Andrew Mace said:
As much of the body design survived past the first prototype, presumably that more or less set spec's for front and rear track?
Or possibly it was because the TR2-early TR3 shared rear axle assemblies with the Mayflower (and others). The track is wider than a Standard Nine I believe.
But I think a related point is important : The TRs were intended as very low-cost sports cars, economical to design, to build, to buy, and to operate. The "economical to design" part is the reason they share so many parts with other ST products; the engineers were simply not given a blank sheet of paper (so to speak). And wide track was considered relatively unimportant to performance at that time.
However, although a wider track does help, the low center of gravity means it doesn't help much (and the CG can be lowered even farther than the factory had it). With the CG that low, you should have no trouble whatsoever outcornering those dually trucks.
More likely, IMO, your problems with "spinning out" are due to lack of rebound travel in the rear suspension. In a hard turn, the inside rear spring reaches the top of it's travel when the axle hits the frame, and rather forcibly lifts the rear wheel from the ground. That suddenly transfers extra weight to the outside wheel, which in turn breaks loose and slides sideways. The sudden transition from understeer to oversteer has thrown many a driver off in the weeds. Or, if there is enough pavement, sometimes the effect is that the rear end starts "skipping" sideways.
This is why I started adding sway bars to my TR3A, to reduce body roll and hence the axle hitting the frame. It's quite effective.
BTW, it's also easy to increase the rear track, if you're willing to modify the bodywork a bit (ala TR3 Beta). The TR4 rear axle will bolt right up, and moves the wheels outwards over an inch. I drove a TR3A so equipped for several years, and it did improve handling (at the expense of having the tires rub the bodywork a bit in hard turns). TR6 wheels will also bolt up, and have increased offset to produce a wider track.