so today...i started removing the engine and put the jack under it...as i started to jack up the car where the frame rails are...i noticed the frame flexed and buckled...i was like...wtf...there's no rust on the frame...it seems strong...but why the hell would putting a jack under the frame cause an indention on the frame?...

luckily i noticed and stopped in time b4 i did too much damage...

so here's my question...has anyone ever had to strengthen their frame?...and...if i wanted to strengthen the frame...how do i even go about doing it?...

do i just go out and grab 1/8" metal strips and start welding onto the frame rails?

 

Mine does the same and as well is a no-rust car, I've thought about sending the car out and getting the frame rails boxed in 1/8" steel from the local fab guys but my crushed pinchwelds and a towel have done well enough for now.

 

are you talking about the "frame" or the bottom of the rocker that they give you as a jack point for the stock jack?

the place they give you for the stock jack is really only for the stock jack, anything else will bend it, its only sheet metal right there, the "frame" is inboard of that.

 

yea...i was well aware of that...it really is the stupid frame rail...i can't believe mazda got away with making them so flimsy...but then again...these were the years of the K-cars so...oh well...

i really do want to strengthen that frame and the unibody...i've seen it done on an old 240Z...but not an rx7....just wondering if anyone has gone down this path...

all u racers out there...ain't flexing a problem for u guys?...or do these things just don't make that much horsepower that it's not a problem?

 

You are jacking against one side of a thin sheet metal box, of course it is going to bend/buckle. It is a unibody car, the strength comes from the whole chassis, not from the "frame." That part of the chassis was not designed to jack against, that is why they made jack points at the pinch welds.

Isaac

 

If you wanted to get serious about this the most obvious solutions are seam welding and an actual roll-cage. Those are racer things

Other stuff that you see on cars generally are subframe connectors or frame rail reinforcements that bolt on over the stock frame rails.

subframe connectors come from the GM/Ford world and I've never seen them executed on rx-7s. The frame rail reinforcements are a miata thing. Both owners RAVE about the positive difference they both make, so maybe they could do something for us.

 

If only they made frame rail reinforcements for our 7s.

Like these miata ones would be nice..

http://www.clubroadster.net/vb_forum...ad.php?t=35347

 

I thought that bending was just because my frame is terribly rusted. Makes me wonder what would happen if I ever got in a crash. Not that I bought this car for the safety factor anyway.

I do wonder though, if any of those braces could possibly fit our cars and how much of a difference it would make.

 

If you jack up on the frame rail just put a small length of 2x4 to distribute the load and it won't buckle.
Those reinforcements look nice on the Miata forums. It looks like they did a group buy so I don't think your going to be able to pick up a set to try and fit our car. We definatly need someone to start making those for us...!!! I hate looking at the all the previous dents from whoever jacked the car car w/out knowing any better.

 

here are the miata frame rail stiffeners: http://www.flyinmiata.com/index.php?...umber=13-69010

I talked to Flyin' Miata a while back to see if they would work on the FB. They sent me complete demensions of the stiffeners. I never went through with it. I'll look to see I still have the specs.

 

if you are concerned about stiffness you could simply weld your own cross braces using some square stock or tubing.

 

I bet even those would fit. Try and find them please. I would like to get some to cover up my bent rails from me being a dumbass when I was 15

I'm going to try and contact them and I'll measure mine and see whatsup later today.

 

I found the dimensions.

 

Yahtzee!!! I'm going to contact them and see what they can do

 

thats not the rail, look under the car, and you'll see a "frame" rail, at the front it makes an L shape, and you jack there. or the subframe, or the rear axle, or the rear axle pickup points.

the cars stiffness doesn't come from the thickness of the sheetmetal, but the shape of the box it makes, and K car or no the SA/FB was very stiff for its time, and about 10 years after that...

the racers build a roll cage, generally a no go for street cars...

 

Considering how much my rust free california car sags and creaks in every day situations anything to stiffen it up for just a road car would be great.

 

After a few quick measurements, it appears the rails for the miata are a little off but will still fit. Ours are 48" in length the rails are 43. Our height is 5/8" the depth of the rails are 2". Our width is 2.25" the rail is 2.75.

 

Those frame rails aren't exactly unicorns. I think I picked mine up on the forum for 75-100. Hell if anyone asks me nicely I'll go see if my uninstalled set would fit under the FB...

 

Ehhhhhh for $159 it would of been nice if by chance Mazda used the same dimensions. Mine are all jacked up.

 

The problem with those frame braces is the Miata floor is fairly flat, whereas the RX-7 floor along the frame isn't. They won't just bolt on, since they won't sit flush against the floor. It would take some pretty extensive modification to make those bolt up, and at that point you might as well make your own. The frame does need some bracing though. There is a serious difference when I jack up my car with and without the RE-Speed triangulated brace. The doors close smoothly when it's on but need a good slam when it's off. Depending on the work you want to put into it you could strip the interior and seam weld the interior. Adding triangular fender braces along with a 3-point strut brace would be an easier but less effective fix.

 

I just got a new welder, and my car is a totally bare shell.... seriously considering this right now...