Hmm...i wonder if this would be any better then the vert crossmember....it's certainly less in the way and lighter!!

 

If you have a vert I'd probably leave it on as it looks like it'll add a bit of torsional rigidity to the car that mine won't. According to a thread I found the vert crossmember won't fit on a coupe without modifications to the chassis and the subframe to add mounting points, so the best option would be to use a bar of this style, or of the Mazdaspeed style.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/vert-chassis-brace-fc3s-433768/

I like mine because it's easy to make with basic tools, it's not too heavy, it's very stiff, and it's up high and out of the way. If I had a welder, or more time time to play around with it I'd have gotten some tabs welded onto the bushing clamps and run a bar directly between them, rather than between the mounting bolts, but I don't think it's worth much fuss over, as it's probably not much stiffer.

When I go home for spring break I'll try to remember to take some pictures of the aluminum prototype to show the massive bend in it (15 degrees at least) to convince all those who doubt the chassis flex there. It'll convert all non-beleivers for sure. I've been meaning to post a picture of it for a while now, but I never quite got around to it.

I think that this would make good archive material, as I know that the typical FC owner isn't rich and wants to upgrade the car, so instructions on how to do these cheap DIY mods are very handy to have in there so that everyone can see them easily. Come on people show your support to help me get in the archives again!

 

is there any proof that this does anything?

 

are you joking?

 

I don't have a damn clue what it does, exactly. Gogo explain.

 

It most certainly does do some good. I tried a piece of aluminum flat bar (1.5"x.25" or so) as a prototype and a week later with no auto-x or anything, just commuting and some mildly spirited driving, it was bent with kink in the middle at about 15 degrees or more. This was proof enough for me that there is some significant chassis flex in between the rear ends of the two front control arms. It's hard to get any sense of a difference in feel for me, but my suspension is nearly stock, so it's hard to tell anyway, but I know that it's doing something to reduce flex between the suspension mounting points, and that's always a good thing. I have a theory that a significant portion of the flex is during braking, so who knows, but for $15 and a few hours of work it's most definetely worth it.

 

hey Black91n/a , where in Bc do u live? im in the north shore....

 

I can't see how it could flex a measureable amount even.

a lot of **** has to bend for it to flex there.

 

Right now I'm in Vancouver, living at UBC where I'm studying Mechanical Engineering, my home is in Kamloops, and I have no idea where I'll be in 3 months, it all depends on where the work is, for instance in the fall I was in Surrey. That's why I have no city posted, it's always changing.

You'd be surprised at what will bend and flex. Keep in mind that the car is built from a bunch of thin sheet metal. All I know is that there must have been some significant flexing there, enough to bend the bar that I had in there. Mazda thought that that area needed reinforment on the convertible, so it must be flexing there, or they wouldn't have put a brace on there.

 

I just don't see how it could flex more than a few thousandths of an inch...

 

Somehow I missed this the first time around. Nice work! I think I just found another weekend project.

 

Thanks for the compliment, I'm always looking for little projects that I can do myself, and I'll always share with the board, as I know the information here has helped me many times, so I like to give back whenever I can. I'll be able to post some pics of the bent prototype bar in a few days when I go home. I don't know how else I'll ever be able to convince the doubters.

 

I've got some pictures of the prototype now. You can clearly see the bend in the middle. That part was straight when I installed it and was bent when I took it off a week later. It hit nothing. The ends are slightly bent, this was done by me to keep the center section straight when installed.

 

anyone know if the stock convertable lower arm bar fit in a non convertable?

 

dude slo. read back a page or so. black91n/a posted a link for just that convo....

Brian

 

Ya, I think that should convince the doubters.

 

Just ordered the Mazdaspeed lower arm bar from CorkSport.....looks to be the strongest at multiple flex planes.....we did a ton of testing with another non-Mazda autocross car, and the Neuspeed bars with no joints or threaded ends felt the most secure and passed the chassis flex tests (measure body openings and seams, jack the car up at various places, re-measure and see how far the points moved).

FWIW, I have a solid AWR front upper brace, ordered the Mazdaspeed lower arm brace as well as the CorkSport rear upper brace......a chromoly 4-pt roll bar may go in the future once we're done autocrossing and can stand to gain a few pounds. I'd to the roll bar now, but the benefit of stiffness vs weight in a street tire class is not worth it, especially running against the Miatae and CRX.

-JW
'89 GTUs

 

So the Mazdaspeed one replaces the existing mounts?
Thats really interesting! So pretty much unbot the existing ones and bolt int he bar. Pretty cool, anyone got pics?

 

Yes.

 

Black91n/a, that's really interesting. Makes me want to head out to make my own.

btw, cool that you're at UBC... I attend there 5 days a week :p

 

Awesome thanks for that mate! much appreciated!

 

interesting stuff, i need to give this a try!

 

Go ahead and give it a try! It's not hard to do.

 

Bump for you Black91n/a. I like DIY and I like saving money. Thanks!

 

So does the mazdaspeed lower bar clear RB headers. Looks very nice, and i dont have the tool or time to make one my own. Mad props to you for doing this project.

Thanks

Jason NYC
NYRA President
www.nyrotary.com