Larger tires, anyone?

I haven't seen any problem getting tires in the stock size, though finding someone who carries them in stock may be a problem in some places.

You don't want to change the diameter much, as it can mess up the Prius system.

Examples of sizes that could be "compatible" are:
for the Nokian WR
Stock: series 65 size 185/65R15 load rating 88H weight 17.2 lbs rim size range 5-6.5 overall dia 24.4" overall width 7.4" tread depth in 32nds 12.5 revs/mile 850

Oversize:series 60 size 205/60R15 load rating 91H weight 20.1 lbs rim size range 5.5-7.5 overall dia. 24.7" overall width 8.2" tread depth in 32nds 12.5 revs/mile 842

Be aware the stock tire is a "metric" size (starts with "P") and comparisons may not be entirely accurate with non-metric sizes. Stock rim size is 6jj.

Note the weight goes up so performance would go down a bit. It may be best to stick with the stock size.

 

<div class='quotetop'>QUOTE(Wryter @ Jun 21 2007, 02:23 PM) [snapback]466027[/snapback]</div>

I did it by buying the Touring version which comes with 16 wheels.

 

We had the same fears as you do. Our Tire's Warehouse specialist told us to play it on the safe
side and not go over 16", due to the extra stress on the CVT and the whole electronically controlled
car. So far we have been happy with the good looking "legs" on our Prius. As for the circumferance
calculations, there are a couple sites to check and resolve the larger circumferance:
www.101tires.com/tiresizecalculator.asp?action=submit
For our calculations, it was only 1.622%. So far, we have 1100 miles and the wider tread is nice.
But its true what you say. At 16" there's a lot more choice. At 17" there is a LOT.
Here is a jpg of our Montegi 16" wheels & tires
[attachmentid=9109]

 

Key points for tire choice are revs/mile and rolling resistance. The standard OEM tire is 855 rev/mile on standard Prius, I don't know about Touring model. Tire weight won't make that much difference, though wheel weight will, so big heavy rims with big heavy tires will give you a fuel efficiency hit.

Be a bit wary of those tire size calculation sites, they can be off by quite a lot. LYLUVLY's URL wouldn't work for me, but Miata.net's tire size calculator says the stock tire is 824 rev/mile, not the 855 Toyota and Goodyear give. I put on Pirelli Cinturato P3000 195/60R15 tires which have 855.6 rev/mile, but the calculator says they are 833 rev/mile. When you find a tire you are interested in, go to the manufacturer's web site and find the tire's specs.

Finding out about rolling resistance, specifically low rolling resistance, is difficult. There are no DOT standards for rolling resistance. I think the best hope is to find a tire advertised as LRR and hope for the best. In general, a tire with high tread-wear ratings will have a bit harder rubber and be easier to roll.

For maximum fuel efficiency you would want skinny, hard tires with very high pressure inflation. But it wouldn't be a fun car to drive or very safe. For handling and curves you want soft wide tread and low side walls. But those take a lot of power to turn.

All tires are a compromise, just remember your life is riding on them...

 

<div class='quotetop'>QUOTE(Bill Merchant @ Jun 22 2007, 12:18 AM) [snapback]466237[/snapback]</div>

Bill, Are you totally satisfied with the Pirelli Cinturato P3000 195/60R15? I understand what you said about compromise, but how much of a milage hit did you take, if any? I have begun to notice my tires don't really have that much traction, and I worry about the winter. I have been thinking about the wider 60 series. Want new rims too, but not enough to give up MPG.

Do you run lower pressure in the winter?

What tires does your other Prius have?

 

An alternate size for the standard rims is 195/60/15. The Goodyear TripleTred (favored by some people) does not come in 185/65, and this is the closest you can get in the larger size and have approximately the same revolutions per mile.

 

From tire experts (industry insiders), run -higher- pressure for better snow traction. The tires "clean" better and dig into the snow easier.

I was advised by the experts that a larger wheel will end up heavier (larger rim, smaller tire). Unless of course, you go to extremes such as a super light magnesium wheel. But that can cost a LOT!

So I'm sticking with the 15" stock wheels, and going Nokian WR tires for great traction year round as well as LRR. It's just the size I'm contemplating. As per my earlier post. I'll probably stick with stock size.

 

<div class='quotetop'>QUOTE(Bill Merchant @ Jun 22 2007, 12:18 AM) [snapback]466237[/snapback]</div>

Thanks Bill. Any kind of input is welcomed and your inputs are very well correct.
Here is the site address again: http://www.1010tires.com/tiresizecalculato...p?action=submit
I just was there and copy and pasted the URL. This site takes on width, diameter, and all those other
dimensions which we do not understand. However, the tire manager was more restraint on our choice
than we were. He was very concerned with safety and stress on the Prius with heavy tires, etc, than us.
The tires we purchased were Potenza 205/50R16 87H on 16" Montegi 7 spoke wheels. Our 1000 mi
last week was just great. We averaged 46.5mpg--N on 101, and S on interstate 5. The wider stance
seemed to give a much smoother ride, over the old Integrity P185/65 R15. We kept our speed
between 65 and 70. Cruised at 65 and passed at 70. Just like you said, your life is riding on them.

 

<div class='quotetop'>QUOTE(NoMoShocks @ Jun 22 2007, 12:43 AM) [snapback]466244[/snapback]</div>

I'm very happy with the Pirelli tires. I'm getting a pinch over 48 MPG right now, coming up on the 5000 mile mark. I use the same pressure winter and summer. The 2005 has Goodyear Assurance ComforTred tires in the stock 185/65R15 size. Neither Prius is a Touring model and both have the stock 15" rims. Both the Goodyear ComforTred and Pirelli P3000 are superior to the Goodyear Integrity tire for ride, quietness, and wet and dry traction, IMHO.