Technical FAQ
Jan Ullrich (GER) keeps up the pace during the...

Technical FAQ: Do pro riders actually race on their sponsored bikes?

In the old days, pro riders like Jan Ullrich often raced on custom bicycles painted to look like a sponsor's bike. Does this practice still occur? One reader wants to know.

Have a question for Lennard? Please email us to be included in Technical FAQ.

Dear Lennard,
How many riders in the grand tours are actually riding their sponsor’s bikes, as I am aware that Pegoretti built bikes for certain riders.
— Ken

Dear Ken,
In the days of steel and aluminum bikes, it was common for pro riders to have their frames custom built for them by another builder and painted like the frames of their sponsor. Since the tube shapes and diameters were not unique, paint could make them look relatively indistinguishable from the frames they were meant to mimic. Builders like De Rosa, Masi, Colnago, as well as Pegoretti, (and on this side of the pond, Serotta and Marinoni) made their reputations early in their careers that way.

Nowadays, the shapes of the carbon bikes are so distinctive that it would be apparent when a rider is not on their sponsor’s frame. So, it now rarely happens that ProTour riders are on frames other than those of their sponsor. That does not mean it never happens; here is an example from 15 years ago, when Walser built special carbon frames for Jan Ullrich that were painted to look like Giant or Bianchi frames.
― Lennard

Dear Lennard,
I followed your columns on chain friction, and being a track cyclist, I have a question about chain friction with track gearing.

If you have 2 chainring/cog combinations that are the same gear inches (for instance 52 x 14 and 48 x 13 are both very close to 100 great inches), does one combination have less chain friction than the other? Is there a measurable power loss with one combination vs the other?
— Mark

Dear Mark,
Yes, the 52 X 14 has less chain friction than the 48 x 13 due to the chain links going through less articulation on the larger cog and chainring. It’s explained here.
― Lennard

Dear Lennard,
How do you know if and when carbon soled bike shoes are fatigued and materially less effective?
— Michael

Dear Michael,
In general, fatigue will not be an issue, unless there is impact damage to them. If the sole shows cracked or delaminated fibers or flexes more than it used to, it’s time to say goodbye to them.
― Lennard

Dear Lennard,
I wanted to respond to the Q&A posting from Sept. 17. Zipp would never advise a customer to sand their wheels; this claim in your response is incorrect. Regarding the hooks on Zipp rims, these go through multiple inspections throughout the process of the build. Safety is foremost in our products. If a consumer were to ever discover a sharp edge, it would be covered under our warranty and replaced at no cost.

We appreciate you taking on these types of questions and we invite you to contact us directly anytime as a technical resource.
— Michael Zellmann
Senior Corporate and NA Road Communications Manager
SRAM LLC

More on lightning strikes:

Dear Lennard,
I’m a physicist who was struck by lightning years ago. I agree with the responses from your various readers — millions of volts won’t be stopped by bits of rubber or 3″ gaps.

Current will follow the lowest impedance path. Impedance includes inductance and resistance, minimizing inductance is why lightning bolts will split. I think that your discussion of bolts hitting signs and traveling along the surface is oversimplified. The huge transient currents of a major strike will set up associated fields that can also drive currents through a person, and bolts don’t necessarily hit only one target.

People are also fine conductors. Pressing an ohmmeter against your skin will yield a high number (usually megaohms), but lightning will see you for the bag of salt water that you really are, but my experience below indicates that materials might matter a bit. And, of course, everything will be covered with water in a storm.

I was struck while skiing on Mt. Baldy near LA. As happens in mountain storms, there were a lot of minor strikes. While I could feel the electricity all over, the main current went through my aluminum ski pole. The glove on that hand was steaming, and my hand was numb for a while, then very painful over the next hours as the nerves reawakened. No real damage. I went to the ski patrol hut with my young son (also probably struck, also no damage) just to check in – there were a couple of dozen people in there with various minor lightning-related injuries, so we turned around and left.
— Peter

Dear Lennard,
Your column is great. In case you were interested, lightning sends out a leader before making the main strike. It’s crazy. This three-minute video of 4K clips has a few that are super slow motion and show the electrical leaders “looking around” for something to hit before the main lightning bolt. The path they take is unbelievable.

It highlights the relative futility of hiding (you still have to get lucky), but in a case where there is lightning (esp. if you are dry), being on your bike with tires could cause you to not become a source for a ground-based leader. You could be partially correct after all!
— Randall, Engineer

Dear Lennard,
Back in the 70’s when I co-owned a bike shop in SF, a customer told us of cycling in the Sierra when lightning struck his aluminum brake lever and arced to a hydrant he was just passing by. Scared the hell out of him, but unhurt and kept riding. One of his nine lives I guess.
— Michael

Regarding calculating e-bike power:
Dear Lennard,
While you (nearly) used the correct equation to calculate the power produced by the electric motor of your pedelec you made two mistakes and a typo.
1. Using the torque the motor produces while multiplying it with the angle speed of the rear wheel. That would only be (accidentally) correct if the sprocket on the motor’s spindle had the same size as the sprocket the chain wraps around on the rear wheel. If those two sprockets are of different size, then the torque at the rear hub will differ from the torque at the motor’s spindle. It would also be correct for a motor which is located in the rear hub.
2. Additionally, in the correct formula it’s the angle speed, which is 2 x Pi x f with f being the rotational frequency and not only the frequency.
3. There is a typo when looking at the units resulting from the equation you wrote up. The resulting unit would be Nm²/s while the unit Watts for Power is Nm/s.

So, to answer James’ question you would have to multiply the torque of the motor (assuming it puts out its max. torque while you’re going at 45 km/h which I doubt) with the gear ratio and then multiply it with 2 x Pi x the rotational frequency of the wheel you calculated.
— Horst

Dear Horst,
Thanks for catching all of those things. Great catch on that torque difference.

I did catch the typo on the units, but not until a few days later, by which time the Tour de France had started. While I think of little besides the Tour in July, it’s more focus-intensive for VeloNews staffers who have the keys to back end of the site and who can make such a change to one of my articles that has already been posted. They are so busy during the Tour that I wasn’t about to bug them to take out the extra “m”.

A lot of other readers also caught the missing 2pi. Thanks to all of you.
― Lennard


Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder (www.zinncycles.com) and purveyor of non-custom huge bikes (bikeclydesdale.com), a former U.S. national team rider, co-author of “The Haywire Heart,” and author of many bicycle books including “Zinn and the Art of Road Bike Maintenance,” “DVD, 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 in physics from Colorado College.

Follow @lennardzinn