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Technical Q&A with Lennard Zinn – Cogs, Chains and other things

Marketing ploy?Dear Lennard,Shimano's website lists the Dura Ace 7800 hubset as being only 10-speedcompatible, but the Ultegra 6600 hubs are listed as both 9- and 10-speedcompatible. Is there actually a difference or is this "10-speed only" designation a marketing ploy?RobertDear Robert,The Dura-Ace hub has an aluminum 10-speed freehub body, while the Ultegrahub has a steel 9-speed freehub body. The 10-speed freehub body has a largerouter diameter and deeper splines. The deeper splines are more resistantto damage to the freehub body’s spline ribs due to torque on the cogs forcingthe

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By Lennard Zinn

Marketing ploy?
Dear Lennard,
Shimano’s website lists the Dura Ace 7800 hubset as being only 10-speedcompatible, but the Ultegra 6600 hubs are listed as both 9- and 10-speedcompatible. Is there actually a difference or is this “10-speed only” designation a marketing ploy?
RobertDear Robert,
The Dura-Ace hub has an aluminum 10-speed freehub body, while the Ultegrahub has a steel 9-speed freehub body. The 10-speed freehub body has a largerouter diameter and deeper splines. The deeper splines are more resistantto damage to the freehub body’s spline ribs due to torque on the cogs forcingthe splines of the cog to dig into the soft aluminum ribs of the freehubbody. If you have ever had a 9-speed aluminum freehub body on which thecogs got stuck and were very difficult to remove because they had dug intothe spline ribs, you know what I am talking about.The inner diameter is the same on both Shimano 10-speed and Shimano9-speed cogs, as is the shape of each spline tooth at its inner end. Thatmeans that both a 9-speed and a 10-speed cog can fit onto a 9-speed freehubbody (the thinner one with shallower spline valleys and lower spline peaks).But a 9-speed cog WILL NOT fit on a Shimano 10-speed freehub body, becausethe spline peaks are too tall (the outer diameter of the freehub body islarger than the inner diameter of a 9-speed cog at its largest).It’s not a marketing ploy. It just won’t fit.
LennardStumped
Dear Lennard,
Do you think powder coating a set of circa 1990 Shimano 105 crankswould do any damage to the structural integrity of the aluminum? I readthat the curing process calls for heating in an oven at about 300 to 400degrees for 20 to 30 minutes.
ScottDear Scott,
I would be willing to bet that temperatures in that range are so lowthat it would not appreciably change the mechanical properties of a heat-treatedcrank. That said, the powder-coating step is actually part of the heat-treatingprocess for some frames made out of 7000-series aluminum, which are generallycooked like a turkey for about eight hours. Campy Veloce cranks used tobe powder coated, and I do not know if that was done after heat treating,or if that was part of the heat treat.So, the bottom line is that I do not really know. Anybody?
LennardFeedback on previous columns:
Dear Lennard,
I can relate with Russ’s friends Ergo Power problem. I had a1999 Record shifter that had shifted fine until a small spill and thenit was really weak in the bottom 3 cogs, then the typical click betweenshifts returned for the other cogs.I read about the broken post problem and decided to give my shiftersan overhaul. Found out that while the post did not break off, thering that it was connected to had cracked all the way through right nextto the post. That crack opened up a tiny bit every time I shiftedand was the major cause of my shifting problems. After replacingthis and the G springs, this six-year-old shifter works better then ever.
PetePlugging a product
Dear Lennard,
In an earliercolumn you recommend the Third Eye Chain Watcher and Deda Dog Fangas completely effective solutions to downshift chain derailments.If you ever have occasion to offer such advice again, I think it mightbe improved with a couple of minor modifications.1. You might want to reconsider describing the plastic guides as “completelyeffective” (see the first image) and take a look at the experiencesof others.2. Perhaps you could consider adding the JumpStop to future recommendations.I think both modifications would be more in keeping with your firstrate reputation for technical expertise. (Of course, I freely admitto having a bias, so if you’d like to do your own evaluation of a JumpStop, just tell me what size you’d like and I’ll send you one.)
NickDear Readers,
I just received some Jump Stops from Nick and have yet to try them.I have indeed jammed a chain past a Third Eye (hollow plastic) in the past,but it’s rare, and I don’t believe I ever have gotten one past a Dog Fang(solid plastic).
LennardRegarding 7-speed shifting:
Dear Lennard,
A while back you wrote a reader that a “9-speed derailleur should workjust as well as the 8-speed one for your purposes, but the chain probablyneeds to be nine-speed to fit through the narrower jockey-wheel cage.”Lennard, that’s true, yes, the 9-speed rear derailleur will workfine with the 7-speed shifters and cogset but there is no need to use a9-speed chain. A 7- or 8-speed chain, like a Sram PC-48, doesn’t interferewith the distance between the 9-speed rear derailleur cage and, indeed,a 9-speed chain may be too narrow to shift the 7-speed spacing.
Peter Chisholm
Vecchio’s Bicicletteria
Boulder, ColoradoLennard,
I read your reader’s question on keeping a 7-speed rig going with amodern derailleur. Consequently, I wanted to offer a solution thatworked for me until I upgraded my ride.It wasn’t clear from your reader’s question whether economics or oldformat dropout spacing was his motivation for keeping his setup going.However, I had an old frame with 126 mm rear dropout spacing, and didn’twant to spread the rear triangle.I got a tip from SheldonBrown to run only eight of the nine cogs of a Shimano cluster on my7-speed 105 freehub. Of course, you lose one of the bottom cogs, and digressfrom the HG ramp alignment progression at one position, but the stack-upworks out to be about the same (short a couple tenths of a mm) as the 7speed cluster. This space is easily taken up with the cassette retainingnut.In addition to the new derailleur and cassette, you need a new shifteras well. On the bright side, this collection of parts is comparativelycheaper than scraping an already lightweight frame for a new bike.This solution worked well for me for a season. It shifted veryreliably, and allowed me to get STI style shifters on my old bike.
Chris


Technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of several books on bikes and bike maintenance including the pair of successful maintenance guides “ Zinn & the Art of Mountain Bike Maintenance” and “Zinn & the Art of Road Bike Maintenance.”Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn. Zinn’s column appears here each Tuesday.