Menu

Technical Q&A with Lennard Zinn – Treasures from Milan

  • By Lennard Zinn
  • Published Sep. 23, 2003
  • Updated Sep. 28, 2010 at 4:45 PM EST

By Lennard Zinn

Technical Q&A with Lennard Zinn – Treasures from Milan

Photo:

Dear readers;
I am writing this from Italy, a few days after I had the chance to visit Milan for what has to be one of the world’s best bike shows. So if you don’t mind, I would like to start my weekly column with a look at fewof the treasures I spotted at Milan’s EICMA show.

Conducted under gorgeous warm, sunny weather, the 61st EICMA bicycleand motorcycle show marks the official launch of a new road season. Italy is a great place for a show, and Milan in particular, because of the heritage of great design. As always, gorgeous Italian bicycles are in abundance, and the theme of ever more carbon is carrying forward, although there are also some unique developments in aluminum, steel, titanium and magnesium.

At the center of the show, lord over all he sees, is Ernesto Colnagoin his two-story white Caesar’s Palace, replete with columns bedecked withhis logo in three dimensions. It lacks only a swimming pool (which we will probably see at his booth in Las Vegas). This, the central hall with the main players in the Italian bike industry, is the only one of the halls with a high enough ceiling to even allow a booth like this. He considered a third story, since the structure is built to support it, but opted against it.

The 71-year-old company founder said, “I am not going to live to see the 100th anniversary of my company, so I wanted to go all-out for the 50th!”

Technical Q&A with Lennard Zinn – Treasures from Milan

Photo:

The glistening, reflective white carbon was one of the themes of theMilan show. Bianchi’s Luna uses it in the frame, fork, stem, bars, cranksand seatpost. Unfortunately, the saddle, the derailleur and brake levershave black carbon. Maybe next year they can get it all white!

Alcide Basso has increased the diameters of the tubes on his Diamantcarbon frame to stiffen it up.

Gipiemme’s Meteora carbon clincher has been on the market for a yearand the company claims to have had no problems with the 500 or so thathave been sold so far.

Gipiemme’s white carbon saddle is superlight as well as highly reflective.FIR’s Ronda carbon clincher comes in white carbon as well. This is a detailshowing the construction of the clincher bead walls.

Technical Q&A with Lennard Zinn – Treasures from Milan

Photo:

The Dedacciai DAVS vibration-damping inserts in the fork and chainstaysdamp vibrations propagating through the stiff carbon.

Technical Q&A with Lennard Zinn – Treasures from Milan

Photo:

The De Rosa Merak is made out of hydroformed aluminum tubing from Dedacciai.The tubes are formed in proprietary molds designed by De Rosa using high-pressure oil to force the aluminum into the shape of the mold. It makes for a
voluptuously curvaceous bike!

De Rosa’s Cinquanta is the 50th anniversary bike of the company thatUgo De Rosa founded in 1953 at the age of 19. It is entirely blue-tintedcarbon, including the stem/bar, crank, and seatpost. It is a variationof the King modular bonded carbon frame and can be built in custom sizes.

I will post a few more pictures tomorrow as well, so check back. Now, on to our questions this week:

Training with Ti?
Dear Lennard,
Is there any damage to my titanium frame by riding it on a trainer?

When I look down I see the bottom bracket moving laterally with eachpedal stroke.  My bike is a Schwinn Paramount Titanium, and my traineris a Cateye Cyclosimulator.
–Chris

Dear Chris;
Probably not. It is hard to imagine that you can put more leverageon it than you could on the road sprinting out of the saddle. If your stressesare over 40 percent of the tubing’s tensile strength, you are shorteningits life. If not, you are not. It is hard to know the magnitude of thosestresses without applying a fixed, measurable force until you get thatmuch deflection.
–Lennard

Heart and sole
Dear Lennard;
I read your article “Sole Power” from last year in VeloNews. It was very interesting and very apropos considering that I’m using customorthotics (leg length difference of 2cm).  My question is this, doyou have the sole and upper width forefoot measurements on the other majorshoe brands/models; i.e. Sidi, DMT, Carnac Eclipse, etc.  Findingthe right shoe size – wide in forefoot and narrow/deep in heel (for orthotics)has been difficult especially in size 48 (13.5).  I’m currently usingTime Equipes.  They’re “long” enough and “deep” enough (in heel andinstep) but a touch narrow.  I found your sizing comparisons veryuseful and a lot easier than trying to find a dozen pairs of shoes in-stockat any of my local shops.
–Brandon

Dear Brandon;
Below is what I measured on shoes that fit me.

Width in millimeters in size 46: Carnac: 90mm sole width (101 upperwidth without a foot inside), Shimano carbon: 102 (108); Pearl Izumi: 95(102); Sidi: 94 (102); LUST custom to me: 109 (109) — my feet are 107mmwide at the forefoot.

I have never measured DMT. Sorry.
Lennard

Raking the trail
Dear Lennard;
I was asked to read your article (and the insert from Ted Constantino)concerning frame geometry by a bike shop that I have been working with.Last fall, I was fitted with a Serotta Colorado III bike, Serotta Carbonfork and Mavic Krysium wheels and picked it up Christmas eve.  I finallywas able to start riding it in March but my first big ride was in earlyApril when I decided I was fit enough to tackle some hills.

Unfortunately on the largest downhill the bike started to wobble andI lost control.  Luckily I only had a concussion and a couple of motoristswere kind enough to stop and make sure I was okay.  I rode the restof the way home and took it to the bike shop a few days later.  Itwas noticed that the front wheel was slightly out of the dropouts and thatclouded the issue – was it my fault for a loose front wheel or was theresomething else wrong.  The dealer verified that the wheels were trueand test rode and it was fine.  So I took it out again and the firstreal downhill I encountered the bike wobbled again but I was able to controlit without any mishap.

I returned it to the dealer who shipped the frame back to Serotta aftera test ride and feeling uncomfortable on it.  Serotta found that theframe was 1mm out of alignment (not sure where but it was corrected) andrequested the components to test ride it.  They had no problems withtheir test ride.

At this point, Serotta suggested a new fork to increase trail.

After some further discussions, Serotta will change the fork rake andreplace the bike frame – after doing the fit test again.  After readingyour suggested article, changing the fork rake to increase trail does notseem to be the best decision.  That may play into it but accordingto the article the top tube would be the place to investigate. The otherinteresting thing is that I am 5 feet 11 inches tall and weigh about 145pounds. The dealer (who test rode it) is about my height and weighs about40 pounds more (according to him), and Ted had a comment in hisinsert that referenced a heavy rider might experience wobble while a lighterrider would not.  This is contradicting our situation – would thismean that a different component is the culprit?

Basically I am looking for some advice.  Would you go ahead andtry the new bike frame and fork rake from Serotta or would you have othersuggestions – for example using a more rigid top tube.  And does therider weight issue change things or bring in a new issue to investigate.

I know that Ted wrote the article that I am referencing in this emailbut I was unable to get any of his contact information so hopefully youcan help or forward this along to Ted.
–Peter

Dear Peter;
I would try the new frame they send. I do find it surprising that itwould shimmy with you and not with a heavier rider. Otherwise, I wouldhave to say it needs a stiffer top tube and down tube and perhaps a shallowerhead angle and/or more rake (not necessarily more trail).

Bicycles shimmy because they hit a resonant frequency which causes theback-and-forth flexing oscillation to build and build until the bike canhardly be controlled. It is not an indicator of instability; even thoughthe bike is highly unstable when shimmying, it can be an extremely stablebike just a few miles per hour slower. A heavier rider will also tend tocause a bike to shimmy that a lighter rider might not.
Shimmy is eliminated by increasing the resonant frequency of the bike,which means making it stiffer. Bikes that shimmy badly tend to be onesthat are very flexy, so it takes a long time to make a single back-forthoscillation.

It is especially common with tall bikes, particularly ones with small-diametertubes. All of that open space in the frame allows it to flex back and fortheasily.

A tall bike can be built not to shimmy by using a stiffer top tube –this may be the single most important frame member to stop the shakingback and forth. Larger-diameter tubes using a lowered or sloped top tube(or both) will help. So will a shallower head angle, and/or more fork raketo absorb more vibration in the fork.

More minor things also contribute, like pitted headsets, untrue wheels,wobbly tires and out-of-balance wheels. If you crank your rear wheel upto high speed on a work stand, the whole stand will jump up and down becausethe wheel is out of balance. When you let a wheel spin down without resistance,it will usually stop with the valve at the top, since the rim seam is heavier.

Using a tube with a longer valve, and/or screwing on valve collars untilit stops randomly will help balance the wheel, similar to how tire storesdo it for your car (and you know how shaky a car with unbalanced wheelscan be).

A third-hand quote I heard attributed to Eddy Merckx went like this.When answering someone who asked him how to get rid of a shimmy in a bike,the Cannibal is said to have replied, “sell the bike!” Usually, gettinga new bike is indeed what it takes, because you can only make minor improvementswith better components and a new fork with more rake.
–Lennard


Technical writer Lennard Zinn is a frame builder, 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.

Photo Gallery

FILED UNDER: Bikes and Tech / Technical FAQ TAGS: / / / /

Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and 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. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

Stay updated on all things VeloNews

Subscribe to the FREE VeloNews newsletter