Wider tires, higher air volume, lower pressure. Why?
#76
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https://flocycling.com/blogs/blog/fl...or-wider-wheel
I think you’d want to keep casing tension constant. This article seems to provide a guide on how to do that.
I think you’d want to keep casing tension constant. This article seems to provide a guide on how to do that.
#77
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No need. Looks like the person who revived it found the specific piece of information they were looking for. Nothing left to see here.
#78
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#79
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If you have 30 minutes or so this podcast from VeloNews is very in depth: https://www.velonews.com/2020/03/gea...roubaix_506668
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#81
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#83
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As was pointed out above, the "ideal gas law" or Boyle's law do not apply unless the moles of gas are constant.
Last edited by Gyro_T; 03-16-20 at 12:31 PM.
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I don't really care about the science, all I know is that my 28mm tires (that measure to about 30mm) are more comfortable and corner better than previous 23 or 25mm tires, without sacrificing any noticeable speed. That's all I need to know.
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imo
23c to 25c noticable difference
25c to 28c, barely discernible
25c to 30c+, big step
I'll take 25c TL on a road bike for the ideal compromise
ymmv
23c to 25c noticable difference
25c to 28c, barely discernible
25c to 30c+, big step
I'll take 25c TL on a road bike for the ideal compromise
ymmv
#86
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Why stop there? On my old bike I had 23mm at first, loved the upgrade to 25mm, and could run 28s depending on the brand, but with GP4K I could only fit 25mm up front and 28mm rear. With my new bike I'm rocking 32mm and loving it so much I'm contemplating shelling out for their 35mm model, just to see if it keeps getting better or 32mm was the peak goodness. I had personally applicable Strava data on routes I rode a lot with the 25mm and 28mm tires and then with the 32mm tires, and not only didn't see any drop in performance, but if anything, saw a slight gain. Since my frame and fork support these sizes, I won't ever go back.
#87
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I read the article and plotted the data for pressure vs. diameter. It is very nearly a linear relationship. I think calculating the casing tension may be a more accurate way of determining the "pressure equivalency" I have been seeking. I had a gut feeling it was not a simple proportionality, e.g. the area of tire A 28mm tire=615.7mm2, area of tire B 44mm tire=1520.5mm2. A simple proportionality would say that a 28mm tire at 75 psi would be 30.4 psi in a 44mm tire: Tire pressure A* area of Tire A= Tire pressure B * area of Tire B, so in this case 75 X 615.7= x X 1520.5. Solve for x which give you the 30.4 psi for the 44mm tire. 1) it seemed too low, and 2) too simplistic. I think the casing tension may be exactly what I have been looking for and I will wade through the formulas with my figures. Thank you kindly.
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Wut? A cyclocross bike with tubulars at 32 psi has the same size contact patch as your car?
#89
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I suggest you take a look at the articles smashanddash referenced above. To get comparable "drop" the pressure will vary with diameter. Yes, that is all tied in with contact patch.
#90
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What im saying is it doesnt matter if the tyre is 23 or 32 mm, the area of the contact patch is the same if the tyre pressure and the load on the wheel is the same. If the load is 100 lbs and the pressure is 100 psi the area is 1 sq inch no matter and there is no reason 100 psi should feel any softer or harder just because you put it in a wider tyre or narrower tyre.
Last edited by Racing Dan; 03-16-20 at 03:38 PM.
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What im saying is it doesnt matter if the tyre is 23 or 32 mm, the area of the contact patch is the same if the tyre pressure and the load on the wheel is the same. If the load is 100 lbs and the pressure is 100 psi the area is 1 sq inch no matter and there is no reason 100 psi should feel any softer or harder just because you put it in a wider tyre or narrower tyre.
Understand you are using a base number for clarity, but if both a 23c and a 40c on appropriate rim size, no way 30psi "feels the same"
23c tire would be folded over the rim, i.e pinch flat
#92
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I'm a little confused. Am I closer to perfect on a 700 x 40c 55psi tire than on a 29 x 3 inch 17 psi plus tire? You want me to go 700 x 25? That bike rattles my bones.
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but why should a 23mm bike tire and a 50mm bike tire have the same contact patch size? Shouldn’t your contact patch size be proportional to the size of the tire?
You are certainly wrong that a 100psi tire feels just as hard regardless of tire size.
Last edited by smashndash; 03-16-20 at 10:40 PM.
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Why stop there? On my old bike I had 23mm at first, loved the upgrade to 25mm, and could run 28s depending on the brand, but with GP4K I could only fit 25mm up front and 28mm rear. With my new bike I'm rocking 32mm and loving it so much I'm contemplating shelling out for their 35mm model, just to see if it keeps getting better or 32mm was the peak goodness. I had personally applicable Strava data on routes I rode a lot with the 25mm and 28mm tires and then with the 32mm tires, and not only didn't see any drop in performance, but if anything, saw a slight gain. Since my frame and fork support these sizes, I won't ever go back.
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#95
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I haven't tried GP5Ks yet. I liked GP4Ks, but haven't yet worn out the Compass (now Rene Herse) Stampede Pass 32mm tires currently on the bike. I'm loving these tires so much I'm not sure I'll buy anything else when these ones are finally done. If anything, the most likely replacement for the 32mm Stampede Pass tire will be the 35mm Bon Jon Pass tire. I may try out the 32mm GP5K just to see what it's like, though. The Compass/Rene Herse tires are spendy, but for things I'll use for hundreds of hours if it brings a noticeable benefit in comfort or safety, I'm down. I remember when I rode Gatorskins back in the day, and then tried the GP4Ks. Sure, I had a few flats with the GP4Ks that I might not have had on Gatorskins, but that's momentary pain that only happens every once in a while, while the harsh, dead ride on Gatorskins is something that's with you hour after hour, day after day, month after month. No thanks.
#96
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If you have 30 minutes or so this podcast from VeloNews is very in depth: https://www.velonews.com/2020/03/gea...roubaix_506668
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#97
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Boy I hate to pile in on this zombie thread...
but why should a 23mm bike tire and a 50mm bike tire have the same contact patch size? Shouldn’t your contact patch size be proportional to the size of the tire?
You are certainly wrong that a 100psi tire feels just as hard regardless of tire size.
but why should a 23mm bike tire and a 50mm bike tire have the same contact patch size? Shouldn’t your contact patch size be proportional to the size of the tire?
You are certainly wrong that a 100psi tire feels just as hard regardless of tire size.
However, Many real world tire pressure calculators are based on the 15% drop method. So the tire patch would not only longer (15% of a tire height of 23mm vs 50 mm) but wider too, Yielding a much larger contact patch. One reason we use wide tires for beach cruisers and narrow tires (to about 32mm) for road bikes.
Last edited by xroadcharlie; 03-23-20 at 12:34 PM.
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