By Tom Demerly.
Most Aero? No. Lightest? Usually not. Stiffest? Probably not.
In the world of golden BB metrics Guru Handmade Bicycles hangs their hat on the one tangible that all bike performance arguments come back to: How well does it fit? Nothing is more important in bicycle performance than fit and position. Guru Bicycles are built around achieving the best possible fit and position- and that may be your largest single performance advantage.
This is Part One of a two part article on Guru Bicycles. In it we review the nuts and bolts design of the Guru CR.901 triathlon bike. In Part Two we look at what may be the more important part of the equation: The Process.
Part One: The Bike. Guru’s CR.901.
When you buy a bike you pick your poison. Are you a weight weenie, an aero junkie or a stiffness maven? Everyone seems to have their “golden BB” shopping metric. Ultimately the significance of any of those data points is diminished if the bike doesn’t fit. Performance on the bike starts with fit. This is where Guru owns an edge.
The Guru CR.901 is an aero styled carbon frameset that can be made to any dimension set based on a rider’s measurements and riding styles. That one sentence opens up a greater range of possibilities than all the volumes of wind tunnel test data put together. It also speaks to the bike’s Achilles heel. There is no singularly perfect product, and we’ll talk about that…
Custom framesets have long been the high water mark of cycling bling. Until the last half decade, you had to decide between custom geometry and aerodynamic design. Almost no aerodynamic bikes were sold with custom geometry since they were molded bikes, and the molds could only be made in specific geometries. Your frame material choices were usually limited to weld-able materials. Guru, along with Serotta and Calfee among others, changed that with the introduction of custom carbon fiber, molded bike. The evolution of that bike has become the Guru CR.901.
Stock Geometry on a Custom Frame Brand?
In addition to being a customizable frame that can be built to your dimensions the Guru CR.901 also has a stock frame size geometry sheet. Why would you buy a custom frame brand in their stock geometry? Because this is a great geometry chart. Guru is one of the few companies to boast a 79 degree seat tube angle on their geometry chart, meaning the angle between your torso and femur will remain open and relaxed to make it easier to achieve a real-world aero posture. Head tube heights from Guru’s stock geometry measure about 1 cm head spacer higher per frame size than Cervelo. A 54cm Cervelo P2 has a 120 mm high head tube. The Guru CR.901 in Medium uses a 130 mm head tube. For the majority of riders who are asking for more aerobar height this is a nice feature. On a stack and reach comparison to Cervelo P2 the CR.901is 4 mm shorter in reach on their size Medium compared to the Cervelo P2 in 54 cm. The bike then runs 2.1 cm higher on overall stack. In simple language the CR.901 is higher and slightly shorter in a comparable size.
Guru features 5 stock frame sizes in the CR.901meaning a strong 60-80% of riders will land well within the stock geometry numbers. For the outliers there is Guru’s nearly infinite custom capability. And their greatest vulnerability.
Pick Your Favorite Flavor.
I’m not so bland as to suppose the singular attraction to custom bikes is a unique geometry set. It’s also about the bling. If you should so desire a “Prince Purple” custom Guru paint scheme- even on their stock geometry- it can be done. Guru has a unique tool on their website to experiment with different color schemes, but it wouldn’t let me make a Prince Purple CR.901 with Sydney Green graphics, so there are some safety measures in place. Guru assesses an up-charge for the custom colors, and it is worth it as their paint and finish is flawless when executed correctly. We’ve had a couple difficult guru color schemes arrive with problems though. Five bikes in a difficult pearl white color scheme had an odd yellow “ghosting”. Guru repainted these bikes to perfection. This underscores the role of the dealer in the transaction.
Front to Back on the CR.901.
The Guru CR.901 uses a conventional front brake. Thank you. Nothing proprietary, no special parts. The advantage is serviceability. If you put a Guru in a flight case to take to Ironman new Zealand (I have) you will be able to service the bike in your hotel room with standard tools. If something breaks chances are a bike shop in New Jersey, Kona, Kuala Lumpur and Laguna Phuket will have a replacement part that fits. Try that with your proprietary, integrated, aero front brake. Our review bike used carbon fiber specific brake pads to stop its new Zipp 404/808 Carbon Clinchers that roll on 24 mm wide Continentals.
The Head Tube on the Guru CR.901 is an hour glass shape that holds no secrets with headset or stem specifications. It is a delightfully simple set up. This build also used a basic, adjustable Profile Design carbon fiber base and aero bar with the Shimano Dura-Ace Di2 shifters installed on the base bars and aero bars. Di2 gives the athlete a huge advantage since you can shift from the base bars and aero bars. You can still shift on a climb while pedaling out of the saddle using the base bars then, once over the top, shift flawlessly from the aero extensions in the aero position.
The head tube on the CR.901 transitions to the top and down tubes in a seamless flow both internally and externally thanks to Guru’s internal bladder molding. This internal molding helps compress the composite from the inside making the entire structure stronger with less material. Guru also uses unidirectional fiber lay-up with special emphasis on transitions in frame shape where some manufacturers overbuild their frames. Carbon fiber layers can overlap adding weight and influencing ride comfort Guru’s construction techniques avoid that. Guru also offers different carbon fiber lay-ups for different ride quality and frame sizes. This carbon lay-up option is a key feature.
Cables enter the top tube on top and are semi-routed through the frame. Most importantly, the new bottom bracket configuration makes it impossible to incorrectly route the cables at the bottom bracket. The rear derailleur cable (or Di2 cable in this case) routes through the inside of the right chainstay, popping out for a few inches before joining the rear derailleur.
This CR.901 used conventional battery mounting for the Di2 power pack, borrowing one of the down tube bottle cage mounts. Using the Shimano Di2 battery mounting bracket still allows the use of a bottle cage on the mount- the battery sits below the bottle cage.
The seat tube of the CR.901 is airfoil shaped with a cut-out that partially surrounds the wheel much like a Cervelo P2. Since the rear wheel uses horizontal dropouts with adjuster screws you can precisely adjust the proximity of your rear wheel to the seat tube for best aerodynamics, closer being better in this case. There is plenty of clearance between the chainstays for the popular “bulge” disk wheel designs.
The entire front of the bike stays narrow- and presumably more aero- until it melds into the bottom bracket. The bottom bracket is SRAM/Truvativ developed Press Fit 30, a large diameter, sealed cartridge system that works with most cranksets. Ours was configured for use with Shimano cranks to work with the Di2 ensemble.
Drivetrain on this build is all Shimano Dura-Ace Di2, the single best triathlon drivetrain. While I would like to see better battery integration and/or different race day battery options to make the battery less obtrusive, the system works so well for triathletes it renders single shifter set, cable actuated drivetrains at a disadvantage.
If practicality and ease of use are themes on the CR.901 those themes continue with the seatpost. The head is a beautiful, micro adjust design that is relatively easy to work with. It does not afford as much fore/aft and effective seat tube angle adjustment as Felt and Cervelo but, who uses the rearward saddle position on those bikes anyway outside of professional cyclists? The seatpost binder bolt is flush with the top tube and beautifully concealed when viewed from the side. I was initially worried this clamp may not hold reliably but Guru has yet to be proven wrong on this design. If you use a torque wrench and carbon friction paste inside the seat tube you improve the chances of never having an issue with the seatpost slipping.
If you look at the trailing edge of the top tube you gain a sense of the unusual triangular cross section of the top tube. It tapers toward the seat tube but maintains this triangular cross section throughout its length. This design resists twisting forces, an important addition on a bike with a narrow, airfoil shaped down tube. It’s a key stiffness feature but, in my opinion, requires Guru’s stiffest lay-up to be at its best.
Guru continues to score high marks for real-world design with the rear brake mount and seat stays. The rear brake simply bolts through the seat stays in an utterly conventional way. Again- easy to work with. The seat stays swoop inward in a Serotta inspired curve to increase length and road shock absorption.
The seat stays lead to a pair of box-shaped, deep chainstays that assist the bottom bracket in giving the bike a strong pedal-to-rear-wheel interface. Rear wheel dropouts are replaceable should disaster strike.
How does it ride? The stock build of the Guru CR.901 is nice in the back but a tad disjointed in the front for my taste. I like a very stiff bike- especially front to back. It’s easy to make a small rear triangle stiff but harder to build a narrow, aero front end to match that stiffness. This same phenomenon plagued Felt with their early DA models- it’s gone in the latest versions. The resulting disparity in frame stiffness over the length of the frame creates a “perforation” in front of the bottom bracket. The bike gets flexible there. That has an influence on steering and out of the saddle climbing. No problem with Guru though- this is simply a line on the order form. I would order this frame in the stiffest carbon fiber lay-up- that fixes this criticism. I am one of the middle 80% who does not need custom geometry from Guru so I have raced on their stock frame sizes from Midwest triathlons to Ironman New Zealand- although in this carbon version I would opt for the stiffer lay up as mentioned.
Steering is down the middle- neither remarkably stable nor responsive, so about what you’d like on a tri bike when a lot of your navigation is done from the elbows. I do like the higher head tubes partially for comfort and also for looks- I run a low cockpit and with this slightly higher head tube I can use a low profile handlebar system like the Shimano distributed PRO cockpits.
As we segue way to Part 2 of our look at Guru Bicycles it is important to realize the advantage of custom geometry is also a drawback. You are, effectively, an experiment of one. If you order a custom geometry frameset from Guru they are certainly experienced enough to avoid designing something that simply wouldn’t work or have truly awful handling. They’ve built enough bikes in enough geometries to know the problems that could crop up. However- it is anything but a standard experience. Again- an advantage and a drawback. Custom paint is the same. If you view bikes as tools that are disposable at the end of a season or seasons, to be replaced by the next “greatest thing” then the idea of custom geometry and custom fitting likely doesn’t appeal to you. If you are either a problem fit, want to keep a bike for a number of seasons or both then Guru is a strong option among few alternatives. Finally, as we experienced with paint issues, a handmade bike is subject to the fallibility of any handmade process. That said, Guru’s customer service is generally prompt and responsive. They always own any issues a customer may have.
In our next article we will look at the process used to find an optimal custom geometry for a customer, and allow them to “ride” that custom bike in their configuration before it is ever built, albeit in a virtual setting. It’s this mix of unique capabilities and workmanship that make Guru an interesting story, one to be continued…
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