Tire Size, general opinions welcome.

[4banger]

Just thought I'd follow up on this, between you guys and the extra cost of the other size tires I have devided to stick with 195/65-15s. Im going to run my current tires a little longer but I think im going to go with these Hankooks when the time comes.

Hankook Optimo H727

They weigh 20lbs which seems to be light for this size (the only lighter tires i saw were LRR tires at 18lbs) they have a 100k tread life warranty, 44psi max sidewall, cheap, and pretty good reviews.

[F8L]

I research tire specs and reviews quite a bit for my personal fascination and to help guide the purchase of tires for my friends at PriusChat. I also keep a fairly current list of LRR tires in Prius sizes so forgive me if I am unaware of other options available in sizes smaller than 15".

First, the larger wheel and tire will weight more than the smaller set by simple virtue 17" tires nearly always weight more than 15" tires and most 17" wheels weigh more than 15" wheels unless you have a set of low quality 15s and high quality (expensive) 17s. You also have to consider rotational inertia. Even if you somehow kept the weight the exact same between the 2 sets of wheels, you are changing where the weight is located on the wheel. With the larger 17" wheel you are pushing more mass further from the hub (center or rotation) and just like an ice skater performing a spin, the more mass you move away from the center of the axis, the slow you rotate or the more energy required to maintain a specific rotational speed. In a nutshell, heavier wheels or wheels that move more mass away from the axis will require more Energy to turn and you're not going to get it all back when slowing down.

My Peius came with 15" wheels from the factory. Later on I upgraded to 17" wheels. My mg average dropped from 50mpg to 44-46mpg. For the next 4 years I would swap back and forth between the two sets of wheels and the mpg difference stayed very constant. I eventually learned how to hyper mile the car and the gap in mg widened because the 15" tires simple roll much much further in a glide (coasting with the engine off and no regenerative braking) than the 17s. I eventually purchased new LRR 17s (Michelin Primacy MXM4) and guess what happened? The mpg stayed the same as my old worn out Kumho 17" tires and since the 17s don't glide as well as my 15s the mpg gap has gotten larger as my ability to hyper mile increased. Now my average summer tank with the 15s is approx. 57-53mpg and with the 17s it is 44-47mpg.

One factor to remember is the Prius gear ratio does not change with tire size differences like your car will so you have one extra thing to consider. A taller tire will reduce rpm at a specific speed compared to a shorter tire. Thus mpg will go up. Instead of trying to increase tire diameter with wheel upsizing, do it with tire size instead. This way you can take advantage of the many 14-15" LRRtires available. They are cheaper than LRR 17" tires to boot!

Oh, stay away for the Hankook H727 if you want a true LRR tire. They are not the best handling tire and they are not LRR. Instead look to one of the following instead:

Bridgestone Ecopia EP100
Bridgestone Ecopia EP422
Nokian enTyre
Nokian i3
Continental ContiProContact with EcoPlus
Yokohama dB Super E-Spec
Yokohama BlueEarth-1 (coming soon)
Goodyear Assurance FuelMax


Use the search function on tirerack.com to compare specs like weight, max psi, tread width etc. to compare tires and definitely read/watch the following test on some older LRR tires.

When Round and Black Becomes Lean and Green