Welcome to the North American Subaru Impreza Owners Club Monday May 25, 2015
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
Click here to visit TireRack
Brakes & Suspension Forum sponsored by The Tire Rack

Losing traction? Need new tires?
Click here to visit the NASIOC Upgrade Garage...
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Brakes, Steering & Suspension

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 10-04-2006, 06:09 PM   #1
Alan l.
Scooby Specialist
 
Member#: 90085
Join Date: Jun 2005
Vehicle:
2009

Default Strut tower bars - How do they work?

I'm just curious... what type of chassis movement does a front strut brace actually prevents from happening?

Is it from the two strut towers from moving apart from each other, up and down movement during hard cornering, moving closer to each other?

Theres tons of companies that make strut bars for all types of cars. Most have hinges and some are solid one piece or bolted down like the jdm sti bars. Now depending on what type of chassis flex a strut bar does, being hinged or not might not make that big of a difference.

Just something I've always wondered but never got a definitive answer to.
* Registered users of the site do not see these ads.
Alan l. is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 10-04-2006, 06:13 PM   #2
tankerWRX
Scooby Newbie
 
Member#: 102053
Join Date: Dec 2005
Chapter/Region: TXIC
Location: Baghdad, Iraq
Vehicle:
2007 LGT (Sold)

Default

There is a wonderful FAQ section here at NASIOC, check it out:

http://forums.nasioc.com/forums/showthread.php?t=533787
tankerWRX is offline   Reply With Quote
Old 10-04-2006, 07:10 PM   #3
Mind
Scooby Specialist
 
Member#: 109216
Join Date: Mar 2006
Chapter/Region: MAIC
Location: PA
Vehicle:
08 STI DGM
76-77 Lancia Scorpion(s)

Default

Quote:
Originally Posted by Alan l. View Post
Is it from the two strut towers from moving apart from each other, up and down movement during hard cornering, moving closer to each other?
Yes.

Quote:
Originally Posted by Alan l. View Post
Now depending on what type of chassis flex a strut bar does, being hinged or not might not make that big of a difference.
My take on it is that hinged is fine. This would make the strut bar effective (for the most part) in only tension and compression loading, and in most scenarios, if the strut tops are moving around, they will be changing the distance between each other.

I have a WL rear strut tower bar on my wagon. It's hinged, and is designed so that the center bar section can be changed in length to make sure there are no fitment problems. There are two nuts that are tightened once the bar is at the correct length.

Every now and then those nuts get a little loose, and the bar starts creaking, and basically it creaks whenever it's under load. You'd be surprised at how much creaking there is... even on slight acceleration and mild turns you can tell that the strut tops are trying to flex.
Mind is online now   Reply With Quote
Old 10-04-2006, 08:34 PM   #4
chimchimm5
Scooby Guru
 
Member#: 88501
Join Date: Jun 2005
Chapter/Region: BAIC
Location: NorCal
Vehicle:
2011 WRX Hatch
Dark Grey

Default

I'm amazed that the "easily snappable" strut mount bolts (3) which are used to hold the strut bars don't break under cornering. It's not like the mounting plate holes are perfect matches to the bolts.
chimchimm5 is offline   Reply With Quote
Old 10-04-2006, 09:09 PM   #5
Mind
Scooby Specialist
 
Member#: 109216
Join Date: Mar 2006
Chapter/Region: MAIC
Location: PA
Vehicle:
08 STI DGM
76-77 Lancia Scorpion(s)

Default

Yeah, I've read numerous threads about people only mildly over-torquing those nuts and having them snap. I guess they must be pretty strong in shear but not that strong in torsion, whether it's the actual stud that breaks or the stud gets ripped out of the top mounts.
Mind is online now   Reply With Quote
Old 10-05-2006, 11:46 AM   #6
Scooby921
Merci Buckets
Moderator
 
Member#: 88606
Join Date: Jun 2005
Chapter/Region: MWSOC
Location: Clarkston
Vehicle:
2015 GMC Sierra
'13 JCW

Default

My roommate did a little strut bar research as his senior design project in college. They mounted strain gauges on the front strut brace on his civic. They tested the stock one vs. a Comptech titanium one. Under whatever test conditions they ran, the bar saw around 200lbs of load across it. Switching to a different bar only lightened the car. It didn't transfer any more load.

Now this is on a car that comes with a stock bar. Seeing that it takes 200lbs, I'd say its there for an obvious reason. The Impreza has a rigid chassis to start with. While strut braces may provide some benefit, I don't personally feel they are worth the cost.
Scooby921 is offline   Reply With Quote
Old 10-05-2006, 11:56 AM   #7
Alan l.
Scooby Specialist
 
Member#: 90085
Join Date: Jun 2005
Vehicle:
2009

Default

On the WRX, we have fender/cowl braces that should prevent both shock towers from any vertical movement under load. More so if you have aftermarket braces.

Looking at how most strut braces are designed, its more effective in preventing horizontal movement of the strut towers (coming together or apart). Then a hinged bar would still be beneficial to have because the force is either pulling the bar apart or pushing it inwards. If it were vertical movement, the hinge would just allow the bar to tilt up or down. Basically useless in that regard. Does this make sense?

Last edited by Alan l.; 10-05-2006 at 12:33 PM.
Alan l. is offline   Reply With Quote
Old 10-05-2006, 01:12 PM   #8
Psydotek
Scooby Guru
 
Member#: 44168
Join Date: Sep 2003
Chapter/Region: SCIC
Location: In your pant[ie]s.
Vehicle:
2003 Yellow WRX
with too many lights...

Default

The S204 comes with damper where a rear strut tower bar would normally go.
Psydotek is offline   Reply With Quote
Old 10-05-2006, 02:53 PM   #9
Turn in Concepts
NASIOC Vendor
 
Member#: 93646
Join Date: Aug 2005
Chapter/Region: MWSOC
Vehicle:
Many Track Records
Let us help you go fast!

Default

Quote:
Originally Posted by Alan l. View Post
On the WRX, we have fender/cowl braces that should prevent both shock towers from any vertical movement under load. More so if you have aftermarket braces.

Looking at how most strut braces are designed, its more effective in preventing horizontal movement of the strut towers (coming together or apart). Then a hinged bar would still be beneficial to have because the force is either pulling the bar apart or pushing it inwards. If it were vertical movement, the hinge would just allow the bar to tilt up or down. Basically useless in that regard. Does this make sense?
The problem is they are very flimsy and do not do their job.

I would replace the fender/cowl braces with aftermarket ones before eventhinking about a strut tower brace.
Turn in Concepts is offline   Reply With Quote
Old 10-05-2006, 03:23 PM   #10
rkramer
Scooby Guru
 
Member#: 118209
Join Date: Jun 2006
Chapter/Region: MWSOC
Location: North Dakota
Vehicle:
2015 WRX Limitec

Default

Quote:
Originally Posted by Alan l. View Post
If it were vertical movement, the hinge would just allow the bar to tilt up or down. Basically useless in that regard. Does this make sense?

they are useless for vertical movement... realistically 1/4 to 1/2 of an inch of vertical movement is ALOT. unless you have made the bar out of some extremely high test steel in I-beam configuration, most materials will easily flex 1/4 inch without much resistance that far out. (the width of the mounts)
rkramer is offline   Reply With Quote
Old 10-05-2006, 03:38 PM   #11
bucket7788
Scooby Specialist
 
Member#: 124263
Join Date: Aug 2006
Chapter/Region: MAIC
Location: Now with DB Super 16g and WI!
Vehicle:
2004 WRX Wagon
RomRaider + UTEC Tuned

Default

I have a rear strut bar in my 04 wagon. I believe that it is beneficial.

However, I have not bought into the front strut bar theory (for our cars). My reasoning is that all of the FSB's that I have seen for our cars are not straight. They have angles on both ends, unlike RSB's which are completely straight.

Those angles in the FSB's allow load to either lengthen or compress the FSB like a spring. It acts pretty much like a leaf spring between the strut towers. Thus, our FSB's are not really serving the purpose for which they are intended and if there is any benefit from them, it is minimal.

Pic ripped from JSCSpeed.com. Hope they don't mind.

bucket7788 is offline   Reply With Quote
Old 10-05-2006, 03:50 PM   #12
Alan l.
Scooby Specialist
 
Member#: 90085
Join Date: Jun 2005
Vehicle:
2009

Default

I recently replaced my fender/cowl brace with a larger, thicker afermarket one and felt a huge difference right away. I shouldn't have much vertical shock tower movement now but curious if they can still move horizontally which the cowl braces don't do jack for.

Even though most front strut braces would still flex to some degree, its still adding support by connecting the two towers together. The corning load maybe enough to move one tower but maybe not two together. I guess my conclusion is that a front strut bar is there to prevent the horizontal distance from shock tower A to shock tower B from changing. I don't see how it can help at all with vertical movement unless your bar is solid and super strong with zero flex.
Alan l. is offline   Reply With Quote
Old 10-05-2006, 09:20 PM   #13
Mind
Scooby Specialist
 
Member#: 109216
Join Date: Mar 2006
Chapter/Region: MAIC
Location: PA
Vehicle:
08 STI DGM
76-77 Lancia Scorpion(s)

Default

Quote:
Originally Posted by rkramer View Post
they are useless for vertical movement... realistically 1/4 to 1/2 of an inch of vertical movement is ALOT. unless you have made the bar out of some extremely high test steel in I-beam configuration, most materials will easily flex 1/4 inch without much resistance that far out. (the width of the mounts)
I think it may depend on if the relative vertical movement between the struts causes the distance of the strut tops to change or not. If one strut moves upward, and the other doesn't, then unless the 'moving' strut follows an arc that would always maintain the original distance between the two tops, then the bar would resist in tension or compression.

I don't think the bar is meant to resist flexural/bending stressing, which is why the pin-joint can be used, and why the cross member doesn't need to be that beefy. I think with the pin joint it's not really possible to transmit bending loads to the strut bar, with the exception of the friction you get at the pin joint from torquing the joint.
Mind is online now   Reply With Quote
Old 10-05-2006, 10:01 PM   #14
strohausii
Scooby Specialist
 
Member#: 26770
Join Date: Oct 2002
Chapter/Region: South East
Location: Tampa
Vehicle:
'02 WRX
midnight black

Default

Wouldn't a "correct" strut tower brace anchor to the firewall, and not to each other? (I'm thinking of the Carbing strut brace).
strohausii is offline   Reply With Quote
Old 10-05-2006, 11:50 PM   #15
Mind
Scooby Specialist
 
Member#: 109216
Join Date: Mar 2006
Chapter/Region: MAIC
Location: PA
Vehicle:
08 STI DGM
76-77 Lancia Scorpion(s)

Default

My understanding is that this is what the Fender Brace / Cowl Stays effectively do...

And I've been thinking about this for a bit... do you guys' think the fender brace and strut tower braces are redundant, or do you think having one would increase the need for the other?
Mind is online now   Reply With Quote
Old 10-06-2006, 01:10 AM   #16
chimchimm5
Scooby Guru
 
Member#: 88501
Join Date: Jun 2005
Chapter/Region: BAIC
Location: NorCal
Vehicle:
2011 WRX Hatch
Dark Grey

Default

Quote:
Originally Posted by Scooby921 View Post
My roommate did a little strut bar research as his senior design project in college. They mounted strain gauges on the front strut brace on his civic. They tested the stock one vs. a Comptech titanium one. Under whatever test conditions they ran, the bar saw around 200lbs of load across it. Switching to a different bar only lightened the car. It didn't transfer any more load.

Now this is on a car that comes with a stock bar. Seeing that it takes 200lbs, I'd say its there for an obvious reason. The Impreza has a rigid chassis to start with. While strut braces may provide some benefit, I don't personally feel they are worth the cost.
Years ago when I first learned about the strut bars I wanted to get ahold of these stress measurement probes we had access to in the engineering dept in college. The lab teacher said the little 1 cm stickers were expensive as heck, as they were accurate in the micrometers. Thanks for posting the data.

I just wish we could get access to these things.

I'm pretty sure, like everyone is saying, the strut bar prevents the movement of the towers getting closer or farther from each other (compression or tension of the bar). The towers will obviously flex in other dimensions, but the strut bars aren't meant for that.

Think about it another way, how would you simply and relatively inexpensively prevent the other motions of the towers? I think the strut bar is the best "bang for effort (not buck)" form of bracing. So that's why it's done.

If we really thought about it, we could try adding braces to truss all the joints... Incidentally, I had Korbach Frame Locks on my old car. The Korbach's were another effort to find a bang for buck bracing point.
chimchimm5 is offline   Reply With Quote
Old 10-06-2006, 03:28 AM   #17
drees
Scooby Specialist
 
Member#: 25905
Join Date: Oct 2002
Chapter/Region: SCIC
Location: San Diego, CA
Vehicle:
2003 Silver Wagon
Tuned with Enginuity

Default

If you could get some triangulation into the front strut bar it might be more useful, for example, if you had one that securely attached to the firewall.

For the rear, again, triangulation is key which is why the X-Brace seems to work so well. http://www.iwsti.com/forums/showthread.php?t=56168

It would be nice to have an independent company do some testing of cowl stays, and various strut braces.
drees is offline   Reply With Quote
Old 10-06-2006, 09:51 AM   #18
Alan l.
Scooby Specialist
 
Member#: 90085
Join Date: Jun 2005
Vehicle:
2009

Default

IMO cowl stays and a front strut bar do completely different things so it would be beneficial to have both.

cowl stays prevents mostly only up and down flex of the front strut towers. There is to some degree structural reinforcement to prevent side to side movement of the towers but a strut bar would be much more effective at doing that.

I already have af fender/cowl braces on my wagon. Going to install a front strut bar later tonight. I'll report my findings afte some testing. For me making the chassis stronger not only helps alittle in handling and turn in feel, it makes the car feel better and less cheap when your driving over rough uneven roads that NY is plagued with. This affect is amplified when your have bigger rims with low profile tires and suspension upgrades done.

Last edited by Alan l.; 10-06-2006 at 09:59 AM.
Alan l. is offline   Reply With Quote
Old 11-02-2006, 03:02 PM   #19
phatning
Scooby Newbie
 
Member#: 78433
Join Date: Dec 2004
Location: NJ
Vehicle:
2002 PSM WRX Wagon

Default

I just installed my Carbing strut tower brace w/ built-in master cylinder brace this morning... It was the most PIA strut tower brace install I have ever done and that was with my friend's help. Fitting was really tight because of the mcb extension.

For those of you who plan on installing this piece, you have to do the following:

* You definitely have to jack up the car a little so the suspension would drop down a bit.

* You definitely have to take out the fuel filter in order to make room for maneuvering the stb's mcb extension into place.

* You will most likely have to get a longer fuel hose to replace the existing one (running between the fuel line off the fire wall and the inlet of the fuel filter) as Carbing stb will make it impossible to tighten the hose back on. If you have to change this hose, make sure you do so before placing the stb on top. I learned it hard way; I ended up installing the stb twice basically.

* You may need to move the hose with return valve? (disk look-like thing) to the other side of mcb extension (towards middle of the engine bay) to make room for the remaining two hoses that will remain under the mcb extension.

I haven't driven long enough to notice anything significantly different or just different... Fender braces are next.
phatning is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
TD05 18G 7cm2 turbo: who has one and how do they work out for you? GDAryder Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 29 09-22-2008 12:20 PM
Bellagio garden water acs - how do they work? Sausage Off-Topic 17 10-20-2006 01:53 PM
Fuses ? how do they work ? Extraze Electrical & Lighting 3 04-12-2004 12:50 PM
Koni Inserts...how do they work? HiVoltg12 Newbies & FAQs 3 02-11-2004 03:56 PM
Adjustable sway bars - how do they work? tomrichardson Brakes, Steering & Suspension 5 05-03-2001 12:56 AM


All times are GMT -4. The time now is 01:58 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2015 Axivo Inc.
Copyright ©1999 - 2015, North American Subaru Impreza Owners Club, Inc.