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Tech & Wearables

Technical FAQ: Steel wires in tires, thru-axles, 10/11-speed upgrade, cleat fore-aft

Zinn weighs in on some quotidian questions — like, can constantly removing and replacing a thru-axle damage the threads?

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

Dear Lennard,

I am an experienced (read “old”) road biker. Love your column. Lots of interesting recent discussion about tubeless tires and wheels. I have a tangential question. Over the years, I have had my fair share of flats. As I reflect back, it seems that by far the most common cause is little bits of thin wire. I live and ride primarily in a midwestern city, which to my knowledge, does not have a wire industry. My question is simple — where do these little troublemakers come from?

—Hart

Dear Hart,

I suspect that they come from the carcasses of car tires. Like a bike tire, a car tire’s carcass has plies of parallel threads laid over each other at an angle (“on the bias”) to oppose forces coming from all directions, inside and outside of the tire. In a bike tire, to provide flexibility and strength while minimizing weight, those threads are nylon, polyester, or cotton, sometimes aramid (i.e., Kevlar) or even silk.

While a car tire also has bias plies of nylon cords in its casing, it also often has steel ones as well to increase strength and durability. Steel-belted radial tires are called radial because they have steel belts crossing the tire’s center line at 90 degrees; in other words, the steel wires run parallel to the radii of the wheel. Thanks to those steel belts wrapping across the top, radial tires are much more durable than other car tire designs. Those of us driving in the 1970s, when they first appeared, remember how incredulous we were to hear that a tire could last 40,000 miles, as the Michelin ads of the day for its radial tires proclaimed. Due to their steel belts, radial tires are stiffer and hence ride rougher than bias-ply tires without steel belts; car suspension systems improved in response to give us the buttery ride we take for granted on these stiff, durable tires filled with steel wires.

The vast majority of cars on the road today roll on radial tires with those belts made of steel wires. Let them wear down too far, and those wires get exposed and torn off by the road, waiting for you to ride your bike tire over them.

― Lennard

Dear Lennard,

I have a Specialized Tarmac, which is my first bike with thru-axles. I usually transport my bikes by removing the front wheel and stowing the bike and wheel in the backseat of my car. Doing this with the Tarmac requires repeatedly removing and replacing the thru-axle. I’m worried this will eventually wear out the threads in the fork. Do you know the likely lifespan of those threads?

— Tom

Dear Tom,

I would not worry about it. Those are large-diameter, deep, coarse threads. Even though it is an aluminum bolt and aluminum threads, they are such big threads that I think the likelihood of stripping them is very low, even after thousands of cycles of loosening and tightening. I can’t remember ever seeing stripped threads on a through axle, even on very old bikes transported frequently with the front wheel removed.

― Lennard

Dear Lennard,

One potential explanation for thru-axles (and other fasteners) loosening is the vibration that occurs while transporting the bicycle, whether it’s attached to an external rack or stowed inside a vehicle. Stowed internally, the bicycle is subjected to road vibration (dampened by the vehicle’s suspension) and when transported externally, the bicycle is also subjected to buffeting.

Regarding one reader’s comment about tightening fasteners to a specified torque when a torque wrench is unavailable — it’s possible to practice this at home, tightening with the multitool and then using the torque wrench to check for accuracy. This helps one get a ‘feel’ for how much force to apply with the multitool.

—Dan

Dear Dan,

In the ’80s, I sponsored and managed a women’s racing team, and the vibration of the bikes sitting vertically on the roof of the van on long drives, like from Boulder to the Ore-Ida Women’s Challenge in Idaho, could loosen some fasteners. It also often pitted headsets.

I use the internal torque calibration in my right hand all of the time. When it’s 5Nm, for instance, which is standard for M5 bolts that take a 4mm hex key on stems and shoe cleats, I choke up on the hex key so that I’m holding it at its elbow (or at the hinge of a multitool—never at the long end of the tool) with only three fingers and my thumb: that torque-limits me to 5Nm.

― Lennard

Dear Lennard,

Thank you for the information. Computer problems have kept me from responding earlier. Another question. My bike has a compact crankset; will that make a difference? I must admit it is a bit confusing to read different opinions as to what components need to be replaced. I think, shifters — I am sure the right one but will get a pair to match, obviously cassette, rear derailleur, chain. I have heard different opinions regarding the chainrings and front derailleur.

—Bruce

Dear Bruce,

A compact crank works fine as a 2×11. Generally, a 10-speed double crank, whether compact or not, will work fine in a 2×11 drivetrain. To upgrade to 11-speeds, there should be no need to replace your 10-speed chainrings (unless they are worn out or damaged).

There is a high likelihood that your 10-speed front derailleur will also work with the left lever on your new 2×11 system. If it doesn’t, the front derailleur is the least expensive part of this entire upgrade you’re embarking on.

― Lennard

Dear Lennard,

If I move back the cleats 13mm, have I changed the saddle setback? I would have to move forward the saddle? How many millimeters?

—Endika

Dear Endika,

If, for instance, you move your cleat back 13mm on your shoe, you have effectively shortened the distance from the cleat to your hip. It’s as if your leg were shorter; you need to correspondingly lower your saddle. Since the seatpost moves up and down at an angle to the vertical, lowering your saddle also moves it forward relative to the bottom bracket.

As for whether you need to slide the saddle forward on the rails in addition to the amount it went forward when lowering it, the answer is probably not. When you move your cleat back, your foot moves forward on the pedal, but that does not significantly move your knee forward when the crank is horizontal. If your knee’s vertical alignment over the pedal does not change significantly, there is no need to adjust the fore-aft position of your saddle.

― Lennard


Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder and purveyor of non-custom huge bikes, 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