Introducing Concept Technology's Trapezoidal Softride Tandem geometry.
I designed stiffness into it by using 1-3/4"
top and bottom tubes. The Softride Beam is attached to the Trapezoidal tube that
extends from the rear BB through the top tube. The Trapezoidal design stiffens
the center geometry. Oval seatstays and chainstays are used to strengthen the
rear rhombus. Yes, it lacks many tubes that you might be used to seeing but with
this design, those tubes were unnecessary. Between the top & bottom tubes,
plus the 1-3/8" downtube and 1-1/2" headtube, the handling is precise
For teams requiring a stiffer rear triangle, I use a traditional rear triangle design, extending the front deraileur tube up to the top tube. I also will use 2" top and bottom tubes for riders who need the extra metal.
Victor Chang, Concept Technology