Making custom strut brace

[Negative Boost]

I believe the strut brace isn't about adding structual strength to the chassis but to keep the strut towers in line with themselves, keeping wheel allignments in check when strut towers 'walk'. When you brace the towers to the firewall, then that is adding structual strength as that reduces the amount the towers walk. You have to remember that the towers WILL move and walk even if you have a 2 point strut brace (tower to tower).

Nobody answered my question if you need rose joints from the towers to the firewall. I dont see that you would because its about stopping movement full stop and adding structual strength. And if you did a 3 point strut bar you also wouldn't need rose joints from tower to tower either becuase (in theory) the brace to the firewall would stop the towers walking and stop any play that the rose joints would take up.

I wouldn't weld a 2 point strut brace as it would bend/move and a bending/moving strut brace isn't the best. I'd rather something that didn't bend but actually pivoted at certain points, i.e. rose joints or something like the design Ian posted above.

[Yotaholic]

I read an article on a cheap solution with a good idea a while back and found it interesting so I thought i'd share. It's a cheap addon either way but it would be nice to actually see an improvement for the money .....hmmmm well it's a good read anyway .
Yes it's an Audi but hey it's not about the car just the bar


http://members.aol.com/c1j1miller/strutbrace.html

[AndyTTR]

By the look of it, the brace on that audi doesn't do anything to increase structural integrity. The tops of the struts are connected, so any deflection at one strut top is going to be transferred to the opposing strut top, it might do something to lessen camber / castor changes during conering but I reckon the effect would be minimal.

edit: maybe i'm wrong? What the guy says below does make sense, but i guess it depends on how good and what type your strut-top bushes are.

from the article:

The ultimate goal any strut brace device is to minimize strut rod latteral movement relative to the ball joint, i.e. to minimize camber change caused by latteral cornering forces. To understand the effectiveness of any such device, one must differentiate between a strut to strut brace and a tower to tower brace, and analyize how each differently affects strut rod latteral movement in a MacPherson strut suspension design. The Benz Brace is a strut to strut brace, most others (all others, to my knowlege) are tower to tower braces.

The latteral cornering force exerted by the strut rod is first exerted on the compliant rubber bushing between the rod and the tower, causing deflection therein, and is then passed on from the bushing to the tower, causing tower deflection. In the ultimate corner, this maximum latteral cornering force is transmitted only from the outside strut rod (inside wheel off the ground) to its rubber bushing, causing a maximum deflection of this bushing, and thereon to the outside tower, causing a maximum deflection of this outside tower. Thus the total outer strut rod movement causing camber change is the sum of bushing and tower deflections. Further, realize that stiffness of the welded steel tower is orders of magnitude greater than is the compliant rubber bushing, i.e. bushing deflection is much greater than tower deflection.

A tower to tower braced system divides the tower deflection between both towers but retains in full the larger deflection of the outside bushing, and thus results in only a small camber change improvement over the unbraced condition. Further, because of the high stiffness and resultant small deflections of the towers, to be effective in dividing tower deflection forces between the two towers a tower to tower brace must be extreemly stiff. None are, most having bolts, brackets, and bends. IMO, they serve only as cosmetic window dressing and a lighter wallet.

Contrast this with a strut to strut braced system, in which the brace divides the latteral cornering force equally between the two strut tower systems, bushings plus towers. The resultant movement of the outside strut rod is half of the same unbraced system, and considerably better than the tower to tower braced system because, by design, the t to t has excluded bushing deflection, whereas the s to s has included bushing deflection in the dividing process.

Think about it!

Bernie.

[Ashe]

Only thing I see is if I have a bar going from one rubber bushing surrounded Strut to another rubber busshing surrounded strut, then any lateral deflection I exert on one strut is directly transferred to the opposite strut. not reducing deflection but increasing deflection.

That being said has anyone tried to measure the amount of lateral delflection a standard rubber strut top has at say 200lbs of lateral force?

Strut tower braces are not made to reduce strut to strut deflection, they are an attempt to "close the box" to stiffen the chassis and reduce chassis flex

[willwal98]

Here is my effort, GA28 celica, unmodified crossmember (engine sits a bit high). Triangulated off the firewall.

[Rodger]

Nice one willwal98,

This is what I thought I might do back in post #14. Good to see it would work.

Most front wheel drive cars that have braces that I get to look in have OEM braces to the firewall but are not triagulated. The Manufactures must think the firewall is solid enough.

I would only use rose joints to help fit the bar. To take up any poor fitment/alignment. Nothing beats a solid welded in brace that ties into a cage.

Regards

Rodger

[Negative Boost]

Nice wilwal, does it hit the engine from sudden throttle changes (engine movement)? Looks a little close over the plenum

[willwal98]

Plenty of room over the plenum. The bracket that holds the throttle cable is a little close but it doesn't cause any problems. I have urethane engine mounts which are a little stiffer than rubber, not sure if it helps on not. For anyone considering getting a strut brace I did this mod about 6 months ago and it definitely did improve the handling. We'll worth the hours making it.

[Sam_Q]

I am against using aluminium in braces due to it seemingly having a poor rigidity in small deflections even when thick material is used.

I also didnt do a tri brace for safety reasons, I figure if I have a big front hit it will keep on going through the firewall, but then again if it went that far in to move the strut towers I would be dead anyway.

Heres some pics of mine below, 2.4kg and I think I could lift the front end of my car with it, I used 4130 Cro-Mo steel which I highly recommend.

[emp?]

holy that is beautiful

[Sam_Q]

thanks, visit my worklog link in my signiture for of where that came from.


when I was planning my-tri brace I was thinking of welding a plate on on the firewall that already has 2 nuts welded onto the inside of it, it would also be an angled shape and would also be welded to the lip below it for strength. It would also let me be able to remove it easly which is important for me. This way I would give me a more decent point to attach to. I am still thinking about doing it.

[Sam_Q]

for the sprinter owners I have a question, how did you guys attach to the firewall? is it though the two holes that this black plates on the firewall uses? Whats it for anyway?

[RobertoX]

Just out of curiosity, why use 4140?

[Sam_Q]

sorry my mistake, its 4130

its very strong and rigid for its weight. Weaks havok on drill bits though. The other reason is that they sell it in ultra light gauge sizes that normal steel isn't available in. The thinnest steel I found anywhere is 1.2mm, for this brace I used 22 x 0.9mm or 0.825 x 0.0035 or whatever imperial measurement it's supposed to be originally. For my rear brace it was 25 x 0.9 and even though it was only 0.9mm it was very rigid and light. When I have thinner single sections I can afford to have more peices in a design and therefore a stronger design, just my way of doing things.

Oh yeah and I forgot to mention its not cheap but then again 6061 aluminium alloy isnt either

[RobertoX]

Ah, no worries. It looks very good and 2.4kg is light, I think the commercial one I have is a bit more than that and it would be no where near a stiff just by looking at them.

Did you get the 0.9 stuff from performance metals or did you have another supplier?