When I bought my Miata the frame rails were absolutely crushed. They were so badly crushed that the floor pan was bent and bulging inside the passenger compartment. It looked like someone just threw a floor jack under the car and didn't even look before they picked the car up. It's a miracle the fuel and brake lines weren't crushed.
These frame rails are paper thin. They are not jack points and they add barely any strength to the car. Really, the only thing I can figure they are strong enough to do is reinforce the floor pan. It appears like 2 engineers had an argument. One wanted a light chassis and the other wanted a stiff chassis. They compromised.
Luckily, several companies sell a solution/upgrade to fix this problem. I went with Flyin' Miata's rails however there are a number of other companies that sell similar products. I went with Flyin' Miata because they routinely have "group buys" where they sell 30 or so sets of rails at one time at a lower price. Also they offer a butterfly brace that offers even more reinforcement to those whose cars are compatible.
I'll apologize in advance for the bad photos, it's hard to get good lighting on the underside of a car.
Here's what I had to work with:
Start by arranging the fuel lines in a way that you wont bend or break them. They're kind of in the way, but they're flexible so it's not too bad.
Tools: Big hammers, pry bars, chisels, pliers, and a 10mm wrench (for the fuel line brackets). The steel bar is there to assist the pry bar.
Use the chisel or pry bar to get the flattened rail away from the floor pan. Then grab it with the pliers. Were just bending the old rails out of the way. You could cut them off if you really wanted, but bending them is easier.
Once you've bent the rails away from the floor pan, use a ball peen hammer to deal with any bulges.
Things should be looking a little better now.
If you're worried about rust, hit any bare metal with some paint.
Now repeat on the other side, then apply whatever aftermarket frame rail solution you opted for.
Done.
The car is a lot stiffer now. I immediately noticed the difference when I left my driveway. The ride is smoother and there is less vibration. Even if your Miata isn't a track car, this is a worthwhile upgrade.
Originally Posted by tsingson
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