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Technical Q&A with Lennard Zinn – Caring for carbon

  • By VeloNews.com
  • Published Jul. 1, 2008
  • Updated Aug. 29, 2010 at 10:44 PM EST

By Lennard Zinn

It’s light, it’s strong, it’s worth inspecting.

Photo:

Check that fork
Dear Lennard,
I ride a ten-year-old Litespeed Ultimate. It has a Kestrel fork that it came with and Spinergy Rev-X wheels. I’m a recreational rider and my question is whether the carbon fiber can break down and fail. Some shops have told me that I should replace these and others think it’s no big deal.

What to do? I’m low on funds and that’s the main reason I haven’t replaced them as yet. I will add there are no stress fractures or noticeable wear.

I’m totally anal so everything looks great but of course internally may be a different story.
Keith

Dear Keith,
You should certainly check the wheels carefully, but the fear factor is not as high on wheels as it might be for a fork. If they look okay and feel uniformly stiff with trying different points at the bottom as you stand alongside your bike and push on your bottom pedal to notice the give in the wheels (and frame), then I would be comfortable continuing to ride them with frequent inspection.

Now to your fork, if it’s only 10 years old, I wonder about your statement that it is the original fork, since, while Litespeed did use a lot of EMS forks back in the day, I don’t believe Litespeeds came with those forks into the late 1990s.

Regarding your concerns, you need to worry about damage from crashes and other impact and high-stress events, but you need not worry that the carbon “can break down and fail.”

One of the features of carbon composites is that they do not fail due to fatigue, so the fork and wheels should not break down or weaken over time. So the question is whether they show signs of damage from suffering any kind of crash or impact over the years. If you don’t know the complete history of the fork, or if there are any visual issues, replace it. A fork failure is such a terrible thing to have happen that it is never worth risking it.

I’ve had a fork steerer snap off on me once, and the feeling of total helplessness as I could do nothing other than watch my wheel turn perpendicular to my direction of travel is an image that stays with me to this day. Believe me when I say nothing is worth that risk. This should be your plan of action with any fork, carbon or otherwise (or lightweight frame for that matter.) Damage to the steerer can be difficult to detect visually, especially at the crown-steerer interface, so check carefully. The test I’ve suggested in the past for frames is not very useful on a fork.

I also sent your letter to the folks at Alpha Q for their advice on proper inspection of carbon components. Their response is below.Lennard

Response to this question from Alpha Q:

Dear Lennard,
That’s a good question. I am sure that many readers are not sure what to look for when inspecting a carbon component such as a fork, wheel, bar, post, frame, etc.

Below is an excerpt that covers fork inspection from an inspection guideline that I wrote this past December with our Composites director Neal Haas and our bike engineers. Your readers may find the entire care and maintenance guide useful, as it may answer their lingering questions about inspecting the carbon components on their bikes.

Critical Inspection Points:

- Steerer Tube: Stem clamp location and attachment point
- Steerer Tube: Upper head set area and compression ring/bearing location
- Steerer Tube: Crown race, bearing seat and lower head set area
- Crown Area: Brake hole area (front and rear)
- Crown Area: Tire clearance area
- Fork Legs: Leading edge
- Fork Legs: Trailing edge
- Fork Legs: Inner and outer fork leg surfaces
- Dropout Area: Dropout and dropout insertion area

What To Look For During Inspection

- Cracks in the steerer tube, crown area or anywhere on the body of the fork.
- Dents or large dings that distort or damage the fork surface.
- Splits or tears in the carbon fiber material.
- Opaque spots beneath the paint surface resulting from impact damage.
- Delamination or peeling of material.
- Bent or loose dropouts.
- Any rattle or noise coming from inside the fork.
- Scratches and abrasions that penetrate and/or cut the carbon fiber.

In response to this reader’s (and most of the rest of our) dilemma of low funds, I’m pleased to say that we and many other U.S.-based companies offer a low cost “crash replacement” program to help out people who have wrecked, driven the roof rack into the garage header, or in any other way damaged their expensive carbon equipment. Our replacement program even covers old components, with no age limit. A phone call or e-mail to the manufacturer is a good way to get specifics on these programs.
Bert Hull
Product Development and Sales Manager
Alpha Q Components

Pulley switch
Hi Lennard,
I’m a huge fan of your work, and your books and advice have been vital reference on many occasions.

As regards to the use of Shimano MTB derailleurs with 10-speed systems, I have had some success with swapping the 9-speed pulleys wheels out for 10-speed ones. The shifting will never be as crisp as a dedicated shorter cage road derailleur but is not bad at all, and spoke clearance has never been an issue.
Oli Brooke-White
ROADWORKS Bicycle Repairs
Wellington, New Zealand

10-speed chains
Dear Lennard,
I’ve enjoyed your writing for years, keep up the good work.

Have you had any luck with non-Campagnolo 10-speed chains, particularly the stainless or nickel Wippermann chains? I have a full Record 10-speed kit and am not pleased with Campy’s chains. They feel a bit rough to me and seem to wear quickly, plus needing a special tool is a pain.
Matt

Dear Matt,
I have used both SRAM and Shimano Dura-Ace/XTR 9-speed with my 10-speed Record group, and both of them worked fine. The Shimano worked best. I have not tried the Wippermann. I now have the newest Campy 10-speed chain on, and that seems to be a lot better than the first one I had. I don’t know why. It is quiet and shifts well on a Record 11-23 and on a Wheels Manufacturing 10-speed 11-25 made out of Dura-Ace cogs.
Lennard


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 also on DVD, 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.”

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.

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