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Technical FAQ: Pro bike ‘choices,’ carbon fork fatigue, and fitting tools

  • By Lennard Zinn
  • Published Jul. 5, 2011
The MCipollini RB1000 used by the Farnese Vini-Neri Sottoli team is an aero road bike. Photo: Lennard Zinn

The MCipollini used by the Farnese Vini-Neri Sottoli team. Photo: Lennard Zinn

Q. Dear Lennard,
Eric with Cyfac here. Was just reading your article on Cipollini bikes and wanted to reach out regarding the posting where the rider asks about Cipollini frames and how the team goes about choosing the bikes that they’ll ride.

Would it be worthwhile to your readers to explain that the pro riders do not “choose” their bikes any more? As you know, it’s the sponsorship dollars that hold sway and really dictate what the team will ride. While the team may have a say over model choices here and there, they have no part in the brand decision; that’s a function of which bike company will offer the sweetest deal. Just look back 10+ years ago to see the vast variety of bike companies who were able to operate in the team sponsorship arena. Back then, it was rider or management choice, a handshake, and much lower sponsorship dollars (if any … sometimes, it was just the equipment alone). Since Cannondale entered the arena with the first $1M+ deal, the sponsorship field is open only to those companies with budgets on-hand to foot the bill for $1M+, 300+ bikes, etc…

Up until about 2002, just about every pro had a custom frame as well. Sadly, that’s no longer the case and it sets a false belief that standard works for everyone. Sure, as a custom company, this email to you has its own slant. However, the point above is valid (to me at least and, perhaps, to your readers).

— Eric Sakalowsky
Owner, Velo Europa Imports

Q. Dear Lennard,
A buddy of mine and I were recently debating the merits of regularly replacing carbon forks as a preventive measure. My wife has a 2002 Bianchi Veloce. It has a decent steel frame, a 1-inch carbon fork (w/ a steel steerer), and parts that still work great. We met when I sold her the bike back in my shop days; consequently, the bike has some sentimental value. She continues to love riding the bike, too.

But I’m starting to wonder if the relatively generic fork should be replaced. It shows no outward signs of fatigue (chips, cracks, etc.), but the thought of her fork snapping on a descent is starting to keep me up at night and getting my brain spinning about getting a local builder to put together a nice, new steel fork. So, what’s your take? Is an apparently fine 10-year-old carbon fork a peril or am I just making up excuses to buy bike stuff? (If there’s no peril, believe me, I can think of other ways to buy stuff. This is a zero sum game for the bike industry.)
— John

A. Dear John,
I wouldn’t worry about it, as carbon has very good fatigue life if not damaged by an exceptionally high stress or impact. Here is what Bert Hull, an expert on carbon and other frame materials as a former True Temper/AlphaQ engineer, has to say about it:

“Carbon parts should last for a very long time (aka lifetime) if not damaged, unlike aluminum, which has no fatigue limit. Since I sold my Vitus 979 back in 1990, I can’t remember any aluminum road racing forks being sold. I think that is about the time carbon fiber was hitting the market in strong numbers.

By damage, I’m talking about a wreck or any other over-load situation.

I have tested a lot of steel (mostly True Temper brand tubes) and of course carbon (lots of brands) in fatigue tests and also load-to-fail tests. In high fatigue loading, the carbon forks would eventually lose some stiffness (as much as 5 percent) after many thousands of cycles to represent many years of actual riding conditions. So I would not say the forks would last forever at high loading. You don’t hit high loads on most of your rides though … You should get a lifetime of JRA riding (just riding along).

Steel forks did not lose any stiffness in the fatigue tests. They are typically kind of over built so they never got stressed past the endurance limit (about 50 percent of ultimate tensile strength). In load-to-fail tests, the steel forks bend until they crack, or we would stop when the fork had bent more than 10-20 percent (un-useable).”

So there you go. Sleep easier.
— Lennard

Q. Dear Lennard,
I have a new-to-me road bike with a not very long steerer tube (cut before I got the bike) and I am trying to dial in the stem position. I was sniffing around the ‘net and it appears that with a normal, non-carbon steerer tube, the top of the stem can be a bit taller than the top of the steerer tube — the rule of thumb I saw was that the top bolt of the stem should be level with the top of the steerer tube. Is this the case with carbon steerer tubes as well?
— Elizabeth

A. Dear Elizabeth,
Not really, because it can pinch the top of the steerer and cause delamination. The steerer should stick out of the top of the stem and have a spacer on top of the stem and under the top cap.
— Lennard

Q. Dear Lennard,
In the VeloNews 2011 Buyer’s Guide article “Stack and Reach: Dialing in a New Bike” there is a picture of a T-Square that allows adjustments in two-dimensions (X and Y). I have been searching for something like this for a long time, but I can’t find one anywhere.

Is this a custom-made tool, or can you tell me the manufacturer and model number of the T-Square?
— Steve

A. Dear Steve,
It’s a Serotta International Cycling Institute tool, the SICI X/Y tool. You can get it on the Serotta site.
— Lennard

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.

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