1994 Mazda MX-5 Miata: Chassis Ruminations
July 26, 2010
Wide rubber has added a lot of precision during hard cornering in Project Miata, our 1994 Mazda Miata, as well as providing some seriously beefed-up looks. I anticipated some additional impact harshness from the shorter, more taut sidewalls, too, and they delivered.
After driving it extensively with the big rolling stock, it has become apparent that chassis stiffness is an area of opportunity.
Being a convertible, the Miata chassis is pretty flimsy -- the real roofs of fixed-head coupes add a whole lot of structural rigidity. And our car's wider tires, being in contact with a larger proportion of the road surface, transmit additional inputs that the suspension cannot damp because the chassis throws in the towel first, quivering and shuddering in response. Then the floppy softtop gets in the act, too, doing some shimmying and shaking of its own.
Making the chassis stiffer would allow the suspension to do its job better, which is goodness on all fronts of the ride and handling equation.
A rollbar is a good start. A rollcage would do wonders for stiffness but is totally impractical for street use. More elaborate underbody bracing wouldn't hurt, but doesn't 'close the box', which is where the real gains are to be had.
Really, the car would be best served by bracing that ties together the two disparate ends of the vehicle. Namely, the front and rear bulkheads. Whenever I drive Project Miata now, I've got door bars on the brain.
Jason Kavanagh, Engineering Editor @ 178,678 miles.