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Puncture-proof tubular tires
Dear Lennard, Following up on your article on the new Michelin tires, where you noted that the new tubular was ridden in 2012 by Ag2r at Paris-Roubaix and Le Tour, how common are tubulars with puncture-resistant belts on pro team rigs? I could see it being a good idea at Paris-Roubaix or Strade Bianche, but do they tend to equip them for other races as well? —Clark
Dear Clark,
Essentially all racing tubulars have a puncture-protection belt under the tread. The only exception is superlight time trial and track tubulars. I ran your question by a number of manufacturers and have paraphrased their answers below.
Vittoria: All of Vittoria’s cotton casing tubulars have a PRB layer under their tread. The technical specification of the PRB can change, based on the model. Regarding the question from Clark, some riders use PitStop (prevention against punctures), but this is an additional measure.
Vredestein: Fortezza Pro TriComp has a protection belt; company claims the tire “is famous for being extremely puncture resistant.”
Challenge: All Challenge tubulars have protection under tread, and now for the Almanzo Gravel, have adopted double protection (see photo). The second protection belt is placed inside the tire casing and goes in direct contact with the tube; this is Challenge’s new double protection system.
Tufo: Protective belts in all road tubulars, except the training PRO series.
Clement: Protective belts in all road tubulars.
Schwalbe: Current high-end tubular range includes 22mm and 25mm Ultremo HT, which come with a RaceGuard protection strip. However, a 22mm Ultremo TT is similar to the Ultremo HT, but comes without the RaceGuard breaker.
FMB: Protective belts in all road tubulars.
As you can see, puncture-protection belts are standard in road racing tubulars.
―Lennard
Wheels sizes and gear ratios
Dear Lennard, I am having a hard time wrapping my head around rotational inertia of wheels and gear ratios. The main sources I’ve found online, here and here, suggest that wheels with greater diameter are no faster than smaller wheels. In a perfect world, if two completely identical riders rode two bikes, one with 650C wheels and the other with 700C wheels, in the same gear, say 110 gear inches, with the same cadence, each rides for exactly 30 minutes, would they travel the same distance? I would assume no … but that does lead to another question.
Same riders and same bikes, except the bike with the 650C wheels can ride in a higher gear. Both riders run their max gears; the 650C has 122 gear inches and the 700C has 116 gear inches. Does the lower rotational mass of the 650C wheels have any bearing on energy used?
—Dave
Dear Dave,
Your assumption is false. By definition, the two riders on 110-inch gears travel the same distance. That’s because the gear inches value includes the wheel diameter.
Here’s the formula: Gear size = (number of chainring teeth) x (tire diameter) ÷ (number of cog teeth)
If you want the gear in inches, put in the tire diameter in inches. To find out how far you get with each pedal stroke (gear rollout), multiply the gear by π (3.14159).
Because of this fact, your second question makes no sense. It’s interesting that the larger gear ratio you quote is on the smaller wheel; apparently the chainrings on that bike must be huge. If you’re trying to get at an increase in efficiency (or not) with smaller wheels, you won’t get there from looking at gear inches, particularly if you don’t take into account that the gear inches includes the tire diameter.
There is no universal truth you’re going to find in an equation that says that 650C wheels are faster than 700C wheels or vice versa. Some conditions favor one size and some favor the other. In a nutshell, assuming similar tire and wheel construction, 650C wheels will be faster when it comes to sheer weight against gravity (i.e., climbing), and both weight and rotational inertia when accelerating (racing criteriums). Rolling resistance is higher with decreasing wheel size, so rolling at steady state, especially on rougher surfaces, will favor 700C. I am pretty sure that most wind tunnel testing with average size bikes indicates that the entire bike with wheels is not aerodynamically better with 650C (and can be worse), since the head tube is longer.
―Lennard
Less spoke holes on the hub than the rim
Dear LennardTechnical FAQ
Dear Frank,
No. That’s a great way to make a flimsy wheel. I’ve also tried that. Only once, though!
―Lennard
Feedback on blowing Hutchinson Fusion Kevlar-bead tires off of rims
Dear Lennard, On the bottom question in this article, the reader is having trouble with tires blowing out. Something that I have seen here in Boise, Idaho, is that people seem to think that since the Mavic Ksyrium rim has no spoke holes, that it is a tubeless rim. Another thing is that people have not been noting the difference between Kevlar- and Carbon-beaded Hutchinson tires of the same model. Either of these mistakes can lead to catastrophic failure, and I have seen this mistake made several times by people that do not know that they are making said error. Ksyriums are not tubeless and Kevlar-beaded Hutchinson road tires are not tubeless either. With the details given in the post, I do not know if you could have ruled this out, but in my experience, people keep making this mistake. —Colin
Dear Lennard,
I run Campy Proton clincher rims, and they are slighter larger than Mavic rims. I broke several tire irons and pinched many a tube while I was running Michelin tires. A friend recommended Hutchinson tires, saying that they were a little bigger, and I have been using them for several years now, without any installation problems. Campy USA said that with a slightly larger rim (theirs), a flat tire is much less likely to come off than it would be on a smaller rim. My guess is that if you can’t fit Michelins on Proton rims and you can fit Hutchinsons on them, then you probably shouldn’t run Hutchinsons on Mavics, because Michelins fit fine, and Hutchinsons would be a looser fit.
—Louis
Research shortcomings and kerosene for chain friction
Dear Lennard, Reading your last column in VeloNews, I was reminded of a neat refutation of the idea that larger sprockets give lower friction. It was published in issue 51 of Human Power (2001, p. 14-15), following an original article by Spicer published in the previous issue of that journal.
The author’s insight was that, although larger sprockets indeed have less friction for a given loading, in practical use the higher efficiency from higher chain loading occurring with smaller sprockets more than makes up for this. They prove it using Spicer’s data, too!
—Francisco
Dear Francisco,
This smelled a bit fishy to me, so I had Jason Smith, proprietor of Friction Facts, one of our independent partners at VeloLab, answer your question. He thinks about this stuff night and day, and this is what he said:
What is interesting is how these conclusions are made. This paper is an example of a conclusion, which uses incorrect assumptions, based on data from another paper, which uses incorrect assumptions. It’s a similar effect as the telephone game.
As I’ve mentioned before, Spicer et al’s paper has many correct conclusions. However, with regard to tension versus efficiency, they made a major incorrect assumption in the paper by not segregating the frictional contribution of the chain as it snakes through the pulleys. From Spicer et al’s paper, “Since the chain tension is large only on one side of the drive, this loss only has significant contributions at two points — at engagement of the chain on the front chain ring and departure on the rear sprocket.”
They did not consider the effects of lower span friction in their formulas and calculations, and assumed all friction was due to the top span. We now know that approximately two-to-three watts of friction is created by the lower pulleys and the lower three chain spans due to the applied two-ish pounds of tension from the derailleur arm. We know that it does not vary due to rider load or corresponding chain tension. Spicer et al assumed the total friction he was measuring was due to only the top span, when actually, it is a joint contribution from the top span and the fixed-friction lower spans.
Because the lower span friction does not vary with tension, their incorrect assumption skewed the linearity of the friction versus top tension and efficiency versus top tension graphs, and therefore their results with regard to efficiency versus tension. Additionally, when they plot out their tension versus efficiency results, the efficiency exceeds 100 percent in all three sprocket test cases at higher rider output. This, if correct, would be the discovery of perpetual motion. According to their data, any Tour rider with high enough power output would actually be propelled by the drivetrain rather than slowed by it.
The FF test “Chain Efficiency vs. Load” (http://www.friction-facts.com/free-chain-efficiency-load) has two graphs. The first is the total drivetrain losses vs. friction. Note the zero offset. It is a standard Y=MX+B equation. This fixed offset is due to the pulley and lower span friction, and the linear increase in friction with load is due to the top span. The second graph plots this as an efficiency percent versus load. Now, the efficiency versus load graph is non-linear, and correctly shows a trend of increasing efficiency with increasing load. However, this non-linear increase is not due solely to the friction of the top span. It is due to the combination of the fixed friction in the lower pulley spans and linear increasing top span.
In the second paper, the authors take Spicer et al’s data regarding tension and efficiency (which in my opinion is not good data), and make additional incorrect assumptions. They do not include the friction losses in the front ring in their calculations. The authors state, “We assume that most of the chain loss is associated with the rear sprocket,” and they subsequently create formulas and perform calculations based on this incorrect assumption by leaving out the friction effects of the front ring. This is important, because the meat of their theory is based on the effects of 11- versus 15- versus 21-tooth sprockets. As they keep speed of the rear sprocket constant and power constant, they do not account for the tension needing to be lower on the front ring with the use of a larger rear sprocket, which would decrease overall friction losses. The contributing effects of the front ring are essential, and, if included in the calculations, would contradict the author’s conclusion, in my opinion.
—Jason
Dear Lennard,
Word etymology is fascinating. The root of kerosene comes from the Greek “keros” meaning wax. In a broad sense in chemical terms, paraffin is an oily or waxy mixture of hydrocarbons, hence its use as a word substitute for kerosene in the U.K.
Actually, an easy way to wax your chain (without having to heat-melt paraffin into a liquid) is to dissolve flakes of wax in kerosene (as much as will dissolve). Then you can use a brush to dab it on to your chain. The excess is wiped off, the kerosene eventually evaporates and you’re left with a tidy chain lubricated with wax.
—Steve
