Aftermarket strut tower bars are generally considered to be decorative on many brand new cars. However, it seems to be a bit more logical that a chassis with 100K miles would have developed some flex and could use a cross-member to stiffen things back up.

Background: the specific car in question is a 2004 Subaru Impreza WRX wagon, daily driver with 110K miles, none of them off road or racing. (Note from future me: and now it has 190K miles!)

So, the specific questions:

  1. Does an aftermarket strut tower bar have any measurable effect during an enthusiastic daily commute?

  2. If so, how do you measure the effect?

I have to admit, there have been plenty of times when I have wished that there was a bar across the engine bar just to give me something to lean on (as opposed to the intercooler!). That doesn't seem like a sufficient motivator, though.

EDIT to follow-up on some of the points in the answers: the fundamentals of the suspension have already been sorted: Hotchkis sway bars with new bushings, KYB Excel struts (that are effectively OEM replacements) with Kartboy endlinks. This isn't an autocross car but the easy targets have already been addressed. Now we're literally talking about tightening up an aging chassis.

And the answer can be no, there won't be a difference.


10 Answers 10


From my experience with a number of Subarus (my current oldest one being an MY2000 Impreza turbo with PPP and 130,000 miles on the clock) I can state that a strut brace makes an amazing amount of difference to both my usage (definitely enthusiastic) and my wife's (normal commute plus kids to school etc)

It stiffened the handling up significantly, makes cornering feel much more precise and makes her feel safer when driving. This is an old, well used car - and before adding the strut brace it did feel 'tired' - maybe the wrong word, but everything does get looser with age:-)

For me it just makes some maneuvers on the track feel much less likely to upset the balance of the car - essential at 140mph plus!

  • thanks for the feedback. My second question is still open: can you measure the effect? Is there an effective chassis-stiffometer that we could attach to the car to show the before and after benefits?
    – Bob Cross
    Commented Mar 8, 2011 at 19:28
  • @BobCross - now that is something I don't have an answer for, sorry. I'll ask the guys at my Subaru garage though, and ping an answer back here.
    – Rory Alsop
    Commented Mar 8, 2011 at 21:25
  • thanks - that's the real motivation for the question. We all know that they're cool and we also know the limitations of the "butt dyno": if it was expensive, it must be awesome!
    – Bob Cross
    Commented Mar 8, 2011 at 21:33
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    @Bob - very late response: the garage don't have written figures, but they recommend it (not from a sale - I got mine almost free) but they showed me the flex with it disconnected and then bolted back on while lifting one wheel on a power jack. The twist in the chassis was easily visible to the naked eye without the brace, and about half as much (but still visible) with the brace fitted.
    – Rory Alsop
    Commented Jul 19, 2011 at 13:51
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    @JeffSwensen, thinking further about this, I think a slalom would be much more important in discriminating between a loose and tight chassis. In a steady-state skidpad run, the whole system will take a set and hold it. In a slalom, if the chassis is going to flex from one extreme to another. That will have an effect on the run. NOW, all that said, I don't have a skidpad or a slalom....
    – Bob Cross
    Commented May 16, 2012 at 12:25

If so, how do you measure the effect?

tl;dr: by measuring the tension between the unbraced mount points.

Today, I installed a Whiteline rear strut bar on my 2004 WRX wagon. The car has 162K miles on the odometer and has always seemed in need of a little more stiffness in the area of the rear seats. There's a large volume back there without any sort of cross bracing (unlike a sedan) and the brace certainly seemed worth a try.

In the spirit of my original question, however, I wanted to see if I could measure the effect on the chassis in a static scenario. I tried two situations: flat on four wheels and with the driver's side rear wheel on four stacked 2x10 boards (which puts the wheel about six inches above the ground). I installed the circular fittings on the car and attempted to collect some reference imagery along with a little qualitative data.

NOTE: yes, in an optimal world, I would have used steel wire and a tension gauge. In the spirit of run what you brung, though....

First, leaving the wheel flat on the garage floor:

The inside of my car with some paracord, a reference line and some junk.

What you see there are the connecting holes on the braces with a double line of fairly hefty paracord running between them and tightened with a trucker's hitch. I added the sticky pads for some visual reference at the time. I later added the green line from the bottom of both connecting holes using Paint.net. If you've used a trucker's hitch, you know that you can get the line pretty taught: it made a solid "bwong" when I flicked it.

Here is the equivalent image when one wheel is pretty high up, balanced on some quite sketchy lumber:

I'm so glad that my wife didn't see what I was doing....

This picture is both disappointing and satisfying at the same time. The car clearly isn't made of rubber and tin foil (that's good) but it's also not showing an obvious flex that I could use to say "see? this was clearly money well spent and I am a genius!" Sadly, if you zoom way in, you can see that the front line looks largely the same as in the first image.

What is less obvious is what's going on in the rear line (the part where the knots are). That line is showing some droop (a bit but it's there). What you can't see at all is the change in tension in the line. Whereas before I had a nice "bwong," at this point it was definitely mushy.

At the end of all this, I think I can conclude that, yes, for this specific car, I can measure a definite opportunity for improvement in chassis rigidity that this part will address.

Later, when it's not the snowiest goddamn winter that the world has ever seen, I'll see if I can find a way to measure differences in handling that don't involve me being a huge donkey on public roads.

  • 2
    I got a kick out of reading this. Well thought out and pretty entertaining.
    – 3Dave
    Commented Sep 15, 2015 at 3:25
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    Bwonnnnnnnnnng! Commented Feb 17, 2016 at 16:56

I would say it depends on the chassis. Since the GG chassis Impreza is relatively stiff to begin with, I'd say any effect would be near-placebo. Improvements would be in steering/cornering feel, rather than something that can be measured quantitatively, like better lap times. Also, they make a LOT of different braces for your particular car - not just the strut tower brace. Look into Cusco.

I've put strut braces on S13/S14 240s where the ride stiffened up noticeably and cornering seemed a tad more responsive. However on higher mileage cars, this effect was almost negated by the next weakest link - worn suspension bushings, worn shocks, inadequate anti-roll bars, worn/misaligned tires/suspension. I've put a strut tower brace on a brand new M3 (brace was an actual M Motorsports part) that wasn't noticeable at all given the quality of the chassis.

Also keep in mind that the design of the brace is important. There are cheap ebay braces that just attach at both strut towers that can flex by stepping on it with your foot. Quality braces will mount on several points - both strut towers and two attachment points on the firewall.

edit to be more aligned with your original question.. years ago we worked on an old datsun. New control arms. new steering bits. new racing coilover setup. new wheels and tires. all new bushings replaced. And when the car was pushed to the limit? The chassis flexed. You can almost hear it in some places.

The sure fire solution? Seam welding and/or a roll cage. Your car may be a daily driver, but nothing looks as awesome as a cage in a street car :) (eclipsed only by contusions suffered from smashing your un-helmeted head against the cage).

More anectdotal "information". I had spoken to a pretty established chassis shop that worked primarily on Evolutions. They had seen cars with all manner of aftermarket bracing - front/rear stbs, front "power" brace, braces in the trunk, braces that went under the fender.. braces underneath the car that tied the frame rails together. While these upgrades enhanced steering feel and overall "stiffness", in practice these cars weren't as fast as cars with well sorted out "dialed in" suspension.

  • good points on the basics - I added notes to the original question.
    – Bob Cross
    Commented Mar 9, 2011 at 0:41
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    an interesting suggestion on the roll cage. I've decided to stay married instead.... ;-)
    – Bob Cross
    Commented May 20, 2011 at 20:30

I would say that anything that you can do on the street would be noticeably impacted by a strut tower brace, even during "enthusiastic commuting". The street is no place to be doing "nine tenths" or "ten tenths" driving, and even with spirited driving, on the street you are unlikely to have any noticeable impact.

If you aren't running R compound tires, you probably don't have the traction to make a tower brace do anything, even if you have fairly high performance "street tires".

If you think you're really pushing your car on the street, try going out for an autocross event. You can probably find an "solo" or "autocross" event within an hour or two of where you live pretty much any weekend in the summer. The "solo" events, as the name implies, are doing timed runs against the clock, not other cars, through a course set up with pylons. A properly set up course should have no opportunity for running into any obstacles, and will give you a feel for what sort of environment it takes to need a tower brace.

I've never heard of a car's chassis "getting tired", so putting a brace in would really make no difference.

  • My old Impreza's chassis was definitely tired (now 136,000 miles), and as I wrote in my comment below, it is definitely stiffer with the brace. As my wife drives it these days I am happy it makes things a little safer.
    – Rory Alsop
    Commented Jul 19, 2011 at 13:53
  • @RoryAlsop The tiredness isn't the chassis so much as the struts and bushing. Replacing those would go a long way to improving the feel of the car. Metal doesn't wear out, it will eventually stress crack but these is no loss of strength really prior to that.
    – draksia
    Commented Apr 29, 2014 at 19:38
  • draksia - yes, I regularly replace struts, bushings, entire shocks :-)
    – Rory Alsop
    Commented Jan 3, 2015 at 18:34

Depends on the car I suppose.

I've heard a lot of people raving about how much it helped, but my experience is different.

I upgraded my stock front strut tower brace on the MR2 to the TRD model, installed the rear TRD brace, and also did an underbody brace at the same time. No difference detected at all. The car had around 140,000 miles at the time, with many of those miles at autocross, rallycross, and rough dirt/gravel road rallys. I did the upgrades as I was concerned about the car getting beat to death. Figured I should reinforce it. Turns out that I was worried about it for nothing. :-)

My Eclipse has a cage in it and originally had a front brace, but not a rear one. I added a rear one primarily to give me a place to fasten equipment to on long road rallys. It made no difference otherwise. I removed the front brace as it was always threatening to short out the positive battery terminal. No change noted. The car had about 90,000 miles, with many hard autocross, rallycross, road rally, and open track days on it. However, it has also had an 8 point cage since about 30,000 miles or so. Definitely not as well built a car as the MR2, the braces may have helped if it didn't have the cage, maybe.


It made a noticeable difference on my old Legacy, but I was racing that car. You might not notice it with normal driving. If you are noticing frame flex in your car though, you have problems that a stabilizer bar won't help. If this is bothering you, have the frame checked.

  • As mentioned before, the real challenge is that of quantifiable metrics. Is "noticeable difference" a reading on the butt dyno? Or is there a specific measure that you can cite?
    – Bob Cross
    Commented May 15, 2014 at 2:00

Man, I have just the opposite experience as above.cThree cars of mine have strut tower braces. A 2002 Toyota Avalon, 2004 BMW 325ci and a 1995 M3. All 3 braces were "hingeless", and all 3 cars are unibody contstruction.

All 3 braces made a difference but not all the same. The Toyota Avalon (Solara) brace made the biggest difference. The M3 brace made the least.

No quantitative testing was performed but qualitatively, the "turn in" response times are perceptible on all. I would expect a small increase in handling times as well. Ride quality suffers but minimally.

These, when made specifically for the car, are very easy to install and add minimum weight.

Some vehicles are reinforced better than others. I would suspect the most dramatic effects from Front engine, FWD vehicles.

I hope this helps.


  • 2
    As mentioned before, the real challenge is that of quantifiable metrics. "Turn in" is a subjective measure that's heavily biased by "I spent money on this so I'm going to assume that things are better."
    – Bob Cross
    Commented May 14, 2014 at 18:51

Yeah dude put the Jack under the left front control arm. Jack car up see how far the left front tire gets before the right front tire comes off the ground. Then add a strut brace and repeat the process. If there is any difference in Heights subtract 1 from the other and you'll have your answer.


I know this will be a necropost but i want to put the correct information out there for everyone. Strut tower bars actually lower the lateral Gs a car can achieve. However they do improve handling by reducing body roll. This makes the car more stable, and predictable. As mentioned earlier you may also notice the car is more responsive to steering input do to quicker "turn in". Honestly unless the specific model car you have has poor handling I'd skip it or it would be one of the last things I'd do to fine tune a cars handling. As mentioned earlier, your better off replacing/upgrading all your existing suspension, steering, and related bushings. You really shouldn't noticed the difference strut tower bars make on the street. If you do you're driving in a manner that will get pulled from your vehicle at gunpoint instead of a ticket. Now to answer the question that no one has been able to, and the reason I'm necroposting. If you want to measure the difference it makes. 1. Get a camera and a friend to operate it. 2. Find a tight corner or make one in a big, empty parking lot using cones. Or better yet, do the deer avoidance/emergency lane change manoeuvre. 3. Record the car negotiating the corner as quickly as your skill level will allow. 4. Install the bar and repeat. Watch the footage back to back and you should notice the car is "flatter" in the 2nd pass. The body roll can be measured in degrees off of a still from the video. The main benefit of strut tower bars is the predictability, and added stability, which instills driver confidence, and makes the car easier to drive. While attempting the 2nd pass you should notice it was easier, less dramatic, and you should feel like you had more control of the vehicle. I own a 07 Impreza with coilovers and strut bars.

  • Can you explain how a strut tower connection changes a roll couple? Or how it lowers lateral Gs? The only thing such a unit might do is mitigate some of the chassis distortion, limiting load induced dynamic alignment changes. None of that will change a roll couple at either end, for better or worse. It might actually improve total grip by keeping the contact patches flatter.
    – SteveRacer
    Commented Oct 27, 2017 at 6:43

This is an interesting topic i have stumbled upon. My point dont or none in put to above but i feel car with staggard wheels and rear wheel drive have greater scope. I drive rear wheel mercedes SLK with 34000 miles from new and is model year 2008/09 Face Lift. With above set up you will technically experience understeer when going into fast curves and corners in wintery or wet conditions but is easily corrected with driver input via 1 steering or 2 more power ( speaking from experience) My car is factory fitted sports suspension and no added bars so far. I have uprated entire front suspension wiith Bilstein B6 parts and work carried out professionally.Unfortunately UK road are not the best in world and suspension is very firm, unless you get a chance to drive very quick to smooth out Rump/Thrump. Front wheel drive cars have built in overstear and its opposite to rear wheel drive. To gain anykind of benefits you have to take this into account. Tha law of physics,"a moving body will stay on its path provided it stays within the circle of traction". What ever you do to your car think of Circle of Traction.

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