Old myths or established facts.

Discussion in 'Cycling Equipment' started by Rock Creek Rider, Nov 24, 2018.

  1. dabac

    dabac Well-Known Member

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    How about this:
    Spokes mess up aerodynamics.
    If you're hunting aero advantages, one of the first things is to reduce spoke count.
    However, there's a dependency between the number of spokes you're using and the strength/stiffness - both lateral and vertical - that's required from the rim to make it into a functional wheel.
    Strength/stiffness can come both from shape and from amount of material used.
    Maybe the aero advantage of a narrower rim is offset by having to build the rim heavier to achieve the required stiffness?

    Or a production issue with actually making that narrow, tapered cavities with good laminate saturation and compaction?
     


  2. BrianNystrom

    BrianNystrom Member

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    True.

    No, that's not what the published data indicates; it says that the wider rims are more aerodynamic. Weight is only an issue when accelerating and climbing and there's no reason that a narrower rim would have to be made heavier anyway. The differences in width that we're talking about are small enough that it's not necessary. If you look at the rims on the market, you're going to find that wider rims are heavier than comparable narrower rims from the same manufacturer.

    There's no indication that it's an issue. Carbon rim manufacturing is a pretty mature technology now.
     
  3. CAMPYBOB

    CAMPYBOB Well-Known Member

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    Yup. I have never known or even heard of anyone outside of the track that ran more than 120 PSI. Like you. 105-110 was my pressure and less if it was a wet crit.


    1972 to 2006 almost exclusively of tubs for training and racing. Still race on them. Matter of fact, the Yellow Jersey is getting a call in one hour (when they open for business) and I'm ordering some this morning. Agreed. tommy's statement makes zero sense. None.


    I've got a picture around here, somewhere, that shows me holding a Campy box section rim that's in four pieces (Forget which model Strada. It was the red label, not the Omega yellow label...Hardox, solution heat treated and aged brittle things that they were). The tub is mostly ripped from the rim and the base tape is still stuck to some of the segments.
     
  4. cyclintom

    cyclintom Well-Known Member

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    Well, let me start with your understanding of contact patches. Here is an article published by Schwalbe: https://www.schwalbetires.com/tech_info/rolling_resistance Please go to the section labeled "Why do wide tires roll better than narrow ones?"

    I was under the impression that we are approximately the same weight - 180-185 depending on the season. While you could get away with 120 psi on 20 mm tubulars you couldn't with clinchers.

    I still have a set of those Campy Record tubular wheels in the garage. They are 14 mm from the top edge to the bottom edge. That is a rim that is curved to contain the tubular tire so the actual rim thickness at any point is closer to 8 mm. You may not think of that as paper thin but I most certainly do. The clinchers were almost identical in total depth. Then were simply shaped differently. While they were supported by 36 spokes that just prevented those thin sections from flexing too much. Hard shocks did flex the wheels by stretching the spokes which were not particularly stiff then. I still have a couple sets on the shelf since they broke commonly enough.

    We both agree that the tire is supposed to be the source of compliance but the more narrow the tires the higher the pressure must be and the less compliance they offer.

    I used to ride tubulars because they were the only source of decent tires. Two years ago I threw out an entire box of tubulars half of which were still new. I just ran across come cyclocross tubulars the other day which are new and I will toss as I clean up the garage. Green tubulars knobbies? Where the hell did I get those and why?

    And yes, the rims would go that slack and the tubulars would tear off. Since you couldn't see what was happening generally this was passed off as a bad glue job. Well it was happening with the Pros as well and their mechanics weren't making glue errors. And I only saw base tape separations on repaired tubulars. If there was something I really hated was repairing tubulars and having to re-sew them and then getting the base tape to properly adhere.

    I thought that we'd covered this already - yes the fifth generation carbon fiber bikes are really good bikes with some compliance and in exactly the correct plain. They do not bend laterally but only vertically. But that doesn't change the fact that the vast majority of compliance is in the larger tires used today.

    And they still haven't gotten good at quality control and we are still having odd failures such as a chain stay breaking on one side and taking out the seat stay on that side as well. Forks are now built super strong because failure at that point can cause a death. So there's no compliance there save the wheels.

    I will say that I've relatively recently started using the Vittoria G+ tires and I heartily recommend them. The tracking is incredible using my carbon wheels on the CLX 3.0. It is no longer necessary to set up for corners except very sharp turns that you have to slow way down for. Around here you cannot ride even the center of your lane because cars come speeding around these turns taking up most of the road. This means that we try to stay off these sorts of roads. A real problem is Google Maps which now will re-route traffic on these small country roads and suddenly you have cars passing you at 50 mph on a road too narrow for two cars to pass in opposite directions. And traffic coming in the opposite direction and both cars having to put their wheels on the shoulders. Great ride.
     
    #24 cyclintom, Dec 19, 2018
    Last edited: Dec 19, 2018
  5. BrianNystrom

    BrianNystrom Member

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    I just read it and it says exactly what I did. Wider tires have lower rolling resistance due to less deflection.

    I'm currently ~170# and when I last ran tubulars (2011?), I inflated them to 85/95 F/R. Back when I was racing, I only weighed 151-155#.

    When you say "paper thin", I immediately think wall thickness, not depth of the rim, which explains the discrepancy. The numbers above sound correct. [/QUOTE]

    Spokes stretch very little and not all when the wheel is subjected to a shock load (a sharp bump or pothole). This has always been the case. When a wheel is loaded, the tension in the spokes in the load-affected-zone (LAZ) decreases. There is no increase in tension in the spokes from shock loads or normal rolling loads.

    Rear wheels do experience changes in tension due to drive torque. Disc brake wheels also experience changes in tension from braking torque.

    Spokes don't fail from excessive stress (you could hang your entire body weight on a single spoke), they fail from fatigue. Fatigue is caused when the tension in a spoke is reduced to zero and reloaded repeatedly. In a properly built wheel, this should not happen. A few random cycles from shock loads should not fatigue spokes enough to cause failure.

    These are basic facts about bicycle wheels that are documented in numerous places, the classic source being "The Bicycle Wheel" by the late Jobst Brandt. Unfortunately, few cyclists understand how wheels actually work, because it's really counter-intuitive.

    Of course.

    Put 'em on Ebay. Tubulars are VERY popular for 'cross. I forget what the green tread tires are, but I've seen them at 'cross races.

    There were actually some pretty decent clinchers on the market as far back as the early '80s, but they were still somewhat heavy and clincher rims back then weighed a ton, so nobody raced on them. The only bike I had with clinchers back then was a "winter bike" that also had fenders. For that purpose, I didn't care about the weight and didn't want to be dealing with tubular flats when the weather was frigid.

    Tom, this simply is not true. I don't know where you got this information from, but it is just plain wrong.

    First off, rims don't flex much, period. Unless you hit something hard enough to damage the rim, we're talking about small fractions of a millimeter of flex in normal use.

    Second, a good glue job will not fail, even if the rim is severely dented. If you can find a team mechanic or even a good shop mechanic with tubular experience near you, ask about this and they'll tell you exactly the same thing.

    If you experienced glue bond failures, the glue jobs weren't done properly, end of story. I don't care who did them.

    The only other possibility is that the glue job was so old that the glue crystallized and became weak. That was not uncommon with the glues used decades ago. I've seen it happen with Clement red cement (my glue of choice at one point) and with Tubasti, but it typically takes at least a couple of years for it to become a problem.

    I agree with this, but previously you were claiming that the major compliance was in the rims. Technically, carbon frames still have some lateral flex, but the bulk of the designed-in flex is in the vertical plane.

    That may be true for some manufacturers, but not all by any stretch of the imagination. Manufacturing technology has improved to the point that catastrophic failures in normal use are essentially non-existent in quality frames. Failures in quality frames are nearly always caused by either some form of overload or physical damage from an impact. We're talking about overloads and impacts that would bend metal frames. The only difference is in the failure mode of the material.

    Carbon forks have always been built strong; in recent years they've been getting lighter and more compliant, except on disc-brake-equipped bikes.
     
  6. IamDonna

    IamDonna Member

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    [Myth] Cycling is a piece of cake :p
     
  7. BrianNystrom

    BrianNystrom Member

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    "...it's like riding a bicycle" o_O
     
  8. king bily

    king bily New Member

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    Any compliance in the frame and fork is probably bad. But that's part of the reason that they are going to fatter, lower pressure tires. This gives a road bike about as much compliance as it needs and at the same time limits total travel via pneumatic pressure. Compliance in a frame gives far greater travel which in turn can cause handling problems.
     
  9. BrianNystrom

    BrianNystrom Member

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    Actually, frame compliance is fine - within limits - as long as it's in the proper plane, which is predominantly vertical. With carbon fiber frames, the design trend is toward lateral (left/right) and longitudinal (front/back) stiffness for efficient power transfer, with some vertical compliance so the rider doesn't get beaten to death on rough surfaces. How much vertical compliance is built into the frame is determined by the intended use, road racing, endurance riding or gravel/off-road riding.

    Combine this with wider rims/tires and lower air pressure, and you end up with a bike that's very efficient, has improved aerodynamics and rolling resistance, better cornering grip and is reasonably comfortable to ride.
     
  10. king bily

    king bily New Member

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    Picture Of Bicycle Of Postman
    The world bicycle started being used several years after first bicycles appeared for sale. Those first models were called velocipedes.
    First bicycles were created in France, but its modern design was born in England.
    Inventors who first conceived modern bicycles were either blacksmiths or cartwrights.
    Over 100 million bicycles are manufactured each year.
    First commercially sold bicycle “Boneshaker” weighed 80 kg when it appeared for sale in 1868 in Paris.
    More than 100 years later after first bicycle was brought into China, this country now has over half a billion of them.
    5% of all trips in United Kingdom is made with bicycle. In United States this number is lower than 1%, but Netherlands has it at staggering 30%.
    Seven out of eight people in Netherlands that is older than 15 year old has a bicycle.
    Fastest measured speed of driving bicycle on a flat surface is 133.75 km/h.
    Popular bicycle type BMX was created in 1970s as a cheaper alternative to motocross races. Today they can be found all around the world.
    First bicycle-like transportation device was created in 1817 by German baron Karl von Drais. His design became known as draisine or dandy horse, but it was quickly replaced with more advanced velocipede designs that had pedal-driven transmission.
     
  11. BrianNystrom

    BrianNystrom Member

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    OK...
    Is there a point to this list that relates it to the subject being discussed?
     
  12. Lucas Oliver

    Lucas Oliver New Member

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    How can you just so sure its an established fact? How many reviews in your favor you have?
     
    George Young likes this.
  13. king bily

    king bily New Member

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    Spokes stretch very little and not all when the wheel is subjected to a shock load (a sharp bump or pothole). This has always been the case. When a wheel is loaded, the tension in the spokes in the load-affected-zone (LAZ) decreases. There is no increase in tension in the spokes from shock loads or normal rolling loads.

    Rear wheels do experience changes in tension due to drive torque. Disc brake wheels also experience changes in tension from braking torque.

    Spokes don't fail from excessive stress (you could hang your entire body weight on a single spoke), they fail from fatigue. Fatigue is caused when the tension in a spoke is reduced to zero and reloaded repeatedly. In a properly built wheel, this should not happen. A few random cycles from shock loads should not fatigue spokes enough to cause failure.

    These are basic facts about bicycle wheels that are documented in numerous places, the classic source being "The Bicycle Wheel" by the late Jobst Brandt. Unfortunately, few cyclists understand how wheels actually work, because it's really counter-intuitive.


    Of course.


    Put 'em on Ebay. Tubulars are VERY popular for 'cross. I forget what the green tread tires are, but I've seen them at 'cross races.

    There were actually some pretty decent clinchers on the market as far back as the early '80s, but they were still somewhat heavy and clincher rims back then weighed a ton, so nobody raced on them. The only bike I had with clinchers back then was a "winter bike" that also had fenders. For that purpose, I didn't care about the weight and didn't want to be dealing with tubular flats when the weather was frigid.


    Tom, this simply is not true. I don't know where you got this information from, but it is just plain wrong.

    First off, rims don't flex much, period. Unless you hit something hard enough to damage the rim, we're talking about small fractions of a millimeter of flex in normal use.

    Second, a good glue job will not fail, even if the rim is severely dented. If you can find a team mechanic or even a good shop mechanic with tubular experience near you, ask about this and they'll tell you exactly the same thing.

    If you experienced glue bond failures, the glue jobs weren't done properly, end of story. I don't care who did them.
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    The only other possibility is that the glue job was so old that the glue crystallized and became weak. That was not uncommon with the glues used decades ago. I've seen it happen with Clement red cement (my glue of choice at one point) and with Tubasti, but it typically takes at least a couple of years for it to become a problem.


    I agree with this, but previously you were claiming that the major compliance was in the rims. Technically, carbon frames still have some lateral flex, but the bulk of the designed-in flex is in the vertical plane.


    That may be true for some manufacturers, but not all by any stretch of the imagination. Manufacturing technology has improved to the point that catastrophic failures in normal use are essentially non-existent in quality frames. Failures in quality frames are nearly always caused by either some form of overload or physical damage from an impact. We're talking about overloads and impacts that would bend metal frames. The only difference is in the failure mode of the material.


    Carbon forks have always been built strong; in recent years they've been getting lighter and more compliant, except on disc-brake-equipped bikes.[/QUOTE]

    Wider Tires Are Slower
    For almost a century, cyclists ‘knew’ that narrower tires roll faster. Some people realized that in theory, wider tires are faster due to their shorter contact patch, which deforms less as they roll. But the thinking was that in practice, the lower pressure at which wider tires must run limited their performance. If you wanted to go fast, you chose narrow tires
    That is what we thought when we started testing tires almost 12 years ago. And yet, as long-distance riders, i wondered whether the narrowest tires, pumped to the highest pressures, really were optimal for us. What if wider tires were a few percent slower, but their greater comfort reduced our fatigue? Remaining fresh toward the end of a long ride would help us put out more power, so we might go faster in the end. What we needed to know was how much speed we would give up by going to wider tires.
    Aerodynamics
    What about the aerodynamics of wider tires? Many riders believe that wider tires will be slower, because they have more wind resistance. I tested this in the wind tunnel and found that the difference between 25 and 32 mm tires was too small to measure reliably in a real-world scenario. The German magazine TOUR built a sophisticated setup with a motorized dummy rider and found that a 28 mm-wide tire had the same wind resistance as a 25 mm tire when the wind was coming from straight ahead. With a crosswind, the wider tire was very slightly less aerodynamic. Even then, the wider tires required only 5 watt more – on real roads, the reduced suspension losses probably make up for that.
    I tested our tires on smooth pavement at 29.5 km/h (18.3 mph), and found no speed difference between narrow and wide tires. If you ride much faster, then it’s possible that wider tires roll a little slower, but the difference will be so small that it’ll get lost in all the other factors that influence your bike’s speed. On the other hand, if you ride slower, then the advantage of wider tires will be even greater.
    Spinning up
    Wider tires are a little heavier than narrow ones. The difference is smaller than many cyclists imagine – air doesn’t weigh anything – but a wide tire has a little more rubber and casing. Won’t this make the wider tires harder to accelerate? The answer is “No.” The reason is simple: Bicycles don’t accelerate very quickly. Even a professional bike racer’s power-to-weight ratio is far less than that of the slowest economy cars, and those don’t exactly push you back in the seat when you floor the throttle. Bikes don’t accelerate fast enough for small changes in wheel weight to make a difference. That is why professional sprinters can use relatively large wheels (which inherently are heavier) and still win races. The UCI requires a minimum wheel size of 55 cm, yet racers use 700C wheels that are 10 cm larger than required. If wheel weight mattered as much as most cyclists imagine, then pros using the smallest wheels would win every race. And yet, even though many have tried smaller wheels, all have returned to 700C wheels – probably because the larger wheels handle better due to their optimized rotational inertia. (But that is a topic for another post.)
    What this means for us riders is that we can choose our tire width freely, without having to worry about performance. Of course, this doesn’t mean that a wide ‘touring’ tire will perform as well as a narrow ‘racing’ tire. Casing performance determines 95% of a road tire’s speed, and to get good performance, you need a supple high-performance casing. (The other 5% come from the thickness of the tread.)

    Tire width influences the feel of the bike, but not its speed. If you like the buzzy, connected-to-the-road feel of a racing bike, choose narrower tires. If you want superior cornering grip and the ability to go fast even when the roads get rough, choose wider tires.
     
  14. cyclintom

    cyclintom Well-Known Member

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    Do you think that wheel manufacturers actually have engineers? I suppose they do in the sense that these people will test wheels and make any improvements they can think of. But, for instance, the Chinese simply steal a design and make them much cheaper.

    What surprised me is that the carbon aero wheels have almost no response to even 90 degree wind gusts any more than a thin rim wheel. So those aero sections are extremely efficient. I don't think that the wider tires are any more or less aero than any other. I put 28's on my Time and it rides far better than before because they cushion that super stiff frame. With 23's the frame is unrideable. You spend all of your time dreading the next tiny bump.

    I am 185 lbs and run 25's on all of the other bikes. The clinchers at 90 psi and the tubeless at 80 psi and the tubeless at the lower pressure seems to roll faster.

    I just got a set of 50 mm deep aero carbon tubeless rims and using GP5000TL Continentals they went together without a bit of trouble. When these are properly installed you can inflate them with a normal floor pump. I'm still a little wary of them since the previous 40 mm ones delaminated 4 out of 4 wheels. But these didn't have a bit of trouble and didn't make the noises that the last ones did.

    And they are so cheap that you can't get anything close to them for 4 times the price.
     
  15. cyclintom

    cyclintom Well-Known Member

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    king - I don't know where you get the idea that rims don't flex but you can feel them do so under hard loadings. That was the outstanding thing when I changed over to carbon fiber aero rims - they do not flex at all and in hard descents where I have to set up for high speed sharp turns as if I was riding a motorcycle again, with the carbon rims I didn't have to set up and all but simply ride around it. Since the bike and tires were the same the only way that this change could have occurred is if the rims and spokes were flexing.

    What's more - I can put something like my Campy Proton wheels in the wheel alignment stand, tighten them up and push them out of alignment by hand. While this could be caused by the older spoking method using less tension, it is still the rims that are flexing.
     
  16. George Young

    George Young New Member

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    Exactly I have the same point you just can't say its established or not.
     
  17. Rock Creek Rider

    Rock Creek Rider New Member

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    This is proof of what I already knew. A lot of people don't really read the post before replying. If you read through my post again, you will see that I don't really say anything is established fact. I am, in fact, questioning things that used to be considered established fact. Things that, if, back in the seventies, you looked in a popular book about cycling or read articles in Bicycling! you might come to the conclusion that they were established fact, when in fact, they turned out to be myths or, at least debatable. Others have held up to the test of time.
     
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