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Old 05-16-2008, 01:17 PM   #1
eclip5e
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Default Facts: WRX vs STI Spindles / Knuckles

First off:
Lets refer to the suspension housing as "knuckles". The cast-iron bits that join together the strut suspension, tie rods, control arms and hold the hub and bearing unit.

The 2005 STI unit looks like this:


I'm going to get together a bunch of information about what we know about the front and rear knuckles so people know what they need to do conversions.

Facts:
2005-2007 Knuckle Redesign
After 2004 Subaru changed the front STI knuckle design from a press-in bearing design to a bolt-in. This makes it easier to change the bearing and hubs at the track. The strut bracket is also thicker, requiring a wider lower strut bracket on the strut. The bearing is also beefier and has a longer lifespan. The PCD changed from a 5x100 to a 5x114.3 requiring new 5x114.3 rims.

WRX
WRX has a 5x100 PCD.

2002-2004 Front struts are interchangeable between WRX and STI as both use the same knuckle.
2005-2007 Front struts are NOT interchangeable between WRX and STI since the knuckle design diverged.

2002-2007 Front struts are interchangeable between WRX model years.
2002-2007 Rear struts are interchangeable between both WRX and STI model years.

What we need to know:
Is the STI rear knuckle different with respect to the hub as compared to the WRX?
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Last edited by eclip5e; 05-16-2008 at 02:50 PM.
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Old 05-16-2008, 02:22 PM   #2
MasterKwan
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I don't believe the rear knuckles are different. The rear backing plates are differrent. Even for WRX's, the rear backing plated changed depending on what rear brakes the car came with. I have both style backing plates here and had to swap them to install an 06 rear knuckle on an 03 WRX.

What I want to know is if the hub spacing from the face of the hub to the bearing changes between the WRX and the STI.

Only 04 STI front struts will fit a WRX. 05+ front STI struts won't fit a WRX.
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Old 05-23-2008, 03:11 AM   #3
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with machine work and alittle fab work you can make it happen!!!
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Old 05-23-2008, 03:12 AM   #4
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woops that last post was not invisibleSTI it was mufflerman69 just the login didn't change...
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Old 06-12-2008, 04:23 AM   #5
CTKNY
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Is the bearing better/bigger on the 04 sti housing comparted to the 02/03 wrx?
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Old 06-12-2008, 02:14 PM   #6
invisibleSTi
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Quote:
Originally Posted by invisibleSTi View Post
woops that last post was not invisibleSTI it was mufflerman69 just the login didn't change...
Lol I guess I left myself logged in @ your shop, you could have totally ruined me
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Old 06-12-2008, 11:53 PM   #7
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Quote:
Originally Posted by CTKNY View Post
Is the bearing better/bigger on the 04 sti housing comparted to the 02/03 wrx?
Correct on both counts.



~Josh~
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Old 06-13-2008, 07:01 AM   #8
MasterKwan
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I'm pretty sure the 04 STI and WRX use the same wheel bearing in the front. 6Gun sells a kit to both upgrade the 04 to the better wheel bearings at 5x100 as well as one that converts the 04 STI to the better bearing at 5x114.
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Old 06-13-2008, 09:47 AM   #9
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6Gun here, some more facts that may help you guys:

05 STi Front knuckle: The strut bolt holes are also different vs the old knuckles, they are space apart further.

STi rear hubs: are all the same (not sure about 08) with the exception of bolt pattern changing for 05+. So 05 hubs can be pressed into non 05 STis.


STi rear knuckles and bearing: same parts for all of the last few versions of STi's (not sure about 08), I know a few foreign folks with older STi's that are running 5x114.3 rear hubs. So all rear STi bearings are the same strength.

Front hub axle engagement: WRX, Legacy, Forester front axles can be used with STi hubs, pre or post 05. I believe that RS axles will also plug in.


STi rear hubs: do not have the same inner and outer diameter vs the WRX. So, you can't use R160 outer axles with STi hubs. Or use STi hubs with WRX bearings.

****I am almost certain*****
STi and WRX rear axles/CV: At least one of the WRX CVs will fit on a STi axle bar, possibly both CVs. I know many rally shops offer WRX folks 'Hybrid axles'. If this is true, folks could run WRX rear inner CVs (match the R160), an STi axle bar and an STi outer CV which will engage into the STi rear hubs. This may be cheaper than swapping to R180 rear diff and using standard axles.

Rear knuckles WRX vs STi: ****I believe**** there are a few differences including brake mounts, e brake design, wheel speed sensor, and most likely the diameter of the bearing housing has a larger diameter on the STi.
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Old 06-13-2008, 04:21 PM   #10
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Quote:
STi rear hubs: do not have the same inner and outer diameter vs the WRX. So, you can't use R160 outer axles with STi hubs. Or use STi hubs with WRX bearings.
Can you use STi bearings and STi hubs in a WRX knuckle with STi axles? This is for the 6MT swap guys that want to run an R180 and STi axles with WRX knuckles/backing plates/brakes.
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Old 06-16-2008, 09:50 AM   #11
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Quote:
Originally Posted by bluescoobywagon View Post
Can you use STi bearings and STi hubs in a WRX knuckle with STi axles? This is for the 6MT swap guys that want to run an R180 and STi axles with WRX knuckles/backing plates/brakes.
I am not sure.
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Old 09-15-2008, 08:55 AM   #12
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Bump for question...

So I have an 05 WRX...can I use 04 STi knuckles? I broke the ball joint housing bolt and need a new knuckle now! I just want to replace them on both sides since I need new wheel bearing anyways. I'm assuming I can just use 04 STi knuckles and bolt everything back together.

Thanks in advance.
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Old 09-15-2008, 02:30 PM   #13
gling
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Quote:
Originally Posted by mpggomd View Post
Bump for question...

So I have an 05 WRX...can I use 04 STi knuckles? I broke the ball joint housing bolt and need a new knuckle now! I just want to replace them on both sides since I need new wheel bearing anyways. I'm assuming I can just use 04 STi knuckles and bolt everything back together.

Thanks in advance.
Yes you can if you are referring to the fronts. I didn't bother changing the front knuckles in my 02 WRX when I did an 04 STI drivetrain swap.
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Old 09-15-2008, 04:22 PM   #14
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Quote:
Quote:
Originally Posted by bluescoobywagon View Post
Can you use STi bearings and STi hubs in a WRX knuckle with STi axles? This is for the 6MT swap guys that want to run an R180 and STi axles with WRX knuckles/backing plates/brakes.
I am not sure.
I answered my own question here. The rear hubs, knuckles, bearings and backing plates on the STI are completely different and other than the bolts that hold it to the strut, aren't interchangable with a WRX. The STI rear hubs are superior in many ways.
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Old 09-15-2008, 09:24 PM   #15
gling
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Quote:
Originally Posted by MasterKwan View Post
I answered my own question here. The rear hubs, knuckles, bearings and backing plates on the STI are completely different and other than the bolts that hold it to the strut, aren't interchangable with a WRX. The STI rear hubs are superior in many ways.
Not with respect to the bearing as far as I know (not sure about compatibility with struts) - RE: 04 STI. Please correct me if I am wrong though.

Cheers.

Gerald.
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Old 09-15-2008, 10:18 PM   #16
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I'm talking about 05+ I think. I wasn't certain about the 04. I posted pictures in the brake section a couple weeks ago with a direct comparison between the two showing the rear knuckle, hub and bearing. The STI one is much beefier. Seems almost like it's a secret. Everyone knows that the front bearings, hubs and knuckle were upgraded in 05 but, they also upgraded the rears too.
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Old 09-15-2008, 10:21 PM   #17
gling
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Quote:
Originally Posted by MasterKwan View Post
I'm talking about 05+ I think. I wasn't certain about the 04. I posted pictured in the brake section a couple weeks ago with a direct comparison between the two showing the rear knuckle, hub and bearing. The STI one is much beefier.
Clarification noted; 05+ STIs non-inclusive to my above post(s).
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Old 09-15-2008, 10:32 PM   #18
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Old 06-23-2009, 09:48 PM   #19
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Subscribed
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Old 08-03-2009, 04:09 PM   #20
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bump for a nice "sticky" style thread
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