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post #1 of 9 (permalink) Old 05-13-2004, 07:55 PM Thread Starter
 
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Default Pressure for 17" Pirelli tires?

When we recently took delivery of our 2004 Prius, the dealer had taken off the 15" rims and tires that are standard and replaced them with fancy 17" rims with Pirelli tires (R215/45ZR17 87W). These tires have a smaller cross section since the circumferance is the same as the original tires. I assume this increases the dealer's profit! And what do I do with four 15" rims for an '04 Prius???

My question to the dealer was simple: what pressure do these tires require? No one had a clue!! I talked with the local tire people with whom I have been dealing for many years. They spent over 45 minutes with their computers, with calls to other tire dealers, etc. and were unable to get an answer. The Pirelli web site gave the psi for the 15" tires, but not for the 17"

Does anyone know the recommended pressure for these 17" tires when used with a 2004 Prius?
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post #2 of 9 (permalink) Old 05-16-2004, 12:18 PM
 
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I would start with 32 front and 30 rear. If you want a little cushier ride then go to 30 front and 28 rear. If you want a little more responsive handling go to 34 front 32 rear. If you want the best gas mileage look at the maximum pressure rating on the tire sidewall and set to 1-2 PSI below that value (at cold temp).
The low profile (45 series) of your tires should give you pretty responsive handling albeit at a price of a rougher ride.
Have you driven the Prius with the standard 15" tires/wheels? If you have how would you compare the handling of the car with the two different tire setups? Ride comfort? Noise level? etc.

Art
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post #3 of 9 (permalink) Old 05-17-2004, 11:16 AM
 
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Default 17 inch Tire Pressure

Replaced stock wheels/tires with BFGoodrich g-Force T/A KDW 215/45/17 and run pressure of 45F/43R. Amazing difference in stability. Cross winds are no longer noticable. Vehicle appears to be glued to the pavement under just about any (wet/dry) conditions. Ride is marginally harsher and you do lose about 1.5 MPG compared to stock wheels/tires, but still more than acceptable at 48.5 under 80 persent high speed interstate travel.
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post #4 of 9 (permalink) Old 05-17-2004, 12:48 PM
 
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Default Re: 17 inch Tire Pressure

Quote:
Originally Posted by WirelessToy
Replaced stock wheels/tires with BFGoodrich g-Force T/A KDW 215/45/17 and run pressure of 45F/43R. Amazing difference in stability. Cross winds are no longer noticable. Vehicle appears to be glued to the pavement under just about any (wet/dry) conditions. Ride is marginally harsher and you do lose about 1.5 MPG compared to stock wheels/tires, but still more than acceptable at 48.5 under 80 persent high speed interstate travel.
That is good to know. Do you have a photo of your car with those wheels and tires? I am curious to see how the Prius looks with 17" wheels.
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post #5 of 9 (permalink) Old 05-17-2004, 01:11 PM
 
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I'm wondering about something. When you increase the diameter of the wheels/tires of a vehicle doesn't that reduce the number of rotations that wheel makes over a measured mile? Wouldn't that reduce the mileage tally? Wouldn't you be going faster than your speedometer indicated? Might that not disturb some computer assignments in the operation of the vehicle? Hmmmmm. Whatshisname
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post #6 of 9 (permalink) Old 05-17-2004, 03:48 PM
 
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Quote:
Originally Posted by whatshisname
I'm wondering about something. When you increase the diameter of the wheels/tires of a vehicle doesn't that reduce the number of rotations that wheel makes over a measured mile? Wouldn't that reduce the mileage tally? Wouldn't you be going faster than your speedometer indicated? Might that not disturb some computer assignments in the operation of the vehicle? Hmmmmm. Whatshisname
The diameter of the wheel is larger but the overall diameter with the tire can be the same as the stock setup. The tire profile determines the outside diameter of the tire. Basically, the lower the profile number, in this case 45, the smaller the outside diameter. Put another way, the profile is related to the measurement of the inside diameter to the outside diameter of the tire. The lower the profile the shorter this distance is.
So, usually when going to a bigger wheel you would go to a lower profile to avoid the possible problems you mention. The stock tire has is a 65 series profile. The originator of this thread went to a 45 series.
Lower profile tires look more cool but since the sidewall is shorter they don't absorb the bumps as well. Benefits from the shorter and consequently stiffer sidewall are quicker steering response and improved corner handling.
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post #7 of 9 (permalink) Old 05-18-2004, 07:47 PM
 
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Gotcha Takemiya. Good response.Thanks.
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post #8 of 9 (permalink) Old 05-21-2004, 11:44 AM
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Default prius wheels

and as far as your question as to what to do with your extra 15" wheels, I would mount snow tires on 'em and run those in the winter...those low-profile 17's will be terrible in the snow.

if you don't live in snow country (how sad...), there are probably plenty of Prius owners who would buy 'em from you...you can post them in the For Sale Forum here.

I'd buy 'em from you, but I'm still months away from getting my Prius up here in the frozen North.

Rpm
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post #9 of 9 (permalink) Old 05-29-2004, 12:45 AM
 
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I'm using 42 front/40 rear on mine.

For anyone that hasn't seen the 17" wheels:
http://prius.nitro9.org/2004.shtml
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