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Discussion Starter · #1 · (Edited)
Fancy a rear chassis brace but don't want to pay a premium? Here's how you can make your own for cheap.

Tools:
- Marker
- Scissors
- Drill with 7/16" drill bit
- 17mm socket, ratchet
- Hacksaw or something to cut steel

Materials:
- 1x 1" steel square tubing, cut to 39.5"
- 1x 1" steel square tubing, cut to 37"
- 4x M10x1.5x60 bolts
- 4x 10mm washers

Procedures:

1. Remove the inner trunk floor

2. Locate the third row seating mounting holes beneath the jute padding


3. Mark the jute padding around the mounting holes


4. Cut the jute padding to accommodate the braces


5. Cut 1" square tubing to 39.5" and 37" lengths

Here is a mock up of the braces:



6. Mark the position of the mounting holes and drill with a 7/16" bit

7. Bolt up the braces to your car with the M10x60 and 10mm washers


Finished product:


Note that if you use the floor hinges, the floor won't be completely flush:


However, if you just place the pins on top of the hinges, then the floor will be flush:


Driving Impressions:
- No change in NVH
- Feels more planted, especially during turns
- Rotates more willingly through corners
- Feels more solid at high speeds

These braces work well at reducing chassis flex and complements other modifications to tighten up the overall handling.

References:
http://forums.swedespeed.com/showthread.php?222062-Rear-Chassis-Brace
 

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Love this! So you have this in addition to rear sways, correct? I'm holding off on any further mods of this sort until after I've got the swaybars in (which at this rate will happen when hell freezes over) because I'd like to be able to get a good read on what the bars do solo first. Or maybe I'm not holding off, who knows? Either way this is cool and I'd like to give it a go down the road sooner or later.
 

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The only thing I don't like is the english length in a metric car :rolleyes:

I would have also done it in aluminium.

This is probably better quality than the UR chassis braces.
 

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Solid setup! Just a random thought, do you think that a sleeve or bushing in between the square stock would help out at all? It may stop the square from collapsing a little.
 

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Discussion Starter · #7 ·
Love this! So you have this in addition to rear sways, correct? I'm holding off on any further mods of this sort until after I've got the swaybars in (which at this rate will happen when hell freezes over) because I'd like to be able to get a good read on what the bars do solo first. Or maybe I'm not holding off, who knows? Either way this is cool and I'd like to give it a go down the road sooner or later.
Correct! These braces serve a different function than the sway bars but everything works together. The sway bars make a bigger difference though
 

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Yup, I saw Beck's thread and also referenced it at the end of my post.
Didn't see that :p

I was going to give this brace a shot, but I'm skeptical of its effectiveness and I was concerned about the floor not being flush, the dog would hate that. Your trick with the hinge looks like it works.

A test that I thought of that may prove its effectiveness is the "Submarine Compression Test". Tie a string across the mount location just tight without tension and document how much it sags with/without the brace. Maybe have a GoPro or simliar record the results. What do the engineers think? :)

Also, is there a difference between loaded/unloaded with the same test?
 

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Discussion Starter · #9 ·
The only thing I don't like is the english length in a metric car :rolleyes:

I would have also done it in aluminium.

This is probably better quality than the UR chassis braces.
The aluminum stock at hardware stores are pretty thin but I'm curious if it could achieve the same result. I know 6061 has a much lower ultimate strength than A36 though
 

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Discussion Starter · #11 ·
I was going to give this brace a shot, but I'm skeptical of its effectiveness and I was concerned about the floor not being flush, the dog would hate that. Your trick with the hinge looks like it works.
Yeah, I actually saw Beck's thread a long time ago but wrote it off when I found out the floor was no longer flush. I decided to test it with some scrap metal I had and found out the floor only sits <1cm higher when hinged.

If you have cargo mats then I doubt Fido will notice
 

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you'll still crush the tube, the washers will just dome into it.

The right way to do it would be to drill out the tube with a holesaw, drop a bushing in there and weld it, but even a bushing inside the tube would keep it from crushing.

honestly I think I'd be inclined to chop the ends of the tubes off at an angle and just bolt through the lower wall. You won't compromise it's structure, but you'll be able to torque the bolt down much better.
I wonder what would happen if you used rod ends and could tension it?

oh no, I've started asking myself questions.
must not mod wife's dd....
 

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You know, putting the bolt on the bottom isn't a bad idea! You could drill out the hole on top and get some washers for an allen head style bolt. Drop it through the top with a larger hole and bingo!
 

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Discussion Starter · #14 · (Edited)
honestly I think I'd be inclined to chop the ends of the tubes off at an angle and just bolt through the lower wall. You won't compromise it's structure, but you'll be able to torque the bolt down much better.
Do you think it'll make a difference?

Edit: Nevermind. My 17mm socket doesn't fit inside the steel tubing so I won't be able to tighten the bolt against the bottom wall. I may switch to thicker and wider washers though.
 

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So I'm assuming since I have the third row im screwed for this. Looks like a cool project.


Sent from my iPhone using Tapatalk
 

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Do you think it'll make a difference?

Edit: Nevermind. My 17mm socket doesn't fit inside the steel tubing so I won't be able to tighten the bolt against the bottom wall. I may switch to thicker and wider washers though.
I do think that it would. not only could you achieve much greater clamping force, but you'll also remove the leverage the tube has on the bolt right now.

if you socket doesn't fit, go with an internal drive screw.

m10 torx headed bolts aren't difficult to find.
hell, the local parts store probably has them in a blister pack.
 

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Discussion Starter · #17 ·

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yes, but I think you need m10-1.5 thread pitch.
i'd do a torx bolt just because they tend to strip less, you can apply more torque and they generally have a larger head than a cap screw. If you do the cap screw make sure to get a hardened washer.

if you head to an actual car parts store they'll have all of the dorman fasteners, you should be able to find an M10-1.5 Torx bolt. IIRC all of the GM cars in the 90;'s used those damned things for the rear knuckles.
 

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Discussion Starter · #19 ·
I found some M10x25 bolts with a 14mm head and decided to try what nsjames recommended and modified the ends of the brace:



Here is how the 17mm head M10 bolts fit. A 17mm socket can fit, but it's tight.


And the 14mm head M10 bolts:


I bolted the brace back in and I'm not sure if it's better. If anything, the brace seems easier to flex now. I recommend just sticking with the original DIY...
 

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You need to round off the edges not square it off, rounding the corners out maintains structural strength more


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