Body Flex

I have a '94 that had the same problem. I replaced my shocks with Koni sport adjustables, got some good tires (Yokohama AVS 100 ES) and had a professional alignment done. All I can say is it was a whole different car when I got it back. The car feels rock solid now.

The only other thing I can add is that being a '91, yours doesn't have the cockpit brace that mine does (beleive they started in 93 or 94). You can install one yourself and some people think it makes a BIG difference. Check

Good luck.

If the Eibach springs ever get here, I'm having shocks/springs replaced on my 96M. While they're at it, is there anything else (bushings, whatever) I should have replaced? (125K miles).

I'd love to have new bushings, but I suspect the parts and labor would run ~$2000. Complete disassembly of the suspension, press out the 40 old bushings, press in the new ones, reassembly, fresh alignment; plus, some of the bolts might be rusted solid and require the gas wrench to remove. Labor for replacing the shocks at the same time would be a freebie.

If you did it yourself, it would only cost the parts ($350-500) plus the alignment. And a whole bunch of your time.

It's characteristic of Miatas with worn-out shocks, and/or heavy aftermarket wheels. Some annoying cowl shake is normal over railroad tracks and other large bumps--the contents of the glovebox will rattle. An aftermarket front shock tower brace usually raises the threshold of impact to incite the shake and its intensity, but won't eliminate it entirely.

Your car is nine years old, after all. You'd probably see some improvement if you replaced all 40 suspension bushings, but dismantling the suspension is a lot of work. The pros tell me it's a 6-hour job for an experienced mechanic in a well-equipped shop.