Originally Posted by ShannonM

It was supposed to make the rear triangle stiffer, because frame flex was thought to absorb pedaling energy. If memory serves, back when Bicycling used to include measured frame deflection in their bike reviews, such frames often measured stiffer than normal ones with the same tubing. This does make geometric sense. But, since frame flex does not in fact absorb pedaling energy, this is irrelevant for any reason other than subjective preference.

If you like the look, and you like the feel of a stiff, short rear triangle, and if they don't hit your legs, go for it.

The only reason they were made, and the only reason they stopped being made, was fashion. I'd bet that the crapification of GT bicycles in the late 90s and early 2000s is the biggest reason that nobody makes them that way anymore... it was GT's signature thing, so when GT bikes became garbage, the "triple triangle" died along with GTs reputation.

(I always thought it looked coolest on "funny bike" designs. Those Shoguns were the cat's ass when I was a junior racer in the late 80s. Cheapest way to get a cool TT bike. Having a cool TT bike was important back then.)

--Shannon