Delta 7 Sports launched its Arantix MTB frame at Interbike 2007, but this year it had rideable samples at Outdoor Demo. The most cursory glance at the pictures will tell you what's unusual about this frame - you can see right through it. That's thanks to the Isotruss construction - rather than tubes, the Arantix is made from a kind of cylindrical carbon/Kevlar lattice. The claimed advantages are stiffness, low weight, and durability - if one of the bits of lattice cracks or breaks, it doesn't really matter as the rest of them take the load. It's all hand-made, a labour-intensive production process that's reflected in the somewhat stratospheric price.
Claimed frame weight is 1.2kg (2.6lb), which is pretty light but certainly not ground-breaking - most mainstream carbon fibre XC race frames are around (and often below) that weight these days. Out on the trails it's certainly a sprightly ride - the "tubes" in the main triangle have a large effective diameter, making for a stuff platform. It was also surprisingly comfortable given the barely-there tyres, but we were on a Medium demo bike with about a yard of seatpost sticking out, which probably helped. Handling was lively, XCish fare - there's nothing strange about the geometry.
Onlookers (of which there were many - don't ride one of these if you're the shy and retiring type) tended to make comments about cheese graters, and we were definitely a little concerned about abrading the editorial knees on the top tube. But the Isotruss construction isn't actually sharp and pointy, just a bit knobbly. Of more concern is the limited tyre clearance at the back - Delta 7 has made life a little easier for itself by using completely straight seatstays, but you're not going to get much bigger than a 1.9in tyre in there (the demo bikes had 1.8s).
You'd expect some teething troubles from something like this, and unfortunately Delta 7 suffered a number of frame failures at Outdoor Demo (although not in the actual Isotruss "tubes" themselves). Clearly the production process needs a little work, but then the company only launched a year ago. The price of the Arantix was heftily reduced recently, but a frame will still cost you $4,895 (about £2,800 at the time of writing). It's not that hard to see why it costs that much, but given how much more expensive it is than other frames of similar weight from manufacturers with long track records, it's going to be a tough sell...
www.delta7sports.com
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