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Old 12-17-2009, 03:59 PM   #1
JDwhiteWRX
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Default How I got more caster

Most of you probably know this stuff but I thought I'd put my results up for anyone who doesn't, this is such a cheap way to make your car handle a lot better!
You may have heard of the free caster mod which involves flipping a bracket that joins your control arms to the bushing (sorry i don't know the tech names)
This bracket has a slight offset so when you flip it you will be pushing your wheels out and forward and thus you get some more caster. Its the same principle as the gain in caster you get from a ALK, the bushing has an offset and it pushes your wheels out and forward. ALK cost $, free caster mod if free although the ALK does other things too.

Now taking it one step further you can put a spacer in between the control arm and the bracket that you flipped, a picture tells a thousand words!
This is my car with the bracket flipped and a 6mm spacer added, you need 50mm bolts for this, OEM are 37mm.



These are the 6mm spacers, 35mm x 75mm.


The gain in caster I got from this was not huge so I got a 10mm spacer, below is the pic of them fitted


Another very important thing I discovered is that there is movement available from where the rear bushing housing bolts to the car, see the photo


You need to push this as far forward as possible before torquing it up to get the maximum caster.

My current alignment settings are now:

Front camber: Left -2deg 19' Right -2deg 06'

Rear camber: Left -1deg 54' Right -1deg 41'

Front caster: Left 4deg 48' Right 5deg 01'

zero toe all around


The car is a real pleasure to drive and has loads more grip up front.


JD.
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Old 12-17-2009, 04:23 PM   #2
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Great post. Have you tried to get the caster more even side to side? Isn't half a degree difference pretty substantial?

Mine is a bit uneven too, and I believe it has to do with alignment of the holes that you show in you last photo.

What were your caster numbers stock and with the 6mm spacer?
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Old 12-17-2009, 04:32 PM   #3
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On a perfectly flat track you may want more even settings, but on normal street driving you will actually want slightly more front right caster vs front left caster to account for the "Crown of the Road". Usually around .03 degrees more on the Right vs Left pretty much makes up for that.
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Old 12-17-2009, 04:44 PM   #4
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Quote:
Originally Posted by wheatpaste View Post
Great post. Have you tried to get the caster more even side to side? Isn't half a degree difference pretty substantial?

Mine is a bit uneven too, and I believe it has to do with alignment of the holes that you show in you last photo.

What were your caster numbers stock and with the 6mm spacer?
Thanks,

If I knew how to do my own wheel alignments I could possibly do this but all I did was push the mount as far forward as possible and torque up the bolts. I then took the car for a wheel alignment as your toe goes out a fair bit with this mod. Remember caster is measured in degrees and minutes, I'm at 48 minutes, thats close to 60.

The caster with 6mm was around 2deg5' but I had not thought about moving the whole mount forward at this stage and I think the caster gained with the 6mm spacer was lost by having the mount in the rear position if that makes sense.

Quote:
Originally Posted by flukewrx View Post
On a perfectly flat track you may want more even settings, but on normal street driving you will actually want slightly more front right caster vs front left caster to account for the "Crown of the Road". Usually around .03 degrees more on the Right vs Left pretty much makes up for that.
Unfortunately we drive on the other side of the road but yeah i know what you are saying.

Last edited by JDwhiteWRX; 12-17-2009 at 06:48 PM.
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Old 12-17-2009, 05:16 PM   #5
jaredperry
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Great write up! Whats the hole spacing measurement on the spacer?
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Old 12-17-2009, 06:42 PM   #6
JDwhiteWRX
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Quote:
Originally Posted by jaredperry View Post
Great write up! Whats the hole spacing measurement on the spacer?
Thanks,

I can provide measurements but the safest way to do this is to remove the U-brace (sub frame) and then remove the rear bushing mount completely off the car (at this point you would mark the holes for drilling).

Then re-install the bushing mount but install the spacers and bolts into the control arm first as the control arms are Aluminum alloy and there is a risk of cross threading.

Then replace the bolts that hold the rear bushing mount but don't torque up yet, leave them loose.
Then replace the U-brace and torque it up to spec, then use something (large screwdriver etc.) to lever the bushing mount as far forward as possible before torquing up the bolts, I lever it against the u-brace.

When I went from the 6mm spacer to the 10mm spacer I didn't bother removing the u-brace, I just undid the bolts, slid the 6mm spacer out and slid the 10mm spacer in and replaced the bolts. This was not easy to do and there was a risk of cross threading although it didn't happen.
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Old 12-17-2009, 07:21 PM   #7
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Oops, didn't notice you were in Australia. In that case I guess just flip the numbers from Front Left to Front Right.
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Old 12-18-2009, 01:53 AM   #8
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Quote:
Originally Posted by JDwhiteWRX View Post
Another very important thing I discovered is that there is movement available from where the rear bushing housing bolts to the car, see the photo

You need to push this as far forward as possible before torquing it up to get the maximum caster.
This is really an important point.

With the use of a screwdriver as a lever and a clamp I was able to move the rear mount 6mm forward and 2mm outward from where it sat originally. I'm sure this alone would have a bigger effect on caster than just flipping the stud. This should definately be mentioned in ALK installs, etc.

How is clearance with the wheels and the front of the wheel well after the spacer?
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Old 12-18-2009, 11:53 PM   #9
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What were your caster numbers before? Any other mods that would affect it?

That is pretty cool, assuming the bolts hold up of course.
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Old 12-19-2009, 09:55 AM   #10
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I wonder how much strain it's putting on the bushings now. I'm sure they can take it but it would be interesting to see.
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Old 12-19-2009, 12:32 PM   #11
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Do you have the Aluminum control arms with extra caster? Or the aluminum standard control arms?
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Old 12-19-2009, 01:03 PM   #12
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how far did it push the wheels forward? I know the normal free caster mod does so this must alot more. Any side pictures?
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Old 12-20-2009, 12:25 AM   #13
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Quote:
Originally Posted by STiRA-435 View Post
How is clearance with the wheels and the front of the wheel well after the spacer?
Here are some pictures showing the current clearance in front of the wheels. I think there is still plenty of room.




Quote:
Originally Posted by ButtDyno View Post
What were your caster numbers before? Any other mods that would affect it?

That is pretty cool, assuming the bolts hold up of course.
This is the only mod I have done that affects caster, I'm still using factory strut tops.

I don't have any initial measurements from the wheel aligners because it is not considered ajustable they never wrote them down for me on previous alignments. The factory caster is around 3.5 (3deg 3') I believe.

The bolts are 13mm longer than OEM and high tensile FYI.

Quote:
Originally Posted by Daishi00 View Post
I wonder how much strain it's putting on the bushings now. I'm sure they can take it but it would be interesting to see.
yes it would be putting some extra strain on them for sure, there is a option to upgrade these to a firmer polyurethane bushing and you could even go to an offset bushing or ALK and get even more caster, its something I may do in the future.

Quote:
Originally Posted by Dubstar112 View Post
Do you have the Aluminum control arms with extra caster? Or the aluminum standard control arms?
I have the standard aluminum control arms that come with an MY05 Australian delivered WRX. I'm not sure what you guys get over there, but we have 17" wheels, inverted struts, aluminum control arms and 4 pot brakes in MY05.

Quote:
Originally Posted by wantsti View Post
how far did it push the wheels forward? I know the normal free caster mod does so this must alot more. Any side pictures?
I don't have measurements but I have attached a couple of photos above.

Last edited by JDwhiteWRX; 12-20-2009 at 12:32 AM.
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Old 03-24-2010, 06:32 AM   #14
JDwhiteWRX
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Default Dimensions

I've had a few PM's about the spacer size I used so I have measured them and made a diagram.



You will need longer bolts for either 6mm or 10mm spacers, standard ones are 37mm, you will need 50mm long 12mm x 1.25
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Old 03-24-2010, 12:51 PM   #15
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Quote:
Originally Posted by wantsti View Post
how far did it push the wheels forward? I know the normal free caster mod does so this must alot more. Any side pictures?

I didn't do this mod specifically, but here's a shot of my wagon with ~5.3* of caster. It's got '04 STi arms, WL offset bushings, and WL Com-C strut tops. There's still PLENTY of clearance. While the wheel is noticeably pushed forward, maybe 3/4", it still has about an inch or so of clearance throughout the turning angle.

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Old 05-28-2010, 12:54 PM   #16
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Bumping it up for a thread with a decent amount of good info on a relatively painless and free mod for our cars!
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Old 05-28-2010, 05:05 PM   #17
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interesting

anyone knows how much caster bmws and benzes run? When I see an S or 7 series turn the wheels at full lock, they look like they are about to fall off

btw this is what the wheel looks on GC with Spec C caster arms, flipped brackets

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Old 05-29-2010, 08:43 AM   #18
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Can someone explain to me how adding a spacer (6mm or 10mm) between the LCA and it's rear mounting bracket adds caster? Wouldn't that just change toe more than anything else? I thought that (if anything), you would have to insert a spacer between the LCA's rear bushing and the body,...ie, pust the rear of the LCA down.

Where have I got this wrong?
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Old 05-29-2010, 11:13 AM   #19
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Quote:
Originally Posted by renhoek View Post
Can someone explain to me how adding a spacer (6mm or 10mm) between the LCA and it's rear mounting bracket adds caster? Wouldn't that just change toe more than anything else? I thought that (if anything), you would have to insert a spacer between the LCA's rear bushing and the body,...ie, pust the rear of the LCA down.

Where have I got this wrong?
I made a crude little drawing for you lol


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Old 05-29-2010, 07:47 PM   #20
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GOT IT!. Thanks for your effort.
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Old 05-30-2010, 07:05 AM   #21
JDwhiteWRX
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I can update this thread with a little more info actually, thanks for the bump.

With the 10mm spacer and my car lowered on H&R sport springs (35mm drop) I ended up wearing a hole in my fender liners from hard cornering at full lock. I had about 5* of positive caster which pushes the wheels a fair distance forward and with the car being so low the tyres were melting the plastic.

The car is now on 07 STi black springs with d-specs


I have also gone to a group n rear lower control arm bushing and still using the 10mm spacers.


My new alignment came out at 4deg 50 minutes of positive caster both sides and I do not get any more contact of the tyre on the fender liners at my new ride height.



.
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Old 05-30-2010, 04:13 PM   #22
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what difference did it make to use the group n rear lower control arm bushing?
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Old 05-30-2010, 07:45 PM   #23
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Quote:
Originally Posted by inkong View Post
what difference did it make to use the group n rear lower control arm bushing?
There are three main bushings in the front suspension (see photo). Lower control arm rear bushing, lower control arm front bushing and strut tops. I have just replaced bushes 1 & 3 (strut tops, rear LCA) with group n rubber so there less slop when you change direction ie. more direct steering and alignment settings are held solid in hard cornering.

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Old 05-30-2010, 08:01 PM   #24
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Quote:
Originally Posted by JDwhiteWRX View Post
I can update this thread with a little more info actually, thanks for the bump.

With the 10mm spacer and my car lowered on H&R sport springs (35mm drop) I ended up wearing a hole in my fender liners from hard cornering at full lock. I had about 5* of positive caster which pushes the wheels a fair distance forward and with the car being so low the tyres were melting the plastic.

The car is now on 07 STi black springs with d-specs


I have also gone to a group n rear lower control arm bushing and still using the 10mm spacers.


My new alignment came out at 4deg 50 minutes of positive caster both sides and I do not get any more contact of the tyre on the fender liners at my new ride height.



.
Is that actually a groupn bushing or a GTSPEC alk?
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Old 05-30-2010, 08:16 PM   #25
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It was sold to me as a gtspec alk but when I got it I noticed it was exactly the same as the stock bush but just hard rubber and bright blue. I don't mind, it was very cheap.
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