Homemade strut brace

I had some free time in class today and built a rear strut brace. I used 1'' steel pipe (I think it was old gas line, one end was threaded) and the mounts are just 1/4'' steel plate I heated and cut. I then but it on the drill press and drilled two holes per mount. I took a level and hammer and set the brace where I wanted it then drilled holes through the strut tower making sure I didnt hit anything. Added four bolts, nuts and thread lock.

I wire wheeled the whole thing and got it looking shiny. The whole thing was made out scrap laying around the shop and mig welded. All together it cost me nothing. Ill have pictures tomarow!

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You should have had pictures today....

I always wanted to make my own bar(s), but don't have the extra scrap laying around, nor do I have the equipment necessary

Pics

Its not the greatest and it isn't lightweight but it was free and so far works great. Dont mind the dust and dirt, i have to take gravel roads everday.

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Sorry, double posted the same picture.

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.... I may be ignorant so please educate me but I thought they went over the top of the struts and connected with the actual shock mount. Or is this unnessessary?

I hate to say it, but to my understanding, the purpose was to control the movement of the shocks& struts more than anything. These seem (to me) as though they would add stress to the shock towers, potentially enabling failures.

That strut bar looks pathetic...

They're supposed to go ABOVE the shock tower and bolt up with the shock mounts.

Strut and shock bars add rigidity by stiffening the mounts, keeping them from flexing. The only area spanner bars are used are behind the front seats in sedan applications (mostly). This wont reduce body flex during high torque, and certainly does nt work as a shock reinforcement bar. :/

So the towers themselves dont flex, just the small area at the top flexes?

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The loads from the shocks in in the rear and struts in the front tend to try to push the mounting points inward toward the center line of the car. This creates variability in the suspension geometry at the point where you least want it to happen. The bar spanning from one tower to the other holds the spacing between them constant and reduces or eliminates the geometry variability. The best and most effective point to do this is at the shock or strut mount.
In the OPs design the idea of trying to maintain the spacing is there, but I thnk the flexibility of the sheet metal where it's attached is going to defeat the purpose. I suspect there will be some placebo effect from it, but without before and after skid pad results it's going to be really hard to tell if it's made a difference.
OP, one thing you've definitely done if you didn't put some RTV or some other form of metal protectant where you drilled the holes is create a perfect place for rust to start.

Originally Posted by rooster1986

So the towers themselves dont flex, just the small area at the top flexes?

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Yes, you see the two mounting bolts on the rear shock mounts? You should have fabricated a plate that went between the sheet metal and the nuts that secure the rear shock mounts, then welded a bar between the plates to keep the mounts (and/or sheet metal) themselves from flexing inward. This is only (really) noticeable during hard cornering under heavy acceleration. Lateral g force, coupled with torque from the differential causes the mounts to flex and twist slightly.

Reference:

Spanning from rsm to rsm.

edited redundancy

Even if it was made correctly, how many people say adding a rear strut bar made them love their car again?

Sounds like front strut bars are way more aesthetic than functional, can't imagine what a rear brace would be for.

To ruin the placement of your speaker box?

My rear strut bar runs through my box. n00B

My speaker box is muh strut bar.

My rear strut bar was free and does not interfere with speakers, I use it as a clothes hanger for my towel after drying car lol

Originally Posted by TRaV MaNN

My rear strut bar runs through my box. n00B

I have seen this b4 lets have a pic!

From what I've heard/read, the rear bar makes virtually no difference, and doesn't add any noticeable stiffness. Many people say the same thing about the front strut bars, but I've heard from some people who've said the front bars made a big difference. The biggest improvement I've heard reported comes from the addition of the x-brace underneath the car.

Regardless, a lot of race cars have the rear braces welded to the rear shock towers in the exact same position as what is seen above, so I think there is certainly some bracing going on.

But he is calling this a strut brace. The strut isn't being touched at all. I imagine the bar will reduce body roll but it won't be noticeable.

Originally Posted by ZeGerman

From what I've heard/read, the rear bar makes virtually no difference, and doesn't add any noticeable stiffness. Many people say the same thing about the front strut bars, but I've heard from some people who've said the front bars made a big difference. The biggest improvement I've heard reported comes from the addition of the x-brace underneath the car.

Regardless, a lot of race cars have the rear braces welded to the rear shock towers in the exact same position as what is seen above, so I think there is certainly some bracing going on.

If the bar is solid, like the proper one in the pic above, there will be chassis rigidity added. Caveat: to notice the additional chassis stiffness in the rear, your suspension needs to not be stock or even street/track style AND you need to be driving the piss out of the car*.

And If I were to mod the handling on another E36, only AFTER I replaced every bushing, ball joint and control arm in the suspension, would my order would be, X-brace, camber plates, sway bar, springs/dampers, strut braces. Now, I'd likely get the camber plates with the new springs/dampers, but if I were to do it piece meal, I've discovered that camber is more important on an E36 than a front sway bar...








*I strongly discourage doing the latter anywhere but on the track, skid pad or autocross course. Too often a 9/10ths drive in the twisties can result in an 13/10ths OH SH!T!!! moment

Originally Posted by TRaV MaNN

But he is calling this a strut brace. The strut isn't being touched at all. I imagine the bar will reduce body roll but it won't be noticeable.

But you're loosing touch with the fact that the entire point of strut/shock tower braces is to prevent the towers themselves from moving inward. Virtually all race cars with roll cages (which is all race cars) have the rear shock tower braces welded to the towers in the exact same location as the OP.

Example:






And if you want to get technical, they aren't called strut or shock braces, they are called strut/shock TOWER braces. You don't need to be on top of the strut or shock to brace the tower. You just need to ensure that the towers themselves cannot move inward toward one another under heavy load. The OP put his bar in a very commonly used location. The only thing he did differently (and is something that I probably wouldn't do) is how he attached it with the hardware. I'd have welded it, since the idea of drilling holes in that location seems like an unwise idea.

Originally Posted by ZeGerman

But you're loosing touch with the fact that the entire point of strut/shock tower braces is to prevent the towers themselves from moving inward. Virtually all race cars with roll cages (which is all race cars) have the rear shock tower braces welded to the towers in the exact same location as the OP.

And if you want to get technical, they aren't called strut or shock braces, they are called strut/shock TOWER braces. You don't need to be on top of the strut or shock to brace the tower. You just need to ensure that the towers themselves cannot move inward toward one another under heavy load. The OP put his bar in a very commonly used location. The only thing he did differently (and is something that I probably wouldn't do) is how he attached it with the hardware. I'd have welded it, since the idea of drilling holes in that location seems like an unwise idea.

Welding a roll cage across strategic points in the car to add rigidity and reduce body flexing/twisting is different than keeping the shocks/struts parallel.
When e36 mounts fail, they are nt ripped from the sides. It is the top that is mangled and twisted up from lack of support.

exempli gratia:


I think these address two different issues, not the same one.
How would OP's bar prevent the twisting and flexing of the mounts that caused this ^?

A shock tower brace in intended only to increase chassis rigidity, which is why the OP installed a brace. If he wants to protect the towers from ripping out, that's what reinforcement plates are for.

Originally Posted by ZeGerman

A shock tower brace in intended only to increase chassis rigidity, which is why the OP installed a brace. If he wants to protect the towers from ripping out, that's what reinforcement plates are for.

Meh, I thought the whole point was to keep the suspension geometry under loads and g's. Not the chassis. I ve seen spanner bars and roll cages used for chassis rigidity but I still think both attempt to address different anomalies .