E21 Rear Shock Braces and Battery Relocation question

[pofo]

I'm going to make my own brace as its a very simple design and melting some metal together. But I'm unsure what size tubing I should use, I know most cages/roll bars are 1-1/2" DOM or 1-3/4" DOM but I think this is over kill. Has any one made there own before? I was thinking 1" OD but not 100% sure and dont want to add unneeded weight.

[Retoropak]

I'm going to make my own brace as its a very simple design and melting some metal together. But I'm unsure what size tubing I should use, I know most cages/roll bars are 1-1/2" DOM or 1-3/4" DOM but I think this is over kill. Has any one made there own before? I was thinking 1" OD but not 100% sure and dont want to add unneeded weight.

I am planning on 1" x.125 aluminum.

My second choice was 3/4"x .065 DOM




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[pofo]

I am planning on 1" x.125 aluminum.

My second choice was 3/4"x .065 DOM




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I was thinking of aluminum but there might be a lot of flex.

[Retoropak]

I was thinking of aluminum but there might be a lot of flex.

There shouldn't be. Aluminum is fairly stiff and you can oversize the tube to achieve the strength you need and still save some weight over the steel.

I also have 3/4"x0.083 Docol R8 which is comparable to 4130 that i used for my control arms. But its not cheap and i kind of don't want to use it for strut brace.


There is also 4130 which looks like excellent material for this application.



1"x0.065 chromoly should be more than enough.

Aed motorsports also have oval, streamline and egg shape tubes available in the material and size of your choice


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[Somjuan]

Aluminum would be stiff if you heat treat it post-weld anyway. I'd just use a smaller diameter steel. 4130 would be brilliant if you're making your own.

[pofo]

Aluminum would be stiff if you heat treat it post-weld anyway. I'd just use a smaller diameter steel. 4130 would be brilliant if you're making your own.

I have done a lot of aluminum welding and have a lot of scrap angle I could use for the battery box. I think I might go this route as it will be light and i can get some flat stock for gussets and add dimple dies to remove some weight.

[allan633]

I have done a lot of aluminum welding and have a lot of scrap angle I could use for the battery box. I think I might go this route as it will be light and i can get some flat stock for gussets and add dimple dies to remove some weight.

Another good option if you're thinking of relocating a lead acid battery to the trunk is don't do it at all.
Let your rear brace be just that and use one of those new less-than-2- pound lithium batteries under the hood. Not even counting the weight of a lead based battery and brackets, I saved almost 12 pounds in cable by getting rid of my rear mounted battery! And it cranks just as well as always even in sub-freezing weather. Under $100 too.
Kinda can't lose!

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[MortyCrock]

Another good option if you're thinking of relocating a lead acid battery to the trunk is don't do it at all.
Let your rear brace be just that and use one of those new less-than-2- pound lithium batteries under the hood. Not even counting the weight of a lead based battery and brackets, I saved almost 12 pounds in cable by getting rid of my rear mounted battery! And it cranks just as well as always even in sub-freezing weather. Under $100 too.
Kinda can't lose!

Go take your sorcery somewhere else!

[Retoropak]

Go take your sorcery somewhere else!

Haha. You can always push start your car and not worry about battery at all


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[MortyCrock]

Haha. You can always push start your car and not worry about battery at all


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Currently, my e21 is a glorified paperweight... so there's plenty of pushing, just no starting.

[pofo]

Another good option if you're thinking of relocating a lead acid battery to the trunk is don't do it at all.
Let your rear brace be just that and use one of those new less-than-2- pound lithium batteries under the hood. Not even counting the weight of a lead based battery and brackets, I saved almost 12 pounds in cable by getting rid of my rear mounted battery! And it cranks just as well as always even in sub-freezing weather. Under $100 too.
Kinda can't lose!

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I plan on getting one of those light weight battery but I am trying to clean up the engine bay of anything unnecessary and I just repainted and already cut out the tray.




Also just started the battery tray will get the tubing tomorrow some flat plate.

[allan633]

Go take your sorcery somewhere else!

😁! Yeah Morty, it does look like strange magic. That LI battery is so rediculously small!

Very nice work on that m50 (?) engine compartment pofo. Looks great!!

Go take your sorcery somewhere else!

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[pofo]

😁! Yeah Morty, it does look like strange magic. That LI battery is so rediculously small!

Very nice work on that m50 (?) engine compartment pofo. Looks great!!



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Thanks, and its actually an S52 with a m52 cover as the m power one was broke when I got the motor. Hope to turn over next week.

[Somjuan]

Whoa, now wait a minute here, no build thread? Pofo, that looks awesome. My dream swap is an OBD M50, I bet there's a lot of crossover there.

[pofo]

Whoa, now wait a minute here, no build thread? Pofo, that looks awesome. My dream swap is an OBD M50, I bet there's a lot of crossover there.

I need to update but I did start one

https://www.bimmerforums.com/forum/s...k-bit-me/page4

[JBasham]

Congrats on your swap!

You're putting a few extra pounds on the front porch, so a little Optima on the back porch seems like a fair balance. Plus it's practical to have the full-size puppy back there. CCA will never let you down!

[pofo]

welded up the brace tonight just need to clean it up and drill a couple holes and paint. It's very stiff and light, I'm happy with the out come

[cgifool]

Looking good!

[JBasham]

Ohh, pretty . . . .

[Bimmerod]

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If only I had a garage that spacious...... #jealous

Bimmerod

[pofo]

If only I had a garage that spacious...... #jealous

Bimmerod

This is my work, I own a sign shop here in RI. We need the space for large awnings and signs. But it comes in handy when your work slows down in the winter.