This article originally published on BikeRadar
Guru marketing director Phil Pinsky says his company invented the 'superlight' road bike category with the original, 750g Photon. Now he says Guru is inventing the 'hyperlight' category with the new, sub-670g (claimed, 54cm) Photon HL.
Guru has switched from the original Photon's essentially round tube shapes to a more squared-off profile. As with other companies that have moved to similar shapes, Pinsky says it's a more efficient profile that allowed Guru frame designers to trim weight without affecting strength on the tube-to-tube carbon fiber frame.
"Squaring it off gives you a good extra inch of carbon fiber width holding the tubes together," he told BikeRadar. "That allows you to strip out a ton of superfluous material. You don't need seven layers of material if you've got a lot of width."
Adding further reinforcement are strips of carbon fiber added circumferentially at high-stress areas such as the front of the top tube, the front of the down tube, and the chain stays. "It's almost like built-in ribs," said Pinsky.
Other weight-saving concessions include a PressFit 30 bottom bracket shell with a carbon fiber sleeve, a straight 1 1/8in head tube (Guru includes an Enve Composites 1.0 Road fork), carbon fiber housing stops and headset bearing seats, and carbon fiber dropouts. The internal routing is readily convertible between mechanical and electronic drivetrains, too.
According to Pinsky, the Photon HL surpasses the original Photon in terms of stiffness-to-weight, although it sounds like the original one was a touch stiffer overall.
Pinsky says the Photon HL has a 91kg (200lb) rider weight limit and the custom-only frame will be available around the end of April. Suggested retail price is $8,500 for the frame, fork, and headset.
Helping the Guru Photon HL show bike stay under the 5kg (11lb) mark are THM-Carbones Clavicula cranks fitted with KCNC chainrings.
Photon family grows to three
Guru will supplement the top-end Photon HL with two other new Photon frames as well.
The Photon SL features the same tube shapes, straight 1 1/8" front end, PressFit 30 shell, and convertible cable routing as the HL but with a different lay-up and carbon fiber content that bumps the weight up to a still-light sub-750g (claimed) for a 54cm size. Pinsky says this is the most comfortable of the three Photon models and with a slightly taller "Fast Forward Flex" geometry on stock frames (up to 1.5cm depending on size), it's aimed more at fast enthusiast riders.
"It's halfway between our race and endurance geometries so it give you the flexibility to go either way."
Retail price for stock Photon SL frameset is $4,500 and Pinsky says it will be available at the end of March. Custom versions will cost $5,500.
Rounding out the Photon trio is the new Photon R, aimed at racers who value stiffness above all else. The Photon R uses squared-off tube profiles like the other Photon models but the diameters are bigger all around. Guru also gives this model a tapered 1 1/8-to-1 1/2in front end and wider PF86 bottom bracket shell. Seatpost diameter bumps up to 31.6mm, too.
According to Guru, the Photon R is a substantial 30 percent stiffer at the bottom bracket and in torsion than the original Photon while still weighing less than 800g (claimed, 54cm frame) and retaining the same ride quality.
The Photon R will also be available around the end of March and suggested retail price is $5,500 for the frame, Enve Composites 2.0 fork, and headset in stock geometries. Full custom geometry will add another $1,000.