Is it possible to mount larger tires on my current rims??

I mount over-sized, tires on our 2003 Prius because I want the 'over drive' capability of a slower turning tire. I have not done the experiment on our 2010 Prius as the Sumitomo T4s are perfectly fine and easily have two years of service life remaining. But I can share how I approached the problem:

• Critical dimensions: tread width and diameter (see Tire Rack specifications)
• Critical mount: rear wheel well
• Critical test: a 'dip' speed bump as this ensures maximum displacement of the wheels

Protocol, buy one tire of the target dimensions. Mount it on one rim and on one rear wheel. Then run over a 'dip' speed bump (i.e., water drain dip that crosses a street.) Start as the posted speed limit and listen for tire interference with the body. Increase the speed to make sure the tire does not rub the wheel well.

If it works, order the remaining tires and have a happy.

If it rubs on the rear, move that wheel to the front and repeat the test. If it rubs on the front, it won't ever work . . . go down in size. If it works on the front but not the rear, you have the option of running larger diameter tires on the front and a smaller size on the rear.

DO NOT RUN TIRES AT REDUCED PRESSURE!!! This causes the tires to run hot and leads to early failure and high wear rate. This is a safety issue, yours! Remember the Ford-Firestone problem (ask Mr. Google,) people died from sudden tire failures and rolled their cars or changed lanes into on coming traffic. I am not trying to scare you . . . I'm trying to terrify you that underflated tires is like playing with a loaded gun with the safety off.

If you want a 'smoother', American boat-like ride, I would recommend test driving a Ford hybrid. Their suspensions are impressive and more tuned to the American style. If I were going to try and do that with our Prius, I would look at changing the suspension shocks and springs but this will run thousands of dollars. It is not a trivial change but would be the right approach.

Bob Wilson

 

A few people have gone to 205/50R17. The 215/45R17 is slightly smaller OD than the base Prius 195/65R15, whereas the 205/50R17 is virtually the same OD, just slightly bigger. Being slightly narrower, it should improve mpg, and the taller profile'll should absorb shock better.

These are not official OD's, just running formulas on the specified size. Should be close though:



For tires available in this size, with decent rolling resistance, maybe Bridgestone Ecopia EP422 or Michelin Premier A/S? The latter might give up some RR, and is more expensive, but has better reviews on TireRack.

 

My 2010 Auris came with the exact same rims, and Michelin Primacy HP 215/45/17 from the factory. I'm not sure if they are supposed to handle the abuse better, but they feel fine to me on Greek roads, which can get pretty rough.

 

Most 205 /50/17 lrr tires are Xl rated which will have a stiffer sidewall than the 215/45

 

Please post an update after you've driven those EP422 a bit. They're on my list of potentials.