Talk:Bicycle tire

English
For the day when it becomes an issue, this article was originally written in American English. "Tire" is the correct spelling in this case. -AndrewDressel (talk) 13:46, 12 June 2010 (UTC)

Really?
How on earth can there be no page for bicycle tires? - 186.105.219.62 17:35, 12 June 2010
 * Now there is. -AndrewDressel (talk) 13:46, 12 June 2010 (UTC)

To do

 * Find reference for aerodynamic flaps on tires. Rainer Pivit, as translated by Damon Rinard, says filling the gap helps here. -AndrewDressel (talk) 17:28, 16 June 2010 (UTC)
 * Done. -AndrewDressel (talk) 13:56, 21 June 2010 (UTC)

Balloon tires
I have moved the following recent addition here for several reasons:
 * While makers of bikes with these tires laud their low rolling resistance, they can fail to state that maximum tire pressures are low for big tires. This means balloon tires have large contact patches of rubber meeting the road, contact patches being principal causes of rolling resistance. Manufacturers sometimes mitigate against this with soft rubber compounds, to reduce resistance, but in so doing might decrease resistance to puncturing.

Until we can clear up some of these issues, this addition should stay here. -AndrewDressel (talk) 03:13, 21 February 2011 (UTC)
 * 1) I have not heard of makers of bikes with balloon tires claiming low rolling resistance. Is there an example?
 * 2) All tires I have seen have their maximum inflation pressure printed right on the side wall. It there an example of one that doesn't?
 * 3) Is there an example of a manufacturer that reduces rolling resistance of balloon tires with soft rubber compounds?
 * 4) An anonymous blog is not a reliable source.

Airless
Move this here, for if and when anything further develops. -AndrewDressel (talk) 10:44, 30 September 2013 (UTC)
 * As of 2012, prototypes of airless tires have begun to appear, which use springs, instead of some solid elastic material to provide suspension between the rim and the pavement.

Effect of temperature, H2O
The Effect of temperature segment, just after the part about Nitrogen, misses the point about the effect of moisture (water vapor) in the atmosphere (air); recommend deletion of high-school ideal gas stuff and a better explanation of why N2 gas is used. — Preceding unsigned comment added by 144.183.224.2 (talk) 17:45, 7 April 2015 (UTC)

Calculations must be wrong!
The article states:


 * Thus, if a tire is inflated to 4 bar (400 kPa; 58 psi) at room temperature, 20 °C (68 °F), the pressure will increase to 4.4 bar (440 kPa; 64 psi) (+6%) at 40 °C (104 °F) and decrease to 3.6 bar (360 kPa; 52 psi) (-13%) at −20 °C (−4 °F).

This is haywire! 20c to 40c is a 6.8% (call it 7%) increase so the pressure change should be from 4.0 bar to 4.28 bar. Similarly the decrease in absolute temperature is 13.6 (call it 14 percent) not 13 and the pressure reduces from 4.0 to 3.44 bar. If no-one challenges this I will revise in a few days. Stub Mandrel (talk) 22:24, 16 August 2016 (UTC)


 * I would go ahead and fix it now. It's obviously wrong. Kendall-K1 (talk) 22:41, 16 August 2016 (UTC)

Actually it's not so obvious. The pressure inside the tire is really 5 bar, not 4. A 14% reduction brings it down to 4.3 bar, which is 3.3 referenced to atmospheric. Kendall-K1 (talk) 22:29, 5 December 2016 (UTC)

I think we're closer, but not quite there yet, at least as far as the ideal gas law is concerned. The current article states:


 * Thus, if a tire is inflated to 4 bar (400 kPa; 58 psi) at room temperature, 20 °C (68 °F), the pressure will increase to 4.4 bar (440 kPa; 64 psi) (+10%) at 40 °C (104 °F) and decrease to 3.6 bar (360 kPa; 52 psi) (-10%) at −20 °C (−4 °F).

But the increase from 20°C to 40°C is an absolute increase of 293.15 K to 313.15 K, which is a percent change of (100%)(313.15-293.15)/293.15 = +6.82%, not +10%, so the absolute pressure increases from 5.0 bar to (5.0 * 1.0682) = 5.34 bar, and finally the gauge pressure increases from 4.0 bar to 4.34 bar, or (100%)(4.34 - 4.0)/4.0 = 8.53%.

Also, I believe we should probably use the convert macro, mention that this only applies to dry air, and explicitly specify gauge and absolute pressures. All together, this would look something like:


 * Thus, if the atmospheric pressure is 1 bar, and a tire is inflated with dry air, for which the ideal gas law is a good approximation, to:
 * a gauge pressure of 4 bar at room temperature, 20 C,
 * the absolute pressure is 5 bar, and the absolute temperature is 20 C.
 * Then, if the air in the tire is warmed to:
 * 40 C, a 100% increases in °Celcius and a 53% increase in °Fahrenheit:
 * the absolute temperature increases to 40 C, so by only (100%)(313.15-293.15)/293.15 = 6.82%,
 * the absolute pressure also increases by 6.82% to 5.34 bar, and finally
 * the gauge pressure increases to just 4.34 bar, or (100%)(4.34-4.0)/4.0 = 8.53%.
 * Alternatively, if the air in the tire cooled to:
 * 0 C, a 100% decrease in °Celcius and a 53% decrease in °Fahrenheit:
 * the absolute temperature decreases by 6.82%,
 * the absolute pressure also decreases by 6.82% to 4.66 bar, and finally
 * the gauge pressure decreases to 3.66 bar, or (100%)(3.66-4.0)/4.0 = -8.53%.

A work in progress... --AndrewDressel (talk) 10:48, 2 March 2023 (UTC)

Lead image
Per WP:LEAD, the lead image should be immediately recognizable as a bicycle tire, to "allow readers to quickly assess if they have arrived at the right page." Kendall-K1 (talk) 19:55, 16 February 2016 (UTC)
 * Do you think that the current image is not recognizable as a bicycle tire? I do find it interesting that we're using a studded ice tire as the lead image, but it's a tire mounted on what's obviously a spoked bicycle wheel, with a reflector and everything. What would make it more obvious? Ivanvector 🍁  (talk) 23:32, 16 August 2016 (UTC)
 * I already fixed it. Here is the old lead image, which I replaced with the one we have now. Kendall-K1 (talk) 18:59, 18 August 2016 (UTC)
 * Oh that image. Yeah, that wasn't terribly obvious. Good choice with the new pic. Ivanvector 🍁  (talk) 19:34, 18 August 2016 (UTC)
 * Thanks! I agonized over the choice far longer than I should have. I wasn't happy with the snow studs, as I wanted as plain and ordinary a tire as possible; also wasn't sure whether to show it mounted on a rim. Ultimately I decided this was the one that the largest number of people would look at and say, "ah yes, that's a bike tire." Kendall-K1 (talk) 23:03, 18 August 2016 (UTC)

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Solid & airless tires
I combined these two sections earlier today because there's not a lot of content that's not advertising, and the two are very closely related. My edit was reverted, so let's discuss.

The present (reverted) version of the article contains no proper description of airless tires at all, just an uncited note that they're used in bicycle sharing systems (which, absent a source, I dispute) and then a list of commercial products, several of which are cited with blatantly linkspam references to the front pages of manufacturer websites. I put the two sections together because the development of both is focused on the same goal of making a flat-proof tire that doesn't compromise as much from pneumatic tires, and if all we have on airless tires is a product listing then to me it makes more sense to combine the two sections.

As for the date format, it doesn't matter to me what format is used as long as it's consistent throughout the article. I changed it to mdy because there's a "use American English" template on this page and the article seems to follow that. Ivanvector (Talk/Edits) 19:59, 26 February 2018 (UTC)
 * I was hoping to get your input on this. Ivanvector (Talk/Edits) 15:21, 2 March 2018 (UTC)


 * I didn't see your note here. Sorry. I have moved solid tires to be a subset of airless tires and added references to published articles about two airless examples. It does not matter to me what date format is used either. -AndrewDressel (talk) 14:50, 3 March 2018 (UTC)

Diameter to resistance ratio
The end of the rolling resistance section says:
 * Schwalbe Standard GW HS 159 tires have a Crr of 0.00455 for the ISO size 47-406 (20 in x 1.5 in) and, for the same model tire, a Crr of 0.00336 for the ISO size 47-622 (700C): a size to resistance ratio of about −1.8.

The "size to resistance ratio" referred to is a bit wacky. It appears that that is 622/336. But if we wanted to report that ratio properly, that would be (0.622 m)/0.00336 = 185 m. But I don't see any reason to report that ratio--under the simple hypothesis that Crr is approximately inversely proportional to diameter, we'd expect the product of those two to be constant. Which it is.

Ccrrccrr (talk) 18:29, 9 October 2018 (UTC)

OK, so AndrewDressel and I both edited that some and I appreciate his addition of the table, which is better than the orignal two points because it shows that there's some scatter in the data, and prevents overweighting it. But the inclusion of parameters of a linear fit to data seems problematic to me. Whether or not that's the intent, it implies a hypothesis that it's really a linear relationship. Making that hypothesis is, I think OR, and I think it's a bad model. It would predict that a Penny Farthing with 47 mm Schwalbe tires would have negative rolling resistance. While I agree that a Penny Farthing with Schwalbe tires would be absolutely awesome, I'm pretty sure it would not be self propelled. Another problem is that "inverse correlation" can mean either a linear model with a negative slope or a y = k/x relationship, so I would want to clarify that.

Another article, I think it's bicycle wheel, includes the hypothesis that Crr is inversely proportional to diameter. The data are consistent with that hypothesis, also with R^2 = 0.88, if I do a linear fit to 1/D and Crr, with the intercept forced to zero or 0.89 with a non-zero intercept, representing an additional loss term not inversely proportional to 1/D. That is based on OD, approximated as RSD + 2×47 mm, which makes more sense and fits the data better than using just RSD.

So what do we do? I would like to put in that analysis, but I fear being accused of OR. So I think we should just say that the data are roughly consistent with the hypothesis that Crr is inversely proportional to diameter and leave it at that.


 * In hindsight, I agree that including linear fit parameters may imply that it is a linear relationship. At the same time, our mere discussion here on what model might be better implies original research. Therefore, I propose that we present the data and say nothing more about what the relationship might be, until we can find a source, than as diameter increases, rolling resistance tends to decrease. Meanwhile, there is a discussion in Bicycling Science that might provide the relationship and reference that we need. -AndrewDressel (talk) 14:42, 10 October 2018 (UTC)


 * Sounds good. I think we'll be able to find multiple sources. Ccrrccrr (talk) 16:52, 10 October 2018 (UTC)


 * The problem appears that there are more models that we can shake a stick at. Wilson and Papadopoulos, on pages 226-227 mention several, including:
 * $$C_R = f(F_v/p)$$ "or" $$f(F_v/pr^2_w)$$
 * $$C_R = 0.076(F_v/pr^2_w)^{0.60}$$
 * $$C_R = 0.005\{1 + (2.1 bar)/p)[1 + (V/29 m/s)^2]\}$$
 * Might have to leave this one vague for now. -AndrewDressel (talk) 20:35, 10 October 2018 (UTC)


 * Yes, and I have another reference with 1/R^0.75 ... so we either need to leave it be or expand the discussion substantially. Which requires some thought as to how much goes here, vs. rolling resistance vs. maybe bicycle performance.  I am inclined towards expanding it here until it become too big and become a separate bicycle rolling resistance article. Ccrrccrr (talk) 16:30, 11 October 2018 (UTC)


 * I've put in the original reference, which does include a Crr prop. 1/rW curve fit. Wilson and Papadopoulos is being updated for publication next year and a preview shows this very graph. It also gives some of the above models and more and points out that they are contradictory. Theosch (talk) 13:22, 31 October 2018 (UTC)


 * I've looked at it again and its more complicated. Senkel's table shows five Crr values for rim sizes, but he has an additional diagram using tire diameter, which I make out to be rim diameter + 46 mm, and this shows the curve-fit. There is also the same for 200 kPa, but this data isn't in the table. I played with the data a bit and all sorts of curves are possible, but one which works very well is Crr = 0.0003 + 1 / tire-radius. And it says so in the (German) text, even though he neglected the offset necessary for a really good fit. Libre Office Calc gives very similar curves with R^2 = 0.95. So it isn't OR to call Crr proportional to 1/tire-radius. Theosch (talk) 11:44, 1 November 2018 (UTC)


 * Awesome! With three of us working on this, we are going to copyedit this to perfection, and to that end, I:
 * expanded the sentence to mention the similar conclusion presented in "Diagramm 2" about inflation pressure,
 * revert back to using the author's phrase "inversely proportional" and wikilink it, because "being equal to the inverse of the tire radius" depends on the units chosen,
 * leave out the detail implied by the plots that there must also be some positive constant offset, as interested readers can see that for themselves when the click on the provide link to the source paper, and
 * copy edit in an effort to indicate that these are one author's conclusion from the data he collected and presents.
 * Edit on! - AndrewDressel (talk) 13:17, 1 November 2018 (UTC)
 * Perfect! Thank you. You're correct to leave mentioning the offset, as Senkel doesn't seem to. And with your formulation, as my previous version was coincidental. Theosch (talk) 17:58, 1 November 2018 (UTC)

Tire treads
A reader (ticket:2018101810009503) notes that the claim that tire treads (as opposed to tubes) are made of butyl rubber is false. although the claim, appears to have a source, that source appears to be a personal website and may not qualify as a reliable source. I hope some editors will look into this claim and correct it if appropriate.-- S Philbrick (Talk)  14:59, 19 October 2018 (UTC)


 * Fixed, at least for now, I think. Oof. Wonder how long that's been there, and hope it wasn't from me. -AndrewDressel (talk) 16:21, 19 October 2018 (UTC)