1. VeloNews / Bikes and Tech / Technical FAQ / Technical FAQ: Puzzling tire widths; e-bike retrofit options

Technical FAQ: Puzzling tire widths; e-bike retrofit options

By Lennard Zinn • Published
The clouds dropped a bit of rain throughout the day. Viviani ran S-Works Turbo tubulars with Gripton compound. They're marked as 24mm tires, but given the width of the Roval rims, it's likely these tires measured larger than that. Photo: Dan Cavallari | VeloNews.com

Dear Lennard,
Another issue I have been thinking about is wheel diameter and speed. (Relating to tire width question last month.)

When you choose a smaller tire; for instance, a 23mm versus a 28mm; you actually save one centimeter in wheel diameter and over 3cm in circumference. This translates to an easy gear and the ability to spin with more RPMs, which would make you go faster.

So besides the wheel being lighter with the same brand of tire (just in different sizes); you might also have a mechanical advantage going uphill because of the slightly easier gearing. Or another possibility is the choice of a smaller range for your cassette; which again could save weight.

I remember seeing Claudio Chiappucci’s Sestriere bike, and, if memory serves, he had Michelin Hi-Lite clincher tires in size 20mm. I also believe that in those years Miguel Indurain also rode those tires in I believe a wider size. Although clincher tires are probably not used now because of the use of carbon rims and the considerable weight advantage that carbon tubular rims offer. Although I recall that Tony Martin was thinking of (or did?) time trial on them.

Setting aside the clincher versus tubular issue; my question comes down to this. Are 25mm tires used by most pro teams in Professional races, with the exception of TTs and Belgium cobblestone events, just a fad or are they here to stay? Or is this just like high flange hubs forever out of style?
— Jonathan

Dear Jonathan,
That’s a big deductive leap to say that the bike will be faster because the effective gear ratio is lower. Power is energy per unit time, and if a rider puts out more energy with each pedal stroke but does it less frequently (lower pedaling cadence), the power will be the same. Spinning a lower gear is not necessarily faster. It works for some people and not for others. There is a lower peak load on each pedal stroke the higher the cadence at a given speed, but there is generally a corresponding higher respiration rate counterbalancing that. And riders with bigger, heavier, longer legs will lose efficiency spinning them around rapidly compared to riders with short, skinny legs.

As for clincher use on pro teams, yes, some teams do use them, and Tony Martin has for years often used clinchers and has won important time trials on them. And regarding tire widths on pro teams, teams generally now understand that 25mm tires roll faster under a wide variety of conditions than 23mm or narrower tires, and a lot of them have made that change. I don’t see them coming back from that.

Whether something stays a fad or becomes a trend that is sustained depends on whether there is a genuine performance advantage to it or not. If there is no performance gain, then people’s interest will wane, and a fad will die out. If riders will go faster with a given piece of equipment, they will continue wanting it, and it will be a trend that will last until something faster yet comes along. Individual riders, of course, will make choices about their individual preferences, and for small performance differences, they will always have to make a leap of faith and trust that something they cannot feel will save them energy. And sometimes they cannot muster that trust vs. a long-held belief in something else, and they will stick with that something else despite evidence to the contrary. Like Laurent Fignon and Cyrille Guimard did in the 1989 Tour de France, when Greg Lemond and many others before him had produced plenty of evidence that aero bars offered a performance advantage in a time trial. To cite your example, high-flange hubs and tying of soldering of spokes went the way of the dinosaurs because rims and spokes became stronger and they no longer offered a performance advantage; that was a trend that reverted to being a fad.
― Lennard

Dear Lennard,
With all the discussion about road tire width/volume these days and with large differences in internal widths of rims, I wonder why we still see tires sold as “23mm,” “25c,” “28,” etc … when they often don’t measure that width when mounted. A good example is that I have a set of Schwalbe Pro One Tubeless 700x25c tires mounted to ENVE 3.4 Disc rims and they measure just over 28mm. This is fine on my newer bike with clearance for 30mm tires but is annoying on an old Cervelo where a few mm wider/taller means they won’t fit. I have more than once bought “25c” tires only to find they don’t fit and are then not returnable. That raises my question:

Rather than referring to tires by 23/25/28c widths, why couldn’t they be sold as their flattened bead-to-bead measurement instead? (Except for minor tread thickness differences, two tires of the same bead-to-bead size should mount up to the same width when inflated.)
— Bob

Dear Bob,
That’s a good idea. I agree that it is a jungle out there, and you can be the unhappy recipient when your tires don’t clear your frame or fork.

First, there is becoming broad recognition of the ability of wider rims to make a given tire become wider than intended once mounted. On this new bike, Cannondale specifically designed their rims to do just that.

Furthermore, there is a variance of plus or minus 4mm in tire width allowed in the ETRTO width dimensions, so they are not required by regulations to measure to the rated width when mounted. That allowance for dimensional variance applies even with the rim for which they were intended, and of course, rim choice can even push it well beyond that, as the mounted tire width is dependent on the inner width of the rim it is mounted on.
― Lennard

Dear Lennard,
I’ve been running tubeless on my commuter road/cross bike for a few years now. Though extra work in some ways, it also saves my butt, like this morning when I got a significant slice in the tread from glass. My current problem is that my valve cores eventually seize up in two ways. The most frustrating is that I can’t unscrew the valve lock with my fingers and have to pull out some pliers. The other is that the self-sealing function of the valve gets sticky and makes inflating a pain. I assume all of this is due to sealant getting into/on the valve core. Repeatedly replacing cores gets expensive, so my question is whether there’s a good cleaner or solvent I can use that won’t otherwise degrade the seals. I suppose it might depend on what kind of sealant one uses; I’ve been using Stan’s.
— Nathaniel

Dear Nathaniel,
Usually, you can just remove the valve cores and rub the dry sealant off of them, rather than replacing them completely. Also, always save the valve cores from any tires/tubes/tubulars that you are disposing of, so that you’ll have them around whenever you need them, and you won’t have to go out and buy them.
― Lennard

Regarding e-bikes

Dear Lennard,
I want to transform my wife’s Kona Major Jake into a pedal assist e-bike. The reason is that she no longer enjoys riding with me or my friends because of various health issues.

I have read a lot of stuff on the different motors and set-ups. But I am still lost in this hi-tech jungle.

I would like to know what you think is the best manufacturer and supplier of parts to get this job done at a reasonable cost, with a minimum of frustration for a retro grouch such as me?
— Claude

Dear Claude,
This is one I have some experience with. It retrofits into a threaded bottom bracket shell and replaces the bike’s crank and bottom bracket. I think it is pretty easy even for a retro grouch, and it is certainly cheaper than a whole e-bike. It definitely cranks out the power, and, unlike my Bosch e-bike system, it has a throttle, so she can even get power without pedaling.
― Lennard

Related Articles