The Look 595 uses a larger lower headset race for increased strength and reliability.
I notice that more and more frames are using larger headset races on the lower side of the head tube. I am considering a Look 595, and am concerned that I may have trouble finding a replacement headset in the future. Is there an industry wide standard for such things? What exactly are the advantages of a dual-sized headset?
-Jim Rarhaen: Ashland, Oregon
I am sorry to say that after asking prominent bike and component brands, there are no standards, planned or existing, that encompass the recent crop of tapered steerer tubes and dual-diameter headsets. So far, most frame makers are using internal-type headsets, which further complicate the matter. Even if the outside diameters are the same, some bearings center on flat surfaces and others use a heavy chamfer or taper. Until we adhere to accepted standards, anyone who buys a tapered-head tube frame or a bicycle with a similar design should choose its maker based upon its long-term service history (some heady brands are notoriously bad).
The good news is that headsets rarely wear out these days—the bad news is that forks are often damaged in crashes and by airline baggage handlers. In this case (and we have suffered such an occurrence) you had better be able to procure an original replacement, because the chances of finding a replacement fork from another maker—with the same bearing interfaces, length and offset—are as good as leaving your laptop on a New York City bus stop and finding it there the next morning.
There are many claims as to the advantages of tapered road-bike head tubes and steerers (lighter than, stronger than, more responsive steering than, blah blah blah), but only one holds water. The relatively recently adopted unthreaded 1.125-inch steerer tube and the resulting increase in the size of the headset bearings and the frame’s head tube have proven to be rigid, strong and reliable enough for ProTour road and CX racing, so we can eliminate claims related to such performance from the table of truth.
Look, who has the longest unbroken history of carbon fiber frame making in pro road racing, uses the tapered fork steerer design to eliminate the narrow waist at the junction of the fork crown and steerer. This allows their all-carbon HSC6 fork to be laid up as one unit and in a manner that keeps the unidirectional carbon filaments that support the structure flowing from the fork legs, through the crown and up the steerer tube in a smooth, unwrinkled matrix. The more uniformly that the fibers are aligned where the crown flows into the steerer tube, the stronger the fork will be in its most highly stressed area.
Look’s engineers also developed a tapered lower bearing interface that eliminates the stress concentration that a conventional notched-type crown race would cause. The bottom line for tapered road steerers is that, done correctly, it streamlines the manufacturing process and makes for a better one-piece carbon fiber fork. In this light, the Look HSC6 fork and sharp-handling 595 frame are a worthy choice, and because Look employs the same system on a number of its models, replacement parts should not be a problem in the future.
Contact Richard Cunningham for questions or comments, or just to talk bikes at: askRC@roadbikeaction.com