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Technical Q&A with Lennard Zinn
Dear Lennard,
Much has been discussed regarding the compatibility of Shimano 7900/7800 systems but what about the new Ultegra 6700 with the old 6600? I recently sent my crankset to Shimano for warranty repair and Shimano was kind enough to replace the unit with a new 6750 crankset complete with BB and chain. How well will it work with my Ultegra 6600 drivetrain and would I benefit from replacing the cassette with a 6700 series to make full use of the newer asymmetrical chain?
Scott
Dear Scott,
Wayne Stetina, who is responsible for R&D at Shimano American, and who has a long racing pedigree, had 7800 cassettes on all of his 7900 and Di2 test bikes the last 2 years with the 7900 chain, including when I rode his bike set up with Di2 in Boulder City during the 2008 Interbike. So, similarly, there is no compelling reason to upgrade to a 6700 cassette before your 6600 cassette wears out.
Stetina does warn that the 6750 crank and chainrings with your 6600 shifting system will require very precise front derailleur and cable tension adjustment to prevent chain rub in top gear because the throw of the shifter/front derailleur combination isn't quite as far as the slightly wider 6700; it’s actually closer to old 9-speed front chainring spacing width. So the potential problem with that front combination is that, if the front derailleur isn’t perfectly aligned, either the front derailleur won’t want to stay all the way to the outer limit stop, or else it will be rubbing in the trim position in the big/big combination, or in the small/big combination. Wayne has found that it seems to help if the front derailleur is very slightly toed out, so it clears more easily in the large rear cog on both rings, yet still can be tight enough cable tension to hold the front derailleur all the way to the outer limit stop.
Lennard
Dear Lennard,
Any more updates on using Campy Record 11-speed shifters, chain, and cassette on an otherwise 10-speed Campy Record drivetrain? From a previous letter published in VeloNews you mentioned a friend in Oregon running a setup as described above. I'm considering the same setup. Any word on how it's working out would be appreciated.
Charles
Dear Charles,
I had sent my 11-speed shifters for a long time off to Todd Telander, the artist who has illustrated almost all of my books. While he was doing the illustrations for the third edition of Zinn and the Art of Road Bike Maintenance this past winter and spring and into the summer, I was without my 11-speed shifters. So I rode my bike with 10-speed shifters with 11-speed derailleurs. In fact, I used a 10-speed Centaur right lever and a Record left lever. And it worked fine with a 10-speed Campy chain and cogset.
Lennard
Dear Lennard,
I bought a Ridley bike 4 years ago with Campy Record. Recently when I was changing pedals an insert in the crank arm came out along with the pedal. The local shop contacted Campy and was told that this was not a repairable part and the cranks have a three-year warranty. Is there an alternative to buying a new crank set? This appears to be an easy enough fix with a new threaded insert.
Robert
Dear Robert,
I can’t see how you’d repair that in such a way that it could withstand the huge loads that spot sees constantly. I suppose you could contact Calfee or someone else who does carbon repairs, but I would not hold out a lot of hope.
Lennard
Dear Lennard,
While watching the Tour de France this year I noticed a piece of hardware on the riders' bikes that I did not recognize attached to the non-drive-side rear chainstay. It was a red circular tab that hung down, usually two-thirds the way back toward the dropout. Several times a motorcycle cameraman would zoom in on the little device, but I never heard any explanation on what it was.
Clay
Dear Clay,
It's a timing transponder.
Lennard
Feedback on last week’s column regarding filing lawyer tabs:
Dear Lennard,
Would a pro mechanic file the tabs on a mountain bike fork as well? I can understand removing them on a road bike - they do nothing useful. But after your article last year about disc brakes and quick release skewers, I'm sure not taking mine off. In fact I thought it was really cool that my new Fox fork came with some killer retention shoulders, and a cleverly angled slot. I was hoping my bike would come with QR-15 wheels, but this will do just fine. And the since I have DT wheels, I got one of those clever screw-on skewers you mentioned. Now that is a clever idea.
Steve
Dear Steve,
As the below letter points out, I totally missed that part of the question and was not thinking mountain bikes. Absolutely, I think it’s a poor idea to remove the wheel-retention tabs on a mountain bike fork when using disc brakes. As I’ve written here before, the problem is that once the brake is applied, that point on the rotor then becomes the fulcrum, and the momentum of the wheel and rider is working to force the axle down out of the dropouts. The skewer must be extremely tight (again, the DT screw-on skewers are the way to go). Once the wheel starts moving, it tends to taper the magnesium dropout, so the further the axle moves down the looser the skewer becomes. And I’ve seen this movement action wear away the lawyer tabs over time. This is why Fox came up with the front-opening QR dropouts and why so many fork companies embrace through-axles for even lightweight bikes.
I asked our own tech editor, Zack Vestal, who used to be a Trek/Gary Fisher team mechanic, and he had this to say: “You know, there are guys out there that want it done, and the mechanics will do it. But on my team (Trek-VW), never. I never went that far. Wouldn't surprise me if JHK had Matt Opperan filing tabs, and I know Roland Green used to have Gary file his tabs off. Gary Wolff now works for Geoff Kabush, and might be doing it for him, but honestly in my experience most MTB guys, even the most picky, prefer the sense of security from tabs. That said, the new SID forks from RS have some huge tabs, and I bet they get filed down at least a little to speed things slightly.”
When reading Zack’s quote, keep in mind that Roland Green’s heyday eight years or so ago was still the era of cantilever brakes in cross-country racing.
Lennard
Lennard,
I can make fun of these; I'm a lawyer. They're stupid. If QR's are so unsafe, why don't we have bolt-on axles with cotter pins through the nuts so dummies can't under tighten them? The whole deal reeks of a deficiency in early childhood education.
Anyway, I just filed the nubs off my road bike fork as you mentioned. On a Wound Up fork they're just two little nubs.
On my ATB it was a problem since the RockShox fork end cups around the quick release and removing the recess would require some major metal work and paint damage, with the risk of weakening the metal. Not to worry, however. Neuvation, the wheel outfit, sells (or did, when I bought mine) a nifty quick release skewer with a little release tab on the handle. Open it the regular way or if it vibrates open and it opens enough to make the skewer loose, but it won't drop out, as the lawyers intended. Release the little tab while opening, however, and it opens far enough to clear the nubs and drop the wheel straight out. The nice feature is that there's no re-adjustment of the QR needed. When it goes back on and the handle is clamped all the way, it clamps down tight as it did before. Which is the whole point of a quick release, isn't it? Tullio must be spinning in his grave.
Larry
Dear Larry,
FYI: Neuvation’s wheel business is so good that it has ceased selling these skewers.
Lennard
Regarding Shimano 7900 chains:
Dear Lennard,
After consulting Shimano tech reps we were advised that the 7900 chain was compatible with the 7800 series rear derailleur, we installed one on a customer’s bike.
Needless to say it shifted like crap and decided to stick with an original Dura-Ace chain. Perhaps someone else has better luck with this and we are behind the curve with our skills!
We saved the customer some bucks and the drive train worked just like a fine watch.
JD
Regarding: “Are Dura-Ace ST-7700 shifters able to be rebuilt? ...”
Dear Lennard,
Here's something I put together:
http://norvil.net/pedal/service/shimanosti/index.php.
Stan
Regarding pulling over a rear wheel:
Dear Lennard,
Regarding Rick's problem of pulling his rear wheel under load, I'm wondering if he should get the rear dropout alignment checked? If the two faces aren't parallel it might well be causing his issue...
Oli Brooke-White
ROADWORKS/Jazz Apples Cycling Team
Feedback on a recent column regarding a failed SRAM shifter:
Dear Lennard,
I am writing in response to a gentleman who had an issue with a broken SRAM Force shifter. The same thing happened to me recently. It was made aware to me that in early production of the newer shifters, the press fit of that pivot bushing was too tight and overly stressed the bushing holder. The issue has been noted and fixed by SRAM.
The fact that I was able to rebuild my shifter and have it work like new is testament to SRAM's innovative thinking.
John
Dear Lennard,
I read your recent tech feature featuring a letter sent by Larry regarding his broken SRAM Force shifter. I’ve had an identical failure on my 2009 SRAM Rival rear shifter as well (photos attached).
I'd be interested to hear how much exactly Michael Zellmann of SRAM is talking about when he said they "have a handful come in broken out of the thousands that came out." needless to say I’m greatly disappointed by this material failure on what is essentially a brand new (7 months) part. Meanwhile, I've been waiting for an official reply from SRAM for nearly 4 weeks already, having already sent pictures and a written report through my dealer.
King
Dear Lennard,
The response from SRAM regarding a broken shifter in your last column highlights a frustration I've had for years with the bike industry in general.
Local bike shops in my area don't stock the high-end bike components that I want or use. They can order them for me of course, but I can quickly order them myself much faster and cheaper from mail-order houses.
However, when I have a warranty issue, I'm not about to offend my LBS by taking in a part I didn't buy from them for warranty replacement or repair. As a former LBS mechanic, I know that's not fair and it used to piss us off to no end.
Almost universally, the attitude of manufacturers is that if a part breaks, they want you to take it to a local shop. I've stopped buying components from two manufacturers after poor warranty experiences, but others (FOX forks comes to mind) have excellent warranty and repair programs.
When are these guys gonna adapt to the modern marketplace?
Ian
Feedback on shimmy:
Dear Lennard,
With regard to the recent speed wobble question, I've been riding a Steel IF, which I had built 4 years ago, a Crown Jewel. When we built it up I had our local shop guy leave an extra inch on the steerer to give me more room for a more upright position on the bike to alleviate some lower back issues. I had my bars set about 1.5cm high. I had problems with speed wobbles descending for a couple of seasons. I'm a relatively big rider at 6-1 and 180lbs so my frame geometry is bigger as well, which I thought contributed in some manner.
Wobbles were primarily in crosswind conditions when I got "tight" on the bike, so I blamed myself for the situation and prepared for it descending in crosswinds. I ride the Dura-Ace tubeless, which have a semi flat spoke as you know. Then last season I decided to ride the bike at spec and dropped the bars on the steerer as my back was really not an issue. This was the difference. The bike is now so bomber I do not even think about speed wobbles descending anymore. I was amazed at how rock solid the bike became with this small "adjustment." So to some of your readers, this may help them if they have a similar bike set up.
Larry
Feedback on creaking bottom brackets:
Dear Lennard,
I was reading the suggestions on diagnosing a creak/click from the crank. On one of my bikes, I found that I had a strange clicking every pedal stroke on a particular chainring. Rotating it slowly and watching the chain, you could see the chain shift some one side to the other in a certain spot - the chainring was actually slightly bent. Replaced the ring and no more click.Pete
Lennard,
As a follow-up to the follow-up on crank noises I wanted to confirm the possibility of a loose derailleur hanger as a cause!
On a Cervelo R3 I swapped out just about every part (cranks, BB, pedals, wheels) with only a minor improvement in the noise, with the wheel change. The owner was about ready to toss her bike until I read about and tried that fix. Sure enough I found the two bolts holding the hanger on to be loose. A quick cinch (should probably Loctite them...) and the problem is gone! Who would have thought?
Chris
Dear Lennard,
I have a great way to minimize the noise from a BB. Take a couple 1/4" ball bearings and dip them in grease and place them in the end of your handlebar after taking out the plug. It takes a few miles to get the bearings to loosen up enough to rattle but the noise is so bad you won't care about your creaky bottom bracket. This has to be one of the best back shop jokes of all time, save filling your riding buddy’s inner tubes with water.
Mark Ernst
In Competition Sports
Green Bay, WI
Dear Lennard,
As per the instructions given by the Specialized Tech re: creaky S-Works cranksets, Loctite 638 should be used with some trepidation. It is a "high-strength" retaining compound and therefore requires the parts to be heated to 250C for removal. In other words, if your bearings go bad they may be stuck in BB shell for good, unless you've got a hydraulic press at the bike shop or want to burn up your carbon frame with an oxy-acetylene torch. Also, in my opinion, it would make sense to use one of the lower strength compounds (one that requires less than 3000 psi for removal, and no heat). That'd likely keep the bearings from creaking in the shell just fine, but still able to be replaced with a common slide-hammer and blind puller or a hammer and a brass drift.
Clay
Dear Lennard,
1. On the bottom bracket creaking from a few weeks ago, it could be the pedals. I was having similar noises, and after pulling apart the whole bike, and nothing working, I finally decided to go after the pedals, and just a little cleaning and lube fixed it right up.
2. On chain compatibility, I run a 7900 chain with Force and a Red cassette, it works great. No need for trim, perfect shifting, everything is great in my first 500 miles. I chose the chain because it seems to have the best stiffness to weight ratio and I didn't think the design could hurt.
Jobe
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" - now available on DVD, "Zinn and the Art of Road Bike Maintenance," as well as "Zinn and the Art of Triathlon Bikes" and "Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists."
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.
