Lennard Zinn answers more reader technical questions

Questions about fork failure from squirrel collisions, talcum powder and rolling resistance and bottom bracket life spans.

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By Lennard Zinn

Technical Q&A: The cause, and the victim.

Technical Q&A: The cause, and the victim.

Photo: Picasa web album

Dear Readers,
As I head off to Europe once again now, trying to get the outlets to charge my computer in Denver International Airport, where they all seem to be intentionally shut down, I’m thinking about the bike industry in my adopted country of Italy. It was with a heavy heart that I read the news this past week that ITM is going into liquidation and will close its doors in Loria, Italy, and Selcof is being purchasedand is shutting down its production in Rossano Veneto.

Both of these companies are in small towns in the northern Italian state of Veneto, northwest of Venice. More importantly for me, both of them are very close to the town of Asolo, where I lived with my family for a year, eight years ago. I have visited both companies many times (usually by bike, as they are both on nice cycling routes, on quiet rural roads between small towns) and know people in their management as well as many of the rank and file workers very well.

I loved that there are so many small companies making great cycling equipment in northern Italy, but that is obviously changing, particularly with the strength of the Euro currently. These are both very small towns, and I’m sure that the companies will be missed. I think particularly about a test engineer at ITM named Angelo, who every day poured his heart and soul into making sure that ITM stems, bars, seatposts and other products were the best that they could be.

Rossano Veneto is also the home to both Selle San Marco and Selle Italia, and across the street from ITM in Loria is Gipiemme and Selle Isca; may they all continue to thrive.

Dear Lennard,

Two weekends ago a riding buddy’s brother was eight miles in to a century when he sucked a squirrel in to his front wheel while traveling at a good 25-30 mph. He fractured his #10 thoracic vertebrae, but there was no spinal cord damage, so he will recover, albeit with some new and permanent internal hardware.

From what we can surmise, the squirrel got in the wheel and sheared the fork in half. The big chainring is bent, so it appears he came down on on the ring and then on to his right side, hard enough to damage the shifter, but not bend the bars.

We were all just surprised that a squirrel could shear a fork in half like that. Have you ever seen something like that happen before? I would have expected the wheel to just lock up, but I guess at 25-30 mph the force must be a lot more than I would have guessed, and as I understand it, carbon fiber does not do well under compression/impact. And the squirrel does appear to have hit the fork dead center — at the point of highest leverage.
Any thoughts?

Dear Steve,
I have seen this before — not in person but in photos people have sent me of dead squirrels and sheared-off carbon forks. The rider would be just as injured even if the fork had not failed — just the front wheel stopping so abruptly would have put him on his face. Watch out for those squirrels!

Feedback from previous columns:

Regarding talcum powder in bike tires:

Dear Lennard,
I enjoy your Technical Q & A, but I think the June 10 question and answer about talcum powder and rolling resistance is off base. I am not an engineer, but logic tells me (and others who are engineers) that there is no way that a tube can move independently of a tire at the pressures road tires are designed for. The talcum that the manufacturers put into a tube is to keep the rubber from sticking together from the high heat generated during the manufacturing process.
Jobst Brandt calls this “one of the more durable urban legends”. See his take on the topic.

Dear Lorin,
Yes, I answered that one too quickly without thinking it through. Thanks for setting me straight (and thanks the many others of you who also set me straight about it).

Regarding component life:

Dear Lennard,
You write that for most people, a bottom bracket should last “well over a year.” I’ve ridden my S-Works Roubaix about 4,000 miles (recreational, rarely in the rain) during that time, and I’m assuming I should get SEVERAL years of good performance from this bike’s groupo (especially given what it cost!). I must confess that I’ve not even changed the CHAIN once yet).

Shouldn’t a recreational rider (30-40 miles per outing) anticipate several years of life from Dura-Ace components?

Dear Jim,
Yes, you should, in dry conditions. You might look at that chain, though.

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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