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Most times when I see a failed bicycle tyre (one where the threads are showing through) they look something like this, with diagonal threads clearly visible

https://media.wired.com/photos/593331eb4cd5ce6f96c0c96d/master/pass/retired.jpeg

Here's a random manufacturer's cutaway showing diagonal casing threads enter image description here

Here's a line diagram showing the difference: http://cdn1.bikebandit-images.com/blog/images/2016/bias-ply-vs-radial-tires/bias-ply-vs-radial-4.png

So I'd reason that most/all bicycle tires are Cross Ply in build, and not Radial.

My google-fu does return these points:

  • Radial tyres are cheaper to make than the equivalent cross ply
  • Radial tyres are lighter and have better fuel economy than a cross ply
  • Radial tyres track better, where cross ply tyres have been known to "tramline" vehicles.
  • Cross ply tyres have a more rigid sidewall, radial tyres have a more supple sidewall.
  • Suspension needs to be altered in a car to accommodate the differences between ride handling in the two styles.

Usage

  • Automobiles tyres are almost exclusively radial.
  • 4WD tyres are predominantly radial, but cross ply have much better sidewall strength and resist damage better.
  • Motorcycle tyres may be either, where radials are preferred for speed and cross ply are preferred for load carrying (touring or cruising)
  • Truck (ie load carrying vehicles) might use either, with cross ply for load carrying and radial for long distance.

Even wikipedia is ambiguous, saying

Radial tires have occasionally found application on bicycles, used on the 1980s Miyata touring bicycle; models 1000 and 610,[19] and more recently in 2009 on the Maxxis Radiale.[20] Panaracer radial tires were also standard on the Jamis Gentry model bicycle in 1985.

I would have expected that radial construction with "supple side walls" to help a lot in reducing rolling resistance, but its uncommon.

Why are Radial tyre constructions uncommon in bicycle tyres?

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    I would expect that radial tires would not survive as long -- the sidewalls would tend to deteriorate and split vertically. – Daniel R Hicks Jun 19 '17 at 17:13
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    Quoting Sheldon (I don't personally know, taking his word for it): "Radial tires have been tried for bicycles, but they tend to be too floppy from side to side. This floppiness feels quite unpleasant in actual riding--much like the feel of a grossly underinflated tire." sheldonbrown.com/tires.html – compton Jun 19 '17 at 17:43
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    More recently there was a radial racing tire from Schwalbe. They were first recalled then quietly dropped from product line. Recall news is still online: bikeradar.com/news/article/… – ojs Jun 19 '17 at 18:34
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    Some time ago I was wondering about the same question and did some digging online, turned out that Panaracer Radiale wasn't a true radial but had a bias ply layer to reduce floppiness. They had a reputation for delamination, too. I'm wondering why radial tires always fail on bicycles when they are successful everywhere else. – ojs Jun 19 '17 at 18:37
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    Bicycle tyres need stiffer sidewalls. Soft sidewalls will alter the geometry of the system when leaning into a turn and modify the behaviour of the cycle in a turn. Motorcycle radials are wider than their height (around 100/50) which lessens the squashing. Bicycle have an tyres almost circular section.. – Carel Jun 19 '17 at 20:08
4

As far as I can tell, the biggest factor influencing bicycle tires has to do with the 4th bullet point you mentioned, sidewall stiffness, combined with using inner tubes instead of just being a pneumatic tire. Cross-ply tires with their more rigid sidewall would be less prone to snakebite punctures of tubes and would hold rims off the ground with less pressure. Radials would have more of a propensity for the sidewall to collapse with low pressures.

  • 2
    Sidewall collapse is not just a problem because of the potential of snake bites, but also to keeping track in curves. When you lean into a curve, the inner sidewall is unloaded, and if it collapses, the wheel crawls away out of the curve. This is a really nasty feeling, if not downright dangerous. I had such a tire exactly once in my live, and I tell you, I'll never ride that tire's brand again. – cmaster Oct 5 '18 at 9:00
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Radial bicycle tires are very rare. The reason is that the lateral stiffness is much lower than for cross-ply tires. Imagine that you press the sidewall of a tire by your thumb. With a cross-ply casing the cords on which you apply pressure are anchored to the bead wires over a distance of about twice the tire width and the whole section shares resistance to deformation. In case of a radial tire the cords run in the same direction as the force, hence offer very limited resistance. Radial tires are prone to squirming and unstable cornering.

Yet a few manufactures still offer radial tires. I know of the Vittoria Diamante Pro Radiale 700x22 for road bikes and the CST Sensamo Speed 35-622 for touring bikes. The riding experience with the Vittoria tires, published on https://cycletechreview.com/2012/reviews/vittoria-diamante-pro-radiale-tyre-review/ , suggest that they might please persevering afficionado's. It is probably not accidental that the width is limited to 22 mm. The bigger the diameter, the softer the structure get and, probably, the higher the inflation pressure required for stable load carrying (limited load carrying might be the explanation why airplanes and heavy trucks don't use radial tires but cross-ply tires).

In his study of tire properties, Andrew Dressel included a Maxxis prototype 22-622 tire. He reports (page 113) 'The Maxxis prototype, which is described as “radial” and does appear to have cords aligned at about 22.5º, instead of the 45º usually associated with bias-ply, does not have stiffnesses noticeably different from other tires of similar size.' Here the small width combined with the in-between design would explain the results. See https://dc.uwm.edu/etd/386/

  • 1
    Interesting - great first answer. One might have thought low-pressure MTB tyres would benefit from softer sidewalls, but perhaps other factors outweigh that advantage. – Criggie Feb 22 '18 at 2:20
-2

Bicycle rims are not designed for radials. https://www.sema.org/files/attachments/WTC-2011-05-Bias-vs-Radial-Tire-Wheel-Fitment.pdf

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    Welcome to this site. We generally discourage link-only answers here, because links can go bad. For future readers (maybe in five years or so) it would be really beneficial if you made your answer self-contained. I.e. actually tell us the relevant points that the link makes. – cmaster Oct 5 '18 at 9:06
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    This boils down to "they're not cos they're not" Please use the Edit link to expand your answer with the main relevant points. Don't be put off by this - its how we keep the quality high. Do please browse the tour to learn how SE is quite unusual compared to chatty web forums. And welcome to the site. – Criggie Oct 5 '18 at 10:57
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    The article is about car rims and tires and provides no information on bicycles. – Argenti Apparatus Oct 5 '18 at 12:13

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