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FEATURES: DELTA 7 ARANTIX ASCEND
Road Bike Action
March 26, 2010
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If you see a Delta 7 Arantix Ascend once, you’ll remember it for life. Its IsoTruss main “tubes” are made from twisted strands of composite fibers, heat-cured into a woven lattice that seems more apt to be on the International Space Station holding up a solar array than replacing the traditional tubes of a road racing frame. IsoTruss is a patented carbon fiber/Kevlar space frame that was developed at Brigham Young University. Advanced Composite Solutions is the exclusive licensee of IsoTruss technology, and Delta 7 in Payson, Utah, is their cycling division where the Arantix Ascend frame is produced in limited numbers. The Ascend frame runs $5000, and complete bikes cost around $10,000.
The strength and stiffness of a tubular structure increases exponentially as its diameter is enlarged. To achieve the lowest possible weight, frame designers boost the diameter of frame tubes and then reduce the material thickness to the point where one can deflect the top tube of many carbon frames by pinching them with two fingers. By redistributing the same amount of carbon fiber into a geodetic space frame, IsoTruss frame members can achieve the same strength and stiffness as a paper-thin tube of similar size. The thick, triangulated structure of the IsoTruss, however, can resist impacts and abrasion far better.
THE FRAME
So far, Delta 7 uses IsoTruss to replace the main tubes of its Ascend. The truss is then bonded using a tube-to-tube method to conventional carbon lugs at the main frame junctions. The rear triangle is made by Easton with standard carbon molding techniques. The Ascend uses a slightly sloping top tube, and the race-inspired geometry for our 54-centimeter test model sported a 54-centimeter top tube, 41-centimeter chainstay, a 74-degree seat angle, 73-degree head angle, and the wheelbase was 98.5 centimeters. Sizes are available in 50, 54, 56, 58 and 60 centimeters, and Delta 7 offers two complete build options. Delta puts the weight of its 56-centimeter frame at 1056 grams and states confidently that there are no rider-weight restrictions on the Ascend.
THE PARTS
Our 54-centimeter Ascend was buffed out with SRAM Red shifting and braking components; Edge 65-S tubular carbon aero wheels, carbon fork, carbon bar and carbon stem; a Ritchey WCS carbon seatpost; and a Selle San Marco Team saddle. Tires were Bontrager Race Lite tubulars. Conservative component choices moderate the wild look of the Ascend’s IsoTruss frame.
THE RIDE
IsoTruss makes it hard to evaluate the ride of the Ascend without prejudice. It should come as no surprise that most comments after a first ride were about the bike’s frame stiffness and the perceived smoothness over the road. Unless you look down, though, the feel of the Delta 7 is that of any elite-level, torsionally rigid, lightweight carbon frame. Throw whatever your quads have into the crankset and the Ascend will convert your torque into forward movement. Of course, this seems like revelation because most expect Delta’s carbon-truss tubes to react noticeably different than a conventional frame, but such is not the case.
The Ascend feels like a quick-handling criterium racer. Its geometry makes it easy to get on and off the saddle in response to surges in the pace, and its steering is quick enough to respond to a disorganized breakaway attempt. It corners smoothly and feels trustworthy enough to lean way over into fast turns. Its Edge carbon wheels have special braking tracks that stop smoothly without the rubber eraser feel at the caliper that some carbon rims exhibit. The Ascend climbs and accelerates easily, but it lacks a zesty “jump” with the first push of the pedal. That said, The Delta 7 still delivers the groceries when you need to close a gap or win a sprint.
What the Ascend does not deliver is a level of comfort over rough pavement. Not that it is overly harsh, but its woven tubes don’t do anything special to mute the pounding that gets past its deep-profile aero wheels. The ride is similar to the Colnago Extreme Power—just smooth enough to survive a long road race, but if you run over a coin, you might be able to tell if it was a dime, nickel or a quarter by feel alone. Part of the Delta’s firm ride may be the fault of its tire selection. The Bontrager Race Lite tires are the first tubulars we’ve ridden that made us want to switch back to clinchers. The Race Lites feel dull under power and lack the road-smoothing, resilient ride which we usually ascribe to tubular tires and wheels.
THE VERDICT
Prepare a short speech, because Delta 7’s exotic-looking Ascend will have observers asking questions about the IsoTruss frame as long as you ride it. This is not the bike for casual cyclists. The first test rider pegged it as a criterium racer, and most will agree. What makes the Ascend worth considering is its responsive feel, lateral rigidity and light weight. At 14.6 pounds, the Ascend sits close to the edge of the UCI’s weight limit, and it easily handles high-watt sprints without flexing. If you do race crits, it is worth considering that IsoTruss has the potential to survive a nasty crash, which can put you back in the hunt instead of the truck back home.
PRICE: $10,000
WEIGHT: 14.6 pounds (no pedals)
INFO: www.Delta7sports.com
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