Technical FAQ: Carbon component lifespan, future of tubular tire tech

This column was originally published on August 10, 2021.

The 2021 men’s world road cycling championships were won on clincher tires, and the rescheduled Paris-Roubaix this coming weekend — with a chance of wet cobbles — again raises questions about tires and carbon tech.

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

Dear Lennard,
You said you did not know where a reader got the recommendation for routine fork replacement. Maybe it was from misreading Canyon’s owner’s manual. My 2020 Canyon Grail owner’s manual dated April 2017 says to replace carbon stems, handlebars, seatposts, and wheels every three years or 15,000km. Curiously, it does not have a recommendation for routine replacement of the carbon fork but it could be easily misread in the listing of components. And why doesn’t Canyon recommend replacing carbon frames every three years?

Even more curiously (maybe?) is that Canyon’s current online manual has removed that advice and now says “possibly replaced regularly.” Here is the identical section of the new page 43.

I’d be curious about any insight on Canyon’s change — if you think it’s of interest to a broader audience. Maybe Canyon’s manufacturing/suppliers have improved? Their lawyers have gotten braver? Accountants and legal has found carbon doesn’t fail as often as they thought? Other than van der Poel’s handlebar and the Aeroad seatpost, of course.
— Mitchel

Dear Mitchel,
I have found over the decades that manufacturers don’t much like talking about this subject, and my interpretation was that they don’t like telling consumers that parts with their brand on them will fail, as all parts of course eventually will. The question is when this might happen, and nobody wants it to happen while the bike is being ridden.

I remember decades ago, before carbon bike parts, 3T said in its owner’s manuals to replace its (aluminum) stems and bars every three years. I quoted 3T on that in my maintenance books starting in the first edition of Zinn and the Art of Mountain Bike Maintenance back in 1995. Mathieu Van der Poel’s ride notwithstanding, a broken handlebar or stem will generally always result in a hard crash.

My guess is that Canyon heard from customers who freaked out when they read that they were supposed to replace their super expensive wheels and other parts after three years and less than 10,000 miles. That, presumably coupled with the fact that nobody was breaking their wheels and parts very quickly, led them to write that section of the manual less definitively.
― Lennard

Dear Lennard,
As a 30+ year primarily road cyclist; I would like to get your take on what I see as an impending issue for myself. I ride tubular tires; they have been my choice for about the last 25 years or so. I don’t find them to really be that much of a hassle, and at this point, I have the processes worked to the point that I’m happy. It seems, however, that other tire formats are making serious progress, so I am a bit concerned that tubular tires and wheels may be hard to find at some point in the reasonably near future. Until the fairly recent developments with Specialized towards clinchers, it seemed like tubeless was the future. I have learned a bit about tubeless as I also ride gravel so in a lot of ways that seemed ok. However, your articles a few months back made it seem that road tubeless was mostly great, right up until the point that it wasn’t, and then it could be really bad as in crashes related to immediate deflation and the tire coming off the rim. There were numerous accounts of folks having scary accidents that seemed to be related to road tubeless flats. One of the things I appreciate about tubulars is the ability to safely ride a flat to a stop. Granted, I have to carry a tire, but I can get moving again after a flat much faster than most folks I know who roadside wrestle with a clincher. Granted, if I have a second flat, I’m calling my wife, but that’s ok in my world; I just take the hint from “Karma!”

I would really appreciate it if you could share your overall thoughts regarding road tire formats, and what you see in your crystal ball.
— Scott

Dear Scott,
Oh, I wish I had a crystal ball in which I could see the future of bike tires — and everything else! It will be hard to separate my hopes from my prognostication, and here is my take.

I believe that, with the ascension of gravel riding to not only people’s preferred training method but also much closer to the pinnacle of racing, the relative benefits of tubulars over clincher tires (tubeless and tubed) increase as people ride rougher and rougher roads on essentially road bikes. Paris-Roubaix has always been contested on tubulars, and I understand that a number of teams are planning on using tubeless clinchers for it this October. I find this questionable, and hope that, in this pandemic era of limited accessibility of the media to the riders’ bikes, we can actually determine with certainty after the race what tires actually did get used. Yes, the low pressure possible with tubeless clinchers would provide an advantage in rolling resistance and traction over tubed clinchers that would have to be run at higher pressure to avoid flatting. However, that advantage does not exist over tubulars, and there is a far greater likelihood of experiencing a flat due to rim damage. Allow me to explain:

Out of aerodynamic and weight concerns, pro riders are not going to switch from carbon rims to aluminum rims for Paris-Roubaix, and, in my talking to teams about tires and wheels they are planning to use on October 3, most of those that say they will use tubeless clinchers also say that they will be using hook-bead rims. To me, this means that a rider running tubeless clinchers at low pressure who hits a sharp-edged cobblestone at high speed is certain to crack his rim sidewall. Unlike aluminum rims, which bend on such impacts, carbon rims crack. The tubeless clincher may prevent pinch flatting, but accumulate enough rim-wall cracks from sharp impacts to that rim over the course of the race, and air loss due to rim failure, possibly even at a catastrophic rate, is a distinct possibility.

Some of this concern could be mitigated with hookless rims, which have thicker, stronger sidewalls than hook-bead (crochet) rims. However, hookless rims are not made by most of the top pro teams wheel sponsors, and not all tire and rim brands share the belief in their safety. Hookless rims are still more vulnerable to damage than tubular rims, whose edges do not stick up vertically and are broad, rounded, and far further below the height of the top of the tire than the edges of clincher rims, hookless or hooked.

And, tubular tires can be run at a similarly low inflation pressure as tubeless clinchers, due not only to these lower, rounded edges of the rims they are glued onto but also due to the fact that their inner tubes are latex, which can take a pounding without resulting in the snakebite perforations that butyl tubes would suffer. This has been proven for decades by the top cyclocross riders in the world, running 33mm tubulars at super low pressures on rough courses. And, as you said, tubular — because they are glued onto the rims — won’t come off of the rims when flat like clinchers (tubeless or tubed) often do.

Finally, in addition to most racing tubulars being built with more supple, non-vulcanized, super-high-thread-count casings (resulting in lower rolling resistance), their round cross-sections make them better able to absorb vertical hits and side forces than clinchers (tubeless or tubed), which are constrained to a bulb-shaped cross-section by the clincher-rim sidewalls. A thirdhand quote I heard attributed to UAE mechanic Beppe Archetti went something like this: “If they want to run tubeless (clinchers) at Paris-Roubaix, I’ll quit. It doesn’t make any sense.”

And tubeless tubulars do exist. They combine the advantages of sealant-filled, puncture-free riding of tubeless clinchers with the tire-performance and rim-reliability advantages of tubulars. At least 95 percent of the riding I do is on tubulars for all of these reasons, no matter whether I’m riding dirt or pavement.

For prognostication, despite all of these advantages (and generally reduced weight of the rim/tire combo to boot), it’s hard to bet on tubulars always being available. That’s due largely to having to glue them on the rims, and to the high cost of the tires. Products like Carogna double-sided tubular gluing tape make gluing less daunting, but the lack of understanding of the process among the general public relative to the widespread understanding of clinchers — and even tubeless clinchers — means tubulars are a harder sell. And handmade tubulars will always be more expensive to produce than molded, vulcanized clinchers, and tubeless clinchers. If people don’t buy enough of them, they won’t continue to be made.
― 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 on Twitter.