rollie pollie tires

Discussion in 'Cycling Equipment' started by ranger39000, Dec 24, 2006.

  1. ranger39000

    ranger39000 New Member

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    Been ridin 16 yrs but just started noticing a phenomenom upon turning corners. It feels as if my tires are rolling to the extreme other side of the rim opposite the turn. Has anyone else experienced this sensation on clinchers? [​IMG] I currently have Specialized All-Condition on the rims and keep them rock hard most of time.
     
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  2. snaps10

    snaps10 New Member

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    hmm. i ride specialized pro all-condition and haven't felt that. aside from them being the tallest 23 tire that ive ever seen, and weighing my bike down alot, they seem to be very sticky to me. i feel more comfortable descending on them than i do my pro race's. perhaps it just feels that way because they are a true 23. one thing ive noticed, specialized means 125psi when they say 125psi. are you sure youve got them aired to the recommended. at pressures lower than 125 mine feel kinda squishy. im 168lbs (and dropping)
     
  3. alienator

    alienator Well-Known Member

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    Why rock-hard? You're not getting the best out of your tires when they'e over pressurized like that. Heck, 125 psi is probably borderline over pressurized for someone that is 168 lbs. You don't gain anything, except on a glass smooth track, from higher pressures. In fact, you end up actually going slower.
     
  4. ranger39000

    ranger39000 New Member

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    hhmmmmmmmm........ As I always figured it - the less air, the more rubber on the ground. Therefore more rolling resistance. Explanation needs expounding [​IMG].(come on Alienator, Thread needs a little brass ) These tires I get for only 20 bucks at the LBS and hate to giv em up for future purchase, but if I can't resolve the handling problem, I may b forced to spend more....ouch! [​IMG]. Do alot of commuting and go through alot of tires so these r perfect.....except for this little problem.
     
  5. snaps10

    snaps10 New Member

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    one thing i have noticed, with my ever so scientific measuring method (thumb) my specialized at 125 seem softer than my prorace2 at 110. at 125 the specialized feel slow, under 125 the specialized feel very slow. im used to running my tires between 100-110 with the proraces.

    and alienator, i love your posts. im glad you replied here.
     
  6. ScienceIsCool

    ScienceIsCool New Member

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    I'll take a shot at explaining. Imagine your tires being pumped up to a ridiculously high pressure. So high that they resemble a solid steel tire (though grippier. :) ). Now imagine riding along. Lots of vibrations and bumps as you roll over the uneven pavement. What's happening is that your forward momentum is being transferred into bumps and vibrations which lift the entire mass of you and the bike up and down. This is lost energy which slows you down.

    Now imagine underinflated tires that are all soft and squishy. No more bumps and vibrations because the casing of the tire is flexing and absorbing them. In fact there is so much flex in the tire casing that it too is slowing you down. Energy is being lost into the tire casing.

    For each road surface, rider and tire there is an optimal pressure which minimizes the total energy loss to vibration and tire casing flex. From everything I've read that optimal point is somewhere between 90-110 psi for most riders and road conditions.

    John Swanson
    www.bikephysics.com
     
  7. ranger39000

    ranger39000 New Member

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    Science IS cool! [​IMG] Thanx, Science. Exactly what I suspected all along [​IMG]
     
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