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Old 11-23-2007, 11:57 PM   #1
SpDRcrWrex
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Member#: 91350
Join Date: Jul 2005
Chapter/Region: RMIC
Location: Denver, CO
Vehicle:
2005 Impreza WRX
World Rally Blue

Default Understanding Aspect ration on a 17x8 fitment wheel

OK so I've been trying to find the info in a search and have had little luck.

I currently have 17x8 wheels in a 45+ offset. I have 225/45/zr17 Pirelli P-Zero M+S. I have stock STI V7 struts and springs so my 05 wrx is sightly lowered but no more than a stock sti.

Can I fit 235/55/zr17 tires? what is the difference from those and 235/45? I understand the 45/55 is defined as aspect ratio, but I'm not getting the concept of how I can determine if it will fit my current wheel set up.

any help would be great
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Old 11-24-2007, 12:42 AM   #2
UkNuck
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Default

Aspect ratio is the sidewall height as a percentage of the section width

225 x 0.45 = 101.25mm sidewall

x 2 = 202.5mm = 7.97in

+ 17 = 24.97in


235 x 0.55 = 129.55mm sidewall

x 2 = 258.5mm = 10.18in

+ 17 = 27.18in... more than 2in taller


235 x 0.45 = 105.75mm sidewall

x 2 = 211.5mm = 8.33in

+ 17 = 25.33in

Note that in practice ALL sizes are nominal and you need to look at the manufacturer's ACTUAL rolling diameter and rev/mile data for the particular tire.

Best wheel + tire tech site I have found: http://www.carbibles.com/tyre_bible.html
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Old 11-24-2007, 02:16 AM   #3
waktasz
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Even if they did "fit" as in bolt onto your car without rubbing anything, your gearing and speedometer are going to be like 9% off.
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Old 11-24-2007, 10:27 PM   #4
SpDRcrWrex
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Default

right. so this what I've been hunting for.
a little help as to how to figure it out. I used the mazda miata website to help
my brain.

thanks
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