. 78.48" vs 77.34" which means the 17" tires will turn more times in a mile 819.24 ( 17" ) vs 807.36 ( 15" ) plus the 17" tire is wider 8.46" vs 7.68 for the 15". When these factors are hooked together should make the car with the 17" tires have a quicker
0 - 60 time quicker and the mileage less. For this to be true, the air pressure would have to be the same and the test would have to be on the same car.

Dave

 

Tire rack lists the revs per mile as 844 for the 215/45-17 size and 834 for the 195/65-15 size for one type of Michelin, other brands seem to be about the same. I don't know why the CSG calculator is so different.

I suspect the difference in circumference doesn't have much effect on acceleration but no one has measured it yet. I think based on how the car feels the handling is quite a bit better with the wider tires but no one has any skid pad or autocross time differences either. Those of us on this site have noticed a difference in mileage of about 2 MPG due to the higher rolling resistance of the 2 cm wider tires.

In my opinion, having driven both, I prefer the wider tires and am willing to give up a couple of MPGs to get a little better handling and stopping.

 

Air pressure could make the difference, but who know for sure. My Prius has the 17" tires, my wife has a Miata and drives the Prius like she does the Miata, so I too need the wider tires just to keep her out of the ditch

Dave