Ultra-light Guru Photon – Installment 1
by Jim Weaver, Service Manager, Fit Werx VT
Over the past few years, a competition has developed to see who can build the lightest frame. Weights have been dropping precipitously, with new offerings pushing claimed weights into the 750 gram range. While chasing the lowest possible weight on a bike is not an idea we usually espouse (a bike is a sum of its parts and there is a lot more to performance than saving a few grams), we thought it would be a fun project to build a very light custom bicycle. However, we didn’t just want to see how light a bike could be built as that almost always means significant compromises in functionality and ride. Instead, the goal was to build an ultra-light bicycle that is dependable, durable, non-finicky, handles well, rides smoothly and can be used and enjoyed every day. We also wanted the bike to not just be a showcase for the ultra-exotic – it had to use parts that were designed to work well together and that were reasonably priced for what they offered. While this wasn’t going to be an inexpensive bike, there are far more expensive bikes out there than this. As we started exploring this project, a rider told us he would like to be part of this process and this is the story of his Guru Photon.
The Frame: Guru Photon, $4900 + $650 in custom finish.
In 2010 Guru sent a charge into the ultra light-weight category with their Photon and immediately won Bicycling Magazine’s “Dream Bike of the Year” award. The Guru Photon is a full carbon fiber frame and fork and, while not quite as light as absolute lightest mass produced frames, the Photon has a major advantage in that it is a custom-built frame. As a result, the rider will get a frame that is designed to fit and ride for the rider’s needs. This bike wasn’t about compromise and we wanted it to fit as well as possible and there were notable advantages to a custom geometry for the rider. We have delivered several Photons below 14 lbs and have one on the floor that is a similar weight and we could see almost two pounds more weight loss as being possible. Given the palmares and fit of the Photon, it was a great selection for the rider and the overall goals of the project.
Guru manufactures its own carbon fiber frames at its factory outside of Montreal, Canada. These frames do not come out of a mold in China. While you can get a stock geometry Photon, this particular frame was built to geometry specifications we provided Guru after a fitting with the rider. In addition to the custom geometry, the carbon fiber is laid-up to provide ride and handling characteristics that best match the rider’s use and size – so this is a full custom frame at a similar price to many of the ultra-light mass manufactured frames from Asia. The frame for our build weighs 890 grams. The combination of frame, fork, and headset bearings, as pictured, weighs in at 1,260 grams. There are frames out there that claim to be under 750 grams, so this may not sound particularly light. I do not know how every manufacturer weighs their bikes, but what I do know is that we often weigh equipment and find it to be heavier than claimed. I also know that this frame is here, in the shop, fits the rider without compromise, is not small (57cm top tube), and this is the actual weight.
Some frame construction details…. The headset bearing seats on the Photon are not molded carbon fiber, as is common on many mass produced bikes now. Instead, the Photon uses machined aluminum alloy for a better bearing seat and increased durability. The headset bearings supplied with the frame are FSA. The bottom bracket shell is carbon fiber in the industry standard BB30, to be used with a pressed-in shell and bearings. The derailleur hanger is replaceable, and made of aluminum alloy. If the derailleur hanger is bent or broken, it is easily repaired, instead of at best having to be returned to the manufacturer for repair, or at the worst necessitating a whole new frame. Given our experience with the Photon, it is a frame that has proven that it can stand up to our rough roads too. All in all, the Photon is not at all disposable; it is a durable frame, designed and built for the long hall. The finish scheme selected is quite stealthy, with a great combination of flat black offset by gloss black and minimal clearcoat as finish can add 120-250 grams to the weight of a frame.
Ultra-light frames are often rather stiff, and my previous experience with Photons has shown me that it is not an exception to this rule. This of course has its good and bad points. The good is that the rider’s power is efficiently transferred to the wheels with little loss in frame flex. The bad is that a stiff frame can lead to a rougher ride, particularly on Vermont's pock-marked roads. By judicious selection of other components and wheels, however, we can offset the stiffness, while not losing any of the benefits of that stiff frame. So, our choices of other components will take this into account, along with the weight.
Next – Wheel selection.