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i read something on this before and I believe if you going from a 16 to a 17 inch rim then it may throw it off by 1 mph or km/h not sure but it can throw it off yes but so little that it is not worth worry about it and also to it will affect your gas mileage if your worried that too in a negative way unless they are a lighter wheel then your stock ones
 

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Discussion Starter · #3 ·
i read something on this before and I believe if you going from a 16 to a 17 inch rim then it may throw it off by 1 mph or km/h not sure but it can throw it off yes but so little that it is not worth worry about it and also to it will affect your gas mileage if your worried that too in a negative way unless they are a lighter wheel then your stock ones
There the OEM stock 2012 SI wheels so I don't know how much more they weigh than the OEM wheels on my EX-L
 

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probably not that much diff but if i had to guess i think the SI wheels are about 23 to 25 lbs a rim
 

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Discussion Starter · #5 · (Edited)
UPDATE: I called Tire Rack and they said I can go from OEM tires and rim to optional 215/45/17tires with 17 inch wheel it will be the same diameter 24.6 so anyone thinking of going to 17 inch wheels on your EX DX your SAFE as far as speedometer calibration
 

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Weight of the wheel and tire combo has nothing to do with the speedometer reading. The final tire diameter does; smaller means more revolutions per mile so your speedo will read high; larger than stock means fewer revolutions per mile and speedo will read low.
 

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Discussion Starter · #7 ·
Weight of the wheel and tire combo has nothing to do with the speedometer reading. The final tire diameter does; smaller means more revolutions per mile so your speedo will read high; larger than stock means fewer revolutions per mile and speedo will read low.
Yep that's what Tire Rack told me
 

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The variable being the rim diameter increasing and the sidewall area decreasing, resulting in a constant diameter. This means no inconsistencies! Go for it


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ive heard going to big from stock messes with your gear ratios ...idk thats what i heard a long time ago
 

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I have an EX sedan and the stock tires are a 205 so if you going to a 215 you have a larger diameter tire which means the Speedometer will be low relative to actual speed.
 

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Pickle Hammer Power
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:moved:
 

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I have an EX sedan and the stock tires are a 205 so if you going to a 215 you have a larger diameter tire which means the Speedometer will be low relative to actual speed.
Correct me if i'm wrong, but I'm pretty sure the number you're talking about is the width of the tire, not the profile. Therefore, it has nothing to do with the diameter of the wheel, thus meaning that that number wont effect your speedometer.
 

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I have an EX sedan and the stock tires are a 205 so if you going to a 215 you have a larger diameter tire which means the Speedometer will be low relative to actual speed.
Incorrect.

Correct me if i'm wrong, but I'm pretty sure the number you're talking about is the width of the tire, not the profile. Therefore, it has nothing to do with the diameter of the wheel, thus meaning that that number wont effect your speedometer.
Correct.


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Oy. Tire diameter is defined as:

2*tire width*aspect ratio + wheel diameter

Tire width does play into overall diameter.

205/55-16 has a 24.88" diameter
215/45-17 has a 24.62" diameter

So, the stock 16" tire will do 810.65 revs/mile. The Si 17" setup will do 819.18 revolutions. That's 1% difference. So, a reading of 60 mph calibrated to the 205/55 tires will be 60.6 mph with the 215/45 setup. More than reasonable error.
 

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Your speedo will read 1.052% too fast. So if you're going 60 MPH on the EX wheels/tires, when the Si wheel/tires are on, your speedo will be reading 60.6 MPH. Not much of a difference at all. No need to worry about it.
 

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^^ hey we said the same thing.
 
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