Technical Q&A with Lennard Zinn: Of G-springs, cranksets and those little plastic bushings
By Lennard Zinn
KGS Bikes technical writer
This report filed October 18, 2006
Crunch time
Dear Lennard,
I have Campagnolo record 10-speed shifters. In fact the components are all campy record, except the wheels. I have been having a terrible time with the front shifter. It gets hung up and won't shift or is very hard to shift and then it makes a terrible crunching noise. I have the Campagnolo triple front derailleur. Two different mechanics have looked at it, without taking the levers apart, and neither has been able to diagnose it or fix it. Any suggestions?
Debbie
Dear Debbie,
That's the beauty of Campagnolo Ergo Power; you can fix it if something gets jammed inside. Following the instructions in Zinn and the Art of Road Bike Maintenance, take the lever apart and replace any worn-out or broken parts. I would guess that one of the G-springs is broken. The G-springs engage the ratchet and click into the appropriate gear and hold it there. You might as well get a couple of G-springs ahead of time; they're pretty cheap. If your bike shop doesn't stock those, we do.
Lennard
Two questions, a single answer:
Dear Lennard,
I have a 2003 Specialized Allez Compe with an Ultegra-9 group, and am considering changing the triple crank to a compact double 34-50, paired with my 12-25 cogset. Is there a compact crank, such as those by FSA (though not necessarily carbon), which will enable me to keep the rest of my Ultegra-9 drivetrain and STI's intact, and still shift smartly?
Furthermore, could I at some point change the rear derailleur to an Ultegra or DA-9 short-cage, even if I might ultimately change the cogs to 13-27?
I know you've answered a boat-load of compact related questions over the past year, but I haven't seen my particular issue addressed.
Charles
Dear Lennard,
Can a Shimano FC-R700 compact crankset be used with a Dura Ace 9-speed group? If yes, what chain works best?
Bob
Dear Charles and Bob,
You can switch to any compact on the market, and you will get decent shifting performance. Obviously, you will have to reposition and readjust your front derailleur, and a triple FD will be a hair more sluggish than a double FD, but it will work fine. The tiny spacing difference between chainrings will be a non-issue.
It's probably best to run a Shimano 9-speed chain.
Lennard
Great question. Wait for the answer
Dear Lennard.
I understand from bike literature that the new oversize, outboard bottom bracket bearing systems create approximately four percent more friction than a standard internal bearing system from Campagnolo or Shimano. Riders are attracted to them, partly, because they are claimed to increase performance via lighter weight/increased stiffness. Is it possible to measure the performance improvement of the lighter/stiffer crankset against the four-percent friction loss? Are these new systems are, in fact, an improvement?
Bill
Dear Bill,
Look for my column on that very topic in the upcoming print issue of VeloNews. We tested a bunch of bottom brackets, square-taper, ISIS, Octalink, integrated-spindle/external-bearing, and ceramic-bearing. I can't divulge the results until it's published.
Lennard
Coming up to speed
Dear Lennard,
I'd prefer to run a Campagnolo 9-speed cogset on my 'cross bike. The Campagnolo 9-speed components have become somewhat scarce (and pricey), but I have ready access to newer Record and Chorus 10-speed shifters, and front and rear derailleurs.
I know that a 10-speed front derailleur will work just fine in a 9-speed set-up. But, what about the rear? Assuming I switch the index gear in the RH shift lever to a 9-speed version, will the 10-speed rear derailleur shift properly or, will I need to find an older 9-speed version of the rear derailleur? Conversely, switching to a 10-speed cogset may be a simpler, albeit less attractive option, assuming I make the above acquisitions. In that case, will a 10-speed cogset fit on an older, 9-speed Campagnolo hub? Similarly, do 10-speed Shimano cogsets fit on older, 9-speed Shimano hubs? And, lastly, how well do Shimano 10-speed cogsets work with Campagnolo 10-speed shifter/derailleur set-ups?
JW
Dear JW,
If you switch the index gear and ratchet ring to a 9-speed inside the right Ergo Power, it will shift fine with a 10-speed rear derailleur, and you can run a 9-speed chain just fine, too. And 10-speed Campagnolo cogsets fit on 9-speed Campagnolo freehub bodies. A Shimano 10-speed cogset does not work even marginally well with a Campagnolo 10 setup.
Lennard
Follow-up and feedback
Dear readers,
Here is some feedback on last week's column, on "The sounds of suffering," regarding squealing Mavic hubs. Many readers wrote in about it with a number of different theories. Here is a sample of each theory.
Lennard
Dear Lennard,
The problem described by the reader with the Mavic SL wheels is the dreaded "death squeal" of Mavic's hub design.
The plastic bushing Mavic uses as the inboard bearing in their freehub design wears out, and when the cassette body becomes loose, it starts to make that howling sound when freewheeling at high speed.
Tightening the cassette body helps at first, but the noise quickly returns.
A longer-term fix is to replace the cassette body, but because the aluminum-bearing surface on the hub that the plastic bushing rubs against also wears, it's a short-term fix that will repeat itself more and more often as the hub wears out.
I have no idea why Mavic thought it was feasible to use a plastic bushing instead of a real bearing in their cassette hubs, but there it is. Friends of mine who've tried to contact Mavic about this issue as a possible warranty item have been told it's "normal wear and tear".
Ian
Dear Ian,
I thought I'd jump in and explain about that inboard plastic bushing instead of a real bearing. I got the scoop on it when I was up at a Mavic 2007 MTB product intro in Whistler in July and wrote the following about it as part of a longer article for the VeloNews print magazine:
Mavic has a solution for high freehub wear rate. The FTS-X freehub system retains the bushings so often complained about but reduces wear on them with harder pawls.
Mavic points out that its two-pawl FTS system is a very good freehub system only in need of a bit of tweaking. It's efficient and stiff, being a part of the hub body supported by bearings near either end of the axle, rather than being a separate part with correspondingly inboard bearing support. It is extremely simple to disassemble, clean, maintain and reassemble. The bushing on the inboard interior end of the freehub body that riders who have had problems assume is a cheap substitute for a bearing is actually far superior to a bearing and is not the cause of freehub failure at all, according to Mavic. Loaded up to 400 kg under the pedaling force of many riders is no problem for it, as it can withstand almost a ton of load without distorting, whereas a bearing can be damaged with a 300 kg load applied to it. It's 40 grams lighter than a bearing, and when freewheeling, there is no load on the bushing and hence no friction (and it's as slick as Teflon to boot).
So what's been the problem? Over the years, Mavic has upped the hardness of its freehub bodies without increasing the hardness of the pawls, which can wear away and generate fine steel dust capable of grinding down the bushing. Furthermore, the thread-in axle stub can loosen up. And finally, the chain can drop onto the chainstay when freewheeling because the friction of the freehub is so high, not due to bushings or bearings, but due to a sticky lip seal.
In going from the current FTS-L system to FTS-X, Mavic has made the pawls of harder steel and applied threadlock (good for six disassemblies before applying new Loctite) to the axle end screw threads. The new pawls, being so hard, could not be forged with the little tabs to hold them in place, so those tabs are now on snap-on plastic pieces. Mavic has also created a new lip seal made of softer material with a slick surface treatment to reduce frictional drag by 50 percent.
All of these changes are compatible with current Mavic freehub bodies, but the upgrade parts will not be available for until late next season when Mavic gets over the production hump for the 2007 wheels, all of which incorporate the freehub changes.
Lennard
Dear Lennard,
I had a similar noise that came from my Mavic Ksyrium freehub while coasting down the Simplon Pass last May. As you know, there are a number of tunnels on the way down to Domodossola. In the confined area of the tunnels the screeching was so loud that it sounded like my bike was going to explode! The problem turned out to be an almost dry freehub. Removing the axle and applying a little synthetic chain lube (I did not have the mineral oil that the Mavic web site recommends) inside the freehub eliminated the screeching sound and gave me a much quieter coast. When one does this repair, one should be sure to keep an eye on the pawls and springs! (Editor's note: You should really clean and lube the pawls as well. You can find instructions for Mavic freehub overhaul in either " Zinn and the Art of Mountain Bike Maintenance" book or DVD, and "Zinn and the Art of Road Bike Maintenance.")
Jim
Dear Lennard,
The problem with the Mavic SL is from the small rubber gasket in the freehub that requires occasional lube. It makes a screeching noise when freewheeling or backpedaling. The maintenance for this can be found on the Mavic website.
Michael
Dear Lennard,
That screeching sound is often the spring beneath the pawls in the freehub getting free and rubbing against the inside of the freehub body. I have only experienced this with the Mavic Ksyrium SLs.
Dean
Dear Lennard,
It's probably broken pawls in the freehub mechanism. I had a set of original Ksyrium SSCs. While going down a 45 mph descent last winter, they began to screech. Soon it started doing it while coasting down less steep hills, and then it progressed to making the noise while coasting on the flats at high speed.
My local bike shop diagnosed the problem as a broken pawl. The pawls were replaced for about $15, and the wheels has been fine ever since.
Tripp
Feedback on 29er gearing from last week:
Dear Lennard,
I have a theory on the issue of 29'er wheels and the fact that the 11-percent higher gear does not seem to bother people on climbs.
Since the 29-inch wheel has a tendency to "smooth out" surfaces and improve traction a bit, small ruts, bumps and other impediments that can provide extra resistance to a smaller wheel may have less effect on the 29-inch wheel, allowing it to roll (even uphill) a bit more easily.
For example, a small bump on a climb tends to increase the effective grade that the wheel is climbing, as it not only is tractoring up the (say, 10%) grade, but also then has raise up the extra height of the bump. Without getting into the calculus of it, that one-inch-high bump will hit closer to the "normal" contact patch of the tire, temporarily making the wheel feel that it is climbing a steeper gradient. On a 29-inch wheel, that same bump will hit the leading edge of the tire a bit farther away, and it will tend to make the wheel increase the angle of climb a touch less. Even though the wheel will still climb that one-inch-high obstacle, it does it over a slightly longer distance, which is equivalent to a lower percent grade. It will also drop a bit less into a small rut or dip, requiring less effort to "climb back out of" that same depression.
Scott
Feedback on "chain issues" from last week:
Dear Lennard,
I've experienced similar issues as Bob has in trying to run a Shimano compact crank with a 9-speed drivetrain, and thought I'd pass this along in case it's helpful: My local shop suggested trying to use a (Shimano) 10-speed chain, and it has helped a little bit (I gained 1 extra cog on the back without chain rub) without any compatibility issues. Since then, SRAM has come out with their 10-speed chain, and I'm told it's slightly narrower still (on the outside), so I may try that when this chain wears out.
Walter
KGS Bikes technical writer Lennard Zinn is a frame builder (www.zinncycles.com) a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides "Zinn and the Art of Mountain Bike Maintenance" and "Zinn and the Art of Road Bike Maintenance" as well as "Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists."
Zinn's KGSBikes.com 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 (veloqna@comcast.net) Zinn's column appears regularly here on KGSBikes.com.
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