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Discussion Starter · #1 ·
I apologize if this is a repost of often-discussed, or maybe I just did a poor job of searching the forum...


My car is the 2015 WRX Limited, so it came with 17x8 wheels. If i have no other suspension modifications, can I upgrade to 9"-wide wheels without concern of the tires rubbing inside the wheel well?

Thanks!:wave:
 

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Discussion Starter · #3 ·
Well, I wanted to stay with 17's for both weight and smaller diameter (not to mention price! :D ). Will 9.5's even fit?
 

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yes with no rubbing issues. go google it so you have an idea. i am planning on getting this kind of set up also
 

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Discussion Starter · #5 ·
Right on, post pics when you do!

Please excuse my ignorance, but what's the "+38" you mentioned in your first post?
 

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Right on, post pics when you do!

Please excuse my ignorance, but what's the "+38" you mentioned in your first post?
Wheel Offset
 

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OK, so that means pushing it out wider, thus lower center of gravity overall? Or am I not sciencing correctly? :)
Just stick to the recommended offset range.
 

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Discussion Starter · #12 ·
Yeah, changing your diameter will throw off the speedometer slightly, but it's pretty minimal is you get a tire size that brings you close to OEM spec. diameter.
 

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I’m not going to speak about whether or not you should stick to factory specs but I have 18 x 9.5 +38 and there is still a bit of room left. I didn’t have to roll my fenders for them. I have been told, however, that it has changed my mph reading ever so slightly
what is your tire size again?
 

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Why's that, zax?
The recommended offset range is the result of a fair bit of engineering beneath the skin. 90% of people that modify cars tend to oversimplify requirements and assume that the OEM "doesn't know." OEMs employ the best automotive engineers on the market and you should treat the recommendations as priority information.

The OEM suspension on your car is designed around these requirements.
 

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Discussion Starter · #16 ·
Gotcha, that makes sense, Zax. With respect, however, the student in me is curious as to WHY that offset is not better. Don't get me wrong, I believe you that the OEM is correct in their engineering, I'm just trying to learn & understand the science behind it.
 

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I wont speak for ZAX but IMO the offset may be better for looks and even handling but putting the wheels farther out than designed/intended puts more stress on the suspension and can cause suspension parts to fail or fail sooner.
 

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We must assume OEM designed for some optimized (with multiple variable inputs and trade-offs considered) wheel offset for their wheel bearing location. If you move the offset, you are changing the force location (torque) imparted on the bearing through the centerline of the wheel.

"CG" is not affected at all by this.
 

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Discussion Starter · #20 ·
We must assume OEM designed for some optimized (with multiple variable inputs and trade-offs considered) wheel offset for their wheel bearing location. If you move the offset, you are changing the force location (torque) imparted on the bearing through the centerline of the wheel.

"CG" is not affected at all by this.
Yeah, i think I used the wrong term to describe what I'm thinking of.... center of gravity is indeed the incorrect result of widening the wheel stance. It's been a while since physics class; what am I thinking of?
 
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