Wheel Size Preference for Gen4

i agree. if 14" rims improved mpg's, that would be a great choice.

 

So true about the obsession for larger wheels & low profile tires. Go to the thread about aftermarket wheels, and you find I may be the only one who wanted a customized aftermarket look WITHOUT going to a larger wheel diameter and low profile tires. Nearly all of the 15 inch aftermarket wheels were wider than OEM 6 inch width. Bigger is NOT always better.

 

The functional size of rims is dictated by the size of the brake assembly that it has to house within.

In racing, the maximum diameter of the wheel assembly (which affects the contact patch, which affects the overall potential performance envelope of the racing vehicle) has effects on the necessary structure of the vehicle to bear the increased leverage and loads (which has ramifications on the total cost of the racing class, which is always something a racing body seeks to control in order to facilitate adequate participation), which is why it is always limited to a spec. Of course, within that maximum diameter spec, a racing team is often free to pursue whatever the manufacturing technology will allow to give the most effective (read: biggest) brakes-to-contact-patch-to-unsprung-mass ratio to arrive at optimum performance for a given venue.

In production-car-based track racing, this often takes the form of big brakes housed within big rims that will accommodate them, which necessitates low-aspect-ratio racing slicks. The aesthetic that people fixate on is based on that.

In terms of high-fuel-efficiency hybrids such as the Prius [as opposed to more-performance-oriented (i.e. Lexus) luxury hybrids and maximum-performance-oriented (McLaren & Porsche) supercar hybrids]... unless low-rolling-resistance-tires suddenly undergo a breakthrough in which grip is substantially raised without raising rolling resistance... existing brakes do not have to be much bigger. Therefore a functional rim size does not need to be more than 15-16"

See, people enamored with the low-aspect ratio tire look will preach about sidewall flex. They're either ignorant or conveniently forgetting that F1 racecars have had gigantic sidewalls for decades. Different creatures than normal cars? Absolutely. But the physics of tire side-loads remains the same, and tires can be easily engineered (and are commonly available!) with rock-stiff sidewalls. The sidewall stiffness of a set of semi-racing Falken Azenis' will kick the snot out of expensive max performance street tires in a +1 size.

So yeah, it's about looks. That's about it.

So yeah, I'm with you guys in terms of function over style. Unless the Prius was going to be aimed at something else altogether... it should stick with roughly the same brake proportions, and hence roughly the same rim proportions.

Of course, if we increase the car's ability for regenerative braking (might necessitate active torque distribution differential), we could even decrease brake sizes...

 

15" would be optimal. It is easier to buy tires for and cheaper tires. 14" wheels are hard to find a wide variety of tires in comparison ( 85 celica gts has 14" and I hade very little selection on tires for it and they all sucked).

 

I hope they stick to 15 inch wheels. It seems to have worked well for the gen 3.

 

Here in UK I have an Auris Hybrid Ts and Toyota would not supply it on other than 17 " wheels and told me (and my insurance company) that it was not homologated for 16". Even the spec sheet says there is a 9mpg penalty, and it is not exempt from congestion charges on 17" wheels. My average is 10 mpg down on my old Gen 3 despite same running gear.
I am looking to go to the Gen 4 but can not find one to test drive on 15" wheels. Dealers tell me they can not sell the demonstration cars on 15" wheels so will not order them. TOYOTA GB just do not want to sell cars on 15" despite the reviewer's saying the choice is a no brainer.
At least in UK we can now pick the size wheels on all grades of Gen 4.

 

After having 3T for a few months (17") I will add my 2c. Based on Toyota's specs, and my own observations, I don't think there is an MPG penalty compare to 3. I also don't experience any additional noise level. Cannot compare with 3, but it is pretty much the same as was my 15" Gen 2. The ride I expected to be much more rough, but was surprised how smooth it is.

There a few disadvantages. Some about the price you mentioned. But one other is that the radius is some 2 feet bigger in 3T. That I can feel. You make U-turns in a number of standard places following your routine, and some of them I cannot fit any more.

As for the look, I never cared about this aspect. But now, each time I approach my car, have to admit - it is kind of cool!