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Old 07-14-2008, 09:37 PM   #1
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Front Strut Support Reinforcement

Like many of you I want to make my car faster and handle better without spending tons of money. So I'm always looking for cheap and easy mods. I think I came up with a good one this weekend and I'd like your feedback as a group.

I've felt for a while now that the stock front strut braces are pretty good. I've even gone so far as to remove mine and examine them. When I saw this post by Loren on Renntech it got some thoughts going:

http://www.renntech.org/forums/index.php?showtopic=5678

Of course this applies to the Boxster as well as the 911 Carrera as we have the same front end and both cars have the same strut tower braces as the GT3 Cup Car! Here's the drawing from Loren's post as well as a photo of one of the bars in my 2000 Boxster S where it mounts to the strut tower on the passenger side.





The only problem with this setup IMHO, which became readily apparent when I took mine out, is that the mount at the firewall is a single point that allows movement and rotation. It seems to me that it would be a lot stiffer if the two bars were tied more directly together towards the shock towers or in the middle. There's just enough space behind the battery that you could tie them together in the middle and stiffen up the structure. But how to clamp a bar across the two strut tower braces to hold them together? Well here's the solution that my son (16 yrs old) and I came up with this weekend during a little father/son time together:





Basically what you're looking at is one of my main lower stress bars for the Boxster/Cayman (group buy in the Classified section) that I adapted to fit the front strut braces and clamp them together using some custom brackets. With everything snugged up it's VERY tight and rigid. The brackets and bar don't move a bit. With the way the bar is designed you can turn it to put tension either pulling in or pushing out on the strut tower bars, or you can leave it neutral. I put tension pushing out to keep the bars from flexing inwards under hard cornering.

The bar is low enough that it still fits under the stock plastic covers too.

My son had the job of polishing up the custom brackets. I think he gets kudos for a job well done.





The bar is the same steel bar used for the lower stress bar. I just painted this one red to make it look pretty. The heim joints are also the same super beefy ones used on the lower stress bar. So this setup should be good for holding something like 4 tons...

So what do you think???
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Old 07-14-2008, 09:58 PM   #2
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Isn't that almost the same concept as installing one of these;
http://cgi.ebay.com/ebaymotors/Porsche-Boxster-996-Schnell-Front-Strut-Brace-Bar_W0QQcmdZViewItemQQ_trksidZp3286Q2em14Q2el1318Q QhashZitem180265129718QQitemZ180265129718
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Old 07-14-2008, 10:00 PM   #3
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When you say "it doesn't move a bit" I believe you are implying by hand and I think you underestimate the forces encountered during "spirited" driving. Bumps and shocks to the shock tower I believe will cause the pinch connection to slip. I could be wrong so drive it for awhile and see if there has been any signs of movement - i.e., finish removed where the the connection pinches.
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Old 07-14-2008, 10:09 PM   #4
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That right there is some impressive father/son bonding

It looks great and makes sense! how much are you selling them for? have you tried vigerous driving with it yet?

Once again, looks real nice
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Old 07-14-2008, 10:53 PM   #5
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Everyone here knows how much I like to mod my car but the front strut tower brace is not needed. Did you know Cup Cars do not even use them? I would have to say that if they drive the car at 10/10th where I drive mine 7/10th even on a track I do not need this mod.
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Old 07-14-2008, 11:34 PM   #6
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Does anyone here think to have someone drive their Boxster into the driveway with the bars exposed to see if they move or bend any as the car drives over the water drain?
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Old 07-15-2008, 12:10 AM   #7
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Here is a different version of a strut brace. It came out about 6 years ago. Only version that made some sense to me. You don't see it mentioned anymore.
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Old 07-15-2008, 07:07 AM   #8
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Quote:
Originally Posted by wconley
I think you underestimate the forces encountered during "spirited" driving. Bumps and shocks to the shock tower I believe will cause the pinch connection to slip.

Absolutely Walt, good observation! I realize that the pinch connection of that bracket won't hold the bar tight. It's hard to see in the photos, but the bolts that hold the bracket also come into contact with the bar and help to hold it in place. So it's not the frictional force of the pinch that I'm counting on, but rather the mounting bolts to hold the bar in contact with the braces. Of course it's not perfect though with the garage built brackets that I made. I've got a guy who works for me who's a machinist and I'll probably have him make me some precision brackets that will tighten it up to the gnat's ass. I want to try out this concept first though before taking it the next step.
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Old 07-15-2008, 07:09 AM   #9
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Yes, same function just a different way of doing it at approximately half the cost.
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Old 07-15-2008, 07:15 AM   #10
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Quote:
Originally Posted by fragdude
how much are you selling them for? have you tried vigerous driving with it yet?

This isn't anything that I'm selling... If there's enough interest I could always do a group buy like I did for the lower stress bars. But right now I'm just sharing a little project of mine. I would need to get the brackets made by a machinist to keep quality up and costs down.

I won't get a chance to drive it hard for a while. Again this is just the beginning of some trial work on this. I go in tomorrow for some surgery (motorcycle accident) on my left foot. So I won't be driving a manual transmission car for at least two weeks. I'll let you guys know once I've got some feedback though.
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Old 07-15-2008, 07:23 AM   #11
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Quote:
Originally Posted by JP-s-in st. louis
Everyone here knows how much I like to mod my car but the front strut tower brace is not needed. Did you know Cup Cars do not even use them? I would have to say that if they drive the car at 10/10th where I drive mine 7/10th even on a track I do not need this mod.

I beg to differ. The GT3 Cup Car does indeed use a strut tower brace. That's exactly what I posted a diagram of. If you look at Loren's post at Renntech that I provided a link to he explains how the Cup Cars use the same brace as what we've got stock in our cars. The additional bar that I added just reinforces and stiffens the strut tower brace already in our cars and the Cup Cars.

But is the GT3 Cup Car really the ultimate in racing? The Porsche GT3RS race cars do have an additional strut tower brace... factory from Porsche. So I'm imagining that there is indeed some room for improvement here if Porsche also increased the stiffness on the GT3RS racer. But I agree this probably would only apply at 10/10ths.
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Old 07-15-2008, 07:58 AM   #12
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Quote:
I won't get a chance to drive it hard for a while. Again this is just the beginning of some trial work on this. I go in tomorrow for some surgery (motorcycle accident) on my left foot. So I won't be driving a manual transmission car for at least two weeks. I'll let you guys know once I've got some feedback though.
Hope all goes well and do tell us how it is when you do get to drive it
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Old 07-15-2008, 10:42 AM   #13
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Quote:
Originally Posted by Kirk
I beg to differ. The GT3 Cup Car does indeed use a strut tower brace. That's exactly what I posted a diagram of. If you look at Loren's post at Renntech that I provided a link to he explains how the Cup Cars use the same brace as what we've got stock in our cars. The additional bar that I added just reinforces and stiffens the strut tower brace already in our cars and the Cup Cars.

But is the GT3 Cup Car really the ultimate in racing? The Porsche GT3RS race cars do have an additional strut tower brace... factory from Porsche. So I'm imagining that there is indeed some room for improvement here if Porsche also increased the stiffness on the GT3RS racer. But I agree this probably would only apply at 10/10ths.
Do you have a picture/diagram of the strut tower brace from the GT3 RS race car?
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Old 07-15-2008, 03:03 PM   #14
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Quote:
Originally Posted by chaudanova
Do you have a picture/diagram of the strut tower brace from the GT3 RS race car?
I will try to get one. I sent Loren a PM about it. Loren just told me there was one and that I would not want it considering what you would pay for it from Porsche Motorsports. I just left it at that. I am checking now though to see if he has got a part number or diagram as I am curious too.
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Old 07-17-2008, 11:14 PM   #15
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Quote:
Originally Posted by Kirk
I beg to differ. The GT3 Cup Car does indeed use a strut tower brace. That's exactly what I posted a diagram of. If you look at Loren's post at Renntech that I provided a link to he explains how the Cup Cars use the same brace as what we've got stock in our cars. The additional bar that I added just reinforces and stiffens the strut tower brace already in our cars and the Cup Cars.

But is the GT3 Cup Car really the ultimate in racing? The Porsche GT3RS race cars do have an additional strut tower brace... factory from Porsche. So I'm imagining that there is indeed some room for improvement here if Porsche also increased the stiffness on the GT3RS racer. But I agree this probably would only apply at 10/10ths.

Kirk here is a friend of mines GT3 Cup he just traded in for a 993TT "S". He raced it in the IMSA series. In addition to that the guy that works on my car built the GT3 Cup that took 6th at 24Hrs @ Daytona.

http://www.truspeedmotorcars.com/vas_inventory_detail.aspx?@page_stock_no=1549

Edit: Did not intend to sound like a prick but I just have seen this car as close as behind the wheel. I did not drive just started and rev'd I did however drive his GT3RS...GAWD that was/is a sweet car!
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Last edited by JP-s-in st. louis; 07-17-2008 at 11:34 PM.
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Old 07-17-2008, 11:24 PM   #16
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The cup cars dont need one, as you can see in the last photo the strut towers are picked up by the cage, so the tower flex is directed through the roll cage. My friend has the last model GT3 and his doesnt have a strut brace.

I have one of the Schnell ones and I am not sure it affected the handling too much but it did reduce a few squeaks from the car
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Old 07-18-2008, 08:55 PM   #17
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Originally Posted by noone986s
The cup cars dont need one, as you can see in the last photo the strut towers are picked up by the cage, so the tower flex is directed through the roll cage. My friend has the last model GT3 and his doesnt have a strut brace.

I think there's some confusion here as to what I'm referring to a "strut tower brace" as, Porsche calls is a "suspension cross-brace". The GT3 Cup Car does show the brace in the last picture and it's the same as what's in the Boxster. It's the black bar that the Moton reservoir is mounted to. It ties the firewall to the strut tower and helps to support it. It doesn't look like your Schnell strut tower brace because it doesn't go straight across between the towers, but instead ties them to the firewall. The brace I added then ties to these two suspension cross-braces directly together.
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Old 07-19-2008, 07:34 AM   #18
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cup cars don't tie the shock towers together; they tie them to the firewall like our cars. there is debate as to whether any of our cars benefit from tying the towers together. there is definitely benefit to NVH, but as to performance, some say yes, others no. not sure i like kirk's idea at all; tie-ins at the tops of the struts are more important, so IMO a conventional brace would work better. in addition, the OEM firewall / strut tower braces are designed for tensile / compression load. loading them in the middle is not smart.
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Old 07-19-2008, 12:30 PM   #19
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Originally Posted by insite
in addition, the OEM firewall / strut tower braces are designed for tensile / compression load. loading them in the middle is not smart.
Why is it not smart? Under tensile or compressive forces the middle brace simply holds the two OEM braces together to keep them working as one unit and reduce flex or movement. The middle brace certainly wouldn't decrease the tensile or compressive forces that the OEM braces can withstand. So I go back to the old mantra I had with the lower stress bar side braces - it can't hurt and can only help. The main load is still at the shock tower where the force is applied. Any flex or deflection from compressive forces would now be spread over the whole assembly and it should be stronger and more rigid as a result.
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Old 07-19-2008, 01:10 PM   #20
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Quote:
Originally Posted by Kirk
Why is it not smart? Under tensile or compressive forces the middle brace simply holds the two OEM braces together to keep them working as one unit and reduce flex or movement. The middle brace certainly wouldn't decrease the tensile or compressive forces that the OEM braces can withstand. So I go back to the old mantra I had with the lower stress bar side braces - it can't hurt and can only help. The main load is still at the shock tower where the force is applied. Any flex or deflection from compressive forces would now be spread over the whole assembly and it should be stronger and more rigid as a result.
your mantra is flawed: it CAN hurt. in the case of your added lower stress bar side braces, there was no problem. what you're doing here is the equivalent of attatching your lower stress bar to the center of the shear plate.

the OEM braces are designed for axial load. when you add an element that produces stress in the normal direction, you can bend stuff. even if nothing bends badly, the flex in the OEM arms will essentially negate any positive benefit you might have gained from triangulating them. that, and the clamps won't do.

ideally, we want to triangulate the OEM bars by tying the actual struts together. this is best done by....SURPRISE: tying the actual struts together.
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