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Old 08-15-2003, 07:45 PM   #1
WRXed
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Default BIG difference in OEM vs. Prodrive STi wheel fitments. Why?

The following question was raised but not answered in another thread about Prodrive USA having updated the wheel section of their website. So let me raise it again:

Why are the offsets on their (Prodrives) new wheel fitments for the STi so different from the stock +53? It's one thing to have a wheel that will clear the front calipers (I'm confident these do), but it's another thing to clear the calipers AND preserve optimum suspension geometry. A 9mm offset difference seems extreme to me and I am concerned about scrub radius and wheel bearing isssues.

I know Prodrive enjoys a great reputation in the Subaru community and they know infinitely more about suspension tuning than I do. Can someone explain why a 9mm offset difference is something I shouldn't be worried about? Thanks.

Ed
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Old 08-15-2003, 08:35 PM   #2
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I want to know this as well. What is real interesting is that Rota makes wheels that mimic the Prodrive wheels but have an offset within 5mm of the stock wheel.
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Old 08-19-2003, 11:17 AM   #3
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Before I pronounce this thread dead, I am bumping this in the hope that someone will respond.
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Old 08-19-2003, 12:49 PM   #4
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I was curious so i looked this up. I copied these the from the tirerack and prodrive websites. You should call prodrive and luke at tire rack. They may be able to answer your questions.

tirerack.com
"When the width of the wheel changes, the offset also changes numerically. If the offset were to stay the same while you added width, the additional width would be split evenly between the inside and outside. For most cars, this won't work correctly."

prodrive-usa.com
"All Prodrive wheels are specifically designed for high strength and OEM fitment, for maximum performance and wheel-bearing life. Correct offset wheels ensure no increase in steering kickback, torque steer or tramlining."
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Old 08-19-2003, 01:46 PM   #5
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Has anyone tried contacting Prodrive-USA directly and asking by phone?

- Janq
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Old 08-20-2003, 01:06 AM   #6
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Default ttt

Perhaps you would have better luck in the wheels/tires forum? I did a when I saw Prodrive's post too.

josh
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Old 08-21-2003, 03:29 PM   #7
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so this means that if we were to get 18x8 wheels the offset woudl have to be much less than 53mm correct?
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Old 08-21-2003, 03:43 PM   #8
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Quote:
"When the width of the wheel changes, the offset also changes numerically.
The point about some of the Prodrive wheels is that in standard STi size (17x7.5") the GC010 forged wheel is available with either an ET38 or ET46 offset.........the 46 offset is probably OK (if it actually clears the Brembos and it's not absolutely clear that this wheel with this offset does) but the 38 seems extreme given that the standard offset is ET53.

The closer you can get to ET53 (if you use a 17x7.5" rim) the better off you will be.
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Old 08-21-2003, 09:11 PM   #9
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Why would you want 18's? You lose performance. It may look better but the wheels are heavier and you sacrifice some handling?
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Old 08-21-2003, 09:15 PM   #10
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Quote:
Originally posted by essogas
Why would you want 18's? You lose performance. It may look better but the wheels are heavier and you sacrifice some handling?
Total not true!
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Old 08-21-2003, 09:17 PM   #11
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Quote:
Originally posted by essogas
Why would you want 18's? You lose performance. It may look better but the wheels are heavier and you sacrifice some handling?
Not according to Prodrive.
Not according to tarmac rally setups.
Not according to any racing class that allows them.
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Old 08-22-2003, 05:37 PM   #12
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you will actually affect performance, acceleration and reaction a bit. But since the Forge Allow wheels are very light the performance drop is being reduced considerably.
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Old 08-25-2003, 09:31 PM   #13
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This still doesn't explain why the offsets are so screwy. I personally think it's due to lazyness/cost. An 18x7.5 wheel should still have an offset of 53mm.
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