I am planning on making my own body and diff stiffeners this winter. I have done a quick photoshop job of what I am planning on doing. I am trying to keep them simple yet functional. I am basing them off of the mazdaspeed and Auto Exe braces. The front brace is basically like the mazdaspeed. The rear is a simple design of the Auto Exe but with the addition of a Diff brace. I am thinking of making them out of square or rectangle steel tubing to try to keep the weight down.



The green line represent a possible brace under the trans, I am also thinking of attaching it to the trans. I have to do a little more research on this.

Constructive criticisim is welcome.

 

Looks interesting..

I've thought about getting something similar before, but I can't seem to find a straight answer as to what theyd really do. Is it just to keep the drivetrain from moving? Would it increase ride harshness at all?

 

I would need proof that those things do anything before wanting them installed on my car.

It looks like something that either should never be done, or done after every other freshening and update is done on a car.

With that said, I would believe that running a brace under the transmission as you illustrated would be a serious ground clearance problem.

 

http://www.nopistons.com/forums/inde...ic=20174&st=50

Dragon made a transmission brace...

 

911gt2 and Wvrx7,

The obvious reason for the bracing is to help stiffen up the body. I am getting into road racing (track days and high speed autocross) and want to make the car as stiff as possible without a roll cage. The reason for the front brace is to help stiffen up the PPF which is known to be a weak spot. The rear brace is to help stiffen up the rear cross member and also help keep the diff from moving which can help from breaking your diff. There are a lot of threads on the importance of the diff brace.

Rhode-dog,

Thanks for the link, I am thinking of trying to make something like that attach to my front brace.

Anyone else have any thoughts on this.

 

maybe you could ask vosko or that one mod rxrotary2 7 about bracing related things

 

no there i no ground clearence problem. you can get a diff brace from me at KGParts.com or from the rx7store, Gotham Racing, and A-Spectuning. there is another guy (dragon) who makes trany braces but i dont think he has a diff brace. i have trany brace but not on the site. i would rather not sell it.

 

Yea I know about the KG parts brace and Dragons trany brace, I really don't like them. I think that they are way to big and Heavy for the amount of bracing they do. If you notice my rear brace attaches to two spots under the car, the diff and then the rear diff brace. I am trying to tye everything together to provide the ultimate stiffness without going full cage. Also I am thinking of using square tubbing to keep the weight down.

 

Just thought I would point out that Keith's diff brace only weighs about 11 pounds. Much lighter than that, and it prolly won't get the job done.......

 

While I appreciate your reasoned response, I will still disagree.

I have spent more than 6 years around some of the fastest track driven FDs in the country and I don't believe I have ever heard a complaint about the chassis needing stiffening in these areas.

Most of the PPF failures come from compromised drivetrain or engine bushings allowing too much undamped movement. Additionally, many PPF failures are from repeated drag launches.

I simply cannot believe that adding these somewhat spindly looking pieces of bar stock to the front and rear subframes will add ANY additional stability. If there is true movement, then the attachment points of these braces will become the weak point and may allow tearing of the unibody.

You say you want to get into track events and high speed autocross but don't want to use a roll bar. I would assume that your safety is more important than any perceived improvement in rigidity.

When you are using speed and grip levels where chassis rigidity becomes an issue, it is highly advised that you invest in proper rollover protection.

With all that said, UNLESS someone has replaced and upgraded each and every suspension and unibody mounting point and replaced every bushing then there is no absolute way to ascertain that you are having any chassis flex.

Until I am shown substantially different, I will continue to believe that those underbody braces are a mod for mods sake.